The Universe May Be Shaped Like a Doughnut

NewbieV writes "The NY Times (reg., etc.) is reporting that data from the Wilkinson Microwave Anisotropy Probe may suggest that the universe might be shaped like a doughnut or a cylinder: it might be possible, like in the old video game Spacewar, to drift off one 'side' of the Universe and reappear on the other."

Comments

Actually it is very good analogy

[efuseekay]

-Begin Jargon-

A torus (dougnut) is topologically equivalent to a square with sides identified (like the Space War).

-End Jargon-

Discontinuous or stuff like that is not really important concept. Whether you are "magically" transported or not when you reached the end is just a matter of choosing the right coordinates.

Also, curved universes do not enter the argument. Curvature is a statement on Geometry of the Universe, while being a Dougnut is a Topological Statement.Both of completely independent of each other. A Toroidal Universe can be flat (like, hey , a square with sides identified!). A curved universe can be a plain sphere.

Re:Actually Stephen Hawking predicted this already

[sheddd]

Yep; great book; I loved one of his analogies (referring to a finite universe with no boundaries) that went something like this:

Imagine you're a 2-D dude wandering the earth (which is really a 3-D globe like you'd find in a classroom). You can walk and walk and never hit a wall but there's a finite amount of 2-D space. Now imagine you're a 3-D dude... This is where my feeble brain says 'help!'.

The analogy would seem to back up the article; whatever direction you take if you walk long enough you end up where you started.

They are "sound waves"

[efuseekay]

They are sound waves in the looses sense of the word.In the sense that you have stuff (the photon-baryon fluid) and a wave is travelling through it (like sound waves travelling through air).

Gravity waves exist of course, but we have no way of detecting them yet since their signature is much much much harder to detect.

Re:Black hole from the inside.

[Guppy06]

First, let me just start with the qualfier "I Am Not A Physicst."

"Think a "taffy sheet", or a "stem" of the "morning glory" stretching like a stream of honey."

Except it can only get stretched so far until you run into the brick wall that is quantum mechanics. Space-time isn't infinitely smooth, and the finer a view of it you get, the less uniform it is.

This is why physics gets all weird at the infinitessimal center of a black hole, because "infinitessimal" shouldn't be possible.

"space is being stretched at least as fast as it moves (or maybe even faster), so it never makes it out of the hole."

Except that relativity tells us that light is always moving 3E8 m/s faster than that. Even an observer in that space that's getting stretched to the breaking point would measure light as going 3E8 m/s away from him.

"What does a black hole look like from the INSIDE? What would one see from the viewpoint of the matter that was already there when the event horizon formed?"

As you pass through the event horizon, the entire sky would shrink until all you saw was a single point of light in the direction directly away from the center. All light that passes through the event horizon gets pulled towards the center, and unless its journey from its source to the center of the black hole is intercepted by your head, you'd never see it. It would get deflected towards the center of the black hole before it had a chance to reach your retinae.

"An expanding universe, starting from a very small but finite volume and expanding indefinitely, containing a large-but-finite amount of matter, which was initially compressed into an EXTREMELY dense lump"

You're forgetting about the space being taken up by you. As the space you occupy gets stretched out, so do you. And you can only get stretched out so far before you're torn apart (the old quantum mechanics bit again). That finite mass being smeared out into a seemingly infinite volume is you.

"In other words, something like the current universe."

Our universe looks uniform in any direction we look. The view inside a black hole would be a whole lot of nothing in the sky except for that point directly away from the center of the black hole.

I'm pretty sure we'd know if we were inside one.