A beginner's guide to time travel

Learn exactly how Einstein's theory of relativity works, and discover how there's nothing in science that says time travel is impossible.

Actor Rod Taylor tests his time machine in a still from the film 'The Time Machine', directed by George Pal, 1960.

Everyone can travel in time . You do it whether you want to or not, at a steady rate of one second per second. You may think there's no similarity to traveling in one of the three spatial dimensions at, say, one foot per second. But according to Einstein 's theory of relativity , we live in a four-dimensional continuum — space-time — in which space and time are interchangeable.

Einstein found that the faster you move through space, the slower you move through time — you age more slowly, in other words. One of the key ideas in relativity is that nothing can travel faster than the speed of light — about 186,000 miles per second (300,000 kilometers per second), or one light-year per year). But you can get very close to it. If a spaceship were to fly at 99% of the speed of light, you'd see it travel a light-year of distance in just over a year of time. 

That's obvious enough, but now comes the weird part. For astronauts onboard that spaceship, the journey would take a mere seven weeks. It's a consequence of relativity called time dilation , and in effect, it means the astronauts have jumped about 10 months into the future. 

Traveling at high speed isn't the only way to produce time dilation. Einstein showed that gravitational fields produce a similar effect — even the relatively weak field here on the surface of Earth . We don't notice it, because we spend all our lives here, but more than 12,400 miles (20,000 kilometers) higher up gravity is measurably weaker— and time passes more quickly, by about 45 microseconds per day. That's more significant than you might think, because it's the altitude at which GPS satellites orbit Earth, and their clocks need to be precisely synchronized with ground-based ones for the system to work properly. 

The satellites have to compensate for time dilation effects due both to their higher altitude and their faster speed. So whenever you use the GPS feature on your smartphone or your car's satnav, there's a tiny element of time travel involved. You and the satellites are traveling into the future at very slightly different rates.

Navstar-2F GPS satellite

But for more dramatic effects, we need to look at much stronger gravitational fields, such as those around black holes , which can distort space-time so much that it folds back on itself. The result is a so-called wormhole, a concept that's familiar from sci-fi movies, but actually originates in Einstein's theory of relativity. In effect, a wormhole is a shortcut from one point in space-time to another. You enter one black hole, and emerge from another one somewhere else. Unfortunately, it's not as practical a means of transport as Hollywood makes it look. That's because the black hole's gravity would tear you to pieces as you approached it, but it really is possible in theory. And because we're talking about space-time, not just space, the wormhole's exit could be at an earlier time than its entrance; that means you would end up in the past rather than the future.

Trajectories in space-time that loop back into the past are given the technical name "closed timelike curves." If you search through serious academic journals, you'll find plenty of references to them — far more than you'll find to "time travel." But in effect, that's exactly what closed timelike curves are all about — time travel

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There's another way to produce a closed timelike curve that doesn't involve anything quite so exotic as a black hole or wormhole: You just need a simple rotating cylinder made of super-dense material. This so-called Tipler cylinder is the closest that real-world physics can get to an actual, genuine time machine. But it will likely never be built in the real world, so like a wormhole, it's more of an academic curiosity than a viable engineering design.

Yet as far-fetched as these things are in practical terms, there's no fundamental scientific reason — that we currently know of — that says they are impossible. That's a thought-provoking situation, because as the physicist Michio Kaku is fond of saying, "Everything not forbidden is compulsory" (borrowed from T.H. White's novel, "The Once And Future King"). He doesn't mean time travel has to happen everywhere all the time, but Kaku is suggesting that the universe is so vast it ought to happen somewhere at least occasionally. Maybe some super-advanced civilization in another galaxy knows how to build a working time machine, or perhaps closed timelike curves can even occur naturally under certain rare conditions.

An artist's impression of a pair of neutron stars - a Tipler cylinder requires at least ten.

This raises problems of a different kind — not in science or engineering, but in basic logic. If time travel is allowed by the laws of physics, then it's possible to envision a whole range of paradoxical scenarios . Some of these appear so illogical that it's difficult to imagine that they could ever occur. But if they can't, what's stopping them? 

Thoughts like these prompted Stephen Hawking , who was always skeptical about the idea of time travel into the past, to come up with his "chronology protection conjecture" — the notion that some as-yet-unknown law of physics prevents closed timelike curves from happening. But that conjecture is only an educated guess, and until it is supported by hard evidence, we can come to only one conclusion: Time travel is possible.

A party for time travelers 

Hawking was skeptical about the feasibility of time travel into the past, not because he had disproved it, but because he was bothered by the logical paradoxes it created. In his chronology protection conjecture, he surmised that physicists would eventually discover a flaw in the theory of closed timelike curves that made them impossible. 

In 2009, he came up with an amusing way to test this conjecture. Hawking held a champagne party (shown in his Discovery Channel program), but he only advertised it after it had happened. His reasoning was that, if time machines eventually become practical, someone in the future might read about the party and travel back to attend it. But no one did — Hawking sat through the whole evening on his own. This doesn't prove time travel is impossible, but it does suggest that it never becomes a commonplace occurrence here on Earth.

The arrow of time 

One of the distinctive things about time is that it has a direction — from past to future. A cup of hot coffee left at room temperature always cools down; it never heats up. Your cellphone loses battery charge when you use it; it never gains charge. These are examples of entropy , essentially a measure of the amount of "useless" as opposed to "useful" energy. The entropy of a closed system always increases, and it's the key factor determining the arrow of time.

It turns out that entropy is the only thing that makes a distinction between past and future. In other branches of physics, like relativity or quantum theory, time doesn't have a preferred direction. No one knows where time's arrow comes from. It may be that it only applies to large, complex systems, in which case subatomic particles may not experience the arrow of time.

Time travel paradox 

If it's possible to travel back into the past — even theoretically — it raises a number of brain-twisting paradoxes — such as the grandfather paradox — that even scientists and philosophers find extremely perplexing.

Killing Hitler

A time traveler might decide to go back and kill him in his infancy. If they succeeded, future history books wouldn't even mention Hitler — so what motivation would the time traveler have for going back in time and killing him?

Killing your grandfather

Instead of killing a young Hitler, you might, by accident, kill one of your own ancestors when they were very young. But then you would never be born, so you couldn't travel back in time to kill them, so you would be born after all, and so on … 

A closed loop

Suppose the plans for a time machine suddenly appear from thin air on your desk. You spend a few days building it, then use it to send the plans back to your earlier self. But where did those plans originate? Nowhere — they are just looping round and round in time.

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At last, a way to test time travel

By Marcus Chown

17 May 2006

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When would you go?

The title of Heinrich Päs’s latest paper might not mean much to you. To those who know their theoretical physics, however, “Closed timelike curves in asymmetrically warped brane universes” contains a revelation. It suggests that time machines might be far more common than we ever thought possible.

Forget trawling the universe in search of rotating black holes or exotic wormhole tunnels that could supposedly let us hop from one instant to another. According to Päs, a physicist at the University of Hawaii at Manoa, and his colleagues, the door to a time machine could be anywhere and everywhere in our universe. And unlike most other scenarios for time travel, we can test this one here on Earth. “I think the ideas presented are wonderful and exciting,” says Bill Louis, a physicist at Los Alamos National Laboratory in New Mexico and co-spokesperson for the MiniBoone neutrino experiment at Fermilab, near Chicago. “The question is are they true or not.”

Louis is right to be cautious. Although nothing in the laws of nature appears to rule out time travel, physicists have always been uneasy about it because it makes a mockery of causality , the idea that cause always precedes effect. Violating causality would play havoc with the universe, for instance, allowing you to travel back in time and prevent your own birth.

Such paradoxes are what led Stephen Hawking to propose his “chronology protection conjecture”. This basically says that some principle of physics, perhaps as yet undiscovered, will always come to the rescue and prevent time travel…

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Is Time Travel Possible?

We all travel in time! We travel one year in time between birthdays, for example. And we are all traveling in time at approximately the same speed: 1 second per second.

We typically experience time at one second per second. Credit: NASA/JPL-Caltech

NASA's space telescopes also give us a way to look back in time. Telescopes help us see stars and galaxies that are very far away . It takes a long time for the light from faraway galaxies to reach us. So, when we look into the sky with a telescope, we are seeing what those stars and galaxies looked like a very long time ago.

However, when we think of the phrase "time travel," we are usually thinking of traveling faster than 1 second per second. That kind of time travel sounds like something you'd only see in movies or science fiction books. Could it be real? Science says yes!

Image of galaxies, taken by the Hubble Space Telescope.

This image from the Hubble Space Telescope shows galaxies that are very far away as they existed a very long time ago. Credit: NASA, ESA and R. Thompson (Univ. Arizona)

How do we know that time travel is possible?

More than 100 years ago, a famous scientist named Albert Einstein came up with an idea about how time works. He called it relativity. This theory says that time and space are linked together. Einstein also said our universe has a speed limit: nothing can travel faster than the speed of light (186,000 miles per second).

Einstein's theory of relativity says that space and time are linked together. Credit: NASA/JPL-Caltech

What does this mean for time travel? Well, according to this theory, the faster you travel, the slower you experience time. Scientists have done some experiments to show that this is true.

For example, there was an experiment that used two clocks set to the exact same time. One clock stayed on Earth, while the other flew in an airplane (going in the same direction Earth rotates).

After the airplane flew around the world, scientists compared the two clocks. The clock on the fast-moving airplane was slightly behind the clock on the ground. So, the clock on the airplane was traveling slightly slower in time than 1 second per second.

Credit: NASA/JPL-Caltech

Can we use time travel in everyday life?

We can't use a time machine to travel hundreds of years into the past or future. That kind of time travel only happens in books and movies. But the math of time travel does affect the things we use every day.

For example, we use GPS satellites to help us figure out how to get to new places. (Check out our video about how GPS satellites work .) NASA scientists also use a high-accuracy version of GPS to keep track of where satellites are in space. But did you know that GPS relies on time-travel calculations to help you get around town?

GPS satellites orbit around Earth very quickly at about 8,700 miles (14,000 kilometers) per hour. This slows down GPS satellite clocks by a small fraction of a second (similar to the airplane example above).

Illustration of GPS satellites orbiting around Earth

GPS satellites orbit around Earth at about 8,700 miles (14,000 kilometers) per hour. Credit: GPS.gov

However, the satellites are also orbiting Earth about 12,550 miles (20,200 km) above the surface. This actually speeds up GPS satellite clocks by a slighter larger fraction of a second.

Here's how: Einstein's theory also says that gravity curves space and time, causing the passage of time to slow down. High up where the satellites orbit, Earth's gravity is much weaker. This causes the clocks on GPS satellites to run faster than clocks on the ground.

The combined result is that the clocks on GPS satellites experience time at a rate slightly faster than 1 second per second. Luckily, scientists can use math to correct these differences in time.

Illustration of a hand holding a phone with a maps application active.

If scientists didn't correct the GPS clocks, there would be big problems. GPS satellites wouldn't be able to correctly calculate their position or yours. The errors would add up to a few miles each day, which is a big deal. GPS maps might think your home is nowhere near where it actually is!

In Summary:

Yes, time travel is indeed a real thing. But it's not quite what you've probably seen in the movies. Under certain conditions, it is possible to experience time passing at a different rate than 1 second per second. And there are important reasons why we need to understand this real-world form of time travel.

If you liked this, you may like:

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Is time travel possible? Why one scientist says we 'cannot ignore the possibility.'

time travel test

A common theme in science-fiction media , time travel is captivating. It’s defined by the late philosopher David Lewis in his essay “The Paradoxes of Time Travel” as “[involving] a discrepancy between time and space time. Any traveler departs and then arrives at his destination; the time elapsed from departure to arrival … is the duration of the journey.”

Time travel is usually understood by most as going back to a bygone era or jumping forward to a point far in the future . But how much of the idea is based in reality? Is it possible to travel through time? 

Is time travel possible?

According to NASA, time travel is possible , just not in the way you might expect. Albert Einstein’s theory of relativity says time and motion are relative to each other, and nothing can go faster than the speed of light , which is 186,000 miles per second. Time travel happens through what’s called “time dilation.”

Time dilation , according to Live Science, is how one’s perception of time is different to another's, depending on their motion or where they are. Hence, time being relative. 

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Dr. Ana Alonso-Serrano, a postdoctoral researcher at the Max Planck Institute for Gravitational Physics in Germany, explained the possibility of time travel and how researchers test theories. 

Space and time are not absolute values, Alonso-Serrano said. And what makes this all more complex is that you are able to carve space-time .

“In the moment that you carve the space-time, you can play with that curvature to make the time come in a circle and make a time machine,” Alonso-Serrano told USA TODAY. 

She explained how, theoretically, time travel is possible. The mathematics behind creating curvature of space-time are solid, but trying to re-create the strict physical conditions needed to prove these theories can be challenging. 

“The tricky point of that is if you can find a physical, realistic, way to do it,” she said. 

Alonso-Serrano said wormholes and warp drives are tools that are used to create this curvature. The matter needed to achieve curving space-time via a wormhole is exotic matter , which hasn’t been done successfully. Researchers don’t even know if this type of matter exists, she said.

“It's something that we work on because it's theoretically possible, and because it's a very nice way to test our theory, to look for possible paradoxes,” Alonso-Serrano added.

“I could not say that nothing is possible, but I cannot ignore the possibility,” she said. 

She also mentioned the anecdote of  Stephen Hawking’s Champagne party for time travelers . Hawking had a GPS-specific location for the party. He didn’t send out invites until the party had already happened, so only people who could travel to the past would be able to attend. No one showed up, and Hawking referred to this event as "experimental evidence" that time travel wasn't possible.

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Paradox-Free Time Travel Is Theoretically Possible, Researchers Say

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A dog dressed as Marty McFly from Back to the Future attends the Tompkins Square Halloween Dog Parade in 2015. New research says time travel might be possible without the problems McFly encountered. Timothy A. Clary/AFP via Getty Images hide caption

A dog dressed as Marty McFly from Back to the Future attends the Tompkins Square Halloween Dog Parade in 2015. New research says time travel might be possible without the problems McFly encountered.

"The past is obdurate," Stephen King wrote in his book about a man who goes back in time to prevent the Kennedy assassination. "It doesn't want to be changed."

Turns out, King might have been on to something.

Countless science fiction tales have explored the paradox of what would happen if you went back in time and did something in the past that endangered the future. Perhaps one of the most famous pop culture examples is in Back to the Future , when Marty McFly goes back in time and accidentally stops his parents from meeting, putting his own existence in jeopardy.

But maybe McFly wasn't in much danger after all. According a new paper from researchers at the University of Queensland, even if time travel were possible, the paradox couldn't actually exist.

Researchers ran the numbers and determined that even if you made a change in the past, the timeline would essentially self-correct, ensuring that whatever happened to send you back in time would still happen.

