speed of light travel in one year

Universe Today

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How Far Does Light Travel in a Year?

The Universe is an extremely big place. As astronomers looked farther into space over the centuries, and deeper into the past, they came to understand just how small and insignificant our planet and our species seem by comparison. At the same time, ongoing investigations into electromagnetism and distant stars led scientists to deduce what the the speed of light is – and that it is the fastest speed obtainable.

As such, astronomers have taken to using the the distance light travels within a single year (aka. a light year) to measure distances on the interstellar and intergalactic scale. But how far does light travel in a year? Basically, it moves at a speed of 299,792,458 meters per second ( 1080 million km/hour; 671 million mph), which works out to about 9,460.5 trillion km (5,878.5 trillion miles) per year.

The Speed of Light:

Calculating the speed of light has been a preoccupation for scientists for many centuries. And prior to the 17th century, there was disagreement over whether the speed of light was finite, or if it moved from one spot to the next instantaneously. In 1676, Danish astronomer Ole Romer settled the argument when his observations of the apparent motion of Jupiter’s moon Io revealed that the speed of light was finite.

From his observations, famed Dutch astronomer Christiaan Huygens calculated the speed of light at 220,000 km/s (136,701 mi/s). Over the course of the nest two centuries, the speed of light was refined further and further, producing estimates that ranged from about 299,000 to 315,000 km/s (185,790 to 195,732 mi/s).

This was followed by James Clerk Maxwell, who proposed in 1865 that light was an electromagnetic wave. In his theory of electromagnetism, the speed of light was represented as c. And then in 1905, Albert Einstein proposed his theory of Special Relativity , which postulated that the speed of light ( c ) was constant, regardless of the inertial reference frame of the observer or the motion of the light source.

By 1975, after centuries of refined measurements, the speed of light in a vacuum was calculated at 299,792,458 meters per second. Ongoing research also revealed that light travels at different wavelengths and is made up of subatomic particles known as photons, which have no mass and behave as both particles and waves.

Light-Year:

As already noted, the speed of light (expressed in meters per second) means that light travels a distance of 9,460,528,000,000 km (or 5,878,499,817,000 miles) in a single year. This distance is known as a “light year”, and is used to measure objects in the Universe that are at a considerable distances from us.

For example, the nearest star to Earth (Proxima Centauri) is roughly 4.22 light-years distant. The center of the Milky Way Galaxy is 26,000 light-years away, while the nearest large galaxy (Andromeda) is 2.5 million light-years away. To date, the candidate for the farthest galaxy from Earth is MACS0647-JD , which is located approximately 13.3 billion light years away.

And the Cosmic Microwave Background , the relic radiation which is believed to be leftover from the Big Bang, is located some 13.8 billion light years away. The discovery of this radiation not only bolstered the Big Bang Theor y, but also gave astronomers an accurate assessment of the age of the Universe. This brings up another important point about measuring cosmic distances in light years, which is the fact that space and time are intertwined.

You see, when we see the light coming from a distant object, we’re actually looking back in time. When we see the light from a star located 400 light-years away, we’re actually seeing light that was emitted from the star 400 years ago. Hence, we’re seeing the star as it looked 400 years ago, not as it appears today. As a result, looking at objects billions of light-years from Earth is to see billions of light-years back in time.

Yes, light travels at an extremely fast speed. But given the sheer size and scale of the Universe, it can still take billions of years from certain points in the Universe to reach us here on Earth. Hence why knowing how long it takes for light to travel a single year is so useful to scientists. Not only does it allow us to comprehend the scale of the Universe, it also allows us to chart the process of cosmic evolution.

We have written many articles about the speed of light here at Universe Today. Here’s How Far is a Light Year? , What is the Speed of Light ?, How Much Stuff is in a Light Year? , How Does Light Travel? , and How Far Can You See in the Universe?

Want more info on light-years? Here’s an article about light-years for HowStuffWorks , and here’s an answer from PhysLink .

We’ve also recorded an episode of Astronomy Cast on this topic. Listen here, Episode 10: Measuring Distance in the Universe .

• NASA – How Fast is the Speed of Light?
• NASA: Starchild – What is a Light-Year and How is it Measured?
• Wikipedia – Speed of Light
• UCR – How is the Speed of Light Measured?

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3 Replies to “How Far Does Light Travel in a Year?”

Time and measurement are both man made entities. Time is basically a year, broken down into seconds. Measurement is derived from some guys thumb. Consider if humans were 100 times bigger, and measurement evolved the same way, the speed of light would be 100 times slower. Conversely if humans were 100 times smaller the SOL would be 100 times faster. Now consider if we grew up on Jupiter, that has a 10 hour day and a year is 11.8 Earth years. Thats 10,500 jovian days to a jovian year. Seconds would evolve differently on that planet. So how do we know we are correct with the SOL when both sides of the equation are made up bits of fantasy. Cheers Steven.

How we measure time is based on our inertial reference frame. That comes from being at the bottom of a 1 g gravity well, and to the time it takes the planet to rotate once on its axis and once around the Sun. The size of our thumbs or our bodies is completely irrelevant and being larger would change nothing. The same goes for if we were traveling through space, our perception of time would be based on our speed – i.e. our inertial reference frame.

And time itself is not man-made, its a fundamental part of the Universe and the laws which govern it. This is not fantasy, its physics.

You wrote : “fellow Danish astronomer Christiaan Huygens “, that is not right. Christiaan Huygens was a Dutch (Netherland) scientist.

Comments are closed.

How Far is a Light Year?

