What Shape Is the Universe? A New Study Suggests We've Got It All Wrong (quantamagazine.org) 93
An anonymous reader quotes Quanta magazine: A provocative paper published in the journal Nature Astronomy argues that the universe may curve around and close in on itself like a sphere, rather than lying flat like a sheet of paper as the standard theory of cosmology predicts. The authors reanalyzed a major cosmological data set and concluded that the data favors a closed universe with 99% certainty — even as other evidence suggests the universe is flat.
OMG! (Score:4, Funny)
Some of the physicists got gifted a 3D-printer this summer, I'm sure.
Re: OMG! SPiraL galAxies! (Score:2)
You'd think that Slashdot could figure out how to simultaneously filter out ASCII art and low IQs like parent's.
Maybe they need to find some beers to code it for them.
Re: OMG! SPiraL galAxies! (Score:2)
beers->nerds, damnable spellfsck.
Late news... (Score:3)
Uhm, Columbus Day was last month. The Universe is flat? Let's send three spaceships to check it out.
Re: Late news... (Score:1)
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Old myth suggesting that everyone thought the world was flat, and Columbus set sail to prove it was round.
Utter bollocks, of course. Everyone knew the world was round, but Columbus thought it was much smaller than it actually is.
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Columbus probably knew about Eriksson.
The last ship from the Viking settlements in Greenland to Iceland was about 1420. Columbus visited Iceland a few decades later. He might even have met someone from Greenland. He would probably have heard about Vineland. However, all this might not have been general knowledge in mainland Europe.
My theory was that, although Columbus said he was going for Japan, he was secretly looking for a southern extension of Vineland. To keep his motivation secret, he might d
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You can read Columbus's journals for yourself. To his dying day, he was convinced he was in the Indies.
Oh, so I'm the only one who puts misinformation in private files to confuse the archivists in the future?
Old saying: (Score:2)
What goes around comes around.
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The Universe may be a sphere, but we're not stuck on the crust like Earth. Can anybody send a spacecraft outside the bounds of the Universe?
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> Can anybody send a spacecraft outside the bounds of the Universe?
No, by definition.
Re:But the science is settled... (Score:4, Informative)
Yes, I know where you try to jab at. But scientits went back to their data sets and checked if Carbondioxide really has large absorption bands in the near Infrared. And they rechecked if the measured Carbondioxide contain in the atmosphere really has increased from the 270 ppm their ancestors measured in 1900 to the 410 ppm we measure today. And they checked again the atmospheric composition on Venus, on Mars, on Titan and if they really show a Greenhouse effect too, and if the measured Grrenhouse effect fits the prediction from the atmospheric composition. And they ran the calculations for the Blackbody temperature of Venus, Mars, and Earth again. And still, the results keep telling us that there is a Greenhouse effect on Earth, and that it is strongly correlated to the amount of gases in the atmosphere with three or more atoms in their molecules, e.g. Carbondioxide, Water, Methane and diverse Nitroxides. And of those, only Carbondioxide and Water are stable, while Methane and Nitroxides will discompose in the sunlight. And the amount of Water vapor an atmosphere at 290 K and 1033 hPa can contain without the water forming droplets and causing rain is limited. Thus only Carbondioxide, once released in the atmosphere, will stay there forever.
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Thus only Carbondioxide, once released in the atmosphere, will stay there forever.
No, there's a couple of ways CO2 gets removed from the atmosphere on Earth. Plants are the most familiar, think of all that coal which was carbon removed from the atmosphere. There's other ways that life does it as well such as some types of shell.
The other big one is silicate weathering, which is a feedback mechanism. More CO2, more rain, more weathering.
The Earth has likely out-gassed comparable amounts of carbon to Venus and it has mostly been sequestered on the Earth unlike Venus.
The good news is that i
Re: But the science is settled... (Score:2)
AC makes a funny joke about the fundamentalist language used by "but muh science!!" bros.
And.... a "but muh science!!" bro immediately launches into an off-topic fundie rant - proclaiming the purity of his faith, extolling the worthiness of his idols, and urging us all to accept the authority of his church. Classic!
Original Paper (Score:5, Informative)
Freely available on the arXiv:
https://arxiv.org/pdf/1911.020... [arxiv.org]
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hmmm (Score:2)
Proof has new meaning these days.
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Nobody have proven it is flat and no scientist will claim absolute proof. They may individually lean towards a particular theory or claim high level of confidence. Don't confuse sensationalist journalism or pocket science with the real thing.
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The persons that proved this berated you for what? I find your story unlikely and suggest you stop posting crap.
What do they mean "flat" (Score:1)
Re: What do they mean "flat" (Score:2)
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Re:What do they mean "flat" (Score:5, Interesting)
A flat 2D universe is the surface of a plane when seen in said 3D environment
A closed 2D universe is the surface of a sphere when seen in said 3D environment.
A close 3D universe is the surface of the 4D analog of a sphere, and one of the nifty things about it is that "parallel lines" eventually meet.
