Light speed Questions

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Help Board

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I can see your confusion

I'm going to say if you're on a spaceship traveling at the speed of light then you could see the colors of things on the spaceship and you're reflection in a mirror that's on board and also traveling the same speed

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No to both because if you were traveling at the speed of light you would become energy and pretty much explode.

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But what if you didn't explode? Then what?

But if he exploded that would just give him an excuse to welch on bets

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1. If you are traveling at light speed, can you see colors?

2. If you are traveling at light speed, could you see your reflection?

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So, there is no short answer to this.

First, you can't travel at the speed of light due to Einstein's Relativity equations. You can travel slower than it, or surpass it, but not at exactly the same speed. Just like you can't be exactly 6 feet tall. Even if you are 5 feet and 11.99999999 inches, you're still not exactly 6 feet. So when this happens with the speed of light, due to relativity, even if you are infinitely approaching the speed of light, it is still moving at the speed of light away from you just as if you were sitting still.

For your son's question, you can't travel at the speed of light. Any speed below it, no matter how fast, you would still see color and reflections just as you do now. If you are moving faster than the speed of light, you would actually see light that had refracted prior to the time that you are there. Essentially you would be able to look back in time, in theory.

The interesting part is the mirror. Moving faster than the speed of light, you would see light that has already been projected. However, to the reflective nature of the mirror, you could only see reflection for as long back as the mirror had been there. So if you put the mirror there yourself and it entered the space with you, I guess it would just be black, reflecting absolutely nothing. It's an interesting conversation, I'll have to think on it a little more.

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I'm not sure I am understanding. How is it possible to not be able to be a certain height?

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Technically it's impossible to be exactly anything because measurements aren't rational. If something is 6 feet in length, there are actually an infinite number of decimals involved. Either like 6.000000000001 or 5.9999999. There can be an infinite number of 9's, but you're still not quite 6 feet. We count and numbers are exact and finite, but in the real world there is no such thing, infinitely approaching that value is the best you can do.

It's like a ball being perfectly round; we know that if we look closely enough, there are always going to be parts that aren't. So if we measure something and it's 1 inch long, we always know that if we look and measure more closely, you can get more precise. So nothing is ever actually a concrete value.

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From my 15 yr old:


1. If you are traveling at light speed, can you see colors?

2. If you are traveling at light speed, could you see your reflection?

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This is subjective based on what type of science you're using. In the fiction of Star Wars and Star Trek, the answer to both questions is "YES."

The way we understand science and light speed today, the answer is "we can't physically travel at the speed of light, so we don't know."

However in physics, if there was a giant mirror you were traveling towards, your image would be blue shifted and if you were traveling away from it it would be red shifted (as it pertains to your question about colors, so yeah, you could see colors.) That has to do with the way we perceive the light's frequency/wave length with our eyes.

If an object (like a star) is moving away from us, it creates a longer wavelength and a more "red" color. If an object (like a star) is moving towards us, it creates a shorter wavelength and a more "blue" color.

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However in physics, if there was a giant mirror you were traveling towards, your image would be blue shifted and if you were traveling away from it it would be red shifted (as it pertains to your question about colors, so yeah, you could see colors.) That has to do with the way we perceive the light's frequency/wave length with our eyes.

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This would obviously only happen if the mirror isn't moving with you, and probably wouldn't be noticeable anyway for the same reason it doesn't occur when you are running toward a mirror at home. Unless the mirror is billions of miles away and there is sufficient space for it to be noticed. In which case you probably couldn't see the mirror anyway.