How far is a light-year ? It might seem like a weird question because isn’t a ‘year’ a unit of time, and ‘far’ a unit of distance? While that is correct, a ‘light-year’ is actually a measure of distance. A light-year is the distance light can travel in one year.

Light is the fastest thing in our Universe traveling through interstellar space at 186,000 miles/second (300,000 km/sec). In one year, light can travel 5.88 trillion miles (9.46 trillion km).

A light year is a basic unit astronomers use to measure the vast distances in space.

To give you a great example of how far a light year actually is, it will take Voyager 1 (NASA’s longest-lived spacecraft) over 17,000 years to reach 1 light year in distance traveling at a speed of 61,000 kph.

Related Post: 13 Amazing Facts About Space

Why Do We Use Light-Years?

Because space is so vast, the measurements we use here on Earth are not very helpful and would result in enormous numbers.

When talking about locations in our own galaxy we would have numbers with over 18 zeros. Instead, astronomers use light-time measurements to measure vast distances in space. A light-time measurement is how far light can travel in a given increment of time.

• Light-minute: 11,160,000 miles
• Light-hour: 671 million miles
• Light-year: 5.88 trillion miles

Understanding Light-Years

To help wrap our heads around how to use light-years, let’s look at how far things are away from the Earth starting with our closest neighbor, the Moon.

The Moon is 1.3 light-seconds from the Earth.

Earth is about 8 light-minutes (~92 million miles) away from the Sun. This means light from the Sun takes 8 minutes to reach us.

Jupiter is approximately 35 light minutes from the Earth. This means if you shone a light from Earth it would take about a half hour for it to hit Jupiter.

Pluto is not the edge of our solar system, in fact, past Pluto, there is the Kieper Belt , and past this is the Oort Cloud . The Oort cloud is a spherical layer of icy objects surrounding our entire solar system.

If you could travel at the speed of light, it would take you 1.87 years to reach the edge of the Oort cloud. This means that our solar system is about 4 light-years across from edge to edge of the Oort Cloud.

The distance between the Sun and Interstellar Space. NASA/JPL-Caltech .

The nearest known exoplanet orbits the star Proxima Centauri , which is four light years away (~24 trillion miles). If a modern-day jet were to fly to this exoplanet it would not arrive for 5 million years.

One of the most distant exoplanets is 3,000 light-years (17.6 quadrillion miles) away from us in the Milky Way. If you were to travel at 60 miles an hour, you would not reach this exoplanet for 28 billion years.

Our Milky Way galaxy is approximately 100,000 light-years across (~588 quadrillion miles). Moving further into our Universe, our nearest neighbor, the Andromeda galaxy is 2.537 million light-years (14.7 quintillion miles) away from us.

The Andromeda Galaxy is 2.537 million light-years away from us.

Light, a Window into the Past

While we cannot actually travel through time, we can see into the past. How? We see objects because they either emit light or light has bounced off their surface and is traveling back to us.

Even though light is the fastest thing in our Universe, it takes time to reach us. This means that for any object we are seeing it how it was in the past. How far in the past? However long it took the light to reach us.

For day-to-day objects like a book or your dog, it takes a mere fraction of a fraction of a second for the light bouncing off the object to reach your eye. The further away an object is, the further into its past you are looking.

For instance, light from the Sun takes about 8 minutes to reach Earth, this means we are always seeing the Sun how it looked 8 minutes ago if you were on its surface.

The differences between Lunar Distance, an Astronomical Unit, and a Light Year. Illustration by Star Walk .

Traveling back through our solar system, Jupiter is approximately 30 light-minutes from Earth, so we see Jupiter how it looked 30 minutes ago if you were on its surface. Extending out into the Universe to our neighbor the Andromeda galaxy, we see it how it was 2.537 million years ago.

If there is another civilization out in the Universe watching Earth, they would not see us here today, they would see Earth in the past. A civilization that lives 65 million light-years away would see dinosaurs roaming the Earth.

Helpful Resources:

• How big is the Solar System? (Universe Today)
• What is an Astronomical Unit? (EarthSky)
• How close is Proxima Centauri? (NASA Imagine The Universe)

What Is a Light-Year?

An image of distant galaxies captured by the NASA/ESA Hubble Space Telescope. Credit: ESA/Hubble & NASA, RELICS; Acknowledgment: D. Coe et al.

For most space objects, we use light-years to describe their distance. A light-year is the distance light travels in one Earth year. One light-year is about 6 trillion miles (9 trillion km). That is a 6 with 12 zeros behind it!

Looking Back in Time

When we use powerful telescopes to look at distant objects in space, we are actually looking back in time. How can this be?

Light travels at a speed of 186,000 miles (or 300,000 km) per second. This seems really fast, but objects in space are so far away that it takes a lot of time for their light to reach us. The farther an object is, the farther in the past we see it.

Our Sun is the closest star to us. It is about 93 million miles away. So, the Sun's light takes about 8.3 minutes to reach us. This means that we always see the Sun as it was about 8.3 minutes ago.

The next closest star to us is about 4.3 light-years away. So, when we see this star today, we’re actually seeing it as it was 4.3 years ago. All of the other stars we can see with our eyes are farther, some even thousands of light-years away.

Stars are found in large groups called galaxies . A galaxy can have millions or billions of stars. The nearest large galaxy to us, Andromeda, is 2.5 million light-years away. So, we see Andromeda as it was 2.5 million years in the past. The universe is filled with billions of galaxies, all farther away than this. Some of these galaxies are much farther away.

