What happens if...

[SilentP]

...an object moving at the speed of light (if it were possible), or faster, fires a laser ahead of itself?

Does the speed of the laser beam get altered due to the speed of it's emitter, in spite of a 'fixed' speed of light?

Does the craft 'catch' up with the laser?

Does any object in the path of the laser get whalloped by a doppler shift laser beam?

Any other implications?

This is just a random question that's popped into my head, and I don't have the grasp of physics in this area to have any idea what the theoratical behaviours of light and FTL objects would be. I'm quite likely in possession of huge misconceptions about light that makes it not worth thinking about it.

 

[Robert Maxwell]

Nothing can travel at the speed of light except light, so that part of the question doesn't mean anything.

Thanks to relativity, though, if you are traveling at almost the speed of light, and you fire a laser, the laser beam will travel at the speed of light, and you will measure its speed as being consistent with the speed of light. Just one of those quirks of relativity.

 

[SilentP]

Nothing can travel at the speed of light except light, so that part of the question doesn't mean anything.

Fair enough.

Thanks to relativity, though, if you are traveling at almost the speed of light, and you fire a laser, the laser beam will travel at the speed of light, and you will measure its speed as being consistent with the speed of light. Just one of those quirks of relativity.

To clarify what I'm saying, just so I'm making sure I understand what you're answer is, when I say the laser beam is travelling at the speed of light, I mean speed of light relative to a neutral, stationary observor, rather than the beam moving at the speed of light relative to the emitter.

So if we're both meaning the same thing, you're saying that if an emitter is moving, at say, .99c and it fires a laser, which travels at 1c, the laser beam is only moving at .01c relative to the emitter?

 

[iguana_tonante]

No, the laser beam would be measured as moving at 1c relative to all observers, including the emitter. According to general relativity, the speed of light is constant independently of the speed and position of the observer, and has the same value for all observers.

 

[SilentP]

So (if using previous example) the laser beam is moving away from the emitter at 1c (and thusly a lay person might reckon that the laser beam is moving at 1.99c, due to the emitter's own speed of .99c), yet is seen as moving at 1c by a stationary observor?

Sorry if this is taking a while for me to click

 

[Deckerd]

So (if using previous example) the laser beam is moving away from the emitter at 1c (and thusly a lay person might reckon that the laser beam is moving at 1.99c, due to the emitter's own speed of .99c), yet is seen as moving at 1c by a stationary observor?

Sorry if this is taking a while for me to click

You would be more worried about your weight at that speed.

 

[iguana_tonante]

So (if using previous example) the laser beam is moving away from the emitter at 1c (and thusly a lay person might reckon that the laser beam is moving at 1.99c, due to the emitter's own speed of .99c), yet is seen as moving at 1c by a stationary observor?

Yup.

Sorry if this is taking a while for me to click

No worries. Relativity ain't easy for nobody.

 

[Robert Maxwell]

So (if using previous example) the laser beam is moving away from the emitter at 1c (and thusly a lay person might reckon that the laser beam is moving at 1.99c, due to the emitter's own speed of .99c), yet is seen as moving at 1c by a stationary observor?

Sorry if this is taking a while for me to click

This is correct. Relativity is weird. Something moving at the speed of light always appears to be moving at the speed of light, regardless of the speed of the observer.

Say you had two trains approaching each other at the speed of light. You might think each would observe the other's velocity as being twice the speed of light--but no, they would just see that the other train is moving toward them at c.

Again: general relativity is weird.

 

[Lindley]

Remember, speed is measured in distance/time. The distance traveled by the laser beam must be the same for all observers; therefore, observers at different velocities must experience time differently.

That's more or less where you get time dilation at relativistic speeds from.

 

[SilentP]

I get it now ...well I get this aspect of it at least

Cheers

 

[Christopher]

The basic idea of relativity is that the laws of physics are constant for every observer -- there's no preferred reference frame that's absolutely the "right" one. And the speed of light in a vacuum, c, is a factor in a lot of physics equations. So the only way everyone can experience the same laws of physics is if they all measure the same value for c, no matter how fast they're moving. So their perceptions of distance and time change to cancel out the effects their motion would otherwise have on their measure of the speed of light.