h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

Coo-er. That's a bit weird.

Gnomon: "The universe is really peculiar - if you go far enough, you will end up coming back from the other side, although you haven't turned around. This is something similar to the way if you fly to the west you will eventually come back home from the east, but it is weirder."

Isaac Asimov explains this theory very well. I also love his description of hyperspace.



The surface of the earth is two-dimensional, yes? You can travel on two axes (north-south or east-west) (and on combinations of these two cardinal axes), but the entire surface is curved through a third dimension, so that the ends meet up. There are no ends. It's a sphere.

Now, imagine beings restricted to two dimensions. Ignore the fact that the circulatory system wouldn't work. As the move in their 2d world, how could they understand circumnavigation?

We, restricted as we are to three dimensions, cannot understand that the universe meets up at the ends, curved as it is through a fourth dimension. (Not time. That's another dimension, if it's a dimension at all.)



And now for hyperspace. Take an A4 sheet of paper. Put two dots on it, one at each end. Put a snail on one dot, and tell it* to go to the other. Long way. Now fold the paper, bringing the two dots on top of each other. Short way. If the snail momentarily leaves the paper it can reenter it in a different spot.

Can you twist the fabric of the universe, and then momentarily leave it and reenter it in a different location? Travelling through hyperspace is a theoretical possibility, but tricky.

*They're hermaphrodites.



By the way, this theory says nothing about the topography of the universe. Does it have a hole in the middle?

TRiG.

I hate to do this, but I have to leave one of these:



I'm fascinated by this but far too sideways at the moment to pay attention.

As I said somewhere else, the 3-d closed universe can be explained without resorting to the fourth dimension. THere's no hole in the middle because there is nothing that is not in the universe.

Where was it that we discussed this ad nauseam?

Oh yes, it was at F54784?thread=3398320.

Just read that.

By 'hole in the middle' I meant doughnut, not cavity in a hollow football.

TRiG.

Oh, I suppose the universe could be the equivalent of a 4-dimensional torus! Didn't Terry Pratchett say that the world was being carried on the back of a giant torus? Or was that something different?

Ahem...

http://www.pr.mq.edu.au/events/index.asp?ItemID=607

Worm holes that lead through the fourth dimension is one thing. But where are the rabbit holes that get you to Wonderland?

We're in Wonderland, Xan.

That explains quantum mechanics. Doubt you can be a quantum physicisist without believeing five impossible things before breakfast.

Which breakfast is, of course, eaten at Milliways.

Powers of Ten - documentary made in 70s
http://www.youtube.com/watch?v=T4_QHgqZ4eg

powers of 10 - the Simpsons version
http://www.youtube.com/watch?v=yCfDRvDWid0

exactly!!!!!!!!!!!!!!!!

I was thinking of what Gnomon said about spacetime being able to move faster than light, and so expansion could happen faster than that. Doesn´t current physical theories indicate that gravity waves can´t move faster than the speed of light? If space time can move faster than C, wouldn´t that mean gravity waves should be able to as well?