"Say you traveled in time in an attempt to stop COVID-19's patient zero from being exposed to the virus," University of Queensland scientist Fabio Costa told the university's news service .

"However, if you stopped that individual from becoming infected, that would eliminate the motivation for you to go back and stop the pandemic in the first place," said Costa, who co-authored the paper with honors undergraduate student Germain Tobar.

"This is a paradox — an inconsistency that often leads people to think that time travel cannot occur in our universe."

A variation is known as the "grandfather paradox" — in which a time traveler kills their own grandfather, in the process preventing the time traveler's birth.

The logical paradox has given researchers a headache, in part because according to Einstein's theory of general relativity, "closed timelike curves" are possible, theoretically allowing an observer to travel back in time and interact with their past self — potentially endangering their own existence.

But these researchers say that such a paradox wouldn't necessarily exist, because events would adjust themselves.

Take the coronavirus patient zero example. "You might try and stop patient zero from becoming infected, but in doing so, you would catch the virus and become patient zero, or someone else would," Tobar told the university's news service.

In other words, a time traveler could make changes, but the original outcome would still find a way to happen — maybe not the same way it happened in the first timeline but close enough so that the time traveler would still exist and would still be motivated to go back in time.

"No matter what you did, the salient events would just recalibrate around you," Tobar said.

The paper, "Reversible dynamics with closed time-like curves and freedom of choice," was published last week in the peer-reviewed journal Classical and Quantum Gravity . The findings seem consistent with another time travel study published this summer in the peer-reviewed journal Physical Review Letters. That study found that changes made in the past won't drastically alter the future.

Bestselling science fiction author Blake Crouch, who has written extensively about time travel, said the new study seems to support what certain time travel tropes have posited all along.

"The universe is deterministic and attempts to alter Past Event X are destined to be the forces which bring Past Event X into being," Crouch told NPR via email. "So the future can affect the past. Or maybe time is just an illusion. But I guess it's cool that the math checks out."

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Traveling soon? Here’s where you can quickly get a COVID-19 test

Victoria M. Walker

If you've tried to get a COVID-19 test for travel or for peace of mind recently, you might have run into significant delays.

The omicron variant has complicated travel plans and, depending on where in the country you're located, made it difficult — if not impossible — to get a test. Some companies are reporting shortages, and in major cities like New York , blocks-long lines have formed of people trying to get tested.

For more TPG travel news and tips delivered each morning to your inbox, sign up for our free daily newsletter.

Unfortunately, COVID-19 testing is still a reality for the times in which we live.

Earlier this year, some countries dropped testing requirements for fully vaccinated travelers as more people got COVID-19 vaccines. But depending on where you want to go (and as omicron spreads) a negative COVID-19 test result might be required, particularly if you're not vaccinated or are traveling with unvaccinated children.

If you need a COVID-19 test for travel , you might be wondering where you can get one, what type of test you'll need to take, how long it will take to get an appointment (and wait for results), and what it will cost. To help you prepare, we researched where you can get tested in 25 major metropolitan areas. We found that some tests are entirely free , while others require a copay or are covered with insurance. Some will require full cash payment when requested for travel (instead of due to symptoms or exposure).

Some destinations require negative polymerase chain reaction (PCR) tests taken within a certain time , usually 72 hours, before departure. Many facilities can provide results between 48 and 72 hours, but that isn't always true – especially now.

Also, keep in mind that some testing sites deliver results over the phone, which likely won't be suitable for boarding an aircraft or entering a country.

What type of COVID-19 test do you need?

time travel test

Antigen test. Rapid test. PCR test. RT-PCR test. Antibody test. Take-home test. If you've taken a COVID-19 test during the pandemic , you might have been bewildered by the sheer number of options.

Keeping track of which COVID-19 test you need can seem daunting. Not all COVID-19 tests are created equal, and not all are suitable for international travel.

You'll usually need a PCR test (polymerase chain reaction) for travel. These are the most reliable tests for detecting active COVID-19 infections and are considered the "gold standard" of testing. In this guide, we'll primarily focus on testing sites that provide these more accurate PCR tests, though keep in mind that some destinations, like Hawaii, only accept PCR tests from a specific list of testing providers .

The tests that often won't help you with travel are antibody tests, blood tests that can identify if a previous COVID-19 infection caused your immune system to produce COVID-19 antibodies. Some destinations also won't accept rapid antigen tests , which check for proteins on the virus's surface. These tests are popular for quick turnaround times but are less accurate than PCR tests and aren't valid to enter some countries, such as Canada .

Check to see if you can get a rapid PCR test

Though PCR tests generally take around 72 hours for results, some urgent care facilities have introduced "rapid PCR tests," where you can receive your results as fast as 30 minutes. That said, if you're looking for a faster way to get a PCR test, it may cost you as these facilities may not accept insurance.

Some rapid PCR testing options include:

  • COVIDCheck in San Diego, Orange County, Los Angeles, Las Vegas and Denver. Results in six hours for RT-PCR tests. Cost: $349
  • Complete Health Partners in Nashville, Tennessee. Results in 30 to 45 minutes. Cost: $250, not billed to insurance.
  • DMCovid-19 Test offers travel PCR testing by housecall nationwide in all states except Alaska and Hawaii; it also has nine physical locations. Cost: Price varies by location and whether it's in-home or in the office.
  • Elite Medical Center in Las Vegas, Nevada. Results in 24 hours. Cost: $250
  • Frontage Laboratory in Exton, Pennsylvania (35 minutes from Philadelphia). Offers COVID-19 tests for travelers within six hours. Cost: $203 for an RT-PCR test.
  • Medical Offices of Manhattan in New York City, New York. Same-day results. Cost: $175 for the test, which doesn't include doctor consultation.
  • Saguaro Bloom in Scottsdale, Arizona. Offers 24-hour and 90-minute turnaround for RT-PCR testing. Cost: $299 for 90-minute turnaround and $149 for 24-hour turnaround.
  • Test Well in Reno, Nevada, and South Lake Tahoe, California. Offers RT-PCR tests for travel with guaranteed same-day results. The cost is $149 for travel purposes (but you can file a claim with your insurance for reimbursement).
  • Urgent Medical Care and MRI in Jersey City, New Jersey. Results in an hour or less only for travelers who need documentation. Cost: $300 out of pocket, not billed to insurance.
  • Venistat Mobile Labs in New York, New York. Offers RT-PCR test results in less than 24 hours. Cost: $125 when using insurance, $190 without insurance.
  • WeTestU in San Diego, California. Offers mobile RT-PCR testing for travel. Cost: $159 for 24-hour turnaround, $199 for 24-hour turnaround, $259 for same-day (eight hour) turnaround, $329 for one-hour turnaround.
  • Worksite Labs offers PCR test results guaranteed within 24 hours near 20 U.S. airports. Cost: $90

COVID-19 testing at drugstores

If you're in a location without many COVID-19 testing sites, you may want to head to your neighborhood drugstore.

You'll notice several major chains on the list of where to get a COVID-19 test, including CVS , Walgreens , and Rite Aid . All of these often offer PCR testing at no additional cost if using insurance or if you fall under some federal programs for those without insurance.

Passport Health also has a network of clinics in over 100 locations nationwide, primarily for people who need a negative PCR test to fly or return to school.

Even better, you can make these appointments online, which may save precious time instead of waiting in a long line. Many of these locations also offer drive-up testing , where you swab yourself and don't need to leave your vehicle.

Turnaround times can vary by chain and location:

  • CVS : Average turnaround time for receiving results from lab tests is one to two days for PCR tests.
  • Walgreens : Turnaround time is based on when the sample arrives at the laboratory.
  • Rite Aid : Turnaround time varies between 125 minutes to two to five days.

Also, several third-party companies partner with major cities like Houston and San Francisco on widespread testing. These companies, such as Color and Curative , offer results between one to three days.

City-provided COVID-19 testing

time travel test

As the new variant spreads, more cities are handing out free COVID-19 rapid tests for residents.

New York City said it would distribute 500,000 free at-home COVID-19 tests as well as 1 million higher-grade KN95 masks to New Yorkers through community organizations. Residents in Washington, D.C. can pick up an at-home COVID-19 testing kit at select libraries throughout the city . And the White House has promised to distribute 500 million free rapid tests to Americans.

These tests generally won't be approved for travel but could provide peace of mind before (or during) your trip.

COVID-19 testing for children

Many destinations have dropped testing requirements for fully vaccinated travelers . However, vaccinated adults traveling with unvaccinated kids may, in some instances, have different travel requirements. But many countries (even those with strict vaccination requirements) accept proof of a negative COVID-19 test for children ineligible to be vaccinated.

If you're trying to get a COVID-19 test for a child, many nationwide drugstores serve younger patients. CVS and Walgreens serve patients 3 years of age and older, while Rite Aid offers tests at no cost to anyone 4 and older.

But now, some kids may be able to bypass COVID-19 tests if they can be vaccinated, making it far less stressful to travel. The Pfizer COVID-19 vaccine has officially been approved for kids 5 to 11 by the Food and Drug Administration and the U.S. Centers for Disease Control and Prevention. The Moderna and Johnson & Johnson vaccines are only available to people 18 and older at this time.

At-home COVID-19 tests

The CDC expanded the testing program for international travel to the United States earlier this spring, allowing airlines to accept at-home instant tests that include remote supervision.

That's good news for U.S.-bound travelers who may not have many testing options at their location abroad . Travelers flying to the U.S. can use a self-test (sometimes referred to as a home test if it's a NAAT or antigen test with Emergency Use Authorization EUA from the FDA). The test must also have a telehealth service that provides real-time supervision. Here are several popular options:

  • Abbott's BinaxNOW COVID-19 Home Test can be ordered from eMed or from Optum and is CDC-approved for travel to the U.S. There's a second Abbott rapid test you can buy at the drugstore, but it isn't proctored and can't be used for travel.
  • Amazon's COVID-19 Test Collection Kit DTC has received EUA from the FDA and costs $39.99.
  • Cue Health claims to offer results in just 20 minutes — and that it can detect the omicron variant . The test is authorized by the FDA for at-home use and can be used for travel purposes. The company offers two options for travelers: the Cue+ Essential membership, which starts at $49.99 (a more expensive option costs $89.99 per month) or a one-time purchase with a pack of three or 10 tests starting at $225.

Mail-in COVID-19 testing tests

There are many mail-in or in-home COVID-19 testing providers available. Some are not valid in certain states, and some are not available in all situations.

Most will not bill insurance for you, with Pixel being an exception to that general rule. Some mail-in tests are nasal swabs, while others are saliva samples. Some are only valid for adults, and others require a Zoom appointment. But, these are all the gold-standard PCR tests that are considered highly reliable.

A handful of these companies have partnered with various airlines and the state of Hawaii as approved providers, so this can be a legitimate testing option for travel to the state. If your airline has a mail-in testing partner valid for your travel destination, we recommend going through their system as it may get your sample prioritized in the lab's testing order.

Some mail-in COVID-19 testing programs include:

  • Everlywell: Results of the nasal swab available within 24 to 48 hours of the lab receiving the sample. Available to people 18 and older only, and costs $82.
  • Pixel by LabCorp : Results of the nasal swab are available one to two days after arriving back in the lab. Available to people 18 and older. There is no upfront cost, or $119 if you're not eligible for insurance or federal funds.
  • Vault : Results of the saliva test taken via a Zoom call are available within 24 to 48 hours. The test is available to children and adults and costs $119.
  • Azova : Available at Costco.com. The saliva test results, taken via a Zoom call, are available within 12 to 48 hours upon being received by the lab. This test is approved as part of Hawaii's trusted testing partner program and for travel to Bermuda and costs $118.99.
  • OnSight Safe : Results of PCR saliva-based tests are available within 48 hours after being received by the lab; expedited processing is also available. Available for children and adults nationally. Physical testing locations are in New York City, Tampa and Van Nuys, California, and tests start at $127.95.

In-home COVID-19 tests

time travel test

There are at-home COVID-19 tests, but did you know that some facilities offer a concierge service? You can have a testing provider come to your house, apartment or hotel and swab your nose.

In-home testing offers travelers the convenience of not having to wait in a line to get tested. (We're calling it in-home testing, but some facilities also provide testing at your office for large groups.)

Some of the most popular include Welz, which offers same-day in-home rapid testing in New York, Philadelphia and Los Angeles with a 15-minute turnaround. Even better: It's free with your health insurance or even if you're uninsured.

Generally, in-home tests and concierge services should be approved for travel purposes, as long as they meet the CDC's requirements and you get a physical or digital copy of your results. But you'll want to double-check you're taking an in-home COVID-19 test approved by your destination.

How long will test results take to arrive?

Most states or countries that require negative COVID-19 tests for entry (or entry without quarantine) use a 72-hour timeframe, from the test until either the time of your departure or arrival at the destination. Sometimes, however, the window is even shorter.

While there are exceptions, one to three days for COVID-19 test results seem standard nationwide.

You may need to research PCR testing locations that promise same-day results or provide rapid PCR tests analyzed on-site if the arrival of your test results could make or break your trip. Several facilities on the list below have previously reported delays in test results due to an increase in demand.

COVID-19 testing in airports

time travel test

Many U.S. airports offer rapid COVID-19 testing to passengers or travelers on specific flights or heading to particular destinations. This could be a great option if you can drive to the airport to get a test a day or two ahead of your trip.

But we don't recommend waiting to get a test until your travel has already started, as isolating for at least two weeks at a connecting city will likely be an expensive hassle.

Some current airport testing centers available within the U.S. include:

  • Anchorage International Airport : Testing at ANC is free for residents and nonresidents.
  • Bradley International Airport : Open seven days per week. If the passenger's insurer does not cover the test, tests are available for $125 each. Results will most likely be available within 72 hours of testing but can take longer. Testing is only available to passengers traveling through Connecticut's Bradley Airport (BDL) on the day of their flight.
  • Burlington International Airport : Testing is open to all at Vermont's BTV airport Monday through Friday, with appointments recommended and results available same-day or 36 to 48 hours. The test may have a fee .
  • Dallas – Fort Worth International Airport : Those traveling on American Airlines can get a rapid test at DFW on the day of travel for $139, with results available in about 15 minutes.
  • Fort Lauderdale-Hollywood International Airport : Testing is available between 7 a.m. and 9 p.m. Rapid PCR tests are $179, PCR tests are $106, and rapid antigen tests are $74. Rapid antigen test results are returned in about 30 minutes, rapid PCR tests are returned within 45 minutes, and PCR tests have a 48-hour turnaround.
  • Minneapolis-St. Paul International Airport: Tests through the Minnesota Department of Health and Vault Health are done with saliva, return results within 48 hours and are free for Minnesota residents and $94 for others. Tests through Wandertest include Antigen, NAAT and PCR tests and provide rapid results in less than an hour and range from $99 to $199.
  • New York-LaGuardia : PCR testing is free with no appointments necessary in LGA's Terminal B parking garage, with results delivered by phone within 48 hours. However, this won't be very useful for travel verification purposes since the results are verbal.
  • Oakland International Airport : OAK has two testing centers, one in the airport and a second drive-up location. Only passengers heading to Hawaii are encouraged to use this, though technically, any passenger can book the drive-up location. Appointments are required, and there is a $120 lab fee for expedited processing and a $20 administrative fee for Hawaii's mandated travel documentation.
  • San Francisco International Airport : San Francisco-based travelers flying on United Airlines to Hawaii and select destinations in Central and South America and the Caribbean can arrange for a mail-in PCR COVID-19 test. Travelers will receive results in 24 to 48 hours, and the cost is $119.
  • XpresCheck has many airport locations across the U.S. PCR tests are available by appointment or potentially via walk-up; costs vary. Rapid molecular NAAT tests are hand-delivered within 30 to 60 minutes for $200, insurance not accepted. Standard PCR tests will be delivered 48 to 96 hours for $75, and insurance is accepted for lab fees only. Rapid PCR tests are hand-delivered within 30 to 60 minutes for $250.

