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Our Universe Might Be a Giant Three-Dimensional Donut (livescience.com) 182

Posted by BeauHD from the multiply-connected dept.
fahrbot-bot shares a report from Live Science: Imagine a universe where you could point a spaceship in one direction and eventually return to where you started. If our universe were a finite donut, then such movements would be possible and physicists could potentially measure its size. "We could say: Now we know the size of the universe," astrophysicist Thomas Buchert, of the University of Lyon, Astrophysical Research Center in France, told Live Science in an email.

Examining light from the very early universe, Buchert and a team of astrophysicists have deduced that our cosmos may be multiply connected, meaning that space is closed in on itself in all three dimensions like a three-dimensional donut. Such a universe would be finite, and according to their results, our entire cosmos might only be about three to four times larger than the limits of the observable universe, about 45 billion light-years away.
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Our Universe Might Be a Giant Three-Dimensional Donut More

Our Universe Might Be a Giant Three-Dimensional Donut

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  • Is there an actual paper associated with this? (Score:5, Insightful)

    by Digital Avatar ( 752673 ) on Tuesday July 20, 2021 @02:09AM (#61599935) Journal

    Seriously, where's the paper, because this writeup reads like fluff. Show me the data.

    • Re:Is there an actual paper associated with this? (Score:5, Informative)

      by sg_oneill ( 159032 ) on Tuesday July 20, 2021 @04:16AM (#61600163)

      Right here I *think* is whats being referenced;-

      https://arxiv.org/abs/2106.132... [arxiv.org]

      That would be the pre-print. Unsure if tis been submtted to a more tightly moderated journal, but as best as I can work out Ralf Aurich and Thomas Buchert are legit physicists and this isn't a crank paper.

      But like a lot of these more far out claims, I wouldn't put too much weight on it. Until more research to vaidate the idea happens, treat it as "nice idea, possibly not true".

      • Re: (Score:2)

        by HiThere ( 15173 )

        Based on just the summary a hypersphere would be a better model than a donut...at least if you think a donut is a torus. (A doughnut would have a different path length around it in almost every single direction. Most paths would curve through the hole in the center. )

        And at best calling the universe a donut (doughnut?) doesn't handle all four dimensions. You need to explain which two dimensions you are mapping together (e.g. two spacial dimensions).

    • "And that, my liege, is how we know the Earth to be banana-shaped."
      "Tell me again how sheep's bladders may be used to prevent earthquakes."

    • Re: (Score:2)

      by Revek ( 133289 )
      I remember a story like this. I don't remember the title of it, since its was nearly forty years ago. It was your standard SF short story written in the mid 60's. Since we are in this 'donut' we have no way to tell if we are so I think the answer is moot. I mean why a donut it could be a bagel or biscuit?

  • I mean, a donut (hyper-donut (3D curved through a 4D space I guess), is a weird topology. It has axis for example. If our universe is a closed topology a hypersphere would be the most expected topology.

    • Re: (Score:2)

      by Sique ( 173459 )
      It still complies with General Relativity, as Kurt Goedel proved already in the 1930ies, when he was in Princeton together with Albert Einstein.

    • Indeed. All our observations are consistent with the universe being isotropic and homogeneous.

      A hypersphere explains that better than a donut.

      Cosmological principle [wikipedia.org]

    • I'm guessing they mean a 3D torus, which doesn't need to live in any higher-dimensional space, and which doesn't have anything like an axis or anisotropy.

      Think of Pac-Man and how leaving the screen on one side lands you at the opposite side. The Pac-Man playing arena is topologically the same as the surface of a donut, and it's called a 2D torus. Note that you don't need anything 3-dimensional to describe the dynamics of Pac-Man.

      If you imagine now a cube with the same feature of leaving one side bringing yo

      • This is a great analogy. I'm confused though why that's a 3D torus. When I imagine what the Pac-Man screen is doing - basically wrapping the 2D flat world around on itself to make a shell, but correct me if I have that wrong - wouldn't the 3D version of that become something like a 4D sphere? I guess the basic question is what's the difference between a 3D torus and 4D sphere?

        I'm sure that question reflects my lack of understanding, so please correct me if I'm envisioning this incorrectly.

        • Re: (Score:3)

          by jbengt ( 874751 )
          It's not a sphere. In a sphere, "great circles" cannot be parallel. In a torus, they can be.
          To put it another way, if you cut and flatten a sphere, then going east & west circles around the sphere without intersecting, but all north & south paths get you to a single point before going around; that doesn't happen in a torus.
          If you make a "north & south" with parallels like the the east & west latitudes, those don't all cross all of the east-west latitudes; in a torus they do.
          Since it's t

    • Re: (Score:2)

      by wed128 ( 722152 )

      )

      There. You dropped that.

