The Universe May Be Shaped Like a Doughnut 512
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."
So I guess that makes God.. (Score:5, Funny)
Re:So I guess that makes God.. (Score:4, Funny)
ObSimpsons (Score:3, Funny)
I Will Not Hang Donuts On My Person
I Will Not Hang Donuts On My Person
I Will Not Hang
Where is the coffee ? (Score:3, Insightful)
Re:Where is the coffee ? (Score:3, Informative)
Re:So I guess that makes God.. (Score:5, Funny)
Licence and registration please.
Now just how fast do you think you were going there?
Look, sir, the law says you just can't go faster than c. I'll let you off with a warning this time, but don't let it happen again.
homer knew it (Score:2, Funny)
(ps. - third?)
Actually Stephen Hawking predicted this already... (Score:5, Informative)
Re:Actually Stephen Hawking predicted this already (Score:5, Informative)
Re:Actually Stephen Hawking predicted this already (Score:3, Funny)
While someone was trying to explain to a Ford executive that "Taurus" was a different word, and only applied to to an abstract portion of space, not the universe, and the word "Torus" refered to a donut shaped object, said executive got a blank look in his eye, muttered the words, "Hmmmmmmmmmmm, Donut," and wandered off.
KFG
Re:Actually Stephen Hawking predicted this already (Score:3, Insightful)
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.
Re:Actually Stephen Hawking predicted this already (Score:2, Informative)
IIRC, Hawking was talking about the shape of spacetime in that section. And in fact, the results from WMAP indicate that the universe will expand forever, contradicting that particular model of spacetime.
When these people say that the universe may be shaped like a donut or like a cylinder, they are supposing that spacetime can be expressed as the product of a space part and a time part, and that the space part is shaped like a donut (or whatever).
In this model the space part would be the 3-torus T^3, the time part would be an open interval I, and spacetime would be IxT^3. Good luck on visualising that!
Re:Actually Stephen Hawking predicted this already (Score:3, Insightful)
oh no (Score:2, Funny)
Mmmmm... (Score:2, Funny)
Coming up... (Score:5, Funny)
Re:Coming up... (Score:5, Funny)
I think you mean: "The Krispy Kreme Endowment for Excellence in Kosmology."
Silly students (Score:5, Funny)
I guess they forgot to carry the 1.
Re:Silly students (Score:5, Informative)
Is it possible??? (Score:2)
If you travel through the universe far enough you will get back to where you started.
I guess the ancient ones were wise to this when they said:
No matter where you go, there you are!
Re:Silly students (Score:2)
Re:Silly students (Score:2)
Re:Silly students (Score:3, Insightful)
Okay... (Score:2, Insightful)
How about the Star Trek: TNG references? (Score:5, Funny)
LOL (Score:2)
Old hat (Score:4, Funny)
Obligatory free link (Score:3, Informative)
More images from probe homepage [nasa.gov]
Mmmmm.... (Score:4, Funny)
Observations (Score:5, Interesting)
So, would this mean that if we can't see one point from two directions now, that if we suddenly can, we've reached the halfway point of the life of the universe? Would we lose the redshift in favour of a green shift?
Re:Observations (Score:3, Informative)
Re:Observations (Score:3, Informative)
Re:Observations (Score:2)
-Zipwow
Re:Observations (Score:2)
In the three versions of cosmic doom, the universe can end up colapsing, expanding quickly at first and then slowing down, or expanding faster and faster until it basically falls apart. In the first case Einstein's Equations (General relativity) lead to a concave universe, the second leads to a flat universe, and the last leads to a convex universe. The only one of these forms that is really easy to picture is the flat universe since it is pretty much what we live in. The concavity or convexity of the universe has mainly to do with how to find the shortest distance between two points. Basically math becomes a pain in the a** because the derivative becomes location dependant.
Re:Observations (Score:2)
Re:Observations (Score:5, Informative)
Secondly, the opposite of a red-shift is a blue-shift. The complementary nature of red and green is a property of human eyes, not of the light itself. Red light is lower in energy; blue light is higher. Things rushing away from us as space expands would leave light from distant objects moving more slowly relative to us if not for special relativistic effects. With the effects, the energy of the light is reduced. However, you're right... when an object is approaching you, light from it is blue-shifted, and that would be what we should expect when the universe starts collapsing.
Re:Observations (Score:2)
I think you mean Blueshift.
Re:Observations (Score:3, Funny)
Greenshift: when something is standing still at high relativistic velocity.
Re:Observations (Score:2)
Re:Observations (Score:2)
Re:Observations (Score:5, Funny)
SETI: "We found a signal! Yipeee! Wait, Is that a Toyota commercial? Damn! It is just us."
Re: (Score:2, Funny)
Shaped like a donut. (Score:2, Funny)
I've actually often wondered this. (Score:2)
mmm....donuts... (Score:2, Interesting)
Let the jokes begin... (Score:2)
Other sources for this story? (Score:2)
The article made it seem like this idea is far from proven. If it IS so wacky then why such attention paid to it?