Hotels offering COVID-19 tests

Many hotels and resorts all over the world now provide on-site testing. If you're staying at a hotel, check to see if they offer on-site COVID-19 testing, as it's an extremely valuable amenity that can save you time searching for a test. In some cases, that test may also be free.

Related: Forget free breakfast: The hottest hotel amenity is a nasal swab

COVID-19 testing is required to enter the US

time travel test

If you're traveling back to the United States from abroad, you need to provide a negative COVID-19 test result before boarding.

However, the White House significantly shrank the time window for testing in response to the omicron variant, which means travelers will need to arrange for COVID-19 tests sooner.

All travelers – vaccinated or not – must get a viral test within one day of departure to the U.S. Even if you've been vaccinated against COVID-19, you'll need to provide a negative test before boarding. There are several exemptions to this rule. Travelers flying back from U.S. territories, travelers arriving via a land border such as Mexico or Canada, and flight crew members do not need to present a negative COVID-19 test.

People who aren't vaccinated face extra testing and hurdles

More cities are following Europe's footsteps and testing out proof of vaccination mandates for certain activities. Some spots in Los Angeles, for example, require proof of vaccination to dine indoors, and New York City was the first U.S. city to establish a vaccine mandate.

The order went into effect on Aug. 17 for everyone 5 and older. Unvaccinated New Yorkers can no longer participate in many indoor activities, including indoor dining, indoor fitness and indoor entertainment.

Since then, cities like Chicago and Washington, D.C. , have also implemented vaccine mandates.

Vaccine passports

time travel test

Travelers may want to use digital health or vaccine passports to enter certain countries or be exempt from strict testing and quarantine requirements. But vaccine passports aren't expected only to hold COVID-19 vaccine records. They can also be used to verify negative COVID-19 results.

For instance, New Yorkers can use the Excelsior Pass if they have had a negative PCR test administered in New York within three days; or took a negative antigen test in New York in the last six hours.

Clear's Health Pass feature is used to verify negative tests required at some sports arenas and approve tourists for quarantine-free travel to Hawaii. CommonPass is an independent app that collects a user's COVID-19 status and verifies their identity. The International Air Transport Association (IATA) also partners with dozens of airlines worldwide on its Travel Pass app , which hosts verified test and vaccine information.

City-by-city guide on where to get a COVID-19 test

Finding a reliable place to get a PCR COVID-19 test for travel with quick results can be challenging, depending on where you're located in the U.S.

Because things change so quickly, you'll need to contact the sites directly to confirm this information is still accurate. But to give you a headstart in your research, these testing facilities may meet your travel needs. If you encounter a location that should be added (or removed) from the list, or if you're a healthcare provider conducting PCR testing, please email [email protected].

Where to get a COVID-19 test in Atlanta, Georgia

Community Organized Relief Effort

  • Various locations throughout Georgia, including Atlanta.
  • Hours: Varies by location.
  • Cost: Free.
  • Appointment required: Walk-up and drive-thru testing available, all sites are subject to early closure once the 500-test daily maximum is reached.
  • Turnaround time: Typically 72 hours.

Summit Urgent Care

  • Various locations throughout the Atlanta metropolitan area.
  • Cost: Accepts most insurance, no copay for virtual visits.
  • Appointment required: No.
  • Turnaround time: Three to five days.

Peachtree Immediate Care

  • Hours: Drive-thru locations open seven days a week from 8 a.m. to 6 p.m., though some locations are closed on weekends.
  • Cost: For most insurance plans, there is no copay or deductible required; a $175 self-pay option is also available.
  • Appointment required: Yes.
  • Turnaround time: Typically three days.

Viral Solutions

  • Cost: No out-of-pocket cost with insurance.
  • Turnaround time: Two days.

ARCpoint Labs of Atlanta-Northeast

  • 3635 Savannah Place Drive, Suite 450-B Duluth, Georgia
  • Hours: Monday to Friday 7:30 a.m. to 6 p.m., Saturday 8 a.m. to 12 p.m.
  • Cost: $169 for lab-based PCR test, $249 for rapid PCR test; Self-pay option only
  • Appointment Required: Yes, but same-day appointments are available.
  • Turnaround Time: Less than two hours for a rapid PCR test, 48 hours is typical for lab-based PCR.

Where to get a COVID-19 test in the Bay Area, California

My Doctor Medical Group

  • 450 Sutter Street Suite 840, San Francisco, California
  • Cost: $240 for visit and swab collection, $125 lab fee for expedited next-day PCR results, $35 for customized additional travel documentation and certificates (in addition to lab report) if needed.
  • Turnaround time: By 5 p.m. next day after collection.

McCampbell Analytical

  • 1534 Willow Pass Road Pittsburg, California
  • Hours: 8 a.m. to 9:30 a.m., seven days a week.
  • Cost: Three-hour results are $699, five-hour results are $450, same-day results are $199 and next-day results are $129.
  • Turnaround time: See above.
  • Embarcadero site at Piers 30/32, Bryant and Embarcadero.
  • Turnaround time: One to three days.

Alameda Health Systems

  • Various locations throughout Alameda County.
  • Cost: Covered by insurance.
  • Turnaround time: Two to three days.

County of Santa Clara

  • Various locations throughout Santa Clara County.
  • Cost: No upfront cost.
  • Turnaround time: Varies by location.

Downtown Medical Group

  • 450 Sutter Street, Suite 1723 San Francisco, California
  • Hours: Monday to Friday from 8:30 a.m. to 4:30 p.m.
  • Cost: $225 for next-day turnaround, $300 for same-day turnaround.

Where to get a COVID-19 test in Boston, Massachusetts

Tufts Medical Center

  • 276 Tremont Street, Boston, Massachusetts
  • Hours: Monday to Saturday from 8 a.m. to 12 p.m.
  • Cost: If insurance does not cover a test, the cost is $135.
  • Turnaround time: 24 to 72 hours.

CareWell Urgent Care

  • Cambridge Inman Square
  • 1400 Cambridge Street, Cambridge, Massachusetts.
  • Hours: Open seven days a week from 8 a.m. to 8 p.m.
  • Cost: Covered by insurance, or $160 if paying out of pocket.
  • Turnaround time: Varies.

Where to get a COVID-19 test in Charlotte, North Carolina

BetterMed Urgent Care – Charlotte

  • Various locations throughout Charlotte.
  • Cost: For those with commercial health insurance, the expected out-of-pocket cost for the medical evaluation and test is your copay. PCR medical evaluation and test will cost $159 plus outside lab costs in North Carolina for self-pay.

Carolina Pharmacy

  • Various locations throughout Charlotte, North Carolina and Lancaster and Rock Hill, South Carolina
  • Hours: Varies by location
  • Cost: Rapid antigen is $89 and rapid RT-LAMP (Molecular/NAAT) is $145. RT-PCR (Molecular/NAAT) is $190. The expected out-of-pocket cost for the medical evaluation and test is your copay for those with commercial health insurance. PCR medical evaluation and test will cost $159 plus outside lab costs in North Carolina for self-pay.

StarMed Healthcare

  • Cost: Covered at 100% for most insurance carriers, or $199 for self-pay. There's a $195 out-of-pocket fee for the lab rush.

Where to get a COVID-19 test in Chicago

WellNow Urgent Care

  • Various locations throughout Chicago.
  • Hours: Open seven days a week from 8 a.m. to 8 p.m. Some locations offer extended hours from 7 a.m. to 11 p.m.
  • Cost: Most insurance accepted, or patients can self-pay $100 plus the cost of the base visit and any other necessary services.

Howard Brown Health

  • Turnaround time: Three to seven days.

Innovative Care

  • 1111 W. Diversey Parkway, Chicago, Illinois
  • Hours: Open 7 days a week from 8 a.m. to 8 p.m.
  • Cost: Covered by insurance, or you can self-pay $250 for the examination and COVID-19 test.
  • Turnaround time: Two to four days.

Prime Care Physicians

  • 1355 Remington Road, Suite Q, Schaumburg, Illinois
  • Hours: Monday to Friday 8 a.m. to 4 p.m.
  • Cost: $125 self-pay, most insurance accepted.
  • Turnaround time: 24 to 48 hours.

Where to get a COVID-19 test in Cleveland/Akron, Ohio

  • Various locations throughout Cleveland.
  • Cost: Most insurance accepted, or patients can self-pay $150 plus the cost of the base visit and any other necessary services.
  • Turnaround time: Results available same or next day. Check testing times to receive same-day PCR results.

The Centers, Midtown Office

  • 4500 Euclid Avenue Cleveland, Ohio
  • Hours: Monday to Friday 8:30 a.m. to 5:30 p.m.
  • Cost: No out-of-pocket costs for most patients. No insurance is required, and Medicaid and other insurance are accepted.
  • Appointment required: Appointments are encouraged, with walk-ins available each day.
  • Turnaround time: One to two days.

Where to get a COVID-19 test in Columbus, Ohio

  • Various locations throughout Columbus.
  • Hours: Open seven days a week, hours vary by location.

Where to get a COVID-19 test in Dallas/Fort Worth, Texas

Ayass BioScience Drive-thru

  • 8501 Wade Blvd Bldg 7 Frisco, Texas
  • Hours: Hours are shown upon registration.
  • Appointment required: Strongly preferred. Walk-ins are permitted but will require filling in paperwork on site.
  • Turnaround time: Same-day results if collected by 2 p.m.

Real Time Laboratories

  • 4100 Fairway Ct. Suite 600 Carrollton, Texas
  • Hours: Open daily; see website for details.
  • Cost: $125 to $250 depending on turnaround time.
  • Turnaround time: Six to 48 hours, depending on the test.
  • 4100 Fairway Drive, Suite 410, Carrollton, Texas
  • Hours: Open Monday to Saturday; see website for details.
  • Cost: Covered by insurance, except for travel requests.
  • Turnaround time: Same-day or next-day results.

L&H Scientific

  • 2801 Osler Drive, Building B, Suite 123, Grand Prairie, Texas, 75051
  • Hours: Monday to Saturday 9 a.m. to 5 p.m.
  • Cost: Prices start at $275 to $425, depending on the turnaround time.
  • Appointment required: Strongly encouraged. Same-day results require testing before noon.
  • Turnaround time: Same-day to one-day.

Where to get a COVID-19 test in Denver, Colorado

American Family Care Urgent Care

  • Various locations throughout Denver.
  • Cost: Most major insurance covered.

Advanced Urgent Care

  • Hours: Seven days a week from 8 a.m. to 7 p.m.
  • Cost: Covered by most major insurance, PCR rapid test at Broomfield clinic is $125.
  • Turnaround time: Same-day for a rapid PCR test, three to seven days for other tests.

Premier Diagnostics

  • Hours: See site for details.
  • Cost: Covered by insurance, the cost of the RT-PCR test is $125 if not covered.
  • Turnaround time: Within 48 hours.

Where to get a COVID-19 test in Detroit, Michigan

CVS Minute Clinic

  • 1935 Campbell, Detroit, Michigan
  • Hours: Pharmacy open until 8 p.m.

Where to get a COVID-19 test in Houston, Texas

  • Various locations throughout Houston.
  • Hours: See the website for more information.
  • Cost: No out-of-pocket cost when billed to your health plan or the government.

Any Test Now

  • Hours: See website for details.
  • Cost: $199.

Memorial Village ER

  • 14520 Memorial Dr. Houston, Texas
  • Hours: 9 a.m. to 3 p.m.‬ every day.
  • Cost: $150 or insurance is accepted.
  • Turnaround: Two to three days.

Rapid COVID Clinic

  • Cost: $250.
  • Appointment required: Appointments preferred, drive-ins accepted.
  • Turnaround time: 36 to 48 hours.

Where to get a COVID-19 test in Las Vegas, Nevada

  • 546 N Eastern Ave Suite 130, Las Vegas, Nevada
  • Cost: $120.

Cuur Diagnostics

  • 3450 S. Maryland Pkwy Las Vegas, Nevada
  • Hours: Monday to Friday from 9 a.m. to 1 p.m.
  • Cost: $125.

Where to get a COVID-19 test in Los Angeles, California

COVID Clinic

  • 124 locations in 15 states, with new locations and states added weekly. Also available at 13 airports including LAX, BUR and ONT.
  • Hours: Generally 8 a.m. to 4 p.m., seven days a week. Location hours may vary.
  • Cost: Free one- to two-day PCR available for the insured and uninsured (conditions apply). $299 for rapid one-hour result PCR test.
  • Appointment required: Yes. Same-day appointments are available.
  • Turnaround time: One to two days for expedited PCR test.

Reliant Urgent Care

  • Various locations throughout Los Angeles.
  • Cost: $195 for 24- to 36-hour turnaround, $175 for one-hour turnaround (not covered by insurance).
  • Turnaround time: Depends on the level of service booked.

OnSite Safe

  • 6411 Sepulveda Blvd., Van Nuys, California
  • Hours: Monday to Saturday; see website for specifics.
  • Costs: $164.
  • Appointment Required: Yes,
  • Turnaround time: Two days, next-day available with expedited processing for an extra cost.

Where to get a COVID-19 test in Miami and Fort Lauderdale, Florida

Quality Health Care Concierge

  • Drive-up address: 900 Broken Sound Parkway NW, Boca Raton Florida
  • Hours: 24 hours, seven days a week.
  • Cost: Partial coverage.
  • Appointment required: Yes, for drive-up and in-home service.
  • Turnaround time: Depends on service booked.
  • 1425-A SE 17th St, Fort Lauderdale, Florida
  • Hours: Monday to Friday 8 a.m. to 5 p.m., Saturday 8 a.m. to 2 p.m.
  • Cost: $179.
  • Turnaround time: Next-day results.