An image of the Andromeda galaxy, as seen by NASA's GALEX observatory. Credit: NASA/JPL-Caltech

In 2016, NASA's Hubble Space Telescope looked at the farthest galaxy ever seen, called GN-z11. It is 13.4 billion light-years away, so today we can see it as it was 13.4 billion years ago. That is only 400 million years after the big bang . It is one of the first galaxies ever formed in the universe.

Learning about the very first galaxies that formed after the big bang, like this one, helps us understand what the early universe was like.

This picture shows hundreds of very old and distant galaxies. The oldest one found so far in GN-z11 (shown in the close up image). The image is a bit blurry because this galaxy is so far away. Credit: NASA, ESA, P. Oesch (Yale University), G. Brammer (STScI), P. van Dokkum (Yale University), and G. Illingworth (University of California, Santa Cruz)

More to explore

What Is a Galaxy?

How Far Away Is the Moon?

What Is a Nebula?

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• NGC 1097 (Spitzer)
• Helix (Spitzer)
• Flame Nebula (WISE)
• Galactic Center (2MASS)
• Cool Andromeda (Herschel)

Space Terms

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What is a light-year?

The fastest thing that we know of is light which travels at a speed of 186,000 miles or 300,000 kilometers per second in empty space. To get an idea of how fast this is, light can travel about seven times around Earth in one second! Astronomers use the speed of light to measure how far away things are in space. A light-year (ly) is the distance that light can travel in one year. In one year, light travels about 5,880,000,000,000 miles or 9,460,000,000,000 kilometers. So, this distance is 1 light-year. For example, the nearest star to us is about 4.3 light-years away. Our galaxy, the Milky Way, is about 150,000 light-years across, and the nearest large galaxy, Andromeda, is 2.3 million light-years away.

Cosmic Distances

The space beyond Earth is so incredibly vast that units of measure which are convenient for us in our everyday lives can become GIGANTIC. Distances between the planets, and especially between the stars, can become so big when expressed in miles and kilometers that they're unwieldy. So for cosmic distances, we switch to whole other types of units: astronomical units, light years and parsecs.

Astronomical units, abbreviated AU, are a useful unit of measure within our solar system. One AU is the distance from the Sun to Earth's orbit, which is about 93 million miles (150 million kilometers). When measured in astronomical units, the 886,000,000-mile (1,400,000,000-kilometer) distance from the Sun to Saturn's orbit, is a much more manageable 9.5 AU. So astronomical units are a great way to compress truly astronomical numbers to a more manageable size.

Astronomical units also make it easy to think about distances between solar system objects. They make it easy to see that Jupiter orbits five times farther from the Sun than Earth, and that Saturn is twice as far from the Sun as Jupiter. (This is because, technically, you're expressing every distance as a ratio of the distance from Earth to the Sun. Convenient!)

For much greater distances — interstellar distances — astronomers use light years. A light year is the distance a photon of light travels in one year, which is about 6 trillion miles (9 trillion kilometers, or 63,000 AU). Put another way, a light year is how far you'd travel in a year if you could travel at the speed of light, which is 186,000 miles (300,000 kilometers) per second. (By the way, you can't travel at the speed of light, as far as we know, but that's a whole other story...) Like AU, light years make astronomical distances more manageable. For example, the nearest star system to ours is the triple star system of Alpha Centauri , at about 4.3 light years away. That's a more manageable number than 25 trillion miles, 40 trillion kilometers or 272,000 AU.

Light years also provide some helpful perspective on solar system distances: the Sun is about 8 light minutes from Earth. (And yes, there are also light seconds !) And because light from objects travels at light speed , when you see the Sun, or Jupiter or a distant star, you're seeing it as it was when the light left it, be that 8 minutes, tens of minutes or 4.3 years ago. And this is fundamental to the idea that when we're looking farther out into space, we're seeing farther back in time. (Think about it: you're seeing all the stars in the sky at different times in history — some a few years ago, others hundreds of years ago — all at the same time!)

Finally, parsecs. This is the unit used when the number of light years between objects climbs into the high thousands or millions. One parsec is 3.26 light years. The origin of this unit of measure is a little more complicated, but it's related to how astronomers measure widths in the sky. Astronomers use "megaparsecs" — a megaparsec is 1 million parsecs — for intergalactic distances, or the scale of distances between the galaxies.

And at the point when distances between galaxies become so epic that even megaparsecs get unwieldy, astronomers talk about distances in terms of how much a galaxy's light has been shifted toward longer, redder wavelengths by the expansion of the universe — a measure known as "redshift." Now that's astronomical.

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• Learning Resources
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• The Universe

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What is the speed of light?

Light is faster than anything else in the known universe, though its speed can change depending on what it's passing through.

The universe has a speed limit, and it's the speed of light. Nothing can travel faster than light — not even our best spacecraft — according to the laws of physics.

So, what is the speed of light? 

Light moves at an incredible 186,000 miles per second (300,000 kilometers per second), equivalent to almost 700 million mph (more than 1 billion km/h). That's fast enough to circumnavigate the globe 7.5 times in one second, while a typical passenger jet would take more than two days to go around once (and that doesn't include stops for fuel or layovers!). 

Light moves so fast that, for much of human history, we thought it traveled instantaneously. As early as the late 1600s, though, scientist Ole Roemer was able to measure the speed of light (usually referred to as c ) by using observations of Jupiter's moons, according to Britannica . 

