Even if we travel at the speed of light why would we experience that light passing us travels at its same speed?

Answer 1

Yes, all light travels at the same speed in a vacuum. The speed of light in other media, such as water or glass, is slower than it is in a vacuum. That is the basic principle that makes lenses and prisms work the way they do. In a given medium, however, all electromagnetic waves travel at the same speed.

Answer 2

Not really, but let's see what that means. What Einstein said that if your are moving at the speed of light, you will still "see" light as moving at the speed of light. Light moves at the speed of light in any frame of reference. If you try to "move along side" a beam of light, you'll still see it moving past at the speed of light. That's because times slows down for you in that accelerated frame of reference. No, you can't see the light except as you would see it if you were not moving at all.

If you travel at the speed of light relative to what? The deeper you look into the universe, the faster objects seem to be moving away. And the light is red-shifted. The answer for faster objects is no, but the light scattered from your hand from closer sources will look perfectly normal.

Answer 3

Einstein's theory of "special relativity" says that the speed of light is constant across all frames of reference.

The speed of light is about 186,000 miles per second, or 300,000 km per second.

Answer 4

One thing to clear up: we can never start out from earth and accelerate to the point where an earth observer will measure our speed as being equal to the speed of light. No physical object can be made to accelerate to light speed as observed from the object's original inertial frame of reference. We simply can't do it, considering what we call normal space, and given the limits of our current understanding.

But it's easier to think about things like one half the speed of light, even though that is just as impossible for us to personally attain. So we'll talk about half the speed of light in what follows.

It makes so much sense to say "If I'm traveling in a ship at one half the speed of light, then the light passing me that's coming from a beacon on earth should be passing me at one half the speed of light. After all, if I'm driving on a road parallel to a railroad, a train is traveling on it in my direction at 60 k/h, and I am driving at 20 k/h, then the train is traveling by me at 40 k/h, right? I subract my speed, 20 k/h, from the train's speed, 60 k/h, to get the train's speed relative to me."

Einstein's mind-blowing insight was that the speed of light in vacuum, c, is the same for all observers, no matter what inertial frame of reference they are in. But what about the guy in the ship, traveling at 1/2 c? How can he ever come up with 'c' as the speed of the light going past him, when he actually does a measurement?

Speed is distance traveled divided by the time it takes to travel that distance. If the guy in the ship can measure the speed of light over a given distance it travels, and he is coming up with the same speed an earth observer measures for the same light, then what would have to be true? Time itself is different for the guy in the ship. Time is passing differently for him. Time itself, and not just the way we measure or experience it. Time, for the guy in the ship, is moving more slowly relative to observers on earth. So if he looks at his watch, he'll notice that it is ticking more slowly? NO! He will experience time going by quite normally, because it is time itself that is passing more slowly. That includes the time that his body and mind are experiencing. So he carefully measures the speed of the passing light and performs all the measurements and calculations accurately. He comes up with 'c'. Time is NOT constant for all observers everywhere in the universe. Not long ago, people thought it was. Newton thought it was.

You might say that the above is just dreamed-up nonsense, except that this time effect has been verified a number of times in different ways. If we accelerate particles in an accelerator and then observe what happens to sub-atomic particles that we know only exist for a given length of time, we observe these particles existing for a longer time than normal, and the length of time they exist is in keeping with what Einstein's equations predict. Time is not constant. The speed of light in vacuum is, as far as we currently know. This idea that time is NOT a universal constant is very strange, and hard to grasp, mostly because we have no way of experiencing this time effect on an everyday practical level.

If one travels at the speed of light and measures the speed of the light traveling in the same direction, he measures that the speed of the light is constant because of infinite dialation of time and infinite contraction of the length scale with the help of which he measuers the speed of light. This is purely theoretical, of course, and cannot happen since time for the traveler would utterly stop; he would be unable to 'do' anything, and when he slows he would experience his travel at c as instantaneous. This is why the above is framed in the context of one half the speed of light.

Answer 5

First of all, it could never happen, since the Lorenz-Fitzgerald equations imply that mass is multiplied by a factor dependent on speed. So in order to accelerate any mass to lightspeed, it would require INFINITE energy and the mass would expand to infinity.

Also, time would stop.

If we assume that faster-than light-speed travel is possible... No effect would be noticeable on board, but the pilots would have a hard time avoiding obstacles (As Holly from Red dwarf explains: "...by the time we see something we've already passed through it!)

Answer 6

No. Light travels at different speeds through different types of matter.

(The speed of light in vacuum) divided by (the speed of light in one type of matter)

is the "refractive index" of that type of matter.

Answer 7

Judging only by the math of special relativity:

==> To me, everything appears fine. If I turn on my headlights, the light moves away from me

at the speed of light. But if I look at you, your mass and the thickness of your body in the direction

of motion are imaginary, and your clock is tallying imaginary time, backwards.

==> To you, everything appears fine. If you turn on your flashlight, the light moves away from you

at the speed of light. But if you look at me, my mass and the thickness of my body in the direction

of motion are imaginary, and my clock is tallying imaginary time, backwards.