Air Land Sea

  • Sheltair FLL, 1100 Lee Wagener Boulevard, Suite 346, Fort Lauderdale, Florida 33315
  • Hours: Monday to Friday 9 a.m. to 5 p.m., Saturday 8 a.m. to 12 p.m.
  • Cost: With insurance, $75 for next-day results, $125 for same-day results. Without insurance, $175 for next-day results, $225 for same-day results. Four- to six-hour expedited results are $450.
  • Appointment required: No, but appointments can be scheduled at covidFLL.com.
  • Turnaround time: Same-day, next-day and four to six hours. Tests for same-day results must be administered before 11 a.m.

Miami-Dade County testing sites

  • Various locations throughout Miami-Dade County.

American Scientific Diagnostics

  • 1860 Old Okeechobee Road Suite 508, West Palm Beach, Florida
  • Hours: Monday to Friday 9 a.m. to 5 p.m., Saturday 10 a.m. to 5 p.m.
  • Cost: $150 for next-day results, $250 for same-day results.
  • Turnaround time: Depends on the test booked.
  • 1515 NW 167th St Suite 410, Miami Gardens, Florida 33169
  • Hours: Monday to Friday 7:30 a.m. to 6 p.m., Saturday and Sunday 8 a.m. to 4 p.m.
  • Cost: $129 for home or office visit, or $89 per test when you drive up to the lab. Mention the discount code LABDX10PTSGUY for an exclusive $10 discount from TPG.
  • Appointment required: Yes for concierge, walk-ins accepted at drive-up locations.
  • Turnaround time: Within 24 to 36 hours.

Where to get a COVID-19 test in Minneapolis/St. Paul, Minnesota

  • 3655 Central Ave NE, Minneapolis, Minnesota
  • Hours: By appointment.

Where to get a COVID-19 test in New York City and Newark, New Jersey

There are hundreds of testing sites across New York City, and you can also find pop-up mobile testing sites at different locations throughout the five boroughs. Not all of these will return COVID-19 test results in a timely enough manner for travel, however. Even the cited turnaround time may no longer be accurate.

  • 34 West 36th St, New York, NY 10018
  • Hours: 8 a.m. to 8 p.m, weekends 10 a.m. to 6 p.m.
  • Cost: $299 for an expedited RT-PCR with a three- to four-hour turnaround. Insurance can be used for a standard RT-PCR with 36- to 48-hour turnaround.
  • Appointment required: Appointment not required.
  • Various locations in Brooklyn, Queens and the Bronx.
  • Cost: Accepts insurance or costs between $175 and $400.
  • Turnaround time: Results in four to six hours.
  • Various locations across New York City and the boroughs.
  • Cost: CityMD is not collecting copayments for COVID-19 related visits.
  • Turnaround time: Five to seven days.
  • Location in Chelsea with home or office visits for groups of five people or more.
  • Costs: $184.
  • Appointment Required: No.
  • Turnaround time: Two days, with next-day results available with expedited processing for an extra cost.

In-home COVID-19 testing programs include Zeel, which offers COVID-19 swab PCR testing in homes and offices administered by LPNs and RNs to the New York metro area. Available in New York City, Westchester County, Nassau County, North Jersey and Lower Fairfield County, Connecticut. Cost: $249 for the first person tested in-home plus $50 per additional person. Turnaround time: Results within 24 hours.

There are several free COVID-19 testing options available for Newark residents, with no appointment or insurance needed. Get more information here .

Where to get a COVID-19 test in Orlando, Florida

COVID Testing LLC

  • Various locations throughout Orlando.
  • Cost: With insurance, $35 for next-day results, $75 for same-day results. Without insurance, $115 for next-day results, $155 for same-day results.
  • Turnaround time: Same or the next day. Tests for same-day results must be taken before noon.

Paramount Urgent Care

  • Hours: 9 a.m. to 7 p.m.
  • Cost: Free for self-pay and insured patients, excluding Medicaid.
  • Turnaround time: Three to four days.

Where to get a COVID-19 test in Philadelphia, Pennsylvania

Vybe Urgent Care

  • More than 10 locations throughout the Philadelphia area.
  • Hours: Monday to Friday 8 a.m. to 8 p.m., Saturday to Sunday: 8 p.m. to 5 p.m.
  • Cost: Free PCR test, $75 rapid antigen test (self-pay only) and $100 rapid RT-PCR test (self-pay only).
  • Appointment required: Yes, appointments for rapid testing are required. Appointments are not required for other testing options.
  • Turnaround time: Rapid test results are available in less than 24 hours. Non-rapid test turnaround time is two to five days.

American Family Care (AFC) Urgent Care

  • 1444 W. Passyunk Avenue, Philadelphia, Pennsylvania
  • Cost: No charge for PCR tests with insurance.
  • Appointment required: Yes, and telemedicine visit.
  • 620 East Welsh Road, Horsham, Pennsylvania
  • Hours: Open even days a week, 7:30 a.m. to 5 p.m.
  • Cost: $165 for RT-PCR.
  • Appointment required? Yes.
  • Turnaround time: 24 hours for RT-PCR.

Where to get a COVID-19 test in Pittsburgh, Pennsylvania

  • Various locations throughout Pittsburgh.

Where to get a COVID-19 test in Portland, Oregon

  • Various locations throughout Portland.
  • Hours: Depends on location.
  • Cost: Covered by insurance or lab fee of $100, as well as the cost of a virtual visit.

Where to get a COVID-19 test in Sacramento, California

Anyone 18 years of age or older living in Sacramento County can ​get tested for COVID-19 for free after completing an online screening . COVID-19 testing will then be scheduled.

Where to get a COVID-19 test in Salt Lake City, Utah

Intermountain Health

  • Various locations throughout Salt Lake City.
  • Hours: See site for individual location information.
  • Cost: May vary if testing for travel versus symptoms or exposure.
  • Turnaround time: 90% of tests are returned within 48 hours.
  • Cost: Covered by insurance or $125 for RT-PCR test.

Where to get a COVID-19 test in San Antonio, Texas

  • 4115 Medical Dr., Suite 210 San Antonio, Texas 78229
  • Hours: Monday to Friday 9 a.m. to 6 p.m. CST, Saturday 10 a.m. to 5 p.m. CST.
  • Cost: $125 RT-PCR for asymptomatic patients and travelers. Covered by insurance for symptomatic patients and noninsured symptomatic patients but need providers orders.
  • Turnaround time: 24 to 48 hours; Same day turnaround if received by 11 a.m. CST.

Where to get a COVID-19 test in Seattle/Tacoma, Washington

Discovery Health MD

  • Two locations: DoubleTree Suites Southcenter and Seattle Airport.
  • Cost: $176 for next-day RT-PCR test, $349 for one-hour RT-PCR test.
  • Turnaround time: Same or next day, depending on what you booked.

Seattle testing locations

  • Various locations throughout Seattle.

Where to get a COVID-19 test in St. Louis, Missouri

ARCpoint Labs

  • 11255 Olive Blvd, Creve Coeur, Missouri
  • Hours: Monday to Friday 8 a.m. to 5 p.m.
  • Cost: $250 for same-day results.
  • Turnaround time: Same day or 48 to 60 hours, depending on what you booked.

Where to get a COVID-19 test in Washington, D.C./Baltimore/Arlington

Farragut Medical & Travel Care

  • 815 Connecticut Ave NW Washington, D.C.
  • Hours: Monday to Friday 10 a.m. to 5 p.m.
  • Cost: $300.
  • Turnaround time: Two days for expedited testing, or two to five days.

Preston's Pharmacy

  • Various locations in Arlington and Fairfax.
  • Hours: Monday to Saturday, check the website for details.
  • Cost: $45 for three- to five-day PCR testing, expedited processing available for an additional cost.
  • Turnaround time: Three to five days, or faster with expedited processing.

McLean Pharmacy

  • 1392 Chain Bridge Road, Mclean, Virginia
  • Hours: Monday to Friday 9 a.m. to 7 p.m., Saturday 10 a.m to 5 p.m.
  • Cost: $200 for a 48-hour turnaround and $250 for a 24-hour turnaround.

Bottom line

While it has generally been getting easier to obtain a COVID-19 PCR test for travel purposes in some locations, turnaround times can still vary especially as the omicron variant spreads in the U.S. and demand for testing rises as a result.

That means if you need COVID-19 PCR test results in advance of a tight travel deadline, the safest bet is to use a provider that can guarantee same-day or next-day service. Some providers that initially guaranteed results in 24 or 48 hours have increased their turnaround times, in some cases up to seven days. However, these rapid PCR test options will cost extra and aren't always available.

A few providers have also indicated that several insurance companies won't cover COVID-19 testing for travel purposes, so keep in mind that you may have to pay out of pocket.

Some destinations will allow you to quarantine upon arrival until your test results arrive. Finally, if you do test positive (whether or not you are asymptomatic), you will need to be prepared to quarantine in place wherever you are for at least two weeks.

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Motocross Action Magazine

TIME TRAVEL TEST: 2011 KAWASAKI KX450F MOTOCROSS TEST

time travel test

A: MXA gives Kawasaki credit for their willingness to make a lot of changes every year, even though we don’t always see the benefits of the things they do. There were ten significant changes between 2010 and 2011. Here is the list:

(1) Mapping. As you would expect on a fuel-injected bike, the mapping was changed on both the fuel and ignition circuits in search of low-end throttle response.

(2) Muffler. The 2011 KX450F muffler is 20mm longer, and the core is 10mm smaller (35mm versus 45mm). These kinds of changes normally have a significant impact on low-end throttle response.

(3) Piston. Kawasaki claims a “revised piston profile,” but this translates into a rather minor shortening of the piston skirt. (4) Shifter. There is a 2mm larger roller on the revised gear shift positioning lever and increased spring tension to help the shifting. (5) Axle collar. The front axle collar is 2.5mm thicker to increase the rigidity of the front end.

(6) Motor mounts. The steel motor mount plates are thinner to feed more flex into the chassis.

(7) Fuel pump. The fuel pump has been rotated around backwards to make it less susceptible to gas tank flex.

(8) Chain buffer. The chain guide buffer (over the swingarm) is thicker for more durability?but it isn’t thick enough. (9) ECU interface. The connector that hooks to the map reprograming tool is now hidden behind the front number plate. (10) Seat cover The sides of the seat cover are grippier than last year.

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Q: WHAT ARE THE MAJOR ENGINE CHANGES FOR 2011?

A: Haven’t you been paying attention? The engine changes are new mapping, a shorter skirt and a longer muffler. It may seem like very little, but last year Kawasaki introduced the “bridge-box bottom” piston, thicker cylinder skirt, crank with more rotational inertia, repositioned camshaft sprocket, better clutch friction plates, stronger clutch pressure plate, 40mm shorter stainless steel head pipe and bigger radiators.

Q: WHAT EFFECT DO THE THREE ENGINE CHANGES MAKE TO THE POWERBAND?

A: Before we tell you, we want everyone to understand that we loved last year’s 2010 KX450F engine. It made 1.4 more horsepower than the 2009 model and was the best low-to-mid engine in the sport. It was a pro-level engine that gave voice to the concept of “bark.”

Which leads us to the 2011 powerband. It is mellower, smoother, less abrupt, easier to use and less powerful down low. Every MXA test rider came in from his maiden voyage and said, “The 2010 engine felt like a works bike engine; the 2011 engine is toned down.”

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Q: IS THE 2011 KX450F POWERBAND TONED DOWN?

A: Yes, but only off the bottom. The 2010 engine was a thing of beauty. It hit hard, pulled hard and carried farther than any other fuel-injected powerplant. (It should be noted that the KTM 450SXF is not fuel-injected.) On sheer horsepower, power placement and purity of purpose, there is nothing like last year’s 2010 KX450F power delivery. It was “works power for peons.”

The 2011 powerband isn’t as works-like. It is, dare we say it, KTM 450SXF-like. The KTM powerband builds power in a metered manner. Then, as the rpm rises, the Katoom’s power just keeps growing. The mellow low-end transforms itself into a fire-breathing beast and that makes the Keihin-equipped KTM unique in a world of abrupt-hitting and short breadth fuel-injected bikes from Honda and Yamaha.

Guess what? Kawasaki calmed down their low-end thrust to make the 2011 KX450F easier to ride. It is essentially a fuel-injected version of the KTM powerband — mellow off idle, progressively quicker in transition from low-to-mid and blazing fast from mid-to-sign-off.

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Q: HOW FAST IS THE 2011 KX450F?

A: This is a tit-for-tat equation. The 2010 KX450F blasted off the mark and had unequaled thrust from 5000 rpm to 7000 rpm. The 2011 KX450F is a lot more manageable from 5 to 7 grand. Once both engines get going, one abruptly and one smoothly, there isn’t a lot of difference between them. The year-old engine is racier, but we fully understand that the brand-new powerband is better for a broader spectrum of riders. One thing we learned during a year of racing the 2010 KX450F is that not every rider wants to own a works-style powerband or its full expression of thrust. The 2010 KX450F was all-powerful and all-consuming. It didn’t need to be hopped-up because it was already hopped-up beyond pill-popping potential.

The 2011 engine is just as potent, but it is a lot more manageable. It is smoother and almost silky in its ability to accept small doses of throttle. It is infinitely more usable at low rpm than last year’s engine and doesn’t require a 100-percent commitment to forward motion.

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Q: HOW DOES THE 2011 KX450F RUN ON THE DYNO? A: The dyno curves on both the 2010 and 2011 KX450F are very similar‚, where they differ is that the 2010 bike is much stronger off idle (from 5000 rpm to 7000 rpm) and a little stronger on top (from 9000 rpm to 10,500 rpm).

So where does the 2011 bike shine? It would be easy to say that the 2011 KX450F is stronger than its 2010 brother through the meat of the powerband (7000 rpm to 10,000 rpm). And, if you looked at peak horsepower, you might believe it. The 2011 KX450F’s peak power is 54.17 horsepower at 8600 rpm. This is two-tenths of a horsepower better than the 2010 model at peak (53.90). When you look at power output at 1000 rpm increments across the midrange, the 2011 KX450F makes more horsepower than the 2010 model at 7000 rpm, less horsepower at 8000 rpm, more horsepower at 9000 rpm and less horsepower at 10,000. The peak horsepower of both bikes is tucked into the 8000 to 9000 rpm window.

What does it all mean? The 2011 is mellow off the bottom and a little stronger from low-to-mid, while the 2010 is stronger off the bottom and better on top. But, and this is a big but, the only thing you’ll notice in the saddle is the difference in thrust off idle.

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Q: HOW DOES KAWASAKI’S FUEL INJECTION COMPARE TO THE CRF450, YZ450F AND RM-Z450 EFI? A: There is no comparison. Well, there is one comparison, but it is to the Keihin FCR carb on the KTM 450SXF.

