## Question about the speed of light.

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### Question about the speed of light.

So i was asked an interesting question a while ago and it got me to thinking.

If you're driving in a car at night traveling at the speed of light, and you turn on your headlights, what will you see?

For the sake of answering the question I'm assuming this was actually possible, and the road is infinitly long.

What would you see? Would the light not go anywhere(relative to you) because it(and you) is already going the speed of light? Or, can light go...faster than the speed of light...

I mean if your in an airplane and you fire a gun(bad idea,btw) forward, the bullet will go whatever speed the plane is going plus the speed that the bullet leaves the gun at, right? Does the same concept apply to light? Does any of that make any sense?

On a semi-related note...In Star Trek, when they are traveling at warp speed and they look backward, they shouldn't be able to see the stars receeding behind them because the light from the stars would not be able to catch up with them. Yeah, I'm bored today.
Last edited by joeman3429 on Tue Aug 30, 2005 8:56 pm, edited 1 time in total.
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joeman3429

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I'm not totally sure but I'm pretty sure that the light can't go faster than the speed of light so you would see like umm...I really don't know. Just black maybe.
taymo2020

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You would see the light move ahead of you at the speed of light - that is, it would work exactly the same as if you were not moving at all. An outside observer would see you moving as fast the the light from your headlights.

All observers perceive light as always traveling at the speed of light. This has been verified by experiment. As a consequence there are some weird things that happen with time, space, and mass.
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MXP

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Is there a math equation or something that proves why nothing can go faster then c?
taymo2020

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Anything < Speed of Light

Simple as that... Just kidding

t i l e x

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taymo2020 wrote:Is there a math equation or something that proves why nothing can go faster then c?

Things can go faster than the speed of light unless you're talking specifically about the speed of light in a vacuum (ie, the one denoted by the constant c). However, there is a theoretical particle called a Tachyon which travels faster than the speed of light in a vacuum but this particle does not have a real rest mass.

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MXP

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Although matter can't go faster than the speed of light, how about we bend space so it appears we're travelling faster than the speed of light?

Warp Drive
Alcubierre drive

Dante Shamest
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taymo2020 wrote:Is there a math equation or something that proves why nothing can go faster then c?

It's actually relatively obvious that nothing can travel faster than the speed of light. Think about it. What is light? An Electromagnetic wave. And what is an electromagnetic wave..? Energy in it's purest form...And how does one gain velocity? By adding kinetic energy. If you already have energy in it's purest form...how could you possibly add energy to that? You couldn't. Therefore, you couldn't increase your velocity beyond c.
Darawk

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Purest form?

If things were really that simple then there wouldnt be any discussion on tachyons. Also, gamma rays have more energy than radio waves while both are electromagnetic waves.
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MXP

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Colin Jeanne wrote:Purest form?

Light, like all other EM waves, is energy. It has no mass, and it has the ability to do work..

Coline Jeanne wrote:If things were really that simple then there wouldnt be any discussion on tachyons. Also, gamma rays have more energy than radio waves while both are electromagnetic waves.

There are many discussions on things like the VSL(Varying Speed of Light) theory, which do not break any of the principles that I stated, but do account for things travelling faster than the speed of light. The basic concept of VSL is that the speed of light in a vacuum is dependent on the general energy content of the region of the universe that you're in. This would allow for loopholes in what I said to exist. Loopholes that, while my reasoning would remain correct, would allow particles to travel faster than light.

EDIT: After reading the description of Tachyon's on wikipedia, I see no reason why what I said and the existence of such partilces cannot co-exist. In my post, though I don't state it, i'm referring to all "normal" particles. Particles that have been studied and are understood. If particles such as Tachyons do in fact exist, then the fundamental facts upon which my reasoning was based will have to be in some way incorrect. My reasoning based on said facts however, is still valid...it's the underlying premises that could fail. So, if we go ahead and deny current physics, which is certainly a valid and probably smart thing to do, because all systems die off with time..and our current ideas are no different, then yes my explanation is incorrect. However, in the context of Einsteinian physics as it relates to the question "why can nothing travel faster than c?", my reasoning and premises are both perfectly valid.

Tachyon's are to Einsteinian physics what the curvature of space-time was to Newtonian physics.
Darawk

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You're initial statement still doesnt make much sense. You can add energy to light and you can also take energy away from it. The result still travels at the speed of light but has a different wavelength.
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MXP

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Colin Jeanne wrote:You're initial statement still doesnt make much sense. You can add energy to light and you can also take energy away from it. The result still travels at the speed of light but has a different wavelength.

You cannot add energy to light...you can make it more concentrated and intense, but each photon has the same amount of energy.
Darawk

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Darawk wrote:each photon has the same amount of energy.

Photons

The energy, U, of a photon is given by

U = hf

where f is the frequency of the photon and h is Plank's constant.
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MXP

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"but each photon has the same amount of energy"
Then what's the difference between sunshine, the light from a normal lightbulb and gamma rays?

Safari

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Gamma rays have a higher frequency. Higher frequency light has more energy because the photons wobble faster. The speed however is decided by the medium, as for ANY wave. The speed of a wave is characteristic of a specific medium. The frequency is set by us, here by the type of vibrations and electron interactions which cause light to have a certain frequency. The wavelength is automatically adjusted so as to satisfy c=fl,where l is wavelength.

I hate light. :/ None of the theories seem satisfying to me. Some fellow throws in a tachyon and another puts in a string and all weird things happen. It's so annoying especially because they have no solid evidence for anything.

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Jetru

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