[HN Gopher] Scientists wonder if shape of the universe is like a...
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Scientists wonder if shape of the universe is like a doughnut
Author : pseudolus
Score : 41 points
Date : 2024-06-08 17:25 UTC (5 hours ago)
(HTM) web link (www.theguardian.com)
(TXT) w3m dump (www.theguardian.com)
| Keegs wrote:
| This is my favorite possibility, that space has a "finite volume
| but no edges: if you travel farther than the scale of the
| universe, you end up back where you started." It's comforting on
| an existential level to imagine the amount of stuff around us is
| finite.
| fredski42 wrote:
| So how would you explain the fact the galaxies are moving away
| from each other with an ever increasing speed in this kind of
| shape?
|
| Edit: To answer it myself: https://www.quora.com/What-are-the-
| implications-of-the-three...
|
| " The torus moves into itself and comes out at the other end,
| where the locations of 'coming out' could be what is driving
| what we observe as the expansion of the universe."
| wongarsu wrote:
| The donut is getting bigger (but is still finite)
| notjoemama wrote:
| It's also possible particles increase causing expansion,
| this is just theoretical still. But if that's true, then it
| is finite but perpetually increasing. Potentially
| infinitely.
| tengbretson wrote:
| Bigger relative to what?
| mr_mitm wrote:
| Relative to what it was before. It has an intrinsic size.
| Think of it in terms of matter density if you find it
| more comfortable. The density simply goes down over time;
| distandes between galaxies increase.
| tengbretson wrote:
| Density has the same issue. Density can only be measured
| against a baseline established outside of the medium
| being measured.
| nabla9 wrote:
| Intrinsic expansion. Distances between objects in space
| grow.
|
| That's what metric expansion of the universe is.
| Distances grow at speeds that are proportional to their
| distance from the observer.
| mr_mitm wrote:
| This would also be the case on a hypersphere, which would also
| satisfy the cosmological principle. A torus is not isotropic.
| marcosdumay wrote:
| Any closed curve does this. And if that's your only
| information, the simplest encoding for it is a sphere, not a
| doughnut.
| dpflan wrote:
| Related and for those interested: _The Shape of Space_ [1] by
| Mathematician Jeffrey R. Weeks [2,3].
|
| """
|
| The Shape of Space...[t]his lighthearted textbook covers the
| basic geometry and topology of two- and three-dimensional spaces
| --stretching students' minds as they learn to visualize new
| possibilities for the shape of our universe.
|
| Written by a master expositor, leading researcher in the field,
| and MacArthur Fellow, its informal exposition and engaging
| exercises appeal to an exceptionally broad audience, from liberal
| arts students to math undergraduate and graduate students looking
| for a clear intuitive understanding to supplement more formal
| texts, and even to laypeople seeking an entertaining self-study
| book to expand their understanding of space.
|
| """
|
| 1. https://www.routledge.com/The-Shape-of-
| Space/Weeks/p/book/97...
|
| 2. https://en.wikipedia.org/wiki/Jeffrey_Weeks_(mathematician)
|
| 3. https://www.geometrygames.org/
| sseagull wrote:
| Slightly OT, but from the article...
|
| > It sounds like Homer Simpson's fever dream
|
| A donut-shaped universe was explicitly mentioned in The Simpsons,
| in an episode with Stephen Hawking
|
| https://youtube.com/watch?v=Mje7frMYzcY
| NikkiA wrote:
| I've been hearing people posit this theory since I was a child
| in the 1970s, it's not a new theory by any measure.
| newzisforsukas wrote:
| Universe as a doughnut (2003)
|
| https://www.nytimes.com/2003/03/11/science/universe-as-dough...
|
| https://archive.ph/PYEmB
| radley wrote:
| I find the idea of a fixed-size universe to be myopic. I
| personally align with the Quilted Multiverse Theory (albeit more
| fractal, than quilt):
|
| * Matter in the universe only has a finite number of ways it can
| rearrange itself
|
| * If the universe is infinite, patterns will eventually repeat
|
| * If the universe is infinite, there would be an infinite number
| of parallel universes within space
|
| Thus, if you could travel far enough, you will perceptually
| return to where you started. And since perception governs
| presence, does it matter that you're technically somewhere else?
| You're essentially in the same place.
|
| I also love this theory, because it means every possible form
| that can exist, at any point in its development, is taking place
| somewhere, all at the same time.
|
| https://www.worldatlas.com/space/the-quilted-multiverse-theo...
| notjoemama wrote:
| Well, except Boltzman brains kind of suggests none of that is
| true.
| Aardwolf wrote:
| > The Boltzmann brain thought experiment suggests that it
| might be more likely for a single brain to spontaneously form
| in space, complete with a memory of having existed in our
| universe, rather than for the entire universe to come about
| in the manner cosmologists think it actually did.
|
| I don't think that's true though, I think it's more unlikely
| for a brain to form spontaneously, than a simple (simple
| compared to the brain) system of rules that then causes
| galaxies, planets and life with brains to form through
| interacting processes
| patmorgan23 wrote:
| Yeah, things like Conway's game of Life illustrate that
| simple rules can create complex interactions
| grondilu wrote:
| For what it's worth that sounds a lot like what Max Tegmark
| classifies as the "level 1" multiverse.
|
| https://space.mit.edu/home/tegmark/crazy.html
| abeppu wrote:
| ... are there actually only a finite number of ways matter can
| rearrange itself? Or are configuration spaces "actually"
| described by real (or complex) numbers (whether for things like
| distances or angles, or for things like the probability that a
| prepared quantum state will collapse to a given outcome)? If
| real (or complex) numbers are "real", then doesn't the fact
| that configuration states for some perceptually available
| region are described by R^(huge number) mean that merely
| traveling around in R^3 space, one _shouldn't_ expect to see
| repeats?
| ifdefdebug wrote:
| > patterns will eventually repeat
|
| I know that theory, but isn't this a non sequitur?
|
| let's image an infinite universe with only two possible
| patterns. isn't it perfectly conceivable that pattern 1 occurs
| only once and pattern 2 infinitely often?
|
| edit: ok, "patterns will eventually repeat" is obviously true,
| what I meant is that "ALL patterns will eventually repeat" does
| not necessarily follow - which is implicit in the parallel
| universes thought experiment.
| le-mark wrote:
| Consider a video game that consists of a single screen and when
| the player character walks off one side it appears on the other
| opposite side (same for top and bottom). The playing field in
| this case is a torus. Now consider the case of two connected
| tori; at any point the player exits they could find themselves on
| the other screen. Now consider a "foam" of many tori. Has this
| game been made? Or anything that explores this idea of walking
| around connected tori?
| kevindamm wrote:
| Yeah, I think it was called "Pitfall!".
| digitcatphd wrote:
| The best thing about being a theoretical scientist is nobody can
| refute your claims.
| qujine wrote:
| Please, I beg you, let's say it's the shape of a bagel. Ideally
| an everything bagel.
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