Around the turn of the 19th century, physicist James Clerk Maxwell created his theories of electromagnetism . Light is itself made up of electric and magnetic fields, so electromagnetism could describe the behavior and motion of light — including its theoretical speed. That value was 299,788 kilometers per second, with a margin of error of plus or minus 30. In the 1970s, physicists used lasers to measure the speed of light with much greater precision, leaving an error of only 0.001. Nowadays, the speed of light is used to define units of length, so its value is fixed; humans have essentially agreed the speed of light is 299,792.458 kilometers per second, exactly.

Light doesn't always have to go so fast, though. Depending on what it's traveling through — air, water, diamonds, etc. — it can slow down. The official speed of light is measured as if it's traveling in a vacuum, a space with no air or anything to get in the way. You can most clearly see differences in the speed of light in something like a prism, where certain energies of light bend more than others, creating a rainbow.

— How many moons does Earth have ?

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Interestingly, the speed of light is no match for the vast distances of space, which is itself a vacuum. It takes 8 minutes for light from the sun to reach Earth, and a couple years for light from the other closest stars (like Proxima Centauri) to get to our planet. This is why astronomers use the unit light-years — the distance light can travel in one year — to measure vast distances in space.

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Because of this universal speed limit, telescopes are essentially time machines . When astronomers look at a star 500 light-years away, they're looking at light from 500 years ago. Light from around 13 billion light-years away (equivalently, 13 billion years ago) shows up as the cosmic microwave background, remnant radiation from the Big Bang in the universe's infancy. The speed of light isn't just a quirk of physics; it has enabled modern astronomy as we know it, and it shapes the way we see the world — literally.

Briley Lewis (she/her) is a freelance science writer and Ph.D. Candidate/NSF Fellow at the University of California, Los Angeles studying Astronomy & Astrophysics. Follow her on Twitter  @briles_34 or visit her website  www.briley-lewis.com .

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• Kooperkieri54 That's correct. In a vacuum, such as outer space, light travels at a constant speed of approximately 299,792 kilometers per second (or about 186,282 miles per second), which is often rounded to 300,000 kilometers per second for simplicity. This speed is commonly referred to as the speed of light in a vacuum and is denoted by the symbol "c". However, when light passes through a medium, such as air, water, or glass, its speed can change. This change in speed is due to the interaction of light with the atoms or molecules in the medium. The speed of light in a medium is typically slower than its speed in a vacuum because the particles in the medium can absorb and re-emit photons, causing a delay in the overall propagation of light. The change in speed of light in different materials is characterized by the refractive index of the material. The refractive index indicates how much the speed of light is reduced when it passes through that particular material compared to its speed in a vacuum. It's worth noting that while light is the fastest known phenomenon in the universe, it is not instantaneous . what pickleball paddles do the prose use. It still takes time for light to travel from one point to another, and its speed is an essential aspect of many fundamental theories and principles in physics. Reply
• marcuso I thought the speed of an event was relative, with all observers having their own space time, therfore how does this fit into 2 observers seeing the same speed of light ? Reply
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Speed of Light Calculator

Table of contents

With this speed of light calculator, we aim to help you calculate the distance light can travel in a fixed time . As the speed of light is the fastest speed in the universe, it would be fascinating to know just how far it can travel in a short amount of time.

We have written this article to help you understand what the speed of light is , how fast the speed of light is , and how to calculate the speed of light . We will also demonstrate some examples to help you understand the computation of the speed of light.

What is the speed of light? How fast is the speed of light?

The speed of light is scientifically proven to be the universe's maximum speed. This means no matter how hard you try, you can never exceed this speed in this universe. Hence, there are also some theories on getting into another universe by breaking this limit. You can understand this more using our speed calculator and distance calculator .

So, how fast is the speed of light? The speed of light is 299,792,458 m/s in a vacuum. The speed of light in mph is 670,616,629 mph . With this speed, one can go around the globe more than 400,000 times in a minute!

One thing to note is that the speed of light slows down when it goes through different mediums. Light travels faster in air than in water, for instance. This phenomenon causes the refraction of light.

Now, let's look at how to calculate the speed of light.

How to calculate the speed of light?

As the speed of light is constant, calculating the speed of light usually falls on calculating the distance that light can travel in a certain time period. Hence, let's have a look at the following example:

• Source: Light
• Speed of light: 299,792,458 m/s
• Time traveled: 100 seconds

You can perform the calculation in three steps:

Determine the speed of light.

As mentioned, the speed of light is the fastest speed in the universe, and it is always a constant in a vacuum. Hence, the speed of light is 299,792,458 m/s .

Determine the time that the light has traveled.

The next step is to know how much time the light has traveled. Unlike looking at the speed of a sports car or a train, the speed of light is extremely fast, so the time interval that we look at is usually measured in seconds instead of minutes and hours. You can use our time lapse calculator to help you with this calculation.

For this example, the time that the light has traveled is 100 seconds .

Calculate the distance that the light has traveled.

The final step is to calculate the total distance that the light has traveled within the time . You can calculate this answer using the speed of light formula:

distance = speed of light × time

Thus, the distance that the light can travel in 100 seconds is 299,792,458 m/s × 100 seconds = 29,979,245,800 m

What is the speed of light in mph when it is in a vacuum?

The speed of light in a vacuum is 670,616,629 mph . This is equivalent to 299,792,458 m/s or 1,079,252,849 km/h. This is the fastest speed in the universe.

Is the speed of light always constant?

Yes , the speed of light is always constant for a given medium. The speed of light changes when going through different mediums. For example, light travels slower in water than in air.

How can I calculate the speed of light?

You can calculate the speed of light in three steps:

Determine the distance the light has traveled.

Apply the speed of light formula :

speed of light = distance / time

How far can the speed of light travel in 1 minute?