Fuel-injection system to fuel-injection system, Kawasaki has won this war hands-down. Unlike its blue, yellow and red competitors, the KX450F has all the benefits of fuel injection without the herky-jerky low-end throttle response and flat top-end. Kawasaki knows something about setting up an injector system that the other manufacturers don’t (the KX450F has a 43mm throttle body, 45-degree injector angle, 12-hole nozzle and 60-micron fuel particles). Write this down: Kawasaki has the best fuel-injected 450cc engine.

Q: IS THERE ANYTHING NOT TO LIKE ABOUT THE 2011 KX450F ENGINE? < A: Yes. The old-school four-speed gearbox (which had a useless fifth gear tacked on back in 2007) has odd gear ratios. You are either galloping or coasting. We overlooked this gappy gearbox in 2010 because the burst of the KX450F could jump over any gap. With the 2011 model’s smoother low-to-mid transition, the gear bugaboos are back.

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Q: WHAT DID KAWASAKI DO TO THE 2011 KX450F SUSPENSION? A: They gave it a touch-up, not a makeover, redo or total revision. They made small changes that resulted in small improvements.

Forks: If you are looking for qualitative changes to the forks, you won’t be impressed to find that the rebound damping is a little lighter. Nor will you care that Kawasaki saved money by dropping the cartridge bushings, modifying the pressure piston and swapping to a plastic spring holder seat. From a technical standpoint, the oil height is the same, the spring rate is the same, the compression damping is the same, and the performance is within one click on rebound of being the same. Kawasaki claims lighter rebound damping and revised compression for a more linear dampening rate, but a shim-for-shim analysis didn’t confirm this.

Shock: The 2011 KX450F shock is different. The low-speed compression damping is stiffer; the mid-speed damping is softer, and the high-speed damping is stiffer. This might sound a little schizophrenic, but it actually makes sense. By making the low-speed compression stiffer, Kawasaki’s suspension engineers hoped to hold the rear end higher in its stroke through small bumps. By softening the mid-speed, they planned to get a more fluid transition in small to big bump absorption. Then, by stiffening the high-speed damping, they intended to aid bottoming control. Additionally, the rebound damping is a hair slower than it was in 2010.

Q: WHAT DID KAWASAKI DO TO THE 2011 KX450F CHASSIS?

A: Nothing.

Q: HOW DOES THE 2011 KX450F HANDLE?

A: It handles the same as it did last year, which is exactly how it handled the year before and the year before that…ad nauseum.

Obviously, money is tight for the R&D department, but history proves that even when the KX450F R&D department is rolling in dough, they don’t want to make the changes the MXA test crew wants. What do we want? A steeper head angle, shorter wheel base, lower seat height, smaller overall size, better ergonomic riding position, less fork offset and a 15-pound weight loss. Until Kawasaki moves in that direction, the KX450F will maintain the same cranky characteristics that its brethren have displayed since 2006.

This is a big bike and, even worse, it feels like a big bike. It is tall, heavy and long. It doesn’t want to turn as much as it wants to stand up in the center of corners.

Q: HOW STRONG ARE THE BRAKES?

A: A bike this fast and heavy needs the best brakes it can get. Unfortunately, the Kawasaki brakes are not crisp, powerful and accurate. They stop the bike, but not like they should.

time travel test

Q: WHAT IS THE SUGGESTED RETAIL PRICE?

A: The manufacturer’s suggested retail price (MSRP) is $8149.

Q: WHAT DID WE HATE? A: The hate list:

(1) Size. It’s too big, too tall and too heavy.

(2) Shifting. We would hazard a guess that Kawasaki has changed its shift mechanism more times in the last 10 years than all the other manufacturers combined. Why? Because they can’t get it right.

(3) Gearbox. This gearbox is six years old. It wasn’t right the first time, and it hasn’t gotten better with age. As awesome as the powerband is, it could be twice as good with proper gear ratios.

(4) Rear brake pedal. If you want to run the rear brake pedal low, you have to hacksaw off some of the plunger’s threaded rod. (5) Clutch. It feels wimpy from the get-go. Surprise! It doesn’t get any better with use. We put in stiffer clutch springs on day one (which is how long the stock clutch lasted).

(6) Weight. We are into nostalgia as much as the next guy, but not when it comes to bikes weighing as much as they did 25 years ago.

(7) Graphics. If you find a set on the track, they are probably ours. The bottom half of the radiator shroud decal kit fell off before the little nubs on the knobbies wore off.

(8) Tires. When you have a bike that doesn’t want to turn, you don’t put a 90 front tire and 120 rear on it. (9) Chain guide. What chain guide? It wears out fast. Watch both the slider on top of the swingarm and the rubber block in the lower chain guide?watch them disappear before your eyes. (10) Throttle grip. If you want to install aftermarket grips on the KX450F throttle tube, lots of luck. It is vulcanized onto the throttle tube.

(11) Cotter pin. Kawasaki’s lawyers must insist that their motocross bikes come with cotter pins in the axle nut. It drives us crazy. We replaced the Kawasaki axle nut with a self-locking Honda axle nut.

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Q: WHAT DID WE LIKE?

A: The like list:

(1) Powerband. We love this powerband. Yes, there are MXA test riders who preferred the more pro-like 2010 powerband, but the 2011 power delivery still twangs the strings of our heart. (2) Sound. Thanks to the longer muffler (with its smaller outlet), the 2011 KX450F passed the AMA’s 94 dB sound test with flying colors. It made a very soothing 90.5 dB on the AMA test (6 decibels less than last year). Unfortunately, it failed the FIM’s 115 dB two-meter-max test with an ear piercing 119 dB. (3) Starting. Kick it once to activate the electric gizmos. Kick it twice to start it. Never fails.

Q: WHAT DO WE REALLY THINK?

A: This is a kinder and gentler KX450F, which means that it is still more powerful than its yellow, red and blue competition. It’s a bike that all about its engine and less about the other stuff.

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MXA’S 2011 KAWASAKI KX450F SUSPENSION SET-UP

Q: WHAT WAS OUR BEST FORK SETTING? A: For hardcore racing, these are MXA ‘s recommended 2011 Kawasaki KX450F fork settings:    Spring rate: < 0.47 kg/mm    Oil height: 340cc    Compression: 10 clicks out    Rebound: 10 clicks out    Fork leg height: 5mm up    Notes: The chassis is very sensitive to fork height. As a rule, we ran the forks up in the clamps until we got oversteer, then slid them down 2 millimeters.

Q: WHAT WAS OUR BEST SHOCK SETTING? A: Last year’s KX450F had an all-new bell crank and link arms mated to a stiffer 5.5 kg/mm shock spring. This year, the linkage and spring remain the same. For hardcore racing, these are MXA ‘s recommended 2011 KX450F shock settings (for the stock setup).    Spring rate: 5.5 kg/mm    Race sag: 100mm    Hi-compression: 1 turn out    Lo-compression: 8 clicks out    Rebound: 8 clicks out    Notes: We run a Pro Circuit shock linkage on the 2011 KX450F to: (1) Lower the seat height by 10mm. (2) Rotate the bell crank deeper into its curve before the shock starts to move. (3) Make the compression damping a little firmer initially.

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March 18, 2024

The Great Debate: Could We Ever Travel through Time?

Our space and physics editors go head-to-head over a classic mind-bending question.

By Clara Moskowitz & Lee Billings

cemagraphics/Getty Images

Science, Quickly

Clara Moskowitz: Hi, I’m Clara Moskowitz, a space editor here at Scientific American. We’re taking a break this week to look back at some of our favorite podcast episodes. I chose this one about the physics of time travel, because I’m a big sci-fi geek, so I’m fascinated by the topic. But also, it was such a fun debate to have with my colleague and friend, Lee Billings, another space editor here. We each picked a side – I was pro time travel, he was con—and dug our heels in. Check it out!

[Clip: Show theme music]

Moskowitz: We’re here today to talk about time travel. A perennial – dare I say, timeless–topic of science fiction, but is it possible? Is there any chance at all that it could actually happen?

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Lee Billings: No. No, no no no no. (laughs). Well, kinda. Not really. ARGH. I’m Lee Billings.

Moskowitz: I’m Clara Moskowitz, and this is Cosmos, Quickly , the biweekly space podcast from Scientific American . 

Moskowitz: We’re going to have a little friendly debate.

Billings: Really? I came for a throwdown.

Moskowitz: Well, a wrangle. A parley. A confab. Lee, what do you have against time travel?

Billings: So I love the idea of time travel! And in fact I do it all the time—like most everyone else I’m traveling into the future at one second per second. I’m less of a fan, though, of more speculative time travel, which is good fodder for goofy sci-fi stories, but in the real world it’s an implausible distraction.

Moskowitz: But really, we can stay within plausible physics and still see how more extreme versions of time travel are possible. See, Einstein’s special theory of relativity shows that the rate time flows at depends on how fast you’re moving. 

Billings: Einstein strikes again, what a rascal.

Moskowitz: If you’re traveling in a starship at close to the speed of light, you’ll still experience the familiar one-second-per-second ticking of a clock– but an observer back on Earth would see your clock moving glacially slow. To them, you’d be moving through time at a snail’s pace. That means that when you finally got back,  maybe only a year would have passed for you, but a century could have gone by for your friends on Earth. Ergo, you just traveled to the future! 

Billings: Right, right, no one’s disputing any of that! We can even measure this sort of “time dilation” right now on Earth, not with starships, but with subatomic particles. Some of those particles have very short lifetimes, decaying almost instantaneously. But if we drastically speed them up, like in a particle accelerator, we find they endure longer in proportion to how fast they’re going. So riddle me this, though, Clara: How can we travel into the past? That’s something so hard to do–effectively impossible, almost–that it’s scarcely worth thinking about.

[Clip: Back to the Future : “This is what makes time travel possible. The flux capacitor!”]

Moskowitz: I get it—no one has yet conceived of a way to journey to the past. But the crazy thing is it’s not impossible. Time is one of the four dimensions in the universe, along with three dimensions of space. And we move through space in all directions just fine, and according to physics, travel through time should be just as possible.

One way that people have looked into is via a wormhole—a shortcut bridge through spacetime that was predicted by general relativity. Wormholes can connect distant points in spacetime, meaning you could conceivably use one to bridge not just the gap between here and a distant galaxy, but the span between 2023 and 1923. 

[CLIP: Interstellar : “That’s the wormhole.”]

Billings : Ah yes, wormholes—the last refuge of scoundrels and desperate physicists. The trouble with wormholes Clara, is that, unlike a DeLorean, we have no evidence they actually exist—and, even if they did, it seems the only ways to make them traversable and stable involves using negative energy or negative mass  to prop them open. And, guess what, just like wormholes themselves, we have no evidence these weird forms of matter and energy actually exist, either. And let’s just beat this dead horse one more time—even if wormholes exist, as well as the means to make them traversable, to go back in time seems to require anchoring one end in a region of very warped spacetime, like around a black hole, or accelerating it to nearly lightspeed. Are you sensing a theme here, Clara?

Moskowitz: Yeah, yeah. All I can say is that just because there’s no evidence any of these things exist, there’s also no evidence they don’t or can’t exist. Wormholes are real solutions to the equations of general relativity, and even negative energy and mass are concepts that come up in the math and aren’t prohibited.

Billings: Well how about some more practical arguments, then? If time travel were possible, wouldn’t we have met some time travelers by now? Wouldn’t someone have gone back and killed Hitler—or at least prevented me from wearing that ridiculous outfit to my high school prom? You know there’s a famous story about physicist Stephen Hawking, who invited time travelers to come to a party he was holding. The trick was the the party happened in 2009, but the invitation came out in a miniseries that was broadcast in 2010—thus, only time travelers would have been able to attend. 

[CLIP: Stephen Hawking Time Travel Party: “Here is the invitation, giving the exact coordinates in time and space. I am hoping in one form or another it will survive for many thousands of years.”]

Billings: Sadly, the hors d'oeuvres went uneaten and the champagne sat unopened, because, clearly, time travel to the past is impossible! 

Moskowitz: I admit a party with Stephen Hawking should have been pretty alluring to time travelers, if they were out there. But you’re forgetting about the International Clause of Secrecy that all time travelers probably have to swear to, making sure to hide their identities and abilities from those in earlier eras.  

Billings: Hmm, yes the clause of secrecy here. Feels like we’re really veering into science fiction territory special pleading here. And don’t forget all the paradoxes that we have to worry about too. There are lots of good reasons to think time travel might introduce insurmountable paradoxes in physics. The most famous being the grandfather—or grandmother—paradox. If time travel were possible into the past, so the thinking goes, then a person could go back in time and kill their own grandparents, thus making it impossible for them to be born and impossible for them to travel back in time to ever commit the murder, and so on and so on.

Moskowitz: I wonder if it could be like a many-worlds scenario, where each change a time traveler makes to the past spawns a whole new universe that carries on from that point. So if I went back in time and killed one of my forebears, then a new branch universe would begin where that whole line of descendents, including me, never existed. I mean, it sounds crazy, but then again, physics is pretty enamored with multiverses, and they seem to pop up for lots of reasons already. Maybe it’s not impossible? 

Billings: If not impossible, then I’d say, implausible.

Moskowitz: Well, I’m forever an optimist, Lee! Thanks for listening to the Cosmos, Quickly .

Billings: Our show is produced by Jeff DelViscio, Tulika Bose and Kelso Harper.  Our music was composed by Dominic Smith.

Moskowtiz: If you like the show, please consider rating or leaving a review. You can also email feedback, questions, and tips to [email protected]

Billings: For more spacetime hijinks and all your science news, head to SciAm.com. This has been Cosmos, Quickly . I’m Lee Billings. 

Moskowitz: I’m Clara Moskowitz. 

Billings: And we’ll see you next time, in the future!

time travel test

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SpaceX Blazes Forward With Latest Starship Launch

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SpaceX Launches Starship for Third Time

The rocket, a version of which will eventually carry nasa astronauts to the moon, traveled almost halfway around the earth before it was lost as it re-entered the atmosphere..

“Five, four, three, two, three, one.” “This point, we’ve already passed through Max-Q, maximum dynamic pressure. And passing supersonic, so we’re now moving faster than the speed of sound. Getting those on-board views from the ship cameras. Boosters now making its way back, seeing six engines ignited on ship. Kate, we got a Starship on its way to space and a booster on the way back to the Gulf.” “Oh, man. I need a moment to pick my jaw up from the floor because these views are just stunning.”

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By Kenneth Chang

  • March 14, 2024

The third try turned out to be closer to the charm for Elon Musk and SpaceX, as his company’s mammoth Starship rocket launched on Thursday and traveled about halfway around the Earth before it was lost as it re-entered the atmosphere.

The test flight achieved several key milestones in the development of the vehicle, which could alter the future of space transportation and help NASA return astronauts to the moon.

