What would happen?

[Nevermore]

What would happen if you were in a car going ftl, and turned on the headlights?

[Klaynos]

Well as you're breaking one of the fundemental laws of physics, anything you want...

 

If you wehre travelling close to light speed then everything would appear as normal within your rest frame...

[RyanJ]

What would happen if you were in a car going ftl, and turned on the headlights?

 

The question is pretty much invalid as you can't go faster then light. My guess would be that you would overtake your light rays though I don't have any proof for this...

 

Cheers,

 

Ryan Jones

[Cap'n Refsmmat]

This has been answered nearly two years ago:

http://www.scienceforums.net/forums/showthread.php?t=4451

[5614]

My guess would be that you would overtake your light rays though I don't have any proof for this...

This is incorrect as you have not taken into account relativistic effects which say that the light will always travel at c (the speed of light) relative to you (or technically 'any inertial observer'). ie. you will see the light heading away from you at the speed of light.

[bascule]

If you were going c you couldn't "turn your lights on" because for you time would cease to pass. But provided you could the light would continue to go c away from you. Saying that you're 'going ftl' basically removes whatever ability relativity has to answer the question.

[ecoli]

well, if you can get passed the fact that you have mass and so it's impossible to reach the speed of light, let alone exceed it, perhaps travel backwards in time?

[RyanJ]

This is incorrect as you have not taken into account relativistic effects which say that the light will always travel at c (the speed of light) relative to you (or technically 'any inertial observer'). ie. you will see the light heading away from you at the speed of light.

 

So I did (was and am very tired.. no coffee ) not that it really matters because its not possible anyway...

 

Cheers,

 

Ryan Jones

[Shwarzchild]

You would be shorter in length, increase in mass, and slow down (from an observers view), but to yourself, you'd feel normal.

[Daecon]

By the time you see something, you'd already have crashed into it.

 

"Watch out for that pedestrian... oh, never mind."

[5614]

By the time you see something, you'd already have crashed into it.

Not if your reaction times were quick enough

[RyanJ]

Not if your reaction times were quick enough

 

I think it would redefine the term quick reaction... and I would also like to see somewone react that fast

 

Cheers,

 

Ryan Jones

[padren]

Well, here is a modification of that, which I wouldn't doubt was asked before but I didn't see it in the other thread so:

 

If you were driving at half the speed of light to planet Cruton, which is stationary, and you flashed your headlights as you passed a lamp post that just flicked on for a moment at the same time, what would happen with the light?

 

1) I assume, the light from both your head lights and the lamp would reach Cruton at the same time.

 

2) Someone at the lamp post would see both lights due to arrive at the planet twice as fast as you would, and if you were one light year from the planet, then it would take one year for the light and two for you.

 

3) From your reference, both flashes of light are putting distance between you and them at the rate of c. This distance you see, is identical to the distance seen by the person at the lamp post between them and the light, and they see the distance between you and the light as a smaller distance than you see. Additionally, you see the light as going to arrive sooner at the planet, since its traveling at light speed relative to your half light speed velocity.

 

 

 

I don't understand how to resolve the contradictions in 2/3 and I think its probably a common hiccup in trying to understand relatively. How is this resolved?

[mimefan599]

Relativity tells us that it would travel away from you at the speed of light, but because you are going faster than light, no science can help you.

[5614]

padren:

 

1) Yes.

 

2) They would not observe you as travelling at half the speed of light. Due to a bunch of relativistic effects (length contraction and time dilation) they would observe you as going at a different speed to what you think you are going at. It would take one light year for the light to reach Cruton.

 

3) Both flashes move from you at c.

The distance you see if different from what the stationary observer (at the light post) sees.

As it is moving away from you at c you know it will reach the planet before you.

 

If you can get a copy of The Elegant Universe by Brian Greene I suggest reading, well, start off with Part II chapters 2 and 3 (starting at pages 23 & 53 respectively). They'll explain the basics, like exactly what you are asking, of special relativity in simple and easy to relate to terms using nice everyday examples.

[JustStuit]

If you were going c you couldn't "turn your lights on" because for you time would cease to pass. But provided you could the light would continue to go c away from you. Saying that you're 'going ftl' basically removes whatever ability relativity has to answer the question.

Wouldn't the time only stop relative to the outside observer? It would still feel the same to you woudn't it?

[5614]

Good point, assuming you are at a constant velocity then it is always the other persons clock which is slow, yours is always normal. (If one is accelerating then you can tell whos clock is slow.) Either way no clock ever stops, that could only happen if you travelled at c and if that happened then relativity is wrong so no point in discussing what relativity says!

 

I would say that you never think that your clock is slow because it's all relative, it's the observer who thinks you are slow. But when you are accelerating you can tell it's your clock which is slow, but that is only by comparison to another clock. If there were no other clock then you wouldn't know yours is slow.

[padren]

padren:

 

1) Yes.

 

2) They would not observe you as travelling at half the speed of light. Due to a bunch of relativistic effects (length contraction and time dilation) they would observe you as going at a different speed to what you think you are going at. It would take one light year for the light to reach Cruton.

 

3) Both flashes move from you at c.

The distance you see if different from what the stationary observer (at the light post) sees.

As it is moving away from you at c you know it will reach the planet before you.

 

If you can get a copy of The Elegant Universe by Brian Greene I suggest reading' date=' well, start off with Part II chapters 2 and 3 (starting at pages 23 & 53 respectively). They'll explain the basics, like exactly what you are asking, of special relativity in simple and easy to relate to terms using nice everyday examples.[/quote']

 

I've wanted to read that for a while, I'll definately pick it up

 

Wouldn't the time only stop relative to the outside observer? It would still feel the same to you woudn't it?

 

But would you have enough time to turn on the lights before the universe kerploded?