If you're rolling in an entirely stabilised room where you don't even notice you're travelling at all, the die would roll almost at the same speed as the spaceship or whatever, meaning it just acts normal within the room...

Wow, I think I just accidently explained to myself why nothing is faster than the speed of light (according to this theory, I haven't seen any evidence yet) locally and it could be faster beyond the "horizon".

bo_sox48: I also have to roll infinite dice to prove something to SYnapse, not sure if I can get a chunk of a black hole with one hand...

If you can move faster than the speed of light, you can contain and control its movements (and avoid being sucked in due to moving quicker than its escape velocity) by simply rotating around it.

Yes, but how do I bring it back to earth and tell the world about it? If I stop moving faster than the speed of light I can't contain it and the earth gets sucked in. Even if I keep moving faster than the speed of light, I can't talk to you guys since the sound gets sucked in... Or not? Can I contain it that well?

I think I'm just going to roll infinite dice at the speed of light, oh, and one die infinitely, to prove there's no difference... Maybe I'll bring a chunk of black hole the second time.

Several points from earlier in the thread:-

The Universe - as told to me more than 30 years ago (it's probably wrong/simplified, but at least I can get my head around this explanation):-

1) Imagine you're from Flatland. You only experience 2 dimensions - forward/backwards and left/right. Your universe appears to be flat to you. To an outside observer who can sense 3 dimensions (forward/backwards, left/right *and* up/down) your universe appears to be on the surface of a large balloon. You move forwards/backwards/left/right on this surface and, if you go far enough in one direction, you end up back where you started - you've circumnavigated your universe!

2) Now it turns out that your universe is inflating. Imagine putting some dots on the balloon with a felt tip pen then blowing it up. Although the dots aren't moving over the surface they are in fact getting further away from each other and the further away one dot is from another the faster they appear to be moving apart (the dots are galaxies).

3) The balloon is being inflated so fast that opposite sides are moving away from each other (in 3 dimensional space) at light speed. The distance to any object more than 18% (18% IIRC) of the way around the balloon will be increasing at more than light speed, so light from further away will never reach you (that's why we can't see more than 18% of our universe).

4)The balloon was very very tiny when the Big Bang occurred and it has inflated a *lot* since then, so the place where the Big Bang occurred - the centre of your universe - is in the centre of the balloon, which from your point of view is in a direction at right angles to both forward/backwards *and* left/right, so it's in a direction you can't point to. A direction you can't perceive or even imagine (unless you're using products from the unregulated pharmaceuticals market). However, if your maths is advanced enough you may be able to do calculations involving more than 2 dimensions and get some idea of the true shape of your universe.

5) Finally: We perceive a universe of 3 dimensions of space and one of time. Our universe is inflating and the centre of our universe is in a direction at 90 degrees to all the others, a direction we can't point (sometimes called "in/out").

A black hole has a finite circumference and an infinite radius.

Here in the UK, "maths" is short for "mathematics", not "mathematical".

Hope this helps.

Great post, STA -- but I would take issue with one thing. It is indeed helpful to imagine the surface of a balloon, what it would feel like if you lived in two dimensions there, and the way it expands.

However, it's best to avoid thinking of the universe sitting in any "larger" space, the way the 2-dimensional balloon sits in 3-dimensional space. In particular, one should avoid thinking of directions "outside spacetime." Not only can we not imagine those, but they are not geometrically meaningful even at the mathematical level. They would be if one modelled the universe (spacetime) as sitting inside a larger-dimensional space, but in general relativity, you don't do this.

In particular, I would not think of the big bang as a point off in some higher dimension, nor is meaningful (geometrically or otherwise) to talk of the distance "across the gap."

So it's impossible to give mathematically meaningful content to the idea that the center of the universe lies off in "some other direction." (At least in a non-arbitrary way). Rather, just say that, like the surface of the balloon, it HAS no center. This is also true of the surface of the earth. Of course, Texas is the center of that, but every analogy has to fail somewhere.

But a 4th physical dimension is very plausible. If we werr two dimensional creatures who knew nothing of the third physical dimension would you be arguing this same "it is mathematically irrelevant" line?

Re: the final paragraph

Methinks you're confusing the centre of the surface if the Earth with a black hole

Draug,
"
But a 4th physical dimension is very plausible."


A 4th physical dimension is not only plausible, it is absolutely central to general relativity (GR). Notice I used the term "spacetime" throughout my post. Spacetime is four dimensions. What I'm saying is that it does not make geometric sense (in the context of GR) to talk of a fifth dimension "outside" spacetime. The theory of general relativity assumes a four-dimensional spacetime that includes everything, so any embedding of spacetime in higher dimensions will be arbitrary (there would be many ways of doing it that would lead to inequivilent statements about the added dimensions, so no physically or geometrically meaningful statements about spacetime would result).

" If we werr two dimensional creatures who knew nothing of the third physical dimension would you be arguing this same "it is mathematically irrelevant" line?"

One can do geometry with any number of dimensions, and one can certainly imagine our universe as being embedded in a five-dimensional or higher space. However, we're discussing specifically what General Relativity says about the geometry of our universe. It says nothing about any fifth dimension, and in particular, there is no non-arbitrary way, in the context of GR alone, to make talk of such a fifth dimension well-defined or meaningful.

So the two dimensional being has a 4th spacetime dimension. My logic still applies. I just wasn't including.time as a.physical dimension.

Actually, I believe I subtly misinterpreted STA's analogy; he was indeed viewing the surface of the balloon as three-dimensional, not four-dimensional (and hence, it's able to expand). In that sense, one could view the big bang as the center of the balloon, but notice the following issues still:

i) The universe we're seeing is not the surface of the balloon, but some past (smaller) version of the balloon, because light travels with finite speed;
ii) It's still not super helpful to think of points off the balloon (including the center) as points of spacetime, but it is true that one can use mathematics to discuss fourth-dimensional "places" such as the big bang. Confusingly, though, when we look at distant stars, we *are* looking at things "toward" the past, due to point 1.

This page includes a helpful discussion of the balloon analogy.

http://math.ucr.edu/home/baez/physics/Relativity/GR/centre.html

Sorry for the initial misinterpretation of what your analogy was saying, STA.

@Draug,

" So the two dimensional being has a 4th spacetime dimension. My logic still applies. I just wasn't including.time as a.physical dimension. "

I'm not sure what you're arguing anymore. If you're saying that there could be five dimensions (four spatial plus one time), I already addressed that in my previous post. Short version: yes, there could, but GR has nothing meaningful to say about it, and in particular, there is no way to calculate such things as whether our universe is curved inside the five-dimensional space, whether if you left on a "perpendicular line" into the fifth dimension, you would hit our universe again, or so on.

Those things are not determined by GR.

@semck83: No worries. I've been told by others that the "Balloon Model" is an oversimplification, but at least I can understand it. ;-)

There's also this - "The central idea is that the visible, four-dimensional universe is restricted to a brane inside a higher-dimensional space". http://en.wikipedia.org/wiki/Brane_cosmology

SpeakerToAliens,

Correct. But Brane cosmology is not general relativity. It's a fascinating but extremely speculative extension with virtually no experimental support. So I think it's worthwhile to carefully separate the two and what they say. (It's why I was careful to say "in GR" or similar throughout my posts).