Doughnut-Shaped Universe Back In the Race

SpaceAdmiral writes "The once-popular idea that the universe could be small and finite is making a comeback. Many researchers thought that a 'wraparound' universe would mean that distant objects would be seen multiple times in the sky, but new research suggests that a '3-torus' (or 'doughnut universe'), as well as other shapes, could fit our actual observations, particularly the WMAP data."

Re:Pay for the article?

[SpaceAdmiral]

Ha! When I submitted it it was available for free. They must have changed it when they noticed all the /. traffic.

today's Zippy the Pinhead about donuts...

[Will the Chill]

Apparently we'd all be much happier of we had our minimum of 17.3 glazed per day!

http://www.sfgate.com/cgi-bin/article.cgi?file=/comics/Zippy_the_Pinhead_Color.dtl

-WtC

The Problem With Curvature

[Anonymous Coward]

The problem with curvature is that it imples continuity (infinite divisibility), which leads to an infinite regress. Therefore curvature is an unacceptable concept in physics. That continuity should continue to be used by physicists as a fait accompli is sad commentary on the status and credibility of the physics establishment. It's time to abandon the Star-Trek physics and move on.

Re:That's silly.

[spun]

going off one side would bring you back on the other side reflected. There would be some pretty weird consequences if our universe were like that.

Wasn't there at least one short sci fi story about this? Someone gets rotated in the fourth dimension and comes back with their heart on the other side and severe gastrointestinal problems because all their molecules have different chirality.

Re:Questions.

[esampson]

...Or is the idea of an edge just not valid? ...

It isn't valid because a 3-torus is a 4 dimensional shape. To be more accurate it is valid, but not in a way you can conceive of.

Think of it in these terms; you are a two dimensional creature. Your world is defined solely by X and Y coordinates and is of a finite size. Take two opposite sides and bring them together and now your world is a tube. The only edges you can perceive are the ends of the tube. Take the two ends of the tube and bring them together. You are now living on a standard torus (not a 3-torus). As far as you are concerned there is no "edge" to the torus. Roam as much as you want to but you will never reach an edge. The only way for you to experience an "edge" would be if you stepped up one dimension and became three dimensional.

A 3-torus is a similar construct but instead of being a two dimensional world with the X edges and the Y edges brought together it is a three dimensional world in which the X edges, Y edges, and Z edges have all been brought together. From your three dimensional perspective there is no "edge" and the only way to perceive one is to step up a dimension and become a four dimensional entity.

Re:The Problem With Curvature

[Anonymous Coward]

Look at the faces of a geodesic dome. Each face is discrete, but the structure as a whole is curved for all practical purposes.

No, it is not curved for all practical purposes, especially not for the purpose of postulating a doughnut universe.

Who are these modders? Why is this nonsense modded insightful? It's crap. If something is discrete, it is not continuous by definition. Since true curvature requires continuity and continuity leads to an infinite regress, all this business about doughnut universes and spacetime curvature is pure hogwash.

Giant Telescopes...

[jaminJay]

I have some faint recollection from the early 90's that, during WW I or II (or both?), their was some research into the building of a telescope powerful enough that, when pointed straight up, would look right out the 'end' of the universe and in the other in order to spy directly on the exact opposite side of the planet. Now, to search for any links to back that strange memory up...