Light can travel 17,987,547,480 m in 1 minute . This means that light can travel around the earth more than 448 times in a minute.

Speed of light

The speed of light in the medium. In a vacuum, the speed of light is 299,792,458 m/s.

By Darin Anthony - Last Updated: April 17, 2024

How Long Would It Take to Travel One Light Year?

Article Contents

We hear the term “light-years” almost anytime a new star or exo-planet is discovered. But how long would it take to travel one light year?

The fastest human-made vehicle, NASA’s Parker Solar Probe, would take 1,698 years to travel one light-year , the sum of roughly 5.88 trillion miles (9.46 trillion kilometers), the distance light travels in one year.

In September 2023, NASA’s Parker Solar Probe set a new record, clocking a blistering speed of 394,736 miles per hour (635,266 kilometers per hour)—the fastest ever recorded.

But 1,698 years is an incredibly long time. The Parker Solar Probe would have just completed a distance of one light year if it had left during the 4th century (326 A.D.) and maintained its top speed the entire journey.

Let’s look more closely at the speed of light and what it means to travel one light-year.

Understanding Light Years

Speed of light.

Over one hundred years ago, Albert Einstein’s theory of relativity deciphered the math of a cosmic limit. It says nothing can go faster than  the speed of light , which is approximately 186,282 miles per second (299,792 km/s) within the vacuum of space.

To help understand how fast light speed is, we’ll compare it to the longest intercontinental flight in the world today.

A flight from New York to Singapore covers 9,526 miles (15.332km) and, on average, takes 18hrs 40 minutes. If a commercial airliner could travel the speed of light, symbolically, it could make that trip almost 20 times in one second!

Measuring Distances

Understanding the vastness of space begins with grasping the concept of a light-year . It’s a unit of measurement scientists use to note the length of astronomical distances.

Astronomers use two common measurements to help make an incredibly long distance, a huge number, more manageable.

Astronomical Unit (AU) : It’s the distance the Sun’s light takes to reach the Earth. This distance is approximately 93 million miles (150 million kilometers) and takes eight light minutes.

Light-Year (LY): It represents the unit of distance that light travels in one Earth year , which is approximately 5.88 trillion miles (9.46 trillion kilometers).

So, the time it takes Light to travel one light year? One Earth year or roughly 365 days .

When speaking of distances in the universe, an astronomer refers to distances in an (AU) or (LY) depending on how great of a distance.

For example, when referring to the distance of the Andromeda Galaxy from Earth, it is stated as 2.5m (LY) light years( i ). However, the shorter distance to Neptune from the Sun is noted as approximately 30.7 (AU)( i ).

Since a light-year is a larger unit of distance than (AU) it is more likely to be used when expressing bigger numbers.

Travel Time

If we could travel the distance of one light-year from Earth, we would end up in the mid-region of the Oort cloud .

It is the outermost area of our solar system before reaching the realm of deep outer space. The time it would take to journey this one light-year would greatly depend on our mode of transportation.

I’ve put together several calculations using a light-year (ly) calculator. Using the average miles per hour (mph) for current technology we use today. It makes the complexity of traversing such an immense distance very obvious.

See the infographic I have provided below, which has a link to the calculator within the caption.

Let’s look at some of the examples the infographic highlights in relation to how long it takes to travel a light-year.

If you decide to put on some walking shoes and head off towards the mid-region of the Oort cloud , a light year away, be sure to pack lunch. At a normal pace of 3/mph, it would take nearly 224 million years to get there without stopping to eat, sleep, or bathroom breaks.

Walking (3/mph) >>> One Light Year >>> 224M Years

You could pull the car cover off the Corvette stored in the garage for a quicker ride. Even then, traveling at an average speed of 100 mph would take six million and seven hundred thousand years (6.7m years) to travel a light year . That’s without stopping or slowing down.

Drive (100/mph) >>> One Light Year >>> 6.7M Years

How about a ticket on the “Big ol’ Jet Airliner”? It would still take you over one million years (1.118m yrs) to span the distance of one light year on a commercial Jet .

Commercial Jet (600/mph) >>> One Light Year >>> 1.18M Years

The point is that the distances between objects in our solar system, galaxy, and universe are so vast it’s very challenging for our minds to grasp and comprehend it.

As of today, we do not have technology that can travel the distance of a light-year within the span of a human life, but there are future concepts. Let’s take a look.

Future Concepts to Travel Light-Years

Considering our Milky Way galaxy stretches across 100,000 light-years. Even at the speed of light, it takes 100,000 Earth years to journey from edge to edge. To bridge that distance, we’ll need to inspire some new ideas through quantum physics.

But some interesting concepts are in the works right now to dramatically shorten the length of time it takes to travel a light year.

Breakthrough Starshot

In 2016, Physicist Yuri Milner announced an engineering endeavor named “ Breakthrough Starshot ,” with backing support from such notable figures as Stephen Hawking (now deceased), and Mark Zuckerberg.

Their aim is to develop a fleet of light sail centimeter-sized probes called StarChips . These probes are designed to travel to the Alpha Centauri star system , located 4.37 light-years away, potentially within 20 to 30 years at speeds of 15-20% the speed of light.

Currently, using the Parker Solar Probe’s top speed, to travel 4 light-years would take over 7000 years, so that would be an amazing feat.

The project proposes a flyby mission to our next closest star beyond our Sun, Proxima Centauri. It is believed to be home to an Earth-sized exoplanet in the habitable zone.

The concept will leverage advanced laser technology to propel the spacecraft. Current estimates for launch are 2036.