I can see it now.. (Score:2, Funny)
dimensions (Score:4, Interesting)
Re:dimensions (Score:3, Funny)
What is outside of the donut? (Score:3, Interesting)
Re:What is outside of the donut? (Score:5, Informative)
Re:What is outside of the donut? (Score:3, Informative)
If the universe began as a point object (planck-scale sized) and was extremely uniform to begin with, then this uniformity would be reflected in its shape later in life.
OTOH, some of the newer ideas about scalar fields and self-replicating universes would give a contorted, infinitely complex shape on a large scale (imbalances would magnify themselves).
The simplest answer is "because it makes the math easier" (cue mathematician/physicist/engineer jokes...).
Re:What is outside of the donut? (Score:5, Informative)
As the donut (or sphere or what-have-you) represents space itself, the concept of something "outside" it doesn't really work. Only relationships between different parts of the universe are defined. Treating the universe as the surface of some object is just a trick to make it easier to visualize (otherwise it would just be a set of functions defining relationships between points).
Some of the inflationary models put the universe we can interact with within a larger space, but that just gives us disjoint parts of one larger universe. Much like the event horizon of a black hole, the interface between them would represent a boundary across which interaction and information flow is restricted, and different space/time coordinate systems would be used inside and outside them. (The inflationary bubble looks like an infinite space from the inside and an expanding bubble from the outside; all points on the boundary look like they're at the beginning of time from the inside.)
So, no Voyager-esque bright expanding shell or external vantage point in the simplest scenario, and something a bit different from what you're probably envisioning in the various inflationary models that posit bubbles within larger spaces.
that's interesting (Score:4, Funny)
Re:that's interesting (Score:2, Funny)
Beat's "Saddam is a Pretzel" any day...
Re:that's interesting (Score:3, Funny)
Of course, the trick would be figuring out how to go "that-a-way."
So does this mean.... (Score:5, Funny)
Shape of the Universe (Score:2)
Re: (Score:3, Informative)
Oh, GOD NO!!!! (Score:2)
As I was telling Weight-Watchers (Score:2)
Reality is adjustable... (Score:2)
One person thinks its a donut, then he convince's person two etc, etc, until the universe is what we think it is. Isnt this why science keeps coming with new improved idea's ?
its all in our mind...happy dreaming
Re:Reality is adjustable... (Score:2)
Space War Analogy is bad (Score:2, Interesting)
In certain types curved universe the behavior would be quite different. If you start out going in one direction and continue going long enough, you may end up where you started. There would be nothing discontinuous about this motion though. A "straight" path in a curved universe isn't really what we would think of as straight. As you go along your "straight" path the stars that appear to be ahead of you would impercibly change as time wore on. Eventually you could end up back where you started, but considering the likely size of the Universe, it might take you longer than the age of the Universe to do it.
Anyway, curved space is weird to think about, but not as weird as Space War.
Actually it is very good analogy (Score:5, Insightful)
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:Space War Analogy is bad (Score:2)
To put it another way, if you fixed a camera outside the universe (just pretend like there can be an outside of the universe), and watched the ship, it would have to warp around the other side from the proper camera angle.
=Brian
* - Um, well, I'm guessing the analogy's fine. I didn't really read the article. But presuming the parent post is correct aside from what I'm mentioning, then my post is also correct.
Re:Space War Analogy is bad (Score:2)
If the universe does work in the way proposed in the article, and you had a ship capable of traveling many _many_ times the speed of light, observers who stayed behind on earth would see the same behavior (ignoring relativity for the moment of course.) "Oh look, it disapeared off in some direction to galactic north. Oh look, it 'magically' reapeared to the galactic south!"
Actually it's not that bad (Score:3, Insightful)
Actually it's a fine analogy. The problem is the display screen, not the Space War universe. If you were to map a torus onto a flat display, it would seem that you're magically transported. In reality, the discontinuity is the display, not the universe. (In similar games, I'm not sure about this one in particular, you can be "right on the border" and see your ship halfway on either edge. Perhaps Space War lacks this "sophistication".)
Anyway, this is like saying "that is not a picture of something 3D, because the picture is 2D". Just because it's 2D doesn't mean it can't represent something 3D.
Besides, if you want to be really pedantic, the real problem would be the dimensions of the toroid universe in question... it wouldn't really map exactly to a rectangular screen unless you changed a few "universal constants". ;-) (Not that I have a problem with this. ;-))
Dr. Seuss? (Score:2, Interesting)
Who would have thought....
My reaction (Score:2)
Somewhere in the code running the universe... (Score:5, Funny)
if (particle->position.x < LEFT_LIMIT)
particle->position.x += RIGHT_LIMIT - LEFT_LIMIT;
else if (particle->position.x >= RIGHT_LIMIT)
particle->position.x -= RIGHT_LIMIT - LEFT_LIMIT;
Re:Somewhere in the code running the universe... (Score:5, Funny)
Re:Somewhere in the code running the universe... (Score:4, Funny)
Not Sound Waves...Gravity Waves (Score:3, Informative)
They are "sound waves" (Score:5, Insightful)
Gravity waves exist of course, but we have no way of detecting them yet since their signature is much much much harder to detect.