This particular flight was not, by design, intended to make it all the way around the Earth. At 8:25 a.m. Central time, Starship — the biggest and most powerful rocket ever to fly — lifted off from the coast of South Texas. The ascent was smooth, with the upper Starship stage reaching orbital velocities. About 45 minutes after launch, it started re-entering the atmosphere, heading toward a belly-flop splashdown in the Indian Ocean.

Live video, conveyed in near real-time via SpaceX’s Starlink satellites , showed red-hot gases heating the underside of the vehicle. Then, 49 minutes after launch, communications with Starship ended, and SpaceX later said the vehicle had not survived the re-entry, presumably disintegrating and falling into the ocean.

Even so, Bill Nelson, the administrator of NASA, congratulated SpaceX on what he called a “successful test flight” of the system his agency is counting on for some of its Artemis lunar missions.

A crowd of people, many with cameras with long lenses, stand on a sand dune near the ocean.

SpaceX aims to make both the vehicle’s lower rocket booster and the upper spacecraft stage capable of flying over and over again — a stark contrast to the single-launch throwaway rockets that have been used for most of the space age.

That reusability gives SpaceX the potential to drive down the cost of lofting satellites and telescopes, as well as people and the things they need to live in space.

Completing most of the short jaunt was a reassuring validation that the rocket’s design appears to be sound. Not only is Starship crucial for NASA’s lunar plans, it is the key to Mr. Musk’s pipe dream of sending people to live on Mars.

For Mr. Musk, the success also harks back to his earlier reputation as a technological visionary who led breakthrough advances at Tesla and SpaceX, a contrast with his troubled purchase of Twitter and the polarizing social media quagmire that has followed since he transformed the platform and renamed it X. Even as SpaceX launched its next-generation rocket, the social media company was dueling with Don Lemon , a former CNN anchor who was sharing clips from a combative interview with Mr. Musk.

SpaceX still needs to pull off a series of formidable rocketry firsts before Starship is ready to head to the moon and beyond. Earlier this week, Mr. Musk said he hoped for at least six more Starship flights this year, during which some of those experiments may occur.

But if it achieves them all, the company could again revolutionize the space transportation business and leave competitors far behind.

Phil Larson, a White House space adviser during the Obama administration who also previously worked on communication efforts at SpaceX, said Starship’s size and reusability had “massive potential to change the game in transportation to orbit. And it could enable whole new classes of missions.”

NASA is counting on Starship to serve as the lunar lander for Artemis III, a mission that will take astronauts to the surface of the moon for the first time in more than 50 years. That journey is currently scheduled for late 2026 but seems likely to slide to 2027 or later.

The third flight was a marked improvement from the first two launch attempts.

Last April, Starship made it off the launchpad, but a cascade of engine failures and fires in the booster led to the rocket’s destruction 24 miles above the Gulf of Mexico.

In November, the second Starship launch traveled much farther. All 33 engines in the Super Heavy booster worked properly during ascent, and after a successful separation, the upper Starship stage nearly made it to orbital velocities. However, both stages ended up exploding.

Nonetheless, Mr. Musk hailed both test flights as successes, as they provided data that helped engineers improve the design.

Thursday’s launch — which coincided with the 22nd anniversary of the founding of SpaceX — occurred 85 minutes into a 110-minute launch window. The 33 engines in the booster ignited at the launch site outside Brownsville, Texas, and lifted the rocket, which was as tall as a 40-story building, into the morning sky.

Most of the flight proceeded smoothly, and a number of test objectives were achieved during the flight, like opening and closing the spacecraft’s payload doors, which will be needed to deliver cargo in the future.

SpaceX did not attempt to recover the booster this time, but did have it perform engine burns that will be needed to return to the launch site. However, the final landing burn for the booster, conducted over the Gulf of Mexico, did not fully succeed — an area that SpaceX will attempt to fix for future flights.

SpaceX said the Super Heavy disintegrated at an altitude of about 1,500 feet.

SpaceX engineers will also have to figure out why Starship did not survive re-entry and make fixes to the design of the vehicle.

Even with the partial success of Thursday’s flight, Starship is far from ready to go to Mars, or even the moon. Because of Mr. Musk’s ambitions for Mars, Starship is much larger and much more complicated than what NASA needs for its Artemis moon landings. For Artemis III, two astronauts are to spend about a week in the South Pole region of the moon.

“He had the low price,” Daniel Dumbacher, the executive director of the American Institute of Aeronautics and Astronautics and a former high-level official at NASA, said of Mr. Musk, “and NASA chose to take the risk associated with that configuration hoping that it would work out. And we’ll see if that turns out to be true.”

To leave Earth’s orbit, Starship must have its propellant tanks refilled with liquid methane and liquid oxygen. That will require a complex choreography of additional Starship launches to take the propellants to orbit.

“This is a complicated, complicated problem, and there’s a lot that has to get sorted out, and a lot that has to work right,” Mr. Dumbacher said.

Thursday’s flight included an early test of that technology, moving liquid oxygen from one tank to another within Starship.

Mr. Dumbacher does not expect Starship to be ready by September 2026, the launch date NASA currently has for Artemis III, although he would not predict how much of a delay there might be. “I’m not going to give you a guess because there is way too much work, way too many problems to solve,” he said.

Kenneth Chang , a science reporter at The Times, covers NASA and the solar system, and research closer to Earth. More about Kenneth Chang

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Time Travel Reading Answers

Janice Thompson

Updated On Sep 18, 2023

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Time Travel Reading Answers

Recent IELTS Reading Test with Answers - Free PDF

Time Travel is a real Reading test passage that appeared in the IELTS. Check out the Time Travel Reading Answers for IELTS below!

With diligent practice, the Reading Module can be the top-scoring category for IELTS Aspirants. To score well, you must understand how to approach and answer the different question types in the Reading Module.

By solving and reviewing Sample Reading Questions from past IELTS papers, you can ensure that your Reading skills are up to the mark. Take the reading passage ‘ Time Travel ’ below and try more IELTS reading practice tests from IELTSMaterial.com.

Preparing for your IELTS exam? Check out this article and learn some new IELTS Reading Tips and Techniques to Increase your Reading Speed !

Find the reading passage and questions with the Time Travel PDF here.

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Janice Thompson

Janice Thompson

Soon after graduating with a Master’s in Literature from Southern Arkansas University, she joined an institute as an English language trainer. She has had innumerous student interactions and has produced a couple of research papers on English language teaching. She soon found that non-native speakers struggled to meet the English language requirements set by foreign universities. It was when she decided to jump ship into IELTS training. From then on, she has been mentoring IELTS aspirants. She joined IELTSMaterial about a year ago, and her contributions have been exceptional. Her essay ideas and vocabulary have taken many students to a band 9.

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Time Travel IELTS Reading Passage with Answers

READING PASSAGE 3

You should spend about 20 minutes on Questions 28-40 which are based on Reading Passage 3 below.

Time Travel

Time travel took a small step away from science fiction and toward science recently when physicists discovered that sub-atomic particles known as neutrinos – progeny of the sun’s radioactive debris – can exceed the speed of light. The unassuming particle – it is electrically neutral, small but with a “non-zero mass” and able to penetrate the human form undetected – is on its way to becoming a rock star of the scientific world.

Researchers from the European Organisation for Nuclear Research (CERN) in Geneva sent the neutrinos hurtling through an underground corridor toward their colleagues at the Oscillation Project with Emulsion-Tracing Apparatus (OPERA) team 730 kilometres away in Gran Sasso, Italy. The neutrinos arrived promptly – so promptly, in fact, that they triggered what scientists are calling the unthinkable – that everything they have learnt, known or taught stemming from the last one hundred years of the physics discipline may need to be reconsidered.

The issue at stake is a tiny segment of time – precisely sixty nanoseconds (which is sixty billionths of a second). This is how much faster than the speed of light the neutrinos managed to go in their underground travels and at a consistent rate (15,000 neutrinos were sent over three years). Even allowing for a margin of error of ten billionths of a second, this stands as proof that it is possible to race against light and win. The duration of the experiment also accounted for and ruled out any possible lunar effects or tidal bulges in the earth’s crust.

Nevertheless, there’s plenty of reason to remain sceptical. According to Harvard University science historian Peter Galison, Einstein’s relativity theory has been “pushed harder than any theory in the history of the physical sciences”. Yet each prior challenge has come to no avail, and relativity has so far refused to buckle.

So is time travel just around the corner? The prospect has certainly been wrenched much closer to the realm of possibility now that a major physical hurdle – the speed of light – has been cleared. If particles can travel faster than light, in theory travelling back in time is possible. How anyone harnesses that to some kind of helpful end is far beyond the scope of any modern technologies, however, and will be left to future generations to explore.

Certainly, any prospective time travellers may have to overcome more physical and logical hurdles than merely overtaking the speed of light. One such problem, posited by René Barjavel in his 1943 text Le Voyageur Imprudent is the so-called grandfather paradox. Barjavel theorised that, if it were possible to go back in time, a time traveller could potentially kill his own grandfather. If this were to happen, however, the time traveller himself would not be born, which is already known to be true. In other words, there is a paradox in circumventing an already known future; time travel is able to facilitate past actions that mean time travel itself cannot occur.

Other possible routes have been offered, though. For Igor Novikov, astrophysicist behind the 1980s’ theorem known as the self-consistency principle, time travel is possible within certain boundaries. Novikov argued that any event causing a paradox would have zero probability. It would be possible, however, to “affect” rather than “change” historical outcomes if travellers avoided all inconsistencies. Averting the sinking of the Titanic, for example, would revoke any future imperative to stop it from sinking – it would be impossible. Saving selected passengers from the water and replacing them with realistic corpses would not be impossible, however, as the historical record would not be altered in any way.

A further possibility is that of parallel universes. Popularised by Bryce Seligman DeWitt in the 1960s (from the seminal formulation of Hugh Everett), the many-worlds interpretation holds that an alternative pathway for every conceivable occurrence actually exists. If we were to send someone back in time, we might therefore expect never to see him again – any alterations would divert that person down a new historical trajectory.

Time Travel IELTS Reading Passage with Answers

A final hypothesis, one of unidentified provenance, reroutes itself quite efficiently around the grandfather paradox. Non-existence theory suggests exactly that – a person would quite simply never exist if they altered their ancestry in ways that obstructed their own birth. They would still exist in person upon returning to the present, but any chain reactions associated with their actions would not be registered. Their “historical identity” would be gone.

So, will humans one day step across the same boundary that the neutrinos have? World-renowned astrophysicist Stephen Hawking believes that once spaceships can exceed the speed of light, humans could feasibly travel millions of years into the future in order to repopulate earth in the event of a forthcoming apocalypse. This is because, as the spaceships accelerate into the future, time would slow down around them (Hawking concedes that bygone eras are off limits – this would violate the fundamental rule that cause comes before effect).

Hawking is therefore reserved yet optimistic. “Time travel was once considered scientific heresy, and I used to avoid talking about it for fear of being labelled a crank. These days I’m not so cautious.”

Questions 28-33 Do the following statements agree with the information given in Reading Passage 3? In boxes 28–33 on your answer sheet, write

TRUE if the statement agrees with the information FALSE if the statement contradicts the information NOT GIVEN if there is no information on this

28 It is unclear where neutrinos come from. 29 Neutrinos can pass through a person’s body without causing harm. 30 It took scientists between 50-70 nanoseconds to send the neutrinos from Geneva to Italy. 31 Researchers accounted for effects the moon might have had on the experiment. 32 The theory of relativity has often been called into question unsuccessfully. 33 This experiment could soon lead to some practical uses for time travel.

Questions 34–39 Complete the table below. Choose NO MORE THAN THREE WORDS from the passage for each answer. Write your answers in boxes 34–39 on your answer sheet.

Question 40 Choose the correct letter, A, B, C or D. Write the correct letter in box 40 on your answer sheet.

Stephen Hawking has stated that

A Human time travel is theoretically possible, but is unlikely to ever actually occur. B Human time travel might be possible, but only moving backward in time. C Human time travel might be possible, but only moving forward in time. D All time travel is impossible.

Time Travel IELTS Reading Passage Answers

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30. NOT GIVEN

34. past actions

35. inconsistencies

36. Hugh Everett

37. alternative pathway

38. non-existence theory

39. historical identity

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Illustration of stars blurring past from the perspective of moving quickly through space

Why does time change when traveling close to the speed of light? A physicist explains

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Assistant Professor of Physics and Astronomy, Rochester Institute of Technology

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Michael Lam does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.

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Curious Kids is a series for children of all ages. If you have a question you’d like an expert to answer, send it to [email protected] .

Why does time change when traveling close to the speed of light? – Timothy, age 11, Shoreview, Minnesota

Imagine you’re in a car driving across the country watching the landscape. A tree in the distance gets closer to your car, passes right by you, then moves off again in the distance behind you.

Of course, you know that tree isn’t actually getting up and walking toward or away from you. It’s you in the car who’s moving toward the tree. The tree is moving only in comparison, or relative, to you – that’s what we physicists call relativity . If you had a friend standing by the tree, they would see you moving toward them at the same speed that you see them moving toward you.

In his 1632 book “ Dialogue Concerning the Two Chief World Systems ,” the astronomer Galileo Galilei first described the principle of relativity – the idea that the universe should behave the same way at all times, even if two people experience an event differently because one is moving in respect to the other.

If you are in a car and toss a ball up in the air, the physical laws acting on it, such as the force of gravity, should be the same as the ones acting on an observer watching from the side of the road. However, while you see the ball as moving up and back down, someone on the side of the road will see it moving toward or away from them as well as up and down.

Special relativity and the speed of light

Albert Einstein much later proposed the idea of what’s now known as special relativity to explain some confusing observations that didn’t have an intuitive explanation at the time. Einstein used the work of many physicists and astronomers in the late 1800s to put together his theory in 1905, starting with two key ingredients: the principle of relativity and the strange observation that the speed of light is the same for every observer and nothing can move faster. Everyone measuring the speed of light will get the same result, no matter where they are or how fast they are moving.

Let’s say you’re in the car driving at 60 miles per hour and your friend is standing by the tree. When they throw a ball toward you at a speed of what they perceive to be 60 miles per hour, you might logically think that you would observe your friend and the tree moving toward you at 60 miles per hour and the ball moving toward you at 120 miles per hour. While that’s really close to the correct value, it’s actually slightly wrong.

This discrepancy between what you might expect by adding the two numbers and the true answer grows as one or both of you move closer to the speed of light. If you were traveling in a rocket moving at 75% of the speed of light and your friend throws the ball at the same speed, you would not see the ball moving toward you at 150% of the speed of light. This is because nothing can move faster than light – the ball would still appear to be moving toward you at less than the speed of light. While this all may seem very strange, there is lots of experimental evidence to back up these observations.

Time dilation and the twin paradox

Speed is not the only factor that changes relative to who is making the observation. Another consequence of relativity is the concept of time dilation , whereby people measure different amounts of time passing depending on how fast they move relative to one another.