Helical Engine

A space and aeronautics engineer has developed a concept that, in theory, would reach 99% of the speed of light without conflicting with Einstein’s theory of relativity .

Dr Burn, now a former engineer from NASA’s Space Flight Center in Alabama , believes that a system where instead of expelling propellant, it is retained, could generate an almost limitless specific impulse and open the door to interstellar space exploration.

This method involves accelerating ions near the light speed limit within a closed circuit, adjusting their speed to modify momentum. Thrust is generated by oscillating the ions back and forth in the direction of travel.

It’s Designed for long-term satellite operations without the need for refueling or powering voyages across vast distances; this engine operates without any mechanical components, relying solely on ions circulating in a vacuum loop contained by electric and magnetic fields.

If this concept is proven and successful it would mean we could travel a light-year in a little more than one year!

It’s impossible to talk about traveling at the speed of light without discussing the theory of warp drive , which was popularized by the 1960s Star Trek series.

NASA has explored this concept and will continue to do so as science and modern physics expand with future breakthroughs.

The idea behind warp drive is to manipulate the fabric of spacetime to create a bubble or a wave, often referred to as a “ warp bubble ,” that would contract space in front of the ship and expand it from behind , allowing the vessel to move from one point to another faster than light would in normal space.

It would theoretically enable interstellar travel within human lifetimes without violating the fundamental principles of Einstein’s theory of general relativity, which states that nothing can travel faster than the speed of light in a vacuum.

If this concept is ever proven, it will be a game changer for space travel in our cosmic neighborhood and beyond.

For now, the Parker Solar Probe’s top speed makes it the fastest vehicle to span the distance of a light year . The enormity of the universe will make reaching distant stars and exoplanets impossible until we can develop technologies like the Warp Drive, Starshot, or Helical engine.

It’s a humbling distance across our Milky Way. But scientists continue to unlock the mysteries of the cosmos, and one day, we may crack the code to bridge the vast galactic space within the universe.

Astronomy has peaked my curiosity and imagination from an early age. I am always thrilled to read about the latest galactic discovery or planning my next celestial observation. More about me [..]

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How Long Would It Take To Travel A Light Year

Using the fastest man-made vehicle, NASA’s Juno spacecraft, which travels at 165,000 mph (365,000 kmph), it would take 2,958 years to travel a light year. A light year is equivalent to about 5.88 trillion miles (9.46 trillion kilometers).

Traveling at the speed of light would be the fastest way to cover vast distances in space, but current technology makes it impossible for humans or even our most advanced spacecraft to reach this speed.

Can people match the speed of a light year?

According to Einstein, it is impossible to match the speed of light. It is because light is the fastest thing in the universe, traveling at 186,000 miles per second (300,000 kilometers per second). There is not one thing that we could invent that could even match a fraction of how fast light travels.

Some scientists have theorized that a new type of engine, called a warp drive , could potentially allow humans to reach the speed of travel required to match the speed of light. However, even if future spacecrafts were able to achieve this level of propulsion, it would still take thousands of years to travel from one star system to another.

Despite the challenges, scientists continue to study space travel at faster-than-light speeds, as they are optimistic that one day we will be able to explore the vast reaches of our universe and even discover life on other planets.

For now, it would take many thousands of years to travel a light year using current technology. However, scientists remain hopeful that one day we will be able to explore the far reaches of space and perhaps even discover other life forms in distant star systems. Until then, we can continue marveling at the

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Why is the speed of light the way it is?

It's just plain weird.

Paul M. Sutter is an astrophysicist at SUNY Stony Brook and the Flatiron Institute, host of Ask a Spaceman and Space Radio , and author of " How to Die in Space ." He contributed this article to Space.com's Expert Voices: Op-Ed & Insights . 

We all know and love the speed of light — 299,792,458 meters per second — but why does it have the value that it does? Why isn't it some other number? And why do we care so much about some random speed of electromagnetic waves? Why did it become such a cornerstone of physics? 

Well, it's because the speed of light is just plain weird.

Related: Constant speed of light: Einstein's special relativity survives a high-energy test

Putting light to the test

The first person to realize that light does indeed have a speed at all was an astronomer by the name of Ole Romer. In the late 1600s, he was obsessed with some strange motions of the moon Io around Jupiter. Every once in a while, the great planet would block our view of its little moon, causing an eclipse, but the timing between eclipses seemed to change over the course of the year. Either something funky was happening with the orbit of Io — which seemed suspicious — or something else was afoot.

After a couple years of observations, Romer made the connection. When we see Io get eclipsed, we're in a certain position in our own orbit around the sun. But by the next time we see another eclipse, a few days later, we're in a slightly different position, maybe closer or farther away from Jupiter than the last time. If we are farther away than the last time we saw an eclipse, then that means we have to wait a little bit of extra time to see the next one because it takes that much longer for the light to reach us, and the reverse is true if we happen to be a little bit closer to Jupiter.

The only way to explain the variations in the timing of eclipses of Io is if light has a finite speed.

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Making it mean something

Continued measurements over the course of the next few centuries solidified the measurement of the speed of light, but it wasn't until the mid-1800s when things really started to come together. That's when the physicist James Clerk Maxwell accidentally invented light.

Maxwell had been playing around with the then-poorly-understood phenomena of electricity and magnetism when he discovered a single unified picture that could explain all the disparate observations. Laying the groundwork for what we now understand to be the electromagnetic force , in those equations he discovered that changing electric fields can create magnetic fields, and vice versa. This allows waves of electricity to create waves of magnetism, which go on to make waves of electricity and back and forth and back and forth, leapfrogging over each other, capable of traveling through space.

