ok for this question assume that you have an infinite sized void and that you are a point in space (aka no volume/mass)
lets say you are traveling at the speed of light

if you are in this void is motion possible? because there would be nothing reletive to measure your relative motion so no matter how fast you were moving, it would seem to be like not moving at all, but would u actually be moving? (remeber being a point in space means that no laws of physics apply to you)

im trying to use this senerio to understand what motion would be like out side the physics of our universe and why the speed of light seems to be the highest speed allowed by physics

If you're saying you cannot judge your motion based on your surroundings how can you travel at the speed of light? It implies motion because its a unit of measure for distance per unit time. You would have to be in motion to travel at a speed.

Well, not quite, using light speed really changes things -- if you travel at light speed, and some how retain your form of matter, then space shrinks and time stops. However, if you were to say that the normal laws of physics applied in this void, then yes you'd technically be moving, you would have no way of knowing unless a second observer were there to confirm it.

According to a quantum mechanics take on it, if you are without an observer, you may or may not exist and thus you may or may not be moving.

what do you mean laws of Physics dont apply?

I was under the impression that Newtonian physics only TRULY apply in a void...

anyways... BovineDesi is right, as usual. But I do like his take on the quantum mechanics approach.

Well said.

Before it looks like I'm posting just to be a jacka$$, please note that I'm really just trying to clarify some concepts. I really enjoy thought experiments, but it's important to show the sense they make and also the sense that they don't make I'm posting to consider the "dangers" of really any thought experiment. However, without thought experiments, science would suffer for lack of any propelling imagination.

1. It's impossible for any of us to be a point in space and remain human, and a point in space doesn't have a perspective.
2. You can't be in a void; given that it has no volume. Of course, you're talking about a point in space, so your counterpoint is already taken
3. The laws of physics apply equally every"where" (I say it this way in case of special exceptions). The trouble with voids is that we're getting into some funky "territory" if we want to even call it territory.
4. An odd point here: the speed of light remains the same in empty space, regardless of any relative motion of its source.
5. If the force acting on an object is 0, then it's motion is not changed; so what force is acting on the point of space "before" (if that makes any sense to say) it enters the void? If there's no force, then there's no change, so you continue to travel at the speed of light. But then how does a point in space travel at light speed into a void?
6. There's no friction in a void, right? So that would mean that the force that was acting on the point in space as it "enters" a void is unaffected by any previously unconsidered force. Yar?
7. I don't have time to start thinking of these two ideas, but they probably need to come into play: first, inertial coordinates; second, (inertial) frames of reference. This requires a bit of thinking about Newton's first two Laws of Motion. It needs to be constantly remembered that F = MA. If we don't have force, mass or acceleration ... and what's odd is that we have force on the way "in" the void if we assume it's already travelling at the speed of light, or, to the contrary, some force acting upon it in the void from where we begin [this gets to my point about clarifying the inertial schtuff btw] .. then we don't have a lot of ways to describe any motion that could happen "inside" the void. Of course, if we have force, then we have mass and acceleration, which is pretty weird if we're talking about a point of space "travelling" at light speed in a void. Because then we need to ask where it originates. It's as if the thought experiment starts halfway through what we need to know
8. What kind of system are we talking about? Is this a void puzzle or a puzzle about a void and what happened on the way to the void? Relationships are everything.
9. We can't forget about the Laws of Conservation. Energy, momentum, and angular momentum are "immutable" in the sense that they aren't created or destroyed. Since we know that energy is equivalent to mass multiplied by the velocity of light squared, we're going to need to solve for any variable conditions relative to the mass implied by the speed of light at which the point of light is travelling. Not to repeat it forever, but how we managed to arrive at talking about a point in space travelling at the speed of light probably needs to be figured out before we can go back to understanding the conditions through which we can establish anything like relative motion, inert conditions (to cover coordinates and frames of reference). We seem to have energy, mass and acceleration inexplicably caught "in" a void, and this is the whole problem for me. This implies force or at least force on the way into the problem. Nevermind what needs to be said for space and whether we have any observer, units and methods of observation etc.. And yet those things are important, too, if we can really get that far; of course, I could have just at the probelm from that side of things, too. And then I'd start from what BovineDesi said. Trouble is, that would be redundant and I wanted to give the idea a fair trial. Well, a trial, anyway.

Dunno if that helps but it sure takes the fun out of it
I am just goofing around. It's an interesting question. If there's any way you can be or have a point in space in a void travelling at the speed of light, the answer is in the question. Yes, you would have motion, but that's assuming you're there to observe it against the effects of this motion in the avoid or somehow outside it; otherwise the observational criteria come smashing down on the whole thought experiment. So the answer to the thought experiment is "YES" relative to the question taken seriously and "NO" taken to any sensible way of approaching a solution as far as I can tell

Edit: just gonna say sorry for any typos ofc.

This post was edited by RewtheBrave on May 8 2009 09:22am

Fixed your edit >.<;

Rew your reasoning is absolutely right, however I'm not sure people understand the semantics of physics jargon. (i.e. When he's talking about a void, he probably just means space with absolutely nothing else in it)

Though I'm not sure what the whole purpose of assuming we're a point in space instead of an actual mass was...I guess I missed that when I posted, however, if you assume yourself just to be a point in space -- then imo this question gets a lot more technical and complicated even at the most basic level, actually I don't even know how to start answering that question.

yes, sorry my use of language is horrible, i will try to rewrite this to make it more specific.