light speed

[jakesi]

If you had a vehicle that can travel at the speed of light,what happens when you put your headlights on?

[incitatus]

If you were travelling AT light speed you could not turn the lights on. You would be caught between moments, as time dilation would be stretched to its assymptote, i.e. no time would be passing for you. However if you had an infinite amount of infinite time to wait while you turned on the lights then you would observe nothing out of the ordinary: the time dilation effect takes care of the anomaly so it would appear to you that nothing was wrong.

[MistyLady]

Ummm well u did ask kjring!

[incitatus]

ok, in simpler terms, to you it would appear absolutely normal. Relative to your timeframe the light would still recede at lightspeed. relative to a stationary observer the light would not recede at all.

[SuperBunny]

What if you were in reverse?

[jakesi]

So it's like spitting while your cycling forwards on a bike.

[incitatus]

No and yes. Thats a newtonian reference frame problem, and is complicated because when the spit leaaves your mouth it is slowed or accelerated (depending on wether you gob forwards or backwards) by the wind of your passage. The point with relativity is that all reference frames are valid. to you at light speed everything seems normal, light recedes at the correct rate and all in the garden is lovely. You would be a bit lonely though, as you would effectively be in your own little universe. Time for you would have slowed down to zero (moving clocks run slow, remember) so to the rest of the universe you would have effectively ceased to exist. You would not notice this though. The direction of motion is irrelevant to the reference frame. It is only relevant if photons from outside are being considered (the falling lift problem) and at lightspeed the effective curvature of these would be assymptotic so they are irrelevant. so there.