01-05-2003 02:03									#61
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a variety of superstrings theory speaks of that, IIRC.
( another chinese letter for me, superstrings. )

	01-05-2003 02:06									#62
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quote: Originally posted by Edan Are you considering time as one of those dimensions?

Yes. Up/down, left/right, forward/back, future/past.

quote: String Theory requires something like 7 or 11 dimensions, etc And then theres all that other fun higher order physics stuff...

String theory is very much speculation - nothing has been confirmed by experiment, or is likely to be in my lifetime.

quote: However, even ignoring time, there would have to be four extra dimensions. Consider the balloon example. That has 3 dimensions for a 2D balloon person, without time being added in.

No, the 2D baloon person only has two (space) dimensions since he isn't allowed to move off the balloon. Add one time, gives 3. We live with one extra dimension, making 4.

	01-05-2003 02:08									#63
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[emphasis mine]

quote: Originally posted by Rogan Josh No, the 2D baloon person only has two (space) dimensions since he isn't allowed to move off the balloon. Add one time, gives 3. We live with one extra dimension, making 4.

Yes, but the balloon is in three dimensions.

	01-05-2003 02:09									#64
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quote: Originally posted by Azazel a variety of superstrings theory speaks of that, IIRC.

Heterotic String Theory is in 10 dimensions. M-theory is in 11.

I had dinner with Ed Witten once (the God of String Theory). Nice bloke, if a little odd.

	01-05-2003 02:09									#65
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It's not supid if it does interact, just weakly, I just read it as it doesn't interact.

7D

Makes sense to me: Bizzaro World!!! each with 3 dimensions, +time.

	01-05-2003 02:10									#66
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RJ: I'd rather not touch it, at all. 11 dimensions? 10? wow.

I'll just stick to chemistry.

	01-05-2003 02:11									#67
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Edan: but the balloon is 3 dimensional (inc time). It doesn't need to be embedded in an extra dimension.

	01-05-2003 02:14									#68
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quote: Originally posted by Rogan Josh Edan: but the balloon is 3 dimensional (inc time). It doesn't need to be embedded in an extra dimension.

That makes no sense (and is completely opposite to what I learned in my Astronomy classes... admittedly, it has been a while...)

If you take a snapshot of the balloon universe, frozen in time, it will still exist in three dimensions- height, length and depth (at least from our perspective, if not the balloonians).

	01-05-2003 02:16									#69
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I think I understand what he means. How would a 2d space that also would behave the same way (if you go one way, you'll come out from the other side ) form that way? It would be presented as a 3d sphere. and to present it's growth, it will be a baloon, that would grow. This also brings in a 'time' dimesion, so it's already 4d.

Now, let's take that basic 2d space we had, and turn it into our own "3d" space we had. we should have 5 dimensions.

	01-05-2003 02:19									#70
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quote: Originally posted by Azazel Now, let's take that basic 2d space we had, and turn it into our own "3d" space we had. we should have 5 dimensions.

Right. There's simply a dimension that we have no access to.

	01-05-2003 02:20									#71
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like the people we draw on the paper.

	01-05-2003 02:21									#72
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balloonians?

You have to look at it from the perspective of the Balloonians ( ). Since they can never travel into the extra dimension that we see, it may as well not exist to them. In fact, it does not exist to them. Just like only 4 dimensions exist for us.

	01-05-2003 02:25									#73
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quote: balloonians?

Seriously, though, it does exist to us, if infact, we can percieve it by observing nature. (that 4d-sphere universe thing )

	01-05-2003 02:28									#74
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When I first visualised a hypercube it really gave me a funny feeling in my mind. You know that feeling when you do the magic eyes and you finally see your first 3-D image. That's the closest analogy to revelation I can think of.

Anyway see if you can get your head around the2-D representation of a 4-D cube.

Attachment: comparison.gif
This has been downloaded 48 time(s).

	01-05-2003 02:30									#75
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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.

Actually, extra dimensions are a hot topic at the moment because they may provide an alternative to supersymmetry (and the hierarchy problem). So there are lots of papers being published about extra dimensions.

	01-05-2003 02:31									#76
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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.

	01-05-2003 03:14									#77
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quote: 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? )

	01-05-2003 03:16									#78
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Double post.

	01-05-2003 03:22									#79
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Edan, my friend had this exact theory about past/future, and I read about this theory in some book as well.

	01-05-2003 03:25									#80
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Does that somehow absolve me from my wrong-doings?

	01-05-2003 07:07									#81
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quote: 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.

	01-05-2003 08:36									#82
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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?

	01-05-2003 15:19									#83
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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.