Brits seek missing WIMPs of universe

[Az]

No point to. I don't think that one's brain is built for that.

The best way to do is to try to project from the lower dimensions we can understand to the upper ones. like we did here, sort of.

[Edan]

Originally posted by Rogan Josh
Well, the extra dimension would only exist to us if we could perceive it somehow. So for example, if a particle were able to propagate in the extra dimension and then interact with one of our experiments. But, from current experiments, there is no evidence of anything being able to leave our 4 dimensions to come back and tell us about it. Therefore, there is no evidence for the extra dimension.

Fair enough, I suppose it's valid to consider a dimension we cannot access as not existing (to us), though I, myself, wouldn't, if we know that the dimension exists - inaccessable as it is.

And we can perceive it mathematically.

(There's no evidence that the future exists either - after all, who's gone into the future and come back to tell us about it? Or the past, either, come to think about it - how do we know we're not living for an instantanious moment, and that all our memories are really just false? )

[Edan]

Double post.

[Sirotnikov]

Edan, my friend had this exact theory about past/future, and I read about this theory in some book as well.

[Sava]

Does that somehow absolve me from my wrong-doings?

[Ben Kenobi]

The answer (as I understand it - I am not a cosmologist) is that the expansion is only occuring at large scales. So you are not getting any bigger. It is only the measure of distances at large scales (like Earth to the Orion nebula) which are expanding. To make a bad analogy, imagine an explosion which send lumps of rock flying in all directions - the distance between the rocks grows but the rocks themselves don't.

Here's a better analogy, from Asimov I think.

What happens when you bake cookies with raisons?

You put yeast inside the dough to help the dough rise. The universe is the cookie, while the dough is space. The raisons are the planets, stars, and matter in the universe. This is how the universe can expand without increasing the size of the raisons, in the same way that a cookie will rise when heated in the oven.

Another analogy often used is attaching coins to a balloon. As you blow up the balloon, the coins will move farther apart from each other, though still retaining their size. In this analogy, the balloon is the universe, the coins are the planets, and stars. The air in the balloon is space.

In this sense, the expansion of the universe only affects the space between the objects in the universe, not the objects themselves.

I hope that helps.

[The diplomat]

I realize that the universe is probably similar to the surface of a sphere, ie, finite but no edge. But wouldn't this also present the same issue? Wouldn't be possible given enough time, that light goes all the way around the universe and back to where it started, and therefore, we could be seeing duplicates of closer galaxies?

[Dauphin]

A few scientist have claimed that galaxies we see in one portion of the sky are identical to the ones we see in other portions. This would be extremely difficult to verify though.

This would be possible if the universe is like a non-expanding sphere. However, if you travel at a constant speed along the surface of a (sufficiently quick) expanding sphere you will never get back to where you started and so we would not be seeing duplicates.