  • So if I follow this correctly.. (Score:5, Funny)

    by Rick Schumann ( 4662797 ) on Tuesday July 20, 2021 @02:34AM (#61599977) Journal
    ..then instead of the eventual 'heat death' of the Universe, what will really happen is an extra-dimensional cop will come along and eat the Universe?
    Is there extra-dimensional coffee to go along with that? Or is the coffee-shaped Universe an alternate Universe?

    In other science news:
    Scientists at the NASA Ames Research Center have discovered that dude, we can totally power our starship off of shrooms!
  • ...then what's in the middle?!?

  • Yeah, the Hawking Donut (Score:3)

    by clambake ( 37702 ) on Tuesday July 20, 2021 @02:46AM (#61600007) Homepage

    Simpsons did it.

  • Now we can feed the entire planet several time over.

  • A simpler shape with the same behavior.

    • Longitudinal lines lines are not parallel on a sphere, they converge. From previous papers, and math and observations I donâ(TM)t understand, such lines never converge in our universe, which rules out a spherical topology. Donuts and infinite topologies satisfy the âflat geometryâ(TM) that is observed. These guys are now saying a donut is more consistent with the frequencies observed in cosmic background radiation.

      • Longitudinal lines lines are not parallel on a sphere, they converge. From previous papers, and math and observations I donâ(TM)t understand, such lines never converge in our universe, which rules out a spherical topology. Donuts and infinite topologies satisfy the âflat geometryâ(TM) that is observed. These guys are now saying a donut is more consistent with the frequencies observed in cosmic background radiation.

        Suppose you have a 3d universe of points where each point is a struct (as in C) with 6 pointers to its neighboring points. You can construct a large cube of such points and connect them such that everything appears Euclidean - everything connects at right angles, space is flat, with no curvature.

        Now consider the left side plane of such a cube. For those points, where do the left pointers go?

        If the pointers go nowhere (NULL), then your universe has a hard boundary and objects will bump into the boundary when

  • Call the helpline? (Score:3, Funny)

    by GearheadShemTov ( 208950 ) on Tuesday July 20, 2021 @03:43AM (#61600105)

    So the universe might be something like a vertical dipole antenna radiation pattern?
    Hmmm.
    Maybe with the right transmatch we might *finally* be able to get through to speak with Management. Or at least Management's voicemail system:
    Press 1 for all Starfaring Extra Plus questions.
    Press 2 for routing problems.
    Press 3 for how to set up your Starfaring Basics account.
    Press 3 for billing questions (what, you thought any of this would be free?
    For all other questions press 4, or wait for a Team Member to assist you or your successor civilisation.
    We are currently experiencing median waits of -- 3.15576 E 16 -- Hydrogen transition times.
    You call is important to us, please stay on the line.
    Press 5 to hear this menu again.

  • 4D sphere would be cooler

  • This is similar to the topology of the universe described by Iain M. Banks in the Culture series, which is kinda cool.

  • Homer was right. (Score:5, Funny)

    by John Allsup ( 987 ) <slashdot@nospam.chalisque.net> on Tuesday July 20, 2021 @04:57AM (#61600201) Homepage Journal

    Obligatory Simpsons clip https://youtu.be/Mje7frMYzcY [youtu.be]

    • Get your "Homer was Right!" T-shirts right here, folks!

      Sorry, we're sold out of the "Homer was a Dope" T-shirts.

  • What's on the outside? If they're saying our universe has a definitive shape and boundaries, what is beyond that boundary? What is our universe "sitting" in?

    This is the question no one ever answers. It's the same one about the Big Bang. If we assume some fluctuation in the fabric of spacetime caused our universe to spring into existence, where was the spacetime fabric located? You can't say, "It always existed" or some such because then you're falling down the theological rabbit hole.

    Even if our universe

    • Re: (Score:2)

      by zmooc ( 33175 )

      Thanks to modern memory protection you can rest assured that even if there were other processes running on our cluster, you'll never know about it.

    • What's on the outside?

      Asking this is like asking what’s north of the North Pole - our sense of space is determined by our placement within it - the “outside” is just what’s inaccessible behind a horizon like that of a black hole or “the beginning” of time.

      If they're saying our universe has a definitive shape and boundaries, what is beyond that boundary? What is our universe "sitting" in?

      It’s probably more abstract than this as it assumes as the notion of space has an absolute perspective. If you had two people Alice and Bob each at an opposite “edge” of our visible universe, Alice wouldn’t exist y

      • Re: (Score:2)

        by tragedy ( 27079 )

        It is funny isn't it? The way humans just can not handle the concept of infinity but, at the same time, we just can't handle the idea that things could just end and there's nothing after that.

        • It’s natural to assume the universe is like the common everyday things our senses reveal at our scale so likewise it’s natural to be utterly and completely wrong extrapolating that to the rest of reality.

    • Re: (Score:2)

      by jbengt ( 874751 )

      What's on the outside? If they're saying our universe has a definitive shape and boundaries, what is beyond that boundary? What is our universe "sitting" in?