Each person experiences time normally relative to themselves. But the person moving faster experiences less time passing for them than the person moving slower. It’s only when they reconnect and compare their watches that they realize that one watch says less time has passed while the other says more.

This leads to one of the strangest results of relativity – the twin paradox , which says that if one of a pair of twins makes a trip into space on a high-speed rocket, they will return to Earth to find their twin has aged faster than they have. It’s important to note that time behaves “normally” as perceived by each twin (exactly as you are experiencing time now), even if their measurements disagree.

You might be wondering: If each twin sees themselves as stationary and the other as moving toward them, wouldn’t they each measure the other as aging faster? The answer is no, because they can’t both be older relative to the other twin.

The twin on the spaceship is not only moving at a particular speed where the frame of references stay the same but also accelerating compared with the twin on Earth. Unlike speeds that are relative to the observer, accelerations are absolute. If you step on a scale, the weight you are measuring is actually your acceleration due to gravity. This measurement stays the same regardless of the speed at which the Earth is moving through the solar system, or the solar system is moving through the galaxy or the galaxy through the universe.

Neither twin experiences any strangeness with their watches as one moves closer to the speed of light – they both experience time as normally as you or I do. It’s only when they meet up and compare their observations that they will see a difference – one that is perfectly defined by the mathematics of relativity.

Hello, curious kids! Do you have a question you’d like an expert to answer? Ask an adult to send your question to [email protected] . Please tell us your name, age and the city where you live.

And since curiosity has no age limit – adults, let us know what you’re wondering, too. We won’t be able to answer every question, but we will do our best.

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Boom Supersonic just flew its test jet for the first time as it races to build the world's new speediest airliner — meet 'baby boom'

Posted: March 28, 2024 | Last updated: March 28, 2024

<ul class="summary-list"><li>Colorado aerospace company Boom Supersonic flew its XB-1 demonstrator for the first time on Friday.</li><li>Nicknamed the "baby boom," the jet tests technologies for Boom's future Mach 1.7 Overture airliner.</li><li>The speedy Overture is set to enter service in 2030 and has already earned orders from airlines.</li></ul><p>Colorado aerospace company Boom Supersonic wants to bring back the <a href="https://www.businessinsider.com/concorde-supersonic-jet-history-2018-10">era of the Concorde</a> — a beloved faster-than-sound passenger jet that flew for nearly 30 years before retiring in 2003.</p><p>Boom's vision of the next supersonic airliner is a Mach 1.7 plane called the Overture, and the company just <a href="https://boomsupersonic.com/press-release/boom-supersonic-announces-successful-flight-of-xb-1-demonstrator-aircraft">flew</a> its first prototype on Friday.</p><p>Nicknamed the "baby boom," the XB-1 demonstrator is the "foundation" for the futuristic Overture. <a href="https://boomsupersonic.com/xb-1">Boom</a> says it uses the experimental plane to prove innovative technologies key to safe and efficient supersonic flight.</p><p>Here's a closer look at the small but mighty baby boom.</p><div class="read-original">Read the original article on <a href="https://www.businessinsider.com/see-boom-jet-used-test-worlds-next-supersonic-airliner-2024-3">Business Insider</a></div>

  • Colorado aerospace company Boom Supersonic flew its XB-1 demonstrator for the first time on Friday.
  • Nicknamed the "baby boom," the jet tests technologies for Boom's future Mach 1.7 Overture airliner.
  • The speedy Overture is set to enter service in 2030 and has already earned orders from airlines.

Colorado aerospace company Boom Supersonic wants to bring back the era of the Concorde — a beloved faster-than-sound passenger jet that flew for nearly 30 years before retiring in 2003.

Boom's vision of the next supersonic airliner is a Mach 1.7 plane called the Overture, and the company just flew its first prototype on Friday.

Nicknamed the "baby boom," the XB-1 demonstrator is the "foundation" for the futuristic Overture. Boom says it uses the experimental plane to prove innovative technologies key to safe and efficient supersonic flight.

Here's a closer look at the small but mighty baby boom.

<p>In November, <a href="https://www.businessinsider.com/see-boom-supersonic-plane-plans-first-flight-2023-11">Boom Supersonic announced the XB-1 was gearing up for its first flight</a> and that the company had received its necessary experimental airworthiness certificate from federal regulators to operate the test jet.</p><p>Ahead of the flight tests, XB-1 went through a series of ground assessments, including evaluating subsystems, medium-speed taxing testing, and upgrading its engines and landing gear, the company said. </p>

Baby boom took a 12-minute flight across the Mojave Desert, paving the way toward the "revival of mainstream supersonic travel."

In November, Boom Supersonic announced the XB-1 was gearing up for its first flight and that the company had received its necessary experimental airworthiness certificate from federal regulators to operate the test jet.

Ahead of the flight tests, XB-1 went through a series of ground assessments, including evaluating subsystems, medium-speed taxing testing, and upgrading its engines and landing gear, the company said.

<p><span>"Today, XB-1 took flight in the same hallowed airspace where the Bell X-1 first broke the sound barrier in 1947," Boom founder and CEO Blake Scholl wrote in a press release. </span></p><p><span>"I've been looking forward to this flight since founding Boom in 2014, and it marks the most significant milestone yet on our path to bring supersonic travel to passengers worldwide," he continued.</span></p>

Boom said the XB-1's first flight "fully" met all of its objectives.

"Today, XB-1 took flight in the same hallowed airspace where the Bell X-1 first broke the sound barrier in 1947," Boom founder and CEO Blake Scholl wrote in a press release.

"I've been looking forward to this flight since founding Boom in 2014, and it marks the most significant milestone yet on our path to bring supersonic travel to passengers worldwide," he continued.

<p>Boom said the envelope for range, speed, and altitude expands over time and several phases of testing, and its XB-1 inaugural represents just a fraction of what the <a href="https://www.businessinsider.com/meet-overture-the-boom-supersonic-aircraft-that-united-just-ordered-2021-6">Overture will be built to fly</a>. </p><p>According to Boom, its future faster-than-sound plane is expected to bolt at speeds of up to Mach 1.7, or about 1,300 mph, and cruise at up to 60,000 feet — meaning the plane could connect New York City and London in as little as three and a half hours.</p>

According to the company, the XB-1 took off from the Mojave Air & Space Port and achieved a 7,120-foot altitude and speeds of up to 273 mph.

Boom said the envelope for range, speed, and altitude expands over time and several phases of testing, and its XB-1 inaugural represents just a fraction of what the Overture will be built to fly .

According to Boom, its future faster-than-sound plane is expected to bolt at speeds of up to Mach 1.7, or about 1,300 mph, and cruise at up to 60,000 feet — meaning the plane could connect New York City and London in as little as three and a half hours.

<p>In 1947, the <a href="https://www.businessinsider.com/70-years-since-chuck-yeager-broke-the-sound-barrier-what-it-was-like-2017-10">Bell X-1 became the first airplane in the world to fly faster than the speed of sound</a>, soaring over the Mojave Desert, which is designated for special flight use and has a 50-mile supersonic corridor used for Mach speed flight tests over land.</p><p>Other famous planes that took off from the Mojave include a rocket-powered experimental jet called the North American X-15. According to the <a href="https://www.si.edu/object/north-american-x-15%3Anasm_A19690360000">Smithsonian</a>, it was the first winged aircraft to fly four, five, and six times the speed of sound.</p>

The California airfield has hosted several historic airplanes, including the supersonic Bell X-1 and the up-to-Mach 6 North American X-15.

In 1947, the Bell X-1 became the first airplane in the world to fly faster than the speed of sound , soaring over the Mojave Desert, which is designated for special flight use and has a 50-mile supersonic corridor used for Mach speed flight tests over land.

Other famous planes that took off from the Mojave include a rocket-powered experimental jet called the North American X-15. According to the Smithsonian , it was the first winged aircraft to fly four, five, and six times the speed of sound.

<p>Before Boom, <a href="https://boomsupersonic.com/team-members/bill-doc-shoemaker">Shoemaker</a> helmed the first flight of the <span>Block II Super Hornet military jet and piloted electric vertical takeoff and landing prototypes.</span></p><p><span>"Everyone on the XB-1 team should be incredibly proud of this achievement," Shoemaker said on Friday. "It has been a privilege to share this journey with so many dedicated and talented professionals. The experience we have gained in reaching this milestone will be invaluable to Boom's revival of supersonic travel."</span></p>

The XB-1 was flown by Boom chief test pilot Bill “Doc” Shoemaker, who flew F-18 military jets for 21 years and has experience in test flying.

Before Boom, Shoemaker helmed the first flight of the Block II Super Hornet military jet and piloted electric vertical takeoff and landing prototypes.

"Everyone on the XB-1 team should be incredibly proud of this achievement," Shoemaker said on Friday. "It has been a privilege to share this journey with so many dedicated and talented professionals. The experience we have gained in reaching this milestone will be invaluable to Boom's revival of supersonic travel."

<p>According to Boom, Brandenburg is a United States Naval Test Pilot School graduate and a <a href="https://www.businessinsider.com/topgun-instructor-movies-flying-dogfighting-pretty-realistic-2024-3">TOPGUN Adversary</a>.</p><p>Brandenburg and Shoemaker completed hundreds of training hours in flight simulators for both the XB-1 and the T-38 chaser before taking the controls in test flights.</p>

Alongside the XB-1 was a chaser plane called the T-38, piloted by Tristan “Geppetto” Brandenburg and responsible for monitoring the flight.

According to Boom, Brandenburg is a United States Naval Test Pilot School graduate and a TOPGUN Adversary .

Brandenburg and Shoemaker completed hundreds of training hours in flight simulators for both the XB-1 and the T-38 chaser before taking the controls in test flights.

<p><span>According to Boom, ground monitoring of the mission comes from a control room full of engineers and other staff.</span></p><p><span>"The control room engineers are the same ones who designed the aircraft systems and have been operating as a team for every single ground test event conducted over the last two years," Boom said.</span></p>

To ensure safety, the XB-1 underwent rigorous ground and taxi tests before its maiden flight.

According to Boom, ground monitoring of the mission comes from a control room full of engineers and other staff.

"The control room engineers are the same ones who designed the aircraft systems and have been operating as a team for every single ground test event conducted over the last two years," Boom said.

<p>The "augmented reality vision system" involves two cameras mounted on the nose that enable "excellent runway visibility" for the pilots.</p><p>According to <a href="https://boomsupersonic.com/flyby/dynamics-of-aircraft-first-flight">Boom</a>, this can improve aerodynamic efficiency and negate the need for Overture to have Concorde's famous movable nose — which lowered to reduce drag and give the pilots better visibility.</p><p>Meanwhile, Boom said XB-1 also tests strong but lightweight carbon composite materials, supersonic intakes that slow Mach speed air to subsonic speeds, and "digitally-optimized aerodynamics" that improve supersonic efficiency.</p>

Boom listed several key technologies being tested on XB-1, like a new type of pilot display and a fuselage that can withstand Mach speeds.

The "augmented reality vision system" involves two cameras mounted on the nose that enable "excellent runway visibility" for the pilots.

According to Boom , this can improve aerodynamic efficiency and negate the need for Overture to have Concorde's famous movable nose — which lowered to reduce drag and give the pilots better visibility.

Meanwhile, Boom said XB-1 also tests strong but lightweight carbon composite materials, supersonic intakes that slow Mach speed air to subsonic speeds, and "digitally-optimized aerodynamics" that improve supersonic efficiency.

<p>The landing was complicated, but Boom said pilot Shoemaker used the augmented reality system and the help of a "landing signal officer" positioned on the side of the runway to safely land the XB-1 demonstrator.</p>

The handling of XB-1, including airspeed checks with the T-38 and its landing stability at a high angle of attack, was also evaluated.

The landing was complicated, but Boom said pilot Shoemaker used the augmented reality system and the help of a "landing signal officer" positioned on the side of the runway to safely land the XB-1 demonstrator.

<p>Although Boom secured GE as the powerplant supplier for its XB-1 demonstrator, the <a href="https://www.businessinsider.com/another-engine-maker-says-wont-build-supersonic-engine-boom-overture-2022-10">company struggled to find a major engine maker</a> like Rolls-Royce, Pratt & Whitney, and CFM International to help build its supersonic Overture engine.</p>

Powering the jet were three General Electric J85 engines that produce up to a combined 12,300 pounds of thrust, but these won't be on Overture.

Although Boom secured GE as the powerplant supplier for its XB-1 demonstrator, the company struggled to find a major engine maker like Rolls-Royce, Pratt & Whitney, and CFM International to help build its supersonic Overture engine.

Boom's Symphony engine. <a>Pete Syme/Insider</a>

Instead, Boom is building its own engine for Overture called the Symphony. It is expected to run on 100% sustainable aviation fuel, or SAF.

GE's 3D printing division, GE Additive, will provide Boom with "additive manufacturing design consulting and technology" to help create a lightweight and fuel-efficient design for Symphony.

Aviation analyst Henry Harteveldt told Business Insider in 2022, when Boom couldn't find an engine supplier, that building an in-house engine would be challenging but could prove lucrative should Boom sell the design.

<p>The baby boom has three engines, while <a href="https://www.businessinsider.com/inside-boom-supersonics-own-symphony-engine-powering-overture-jet-2023-6">Overture will have four engines mounted on the wings.</a></p><p>Both the XB-1 and Overture are designed with gull wings, which increase safety and decrease engine strain, costs, and noise, according to Boom.</p>

The XB-1 airframe is also different. Parallel to building XB-1, Boom redesigned the Overture's fuselage and wings and added another engine.

The baby boom has three engines, while Overture will have four engines mounted on the wings.

Both the XB-1 and Overture are designed with gull wings, which increase safety and decrease engine strain, costs, and noise, according to Boom.

<p>People today still rave about the time when one could fly to London in less time than it takes to cross Manhattan during rush-hour traffic. </p><p>The fastest-recorded flight of the Concorde was in February 1996 when a <a href="https://www.britishairways.com/content/information/about-ba/history-and-heritage/celebrating-concorde#:~:text=Concorde's%20fastest%20transatlantic%20crossing%20was,to%20heating%20of%20the%20airframe.">British Airways</a> flight from New York to London crossed the Atlantic in 2 hours 52 minutes 59 seconds.</p>

The long-awaited inaugural of XB-1 comes 21 years after the Concorde retired, inching closer to the re-creation of civil supersonic air travel.

People today still rave about the time when one could fly to London in less time than it takes to cross Manhattan during rush-hour traffic.

The fastest-recorded flight of the Concorde was in February 1996 when a British Airways flight from New York to London crossed the Atlantic in 2 hours 52 minutes 59 seconds.