And when he went to calculate the speed of these so-called electromagnetic waves, Maxwell got the same number that scientists had been measuring as the speed of light for centuries. Ergo, light is made of electromagnetic waves and it travels at that speed, because that is exactly how quickly waves of electricity and magnetism travel through space.

And this was all well and good until Einstein came along a few decades later and realized that the speed of light had nothing to do with light at all. With his special theory of relativity , Einstein realized the true connection between time and space, a unified fabric known as space-time. But as we all know, space is very different than time. A meter or a foot is very different than a second or a year. They appear to be two completely different things.

So how could they possibly be on the same footing?

There needed to be some sort of glue, some connection that allowed us to translate between movement in space and movement in time. In other words, we need to know how much one meter of space, for example, is worth in time. What's the exchange rate? Einstein found that there was a single constant, a certain speed, that could tell us how much space was equivalent to how much time, and vice versa.

Einstein's theories didn't say what that number was, but then he applied special relativity to the old equations of Maxwell and found that this conversion rate is exactly the speed of light.

Of course, this conversion rate, this fundamental constant that unifies space and time, doesn't know what an electromagnetic wave is, and it doesn't even really care. It's just some number, but it turns out that Maxwell had already calculated this number and discovered it without even knowing it. That's because all massless particles are able to travel at this speed, and since light is massless, it can travel at that speed. And so, the speed of light became an important cornerstone of modern physics.

But still, why that number, with that value, and not some other random number? Why did nature pick that one and no other? What's going on?

Related: The genius of Albert Einstein: his life, theories and impact on science

Making it meaningless

Well, the number doesn't really matter. It has units after all: meters per second. And in physics any number that has units attached to it can have any old value it wants, because it means you have to define what the units are. For example, in order to express the speed of light in meters per second, first you need to decide what the heck a meter is and what the heck a second is. And so the definition of the speed of light is tied up with the definitions of length and time.

In physics, we're more concerned with constants that have no units or dimensions — in other words, constants that appear in our physical theories that are just plain numbers. These appear much more fundamental, because they don't depend on any other definition. Another way of saying it is that, if we were to meet some alien civilization , we would have no way of understanding their measurement of the speed of light, but when it comes to dimensionless constants, we can all agree. They're just numbers.

One such number is known as the fine structure constant, which is a combination of the speed of light, Planck's constant , and something known as the permittivity of free space. Its value is approximately 0.007. 0.007 what? Just 0.007. Like I said, it's just a number.

So on one hand, the speed of light can be whatever it wants to be, because it has units and we need to define the units. But on the other hand, the speed of light can't be anything other than exactly what it is, because if you were to change the speed of light, you would change the fine structure constant. But our universe has chosen the fine structure constant to be approximately 0.007, and nothing else. That is simply the universe we live in, and we get no choice about it at all. And since this is fixed and universal, the speed of light has to be exactly what it is.

So why is the fine structure constant exactly the number that it is, and not something else? Good question. We don't know.

Learn more by listening to the episode "Why is the speed of light the way it is?" on the Ask A Spaceman podcast, available on iTunes and on the Web at http://www.askaspaceman.com. Thanks to Robert H, Michael E., @DesRon94, Evan W., Harry A., @twdixon, Hein P., Colin E., and Lothian53 for the questions that led to this piece! Ask your own question on Twitter using #AskASpaceman or by following Paul @PaulMattSutter and facebook.com/PaulMattSutter.

Join our Space Forums to keep talking space on the latest missions, night sky and more! And if you have a news tip, correction or comment, let us know at: [email protected].

Paul M. Sutter is an astrophysicist at SUNY Stony Brook and the Flatiron Institute in New York City. Paul received his PhD in Physics from the University of Illinois at Urbana-Champaign in 2011, and spent three years at the Paris Institute of Astrophysics, followed by a research fellowship in Trieste, Italy, His research focuses on many diverse topics, from the emptiest regions of the universe to the earliest moments of the Big Bang to the hunt for the first stars. As an "Agent to the Stars," Paul has passionately engaged the public in science outreach for several years. He is the host of the popular "Ask a Spaceman!" podcast, author of "Your Place in the Universe" and "How to Die in Space" and he frequently appears on TV — including on The Weather Channel, for which he serves as Official Space Specialist.

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• voidpotentialenergy This is just my opinion but i think L speed is it's speed because the particle part of it is the fastest it can interact with the quanta distance in quantum fluctuation. Light is particle and wave so the wave happens in the void between quanta. Gravity probably travels in that void and why gravity seems instant. Reply
• rod The space.com article wraps up the discussion with, "So on one hand, the speed of light can be whatever it wants to be, because it has units and we need to define the units. But on the other hand, the speed of light can't be anything other than exactly what it is, because if you were to change the speed of light, you would change the fine structure constant. But our universe has chosen the fine structure constant to be approximately 0.007, and nothing else. That is simply the universe we live in, and we get no choice about it at all. And since this is fixed and universal, the speed of light has to be exactly what it is. So why is the fine structure constant exactly the number that it is, and not something else? Good question. We don't know." It seems that the *universe* made this decision, *But our universe has chosen the fine structure constant to be...* I did not know that the universe was capable of making decisions concerning constants used in physics. E=mc^2 is a serious constant. Look at nuclear weapons development, explosive yields, and stellar evolution burn rates for p-p chain and CNO fusion rates. The report indicates why alpha (fine structure constant) is what it is and c is what it is, *We don't know*. Reply