Dr. Tegmark's original paper on the web (Score:5, Interesting)
I've admired Dr. Tegmark's home page [upenn.edu] since he was a grad student, not so much for the design skills (ha!) but as an exemplar of mixing serious and non-serious publications for other colleauges and onlookers to enjoy, explore, and learn from. Tegmark gets the web. As for the science, some of it I can actually understand.
I would also commend to the curious Slashdot reader a couple items I found facinating from the 'non-serious' section of his website:
a very cool diagram of "Relationships between various basic mathematical structures" [upenn.edu] from his Theory of Everything [upenn.edu] paper
and another paper addressing the question: Why does the universe have 3 spatial and 1 time dimension? [upenn.edu]
--LP
So... (Score:2)
I'm curious how we'd test that, given that the distances involved would mean that we'd see events so long ago that we wouldn't recognize them. It would explain how the universe would seem infinite, though...
The Universe May Be Shaped Like a Doughnut (Score:2)
Doh!
ObSouthPark (Score:2)
In related news... (Score:4, Funny)
In the Flintstone's Universe (Score:3, Funny)
Homer (Score:2)
Interesting... (Score:3, Funny)
A Thought... (Score:2, Interesting)
Now, if I threw a baseball in a straight line from point x,y,z in the universe, at some point, that baseball would again pass through one of the planes of its starting location? (I'm neglecting all interferences, including gravity)
3-d space curving
cosmic variance (Score:2)
But... it's not really that much lower than in the concordence model, and is more likely just a result of cosmic variance - you can only measure 2 quadrupoles over the entire sky. The quadrupole power in our observable universe happens to be slightly below average - if you did the same experiment at many random points in the universe (esp. if you include points outside our horizon), you'd get a distribution of values whose mean was the concordence model value, with our observation slightly on the low side of the distribution.
[TMB]
Infinite universe is philosophically unattractive (Score:3, Funny)
"Somewhere there are two guys having this same conversation," Dr. Starkman said in a telephone interview, "except that one of them has a purple phone."
Whoa!
Monty Python (Score:2, Funny)
Someone had to say it.
Re:Monty Python (Score:3, Funny)
Black hole from the inside. (Score:5, Interesting)
It's easy to see why enough gravity keeps light ORBITING the gravity from spiraling out and away. But this also explains why light going STRAIGHT AWAY from the center of the hole never gets out - space is being stretched at least as fast as it moves (or maybe even faster), so it never makes it out of the hole.
Well, this got me thinking: "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?"
And the answer seemed to be: "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 - perhaps a quark fluid or denser."
In other words, something like the current universe. Perhaps with the moment of the formation of the event horizon corresponding to the end of the big-bang model's "inflationary period", but eliminating the need for a faster-than-light inflationary period.
Cosmic background becomes the layer of matter and energy just below the event horizon, which is just getting here now. Cosmic background structure represents the matter distribution at that level at that time - a fossil of the orbital dynamics of the accretion cloud. (I don't think you get to see an "inside view" of the infalling half of the Hawking radiation.)
You can go in any direction at up to the speed of light and never reach "the edge", which is (from your viewpoint) receeding at lightspeed.
Not being a professional physicist, at this point I haven't attempted any mathematical models or resolutions with any of the current cosmological models. So I have no idea if I'm just spinning a yarn or if this can be pounded int shape for testing against the real universe. But it might be interesting to try some time.
(The concept of gravity indefinitely stretching the coordinate system also leads to another possibility: Can gravity be modeled as masses constantly "sucking up" the coordinate system, which stretches between them meanwhile?)
Re:Black hole from the inside. (Score:3, Insightful)
"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.
Curvature vs Topology (Score:3, Informative)
You have to remember that the curvature of a torus embeded in 'flat' 3 space is purely an artifact of that embeding and not intrinsic in the topology of the torus. More specifically, there exist mappings from the embeded (intrinsicly curved) surface of the three dimensionally embeded torus to topologically identicle spaces that have everywhere flat intrinsic curvature.
As a thought experiment, consider a cube where the faces are portals to their oposites. Internally, this construct has the topology of a hypertorus but an everywhere flat topology.
For some nice diagrams and comentary that explain curvature (of the important, intrinisic kind) rather well, take a look at this [caltech.edu], just skip over any of the math thats beyond your abilities, it's not really needed to understand the concepts.
Re:The last thing Homer needs to learn... (Score:5, Informative)
Re:The last thing Homer needs to learn... (Score:3, Funny)
Mmmm... (Score:3, Funny)
Re:The WMAP site says otherwise (Score:2)
Nothing. Reality ends there. There is no outside.
Re:The WMAP site says otherwise (Score:3, Interesting)
Re:The shape of a doughnut? (Score:3, Interesting)
Re:The shape of a doughnut? (Score:3, Informative)
imagine travelling across the SURFACE of the torus.
whoops!
Re:doughnut? (Score:3, Insightful)
You're violating the fifth law of thermodonutdynamics here
(97G: No officer will false teeth shall attempt oral sex in a zero gravity environment.)