<p>The trio of global carriers have ordered and pre-<a href="https://www.businessinsider.com/meet-overture-the-boom-supersonic-aircraft-that-united-just-ordered-2021-6">ordered a collective 130 Overture aircraft</a>. American has ordered 20 in a deal worth $4 billion at list price, with options for 40 more.</p><p>Meanwhile, <a href="https://www.businessinsider.com/united-airlines-boom-supersonic-jets-buys-15-fast-airplanes-2021-6">United has ordered 15 Overture</a> worth $3 billion at list price, with options for 35 more. JAL has invested $10 million in Overture and has the option to buy 20 in a preorder agreement.</p>

Boom has already garnered attention for its new Overture from American Airlines, United Airlines, and Japan Airlines.

The trio of global carriers have ordered and pre- ordered a collective 130 Overture aircraft . American has ordered 20 in a deal worth $4 billion at list price, with options for 40 more.

Meanwhile, United has ordered 15 Overture worth $3 billion at list price, with options for 35 more. JAL has invested $10 million in Overture and has the option to buy 20 in a preorder agreement.

<p>Similar to the Concorde, the <a href="https://www.businessinsider.com/photos-boom-supersonic-updated-ultra-fast-aircraft-overture-2022-7">Overture will sport only business class</a> seats. However, this high-luxury product is likely to be expensive, given the high operating costs of a supersonic plane.</p>

The $200 million jet is expected to carry up to 80 people in an all-business-class configuration, but tickets won't be cheap.

Similar to the Concorde, the Overture will sport only business class seats. However, this high-luxury product is likely to be expensive, given the high operating costs of a supersonic plane.

<p>Cost-cutting tactics include implementing systems that improve aerodynamic efficiency, using lightweight materials, and building its Symphony engine with additive parts that will decrease assembly expenses, among other strategies.</p><p>"You'll be able to fly Overture for a quarter the price of a Concorde ticket, or about the same price you'd pay in business class today, Scholl said back in 2019, according to <a href="https://simpleflying.com/concorde-vs-boom-overture/#:~:text=According%20to%20the%20CEO%20of,That's%20the%20most%20important%20thing.%22">Simple Flying</a>. "That's the most important thing."</p><p>He repeated this to <a href="https://simpleflying.com/boom-overture-tickets-will-be-75-cheaper-than-concorde/">Simple Flying</a> again in 2022, reiterating Overture tickets would be 75% cheaper than the Concorde and be "<span>within reach for tens of millions of passengers on day one."</span></p>

Boom, to its credit, is trying to reduce the operating cost of the Overture — effectively decreasing airfare.

Cost-cutting tactics include implementing systems that improve aerodynamic efficiency, using lightweight materials, and building its Symphony engine with additive parts that will decrease assembly expenses, among other strategies.

"You'll be able to fly Overture for a quarter the price of a Concorde ticket, or about the same price you'd pay in business class today, Scholl said back in 2019, according to Simple Flying . "That's the most important thing."

He repeated this to Simple Flying again in 2022, reiterating Overture tickets would be 75% cheaper than the Concorde and be " within reach for tens of millions of passengers on day one."

<p>Boom said it's working with American aerospace and defense technology company Northrop Grumman for Overture's military and government applications.</p>

In addition to its use as a passenger jet, Boom is working to create versions of the Overture for military and government use.

Boom said it's working with American aerospace and defense technology company Northrop Grumman for Overture's military and government applications.

<p>The US government signed multi-million deals with <a href="https://www.businessinsider.com/hypersonic-air-force-one-hermeus-mach-5-2020-8">hypersonic planemaker Hermeus</a>, which is developing a jet that can go Mach 5, or five times the speed of sound — far beyond what Boom is building.</p>

Overture wouldn't be the first faster-than-sound plane to land such a lucrative contract.

The US government signed multi-million deals with hypersonic planemaker Hermeus , which is developing a jet that can go Mach 5, or five times the speed of sound — far beyond what Boom is building.

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Boom’s first test flight could signal the return of supersonic air travel

After years of delays, the colorado-based startup’s xb-1 demonstrator takes flight for the first time..

By Tim Stevens

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Boom XB-1 demonstrator supersonic test flight

Aviation startup Boom Supersonic took a major step today toward its goal of returning commercial supersonic aviation to the skies, after the company’s prototype aircraft, the XB-1 , left the ground for the first time this week. The short, subsonic flight over the Mojave Desert came years later than expected, but it shows that Boom is at least still making progress.

The XB-1 took off Thursday at 7:28AM PT, reached a maximum altitude of 7,120 feet, and a top speed of 246 knots (283 mph). It landed 12 minutes later at 7:40AM.

Boom’s overall mission is to launch Overture, the first supersonic commercial aircraft since the Concorde ended operations 20 years ago . The company has secured contracts with major airlines like American and United , as well as manufacturing and development partnerships with Florida Turbine Technologies and GE Additive.

However, some of the most significant news lately has been the loss of partnerships, specifically with Rolls-Royce. The British manufacturer of jet engines parted ways with Boom in 2022, leaving the startup to develop its own engines.

Boom’s overall mission is to launch Overture, the first supersonic commercial aircraft since the Concorde ended operations 20 years ago

Notably, those engines are not used in the XB-1. Boom’s demonstrator aircraft, originally scheduled to fly in 2017, relies on a trio of 1950s-era J85 turbojet engines, the sorts used to power vintage aircraft like the Northrop T-38 trainer or F-5 fighter. 

Overture, Boom’s full-size supersonic commercial airliner, will use four of the company’s own engines, which are still under development and will be called Symphony. 

In an interview ahead of the flight,  Boom CEO and founder Blake Scholl says that each Symphony engine will deliver roughly three times the combined output of the XB-1’s three J85 engines. 

Overture is Boom’s full-size commercial aircraft.

Engine type is just one of many design differences between the XB-1 and the eventual Overture craft, not the least of which is size. Scholl calls the XB-1 a “one-third scale prototype demonstrator for Overture.”

Scholl says the XB-1 is helpful for validation of simulator data and that its development has already borne fruit in the design of Overture — despite the two looking nothing alike.

“If your prototype looks exactly like your production airplane, it actually implies you’ve learned nothing. And we’ve learned a lot of things from XB-1 through the design, development, manufacturing that have caused us to improve Overture,” Scholl says. 

Boom’s demonstrator aircraft relies on a trio of 1950s-era J85 turbojet engines

The XB-1 also serves another significant purpose: fundraising. 

“The way ventures like this are always financed, you raise some capital, you prove some milestones. And flying this airplane here is a very important one of those milestones. That demonstrates the track record of execution, demonstrates that progress is being made, and enables access to capital and ever higher valuation,” Scholl says. “That’s how you look at SpaceX , any other kind of private aerospace venture, that’s how they all work.”

The current target is for the Overture airliner to take its first flight by 2030, but getting there will be expensive. Scholl says Boom has raised over $700 million so far, but that the overall development of Overture could cost upward of $8 billion.

Beyond finances, one of Boom’s most significant challenges might be right there in its name. 

No supersonic jet has flown since the Concorde shut down over 20 years ago.

Today’s regulations against sonic booms would mean subsonic Overture flights over most major land masses, throttling up only over ocean transits. The deployment of technologies developed on demonstrators like the NASA X-59 , which could turn sonic booms into sonic “thumps,” might ease those regulations in the future. 

Even so, flying at Mach 1.7 only over water would roughly halve the duration of flights between New York to London or Seattle to Tokyo.

The other big missing piece is sustainability. Flying two times faster than a current jetliner necessarily uses a fair bit more fuel in the process. That situation is compounded by the Overture seating just 64 passengers compared to the 853 souls you can sling over the Atlantic in an Airbus A380. 

Sustainable aviation fuel, or SAF , could prevent supersonic travel from becoming an even bigger burden on the environment than today’s aviation industry. SAF is created using renewable sources and is ideally infused with carbon pulled out of the atmosphere via direct air capture . This would, in theory, create a genuinely carbon-neutral aircraft fuel.

The eventual availability and distribution of SAF is an industry problem. Boom’s next steps are proving that its engineers’ designs can not only fly, but that they can break the sound barrier.

Of course, that is the goal for the XB-1, but we have a ways to go before that thing’s sonic booms shake the Mojave sands. CEO Scholl says that XB-1 will undergo a series of up to 15 test flights throughout the year, so-called “envelope expansion” missions, which will eventually push that envelope through the sound barrier.

Boom is also making progress on its Greensboro, NC “superfactory,” which Scholl says is ahead of schedule and will open this summer. But Overture, the airliner that will be assembled there, is years away. 

“We’re still targeting being in the air around the end of the decade on Overture. There’s a lot of work to do between now and then on that airplane, and our goal is to do it safely but also with a sense of urgency because we want this airplane for ourselves, our friends, our family, and our customers,” he says. 

So, the dream of supersonic commercial air travel is still moving toward reality, but those hoping to move quickly through the air will have to sit patiently for a good while longer. 

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What is a time-speed-distance or tsd rally—and why should you compete in one​.

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Transit legs in between longer TSD competitions can be breathtaking yet challenging. Shane Bowman ... [+] and John Williams, with their #17 Jeep Wrangler JL, drive deep into Alaska's wilderness during the 2024 Alcan 5000 Rally.

What happens when you combine a road (or off-road) trip, getting from place to place at specific times while driving a precise route, seeing beautiful places along the way, and doing it all with friends? This is a time-speed-distance, or TSD rally.

Precision Over Speed

Time-speed-distance rallies have been around for a long time and can be done with a myriad of different vehicles. It’s not pricey, it doesn’t require a roll cage or expensive upgrades, and the events are usually held on public roads or established trails. It’s a great way to marry several things: driving, traveling, navigation and enjoying the like-minded community with those around you doing the same thing. It’s a lot of fun and something everyone should try.

Ralliers must obey all street signs, even if they're in other languages. TSD rallies are held on ... [+] public roads or trails.

TSD rally competitions are based on precision, not speed. Teams drive on open public roads and must follow a specific route book that’s given to them by the rallymaster. They must arrive exactly on time for any given direction or checkpoint (CP), or as close as they can, to do well. Teams can take time allowances for “natural occurrences” like red lights, traffic issues and train crossings.

TSD rallies can be a few hours long and take place during the day. Local Pacific Northwest organizations like Oregon’s Cascade Sports Car Club , Northwest Classic Rally or Alfa Romeo Owners of Oregon have been established for many decades and have many events throughout the year. Other groups have nighttime fun, like Seattle-based Northwest Rally Council with their Friday Nighter series.

Some time-speed-distance events are endurance-based and take multiple days. They cover extremely long distances over short periods of time. For instance, the 2024 Alcan 5000 Rally , now in its 40 th year and hosted by the Rainier Auto Sports Club, spanned an incredible 5,000 miles over 10 days.

No one knows when local traffic can slow you down, especially during a time-speed-distance rally. ... [+] Time allowances can be used in certain instances to help get teams back on track.

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Best 5% interest savings accounts of 2024, the 2024 alcan 5000 rally.

That’s where my husband, Andy Lilienthal, and I just came back from. We drove a 2024 INEOS Grenadier Trialmaster 4x4 from a new automaker, UK-based INEOS Automotive for the Alcan 5000 Rally. The SUV had only been sold in North America a short time before we rallied it. This was the perfect opportunity to test its mettle.

Teams traveled from Seattle, Washington throughout Canada’s most remote landscapes before descending on Alaska: the last frontier. There, teams had an optional extreme rally route that took them to Coldfoot (half the way to the Arctic Ocean above the Arctic Circle) or a rest at Fairbanks’ Chena Hot Springs on the competition’s “day off.” Guess which option we took? Fairbanks to Coldfoot, Alaska, and back to Fairbanks in one day, of course!

After Alcan 5000 teams finished Day 2's Blackwater Road TSD rally that consisted of 29.92 miles, we ... [+] headed down the grooved snowy surface another 457.76 miles to our hotel in Peace River, Alberta.

Teams completed daily TSD rally challenges during the Alcan 5000. However, instead of calling it quits after the TSD and joining other teams for midday lunch together, they had to drive up to 650 miles to the evening’s TSD or to that night’s motel for a short night’s rest. Then, reset for the next morning and go again, and again and again—for 10 days straight of harrowing competition—no matter how bad the weather or road conditions get.

Different Rally Orgs, Many Rally Classifications

Teams can compete in different TSD rally classes but beware, different rally organizations have diverse classifications and regulations. We learned this the hard way after a few years of competition.

Each rally organization has different TSD rally segments or classes for teams to enter. Some have a Novice, GPS, and Equipped class whereas others have SOP (Seat Of Pants class), Unlimited, and Historic classes. Some rally groups allow all kinds of vehicles, while some only allow classics or a specific make or model.

For this year's Alcan 5000 Rally, I used a simple kid's calculator and long-form math equations to ... [+] help me figure out exact times I needed to arrive at specific places during each TSD rally. My calculations were spot on as we won the Truck and SUV class.

The Seat Of Pants class, the segment I typically run in, means teams don’t use rally computers or apps to help them pinpoint exact times and how late/early they’re progressing throughout each checkpoint. Depending on the rally rules, duos can use an old-fashioned simple calculator and long-form math equations (or a rally app) to help them figure out exact times they need to arrive at specific places noted in the route book before they compete. Other classes, like Equipped or Unlimited, give teams the opportunity to use rally apps or a computer during competition, with the hopeful zero time in sight within each checkpoint.

Team #22 Wim and Philip van der Poel are in the middle of a time-speed-distance challenge during the ... [+] 2024 Alcan 5000 Rally.

It’s up to the navigator to help keep the driver on pace as teams can get off their targeted “perfect” time due to local traffic, wildlife, streetlights and more. Teams can take time allowances for these cases but need to calculate how much time they’re delayed to the best of their ability to stay on “perfect” time.

Each organization has specific rules of what equipment is and isn’t allowed in each class, too, and those classes vary from one organization to another. For instance, some groups allow a GPS odometer and simple calculator in the SOP, or Seat Of Pant class, whereas other groups don’t. Check with your local rally organizer to make sure a specific piece of equipment is allowed before using it.

Alcan 5000 competitors David Green and Tom Pastore, with their #13 Porsche Cayenne, are ready for ... [+] another transit leg after briefly stopping at a Yukon Territory sign.

In short: Do your research and ask questions. Learn ahead of time what the differences are between classes and what rally aids, or equipment is available to use before you rally. The most important thing is—have fun! Staying on course when you’re a novice is the most important thing. The ability to arrive on time at specific places will come soon enough.

A quick Google search for “TSD rallies near me” should yield local rally groups near where you live. A lot of them have Facebook groups where you can ask questions and learn how things go. YouTube is also a great resource to see how teams compete.

The biggest time-speed-distance or TSD rally takeaways are to stay on route, have fun, and the rest will come as you start playing the game. Precision rallies are an inexpensive way to get out there, get challenged, and get to know like-minded gearheads. It’s certainly opened our world to a new level of fulfillment since we started TSD rallying in 2018.

Mercedes Lilienthal

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