What Would Happen If You Traveled At The Speed Of Light?

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The person traveling at the speed of light would experience a slowing of time. For that person, time would move slower than for someone who is not moving. Also, their field of vision would change drastically. The world would appear through a tunnel-shaped window in front of the aircraft in which they are traveling.

Speed is thrilling to human beings—there’s no denying it. This has been the case ever since the wheel was invented, and the strength of our legs no longer determined speed. The faster one goes, the more thrilled one feels. However, some of you might be intimidated by speed.

In today’s modern age, we’ve developed some really fast objects. We have super-fast bullet trains, incredibly fast planes, ultra-fast fighter jets, and so on. We are also trying to build hyperloop and vactrains, which can be even faster than the fastest aircraft. Still, one thing triumphs over everything in motion—light.

Perhaps some of you haven’t thought about this, but many surely have…What would it be like to travel at the speed of light? Just imagine how thrilling it would be to soar through the boundaries of time and space and experience the universe’s pinnacle velocity!

Einstein’s Theory Of Relativity: How It Changed Our Perception Of Time

Before the 1900s, the world firmly believed in the view of Isaac Newton in terms of mass, motion, and gravity. However, at the dawn of the 20th century, Albert Einstein came into the picture and changed this world forever.

The Theory of Relativity put forth by Einstein cleared up many doubts about mass and energy. The equation of mass-energy equivalence proved that mass and energy are inter-convertible, meaning that mass can be converted into energy and vice-versa. He proposed that there is no standard frame of reference. Everything is relative—even time.

From this, it was inferred that the speed of light is constant and independent of the observer. Therefore, if a person moves at half the speed of light in the same direction as light itself, the light beam will appear the same as it does to a stationary individual. In other words, the speed of light is constant and does not change based on whether the observer is stationary or moving.

What Does Mass-Energy Equivalence Mean?

It means that if an object moves at a velocity that is 10% of the speed of light, it will experience an increase in its mass by 0.5% of its original mass. On the other hand, if an object travels at 90% of the speed of light, then its mass would be approximately two times its original mass.

Also Read: Time Dilation: Why Does Gravity Slow Down The Flow Of Time?

Can We Travel At The Speed Of Light?

No, humans cannot survive traveling at the speed of light.

If an object travels at the speed of light, its mass will increase exponentially. Consider this… the speed of light is 299,792 kilometers per second (186,282 miles per second), and when an object moves at this speed, it behaves like an object with infinite mass. And to propel an object with infinite mass, infinite energy will be required, which is impractical.

That’s the reason why no object can move at speed or faster than the speed of light—attempting to travel faster than light is like bringing your bike to a stop and trying to go slower. It doesn’t make sense!

Also Read: What’s The Maximum Speed Humans Can Accelerate Upto?

What If You Moved Almost As Fast As The Speed Of Light?

If we’re talking about going almost as fast as the speed of light, say 90% of the speed of light, then there would be interesting observations.

For one, the person traveling at such a speed would experience time dilation or, put it crudely: slowing of time. For that person, time would move slower than for someone who is not moving.

At 90% Speed Of Light

Suppose you could have an excursion to Mars and back at 90% of light’s speed. To reach and return from Mars (assuming no stoppage, instant acceleration, and a total covered distance to be 450 million kilometers) back to Earth would take roughly 16 minutes and 40 seconds. But here comes a twist. These 16 minutes and 40 seconds would be for humans observing your Mars trip on Earth. As a space traveler, you would only experience 8 minutes and 20 seconds during the full trip! This is because time dilation comes into effect at such high speeds. Time dilation is a phenomenon that occurs at high speeds, where the faster you move through space, the slower you move through time, meaning the faster you travel, the slower you age. Here, we have an animated video to help you better understand and visualize time dilation.

When you traveled to Mars at 90% light speed, humanity on Earth was older by 16.67 minutes, while you aged by just 8.33 minutes! This difference in aging would become much more pronounced at higher speeds, say at 99.99% the speed of light.

At 99.99% Speed Of Light

Now suppose you could travel at 99.99% speed of light. This time, let’s be more ambitious and travel out of our solar system to Alpha Centauri, roughly 4.35 light years away from Earth. If you travel at 99.99% the speed of light from Earth to Alpha Centauri and back, with instant acceleration and no stopping, this trip would have taken roughly 8 years and 8 months for people on Earth observing your trip. During this trip, you would experience only around 1.5 months. In other words, your fellow mates on Earth would have aged 8.7 years after this trip, while you would have aged only one and a half months in comparison!

Redshift And Blueshift

Besides time dilation, the phenomenon of blueshift and redshift would also come into effect if you were to travel at near-light speed. When you leave Earth, the light waves that bounce off you are stretched, which makes the wavelength longer and makes them look red to people on Earth. This effect is called redshift. On the other hand, while returning from your journey at near light speed, the light waves bouncing off you would get squished and compacted together by the time they reach into the eyes of observers on Earth, making you appear blue to observers on Earth. This is called blueshift.

For you, as you travel at that speed, everything in front appears to be squished together into a blurry tunnel. In fact, after a certain speed, you would only see blackness because the wavelength of the light entering your eyes would be out of the visible spectrum.

Abstract Infinity
Credits:Irena Peziene/Shutterstock

Although traveling at the speed of light is not practically possible, traveling at near-light speed travel can also have interesting consequences such as time dilation, where time appears to slow down for the traveler relative to someone stationary. Time flies at near-light speed, but it also slows down!

Do you really understand what happens if something travels at the speed of light?

Can you answer three questions based on the article you just read?

References (click to expand)
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  2. The Speed of Light - Galileo and Einstein. The University of Virginia
  3. What would happen if you drove your car close to the speed of .... West Texas A&M University
  4. Hughes, T., & Kersting, M. (2021, January 5). The invisibility of time dilation. Physics Education. IOP Publishing.
  5. Is Time Travel Possible? | NASA Space Place. The National Aeronautics and Space Administration
  6. (2014) Time Travel: Time Dilation - ScienceOpen. ScienceOpen
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About the Author

Ashish is a Science graduate (Bachelor of Science) from Punjabi University (India). He spearheads the content and editorial wing of ScienceABC and manages its official Youtube channel. He’s a Harry Potter fan and tries, in vain, to use spells and charms (Accio! [insert object name]) in real life to get things done. He totally gets why JRR Tolkien would create, from scratch, a language spoken by elves, and tries to bring the same passion in everything he does. A big admirer of Richard Feynman and Nikola Tesla, he obsesses over how thoroughly science dictates every aspect of life… in this universe, at least.