Admin said: We all know and love the speed of light, but why does it have the value that it does? Why isn't it some other number? And why did it become such a cornerstone of physics? Why is the speed of light the way it is? : Read more

rod said: The space.com article wraps up the discussion with, "So on one hand, the speed of light can be whatever it wants to be, because it has units and we need to define the units. But on the other hand, the speed of light can't be anything other than exactly what it is, because if you were to change the speed of light, you would change the fine structure constant. But our universe has chosen the fine structure constant to be approximately 0.007, and nothing else. That is simply the universe we live in, and we get no choice about it at all. And since this is fixed and universal, the speed of light has to be exactly what it is. So why is the fine structure constant exactly the number that it is, and not something else? Good question. We don't know." It seems that the *universe* made this decision, *But our universe has chosen the fine structure constant to be...* I did not know that the universe was capable of making decisions concerning constants used in physics. E=mc^2 is a serious constant. Look at nuclear weapons development, explosive yields, and stellar evolution burn rates for p-p chain and CNO fusion rates. The report indicates why alpha (fine structure constant) is what it is and c is what it is, *We don't know*.

• rod FYI. When someone says *the universe has chosen*, I am reminded of these five lessons from a 1982 Fed. court trial. The essential characteristics of science are: It is guided by natural law; It has to be explanatory by reference to natural law; It is testable against the empirical world; Its conclusions are tentative, i.e., are not necessarily the final word; and It is falsifiable. Five important points about science. Reply
• Gary If the universe is expanding , how can the speed of light be constant ( miles per second , if each mile is getting longer ) ? Can light's velocity be constant while the universe expands ? So, with the expansion of the universe , doesn't the speed of light need to increase in order to stay at a constant velocity in miles per second ? Or, do the miles in the universe remain the same length as the universe 'adds' miles to its diameter ? Are the miles lengthening or are they simply being added / compounded ? Reply
• Gary Lets say we're in outer space and we shoot a laser through a block of glass. What causes the speed of the laser light to return to the speed it held prior to entering the block of glass ? Is there some medium in the vacuum of space that governs the speed of light ? Do the atoms in the glass push it back up to its original speed. If so, why don't those same atoms constantly push the light while it travels through the block of glass ? Reply

Gary said: Lets say we're in outer space and we shoot a laser through a block of glass. What causes the speed of the laser light to return to the speed it held prior to entering the block of glass ? Is there some medium in the vacuum of space that governs the speed of light ? Do the atoms in the glass push it back up to its original speed. If so, why don't those same atoms constantly push the light while it travels through the block of glass ?

Gary said: If the universe is expanding , how can the speed of light be constant ( miles per second , if each mile is getting longer ) ? Can light's velocity be constant while the universe expands ? So, with the expansion of the universe , doesn't the speed of light need to increase in order to stay at a constant velocity in miles per second ? Or, do the miles in the universe remain the same length as the universe 'adds' miles to its diameter ? Are the miles lengthening or are they simply being added / compounded ?

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What If Humans Traveled at the Speed of Light? Here's What Happens

S pace is always ripe for theoretical thought exercises, such as the intriguing question, “What would happen if humans traveled at the speed of light?”

Knewz.com has learned that humans would probably not realize we were moving at the speed of light because we cannot feel constant velocity.

However, the main problem would be accelerating to the 671 million miles per hour that light travels, according to an interview published by Space.com .

Rapid acceleration can be extremely painful and even deadly to humans, and we can only handle forces of four to six times the pull of gravity (4 to 6 gs). That makes the 6,000 gs of accelerating to the speed of light completely untenable.

Even more reasonable gs from endeavors like taking off on a space rocket or flying a fighter jet can kill a person because the force makes it difficult for the body to pump blood from the feet to the brain, which is why passing out is such a threat for pilots.

“Your blood will have a hard time pumping to your extremities,” said Michael Pravica, a professor of physics at the University of Nevada, Las Vegas, in the article.

If the g-force does not subside, the person will die because the blood is no longer transporting oxygen throughout the body.

That being said, 6,000 gs would flatten the person like a pancake before that ever became an issue.

The article posited that humans could potentially travel at the speed of light if they accelerated slowly. At the rate of a free fall (1 g), it would take 11 months to reach the speed of light.

Unfortunately, physics still presents a problem, specifically Einstein’s theory of relativity. As objects travel closer to the speed of light, their mass starts to grow, and the theory has proven that it would require infinite mass to travel at the speed of light.

This problem of physics is why humans have never managed to get anything to travel at the speed of light. Scientists have pushed sub-atomic particles to move at 99.9% the speed of light, but never 100%.

As humans are much larger than sub-atomic particles, the amount of energy required to push a human even to 99.9% the speed of light would be “extremely improbable” said Pravica.

However, suppose we allow ourselves to break physics and enable a person to travel at the speed of light, Einstein's theory of relativity argues that the person would age incredibly slowly thanks to time dilation.

Additionally, despite aging slower, people moving at normal speed would appear to be moving in slow motion. So, the speed-of-light travellers would simultaneously be moving much faster than their slow-motion peers while also aging slower.

One fascinating idea is that the speed of light is a foundation of modern physics, but there is no true rule that light must be the fastest object in the universe, according to Discover Magazine .

Our current understanding of physics puts light as the limit of speed, but humans in the distant future could theoretically experience a breakthrough and discover a means to travel faster than the speed of light.

While the idea is fun to ponder, there are significant hurdles that essentially guarantee humans will not be able to travel at the speed of light anytime in the foreseeable future.