      Actually, that's the difference between the analogies and the more-or-less incomprehensible mathematics. The universe doesn't have to be "sitting" in anything to have a definitive shape, i.e. topology.

    • Re: (Score:2)

      by ceoyoyo ( 59147 )

      A torus doesn't have boundaries, that's the point. It's like a pac-man universe: the "edges" are connected so you don't fall off, you just wrap around to the other side. It's finite in size, with no boundaries.

  • Grigori Perelman (Score:3)

    by guestapoo ( 4136621 ) on Tuesday July 20, 2021 @06:04AM (#61600247)
    Remind me about BBC's program several years ago, suggest that the Poincare Conjecture that Perelman proved, may lead to conclusion that the shape of the universe is a donut, and if we, suppose could travel across the universe, we would return to the starting point. (I watched it as an entertainment program, and don't understand much of that.)

  • 3D D (Score:3)

    by Mr0bvious ( 968303 ) on Tuesday July 20, 2021 @06:07AM (#61600251)

    It's called a fuck'n torus.

    And a donut IS three dimensional.

    Where's my pencil gone?

    • > It's called a fuck'n torus.

      Yeah, everything about this universe exists relative to a torus / hyperboloid.

      Did you know that the method discovered for error correction in quantum computing is the same as doing an FFT over a bitfield on a torus?

      None of this is reasonable in an intuitive or natural sense.

      The Universe Hyperboloid is mythologically known as the "Tree of Life".

  • Where if you walked towards the North end of the map, eventually you would cross over to the South [imgur.com]. I think the theory that our universe is a simulation just got a big boost.
  • As opposed to what? 4 dimensional donuts? Aren't all donuts are 3-dimensional?
  • The flatness [wikipedia.org] of space has already been measured within 1% of being perfectly flat. At the lower end, this means the actual size is at least roughly 250 times wider than we can see, making the volume at least 60k times bigger. If space were perfectly flat, then the universe would be truly infinite, but it’s not really possible to actually measure with infinite precision so we will never know for sure.

    • Re: (Score:2)

      by ceoyoyo ( 59147 )

      You have to be careful with the concept of "flat." It doesn't mean the universe is a plane sitting in some higher dimensional space. Topologically flat means that parallel lines don't converge or diverge.

      One possibility for a flat, unbounded universe is that it is infinite. An approximation of this would be a very large universe that isn't actually flat but seems flat to the precision of our measurements.

      The other possibility is a torus, which is finite, flat, and unbounded. The surface of a doughnut doesn'

      • Space itself is a mathematical abstraction. Reality will never match our mathematical models on all scales. It's always matter of close enough. So why use more complex model instead of simpler one? If there is not a single bit of evidence of space diverging from "flat" model then all higher dimensional models are useless. There can be infinite amount of various kinds of them and we'd never know which one to develop until there are experiments that contradict flatness of space.

        • Re: (Score:2)

          by ceoyoyo ( 59147 )

          I'm not sure exactly what you're talking about. Both the toroidal and the infinite space models are flat. This story is about an observation of the cosmic microwave background that is more consistent with the toroidal model.

      • I’m just talking about a measurement showing the flatness is precisely 1 and not 1 followed by a googol zeros and then another 1 so not perfect. Even in closed topological models that are flat there are infinite length straight paths they just curve back on themselves spatially.

  • Isn't the universe used Conway's "Game of Life" usually described as a torus/donut? This means that when you go off to the right, you end up at the left and when you go off to the top, you end up at the bottom.

    If it is, then this really seems like more of an observation worthy of Douglas Adams than a physical fact.

  • Relativity says that there is no difference between me flying away from you at near light speed going "up" and you flying away from me at near light speed gong "down".

    The only way we can meet up again to see which one us 'aged' and which one of took advantage of near light speed time effects, is that one of us has to reverse direction. In effect, this direction reversal is the determinant of the aging.

    But if the universe is one large game of asteroids, as implied here, then there IS a difference between m

  • ...Phish explained this four years ago. [youtube.com]

  • Our universe is the three dimensional surface of a n-dimensional toroid.

  • is GOD !

  • If an object/matter could "circle" the universe and return to the same spot eventually, then it seems like it would be a valid assumption that light could do the same.

    In that regard it could be that some of the "far away" galaxies we see at extreme distances could actually be repeats of galaxies that we've seen closer but at an earlier period in time. Hell one or more of the distant galaxies that we see could indeed be the Milky Way from a distance in the past. Sort of like seeing a reflection of ourselve

  • famous last words: "45 bn ly should be enough for anyone"

    >> our entire cosmos might only be about three to four times larger than the limits of the observable universe, about 45 billion light-years away.

  • Any one who has played Atari's Asteroids video game knows this, although some believe that the early universe was created on a PDP-1.

    https://en.wikipedia.org/wiki/... [wikipedia.org]!

  • Is boring and old hat

  • Comment removed based on user account deletion

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