mass, time and speed

[harper05]

(Hypothetical of coarse) Lets assume you could somehow slow your rate of speed so that you were not moving at all relative to everything else in the universe. Would mass become infinitely small, and time move by infinitely fast?

 

[vogon13]

 

[kg]

(Hypothetical of coarse) Lets assume you could somehow slow your rate of speed so that you were not moving at all relative to everything else in the universe. Would mass become infinitely small, and time move by infinitely fast?

There is something that is traveling the same speed relative to everything, it does have zero mass and time is meaningless to it. It's light but it isn't traveling at a rate of zero.

 

[Saiph]

Afraid you can't be stationary relative to everything. Why? Take two objects that are moving relative to eachother. How do you position yourself so that you aren't moving with respect to either of them? You can pick one, or the other. Not both.

But time would still pass, and it would still have mass.

 

[harper05]

Afraid you can't be stationary relative to everything. Why? Take two objects that are moving relative to eachother. How do you position yourself so that you aren't moving with respect to either of them? You can pick one, or the other. Not both.

But time would still pass, and it would still have mass.

What if you were standing still in the center of the universe, (assuming of coarse you could somehow with out being crushed by gravity or melted by heat, or whatever.) Would you not be stationary with everything moving away from you? and would time move by faster according to relativity? and relative mass would be smaller?

 

[SpeedFreek]

We don't think the universe has a centre, a unique origin point that everything moves away from. We think the universe expands. With expansion, everything moves away from everything else such that, wherever you are, it looks like everything at the large scales is moving away from you. If you track backwards through time, it looks like everything gets closer and closer until everything we can see was in one place - here! We think the view would be the same, wherever you were in the universe. The big-bang happened here, just like it happened everywhere else, but everywhere else was here at the time, and here was everywhere else!

 

[Giulio]

Time is the cause, everything else - the effect.

 

[dangineer]

SpeedFreek has it right. Space itself is expanding. Objects in space are not necessarily moving away from eachother, the space between them is growing bigger. Everything in the universe is really just flying about randomly, but on the whole the distance between everything is getting larger (i.e it takes light more time to get from one object to another). So if you placed yourself at any arbitrary point in the universe, everything would still seem to be getting further away from you no matter which way you looked. The same goes for any observer looking at you. This is also due to the fact that, as far as we know, the universe is expanding uniformly.

 

[ramparts]

Dangineer is right (and since he said speedfreak was right, that makes speedfreak right, too ). Hopefully an analogy will help, because it's very hard at first to think of the universe expanding and not imagine it moving away from a central point.

When we talk about curved spaces in physics, it's very helpful to take away one of the spatial dimensions and consider a universe with two dimensions (a sheet), since we can much more easily visualize curvature on a surface like that. A good analogue in this case is a balloon - imagine putting a bunch of dots on a balloon. Call them galaxies Now start blowing up the balloon. The "galaxies" all move away from each other at a certain speed - and if you pick a galaxy to be "stationary", it looks like everything is moving away from it at a speed proportional to its distance. But of course, good luck finding a center on the surface of the balloon. There is no such thing.

This analogy is imperfect so you shouldn't take it any farther than I have, otherwise it breaks down (and you'll take home some very funny conclusions about the universe!). But I always found that very conceptually helpful.