Before you ask, no I know absolutely nothing about this stuff, but I know some people here are highly knowledgeable in the field, hell one of you works at CERN.

Say there is a supernova 1000 light years away, it knocks a rock at near light speed (say .99 or .98) away, 1000 years later the light from the explosion would reach us right? so wouldn't we be able to also see the rock from during the explosion, as well as the rock itself which would be close behind the light?

Probably easy to explain, possibly also a stupid question.

theres yahoo answers for this

I'm guessing a supernova wouldn't have anywhere near enough energy to get a rock up to 0.99c without completely vaporizing it first.

Well then say, a ship leaving a planet 1000 LY away and going .99 lightspeed.

I don't get what you're asking. The light would take 1000 years to reach us; the rock would take a little over 1010 years. So assuming a powerful telescope able to see a rock 1000 light years away, we could observe it approaching and it would take about 10 years (would be extremely blueshifted of course). Never would we be able to see the rock in two places at once, unless it traveled faster than light. See also: Picard Maneuver.

Yahoo Answers tends to get pretty crappy answers though...

not if you get lucky

Kyle is right. By the time the light from the MOVING rock reached is, the rock would be ten years away. If you really want to bend your brain look into the fact that the speed of light is ALWAYS constant, no matter your speed in any given direction.

Put simply, if you're on a uk motorway travelling at 70mph, and you overtake someone going at 60mph, you see them appearing to go at 10mph RELATIVE to you. Someone coming towards you at 70mph on the opposite side of the road has a relative speed to you of 140mph.

Light doesn't play by these rules: if you're travelling at 0.9c and see another beam of light coming at you, it appears to you not to be coming at you at 1.95c but at plain old c (where c is the speed of light in a vacuum).

I've known this for years and it still breaks my poor little brain.

Ask yourself this: exactly how would we see the rock? What actually happens when we see anything?

Assuming accelerating the rock that way is actually possible; We could potentially see the rock when the first wave of light hits us; it would appear as a shadow in the original wave front

i remember being told by Jim Al Khalili, our physics lecturer at Surrey and also sort of a physics celeb, that the speed of light used to be slower, back when the Universe was smaller (post big bang)

But hey, who cares anyway

if(getThingFlags(source) & 0x8){
  do her}
elseif(getThingFlags(source) & 0x4){
  do other babe}
else{
  do a dude}

The force of the light is equal to mass times the velocity.

What?

It's fyzziks Obi.

Everyone should read Eifelheim by Michael Flynn, it discusses variable light speed theories (as sort of a side quest).

e=mc^2

win

I think you'll find E = MC Hammer.