# Light speed travel

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If we shine a flash light, aren't we traveling at C relative to the beam of light shot out from the flash light? So just how does that time diliation equation stuff work?

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This is Special Relativity's equation for time dilation, where t' is the fraction of t that is dilated, v is velocity and c is the speed of light.

$t' = {t\over\sqrt{1-{(v^2/c^2)}}$

In this case, plugging numbers for $v$ higher than $c$ return an undefined solution.

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I know the equation, but just how exactly are you suppose to measure your speed?

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Your velocity can be deduced from Classical Mechanics. Also the speed of light $c$ in vacuum is constant; $c = 186,000 miles/sec$.

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If we shine a flash light, aren't we traveling at C relative to the beam of light shot out from the flash light?
Light always travels at the speed of light.

So just how does that time diliation equation stuff work?
Light always travels at the speed of light. Time dilation concerns changes in space-time, changes in space affecting time. An object cannot be subject to time dilation with respect to itself or with respect to light. There must be some other object in space-time with which to relate it.
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You measure your speed with respect to some other object. But typically you refer to yourself as being at rest, and measure other speeds relative to you. Your own clock never dilates in your own frame. It's always the other guy's clock.

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You can't measure your speed relative to light. You start at rest- light is moving towards you at 3x10^8m/s. You move forward at a velocity of 1.5x10^8m/s. You measure the velocity of the light coming at you to confirm your velocity... and find lights velocity to be unchanged. c never changes.

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This is Special Relativity's equation for time dilation' date=' where t' is the fraction of t that is dilated, v is velocity and c is the speed of light.

[math']t' = {t\over\sqrt{1-{(v^2/c^2)}}[/math]

In this case, plugging numbers for $v$ higher than $c$ return an undefined solution.

not undefined, imaginary. c would make time undefined.

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Okay, okay, suppose this situation:

You are in the absolute empty space, there is nothing but emptiness, suddenly, a hippo appears out of nowhere. How fast is it going? If you said zero, well, how do you know? You can't measure how fast he is going because there's nothing to measure it from. Similarily, if I shined a beam of light from where I am standing right now, I am traveling at exactly C relative to the light beam, so just how exactly does that equation work?

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photons have no rest frame.

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photons have no rest frame.

They're tired, they're out of breath...but they keep on going.

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Similarily, if I shined a beam of light from where I am standing right now, I am traveling at exactly C relative to the light beam, so just how exactly does that equation work?

The photons would observe you (if that's even possible) as being completely dialated in space and time. You would be 2-D and not feel the effects of time. In fact, this is how photons observe ALL matter. Since photons observe everything to be identical and unchanging, it's not really a reference frame with any use!

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The understanding is supposed to be that anything that travels faster than the speed of light will become infinitely mass which would in turn require infinite propulsion or what ever. (I'm not up on the terms)

But what if like 2 magnets repelling each other could there be a way to repel mass coming from the front of a spaceship so as to not accumulate the mass? (Hope I worded that right) Thereby allowing it to pass the Light Speed Barrier?

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But what if like 2 magnets repelling each other could there be a way to repel mass coming from the front of a spaceship so as to not accumulate the mass? (Hope I worded that right) Thereby allowing it to pass the Light Speed Barrier?

Almost certainly not.

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It's a physicis limitation, not an engineering one.

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But what if like 2 magnets repelling each other could there be a way to repel mass coming from the front of a spaceship so as to not accumulate the mass? (Hope I worded that right) Thereby allowing it to pass the Light Speed Barrier?
I believe you have the wrong notion here. The gain in mass is intrinsic, not extrinsic. That is, the object itself becomes more massive because of its speed, not because it acquires mass externally.
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Back to the original question, yes there is a time dialation, relitive to an observer on the light beam (of course this is not going to be he case as no observer may travel at or greater than c)

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