All through the 60's and 70's the big debate was if the universe was such a closed shape or not, and if this was indeed the same as asking if the universe was a black hole or not. If you perform the calculations for a black hole with a mass similar to what we believe the mass of the universe is, you find that its event horizon is also similar to what we call the "visible universe" and that its average density would be far lower than, for instance, a gas at atmospheric pressure. I suspect some people will jump in and make the argument that everything would be at the singularity, but in fact, event horizons dont require singularities... its the other way around. Now even if the universe is not a black hole, a very large region of it can form a gravitational event horizon without forming a singularity. At the extreme end a hollow sphere is gravity neutral everywhere inside, while in the outside it is gravitationally indistinguishable from a single point mass (aka singularity.)
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I'm sure the smart guys already did, but has anyone done the math on whether the formation of a black hole from a supernova or similar event comes close to matching our assumptions on the Big Bang?
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Re:What do they mean "flat" (Score:5, Informative)
They're referring to the macroscopic shape of spacetime. If you imagine a 3D (+1 time for you nerds) grid of spacetime coordinates, and can picture how that grid distorts in the presence of stars and black holes, the question is how this grid is distorted overall, by the presence of all the universe's energy & matter.
Because there's both positive energy density in the form of particles and fields and dark matter, and negative energy density in the form of "dark energy", the net curvature depends on how well these balance eachother.
Hitherto, it's been thought that they were perfectly balanced, and therefore flat -- at the very least the curvature is so small that the full universe would need to be a minimum of 10^30 times larger than the observable universe to appear so flat.
The article doesn't do any favours by referring to it as spherical, which is a specifically 3D form, which isn't what a 4D curvature would look like. Unless I'm mistaken, it'd look like a ring in just the 4th dimension -- the one along which spacetime curves -- nothing terribly obvious in our usual 3 spatial, except that in principle light rays would eventually return to high the back of a flashlight.
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It's not much different than what you learned, except the measurements then were not good enough to decide what curvature the overall Universe might have. Lately the evidence has piled up for zero overall curvature (flat geometry of spacetime). This new paper doesn't overturn all that, just tries to explain an anomalous observation by invoking a positively curved spacetime (disclaimer -- all I did was read the linked sites in the submission).
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Flat means if you go in any one direction you will never return to your starting point.
Sphere means you can pick any direction at all and if you go far enough you will end up back where you started at. Build a really big perfect (i.e. no spread) laser, point it in the sky and in 50 trillion years it will light up the night sky on the earth (or it would if the planet was constantly moving).
Re:What do they mean "flat" (Score:5, Interesting)
This can be a little tricky to talk about or visualize, because our brains aren't wired to perceive additional dimensions. But I'll take a stab at it. We'll have to talk by analogy though
Picture a sheet of paper lying on the table. Now put a 2D universe on it - a bunch of little stick figures, living their lives, talking about how they know what "flat" means when you're talking about a line, but what does it mean when you're talking about a 2-dimensional thing? And it's going to be kind of hard to see from their perspective. 2-D light only travels along the surface of the paper, so even if you came along in 3D space and curled the paper into a tube, they couldn't see across the gap to the other side of the tube, still just along the surface. But something important would have changed - while the universe was flat they could see forever in in every direction, but now that you've curved their universe back on itself - if they look directly parallel to the direction you curled the paper, they'll look all the way around the tube and see the back of their own head. From their perspective within the 2D universe they're looking in a perfectly straight line and something profoundly weird is going on. But from our perspective we can see that the line is in fact curved, because the paper it's drawn on is curved - the curve is just happening in a 3rd dimension that they can't see.
Does that make any sense? If our 3D universe were curled into a small enough 4D tube, we could look out into space in the right direction, and see the opposite side of Earth looking back at us, because our whole 3D universe is looped back on itself in a direction we cant see.
Of course there's no particular reason the curvature would have to be a tube, you could wrap it into a mobius strip instead, or just stretch and wrinkle it without curving it back on itself at all. That's essentially Einstein's insight with General Relativity - there isn't actually any "force of gravity" pulling the Earth towards the sun - instead the sun stretches the universe itself in such a way that when the Earth travels in a straight line, it keeps ending up back where it started. Or something like that - I admit I don't really understand the details.
Physicists though like to keep things simple - so when they talk about the shape of the universe they're mostly ignoring the "gravity wrinkles" , and in the absence of a compelling argument usually assume it's the 4D analog to one one of three simple shapes that are curved uniformly in all places and directions. Each of which has distinctive geometric properties. Using our 2D analogy the corresponding 3D shapes would be:
-- A flat plane = no curvature. Things keep going in all directions forever (or maybe there's a boundary somewhere), a straight line is actually straight no madder how many dimensions you're looking at it from, and if you fired parallel laser beams out of your eyes, the center of those beams would stay a fixed distance apart.
-- a sphere = positive curvature - go far enough in any direction and you'll end up back where you started - straight lines all follow "great circles" (e.g. lines of longitude are straight, lines of latitude are actually curved), so your parallel laser beams would actually end up crossing each other because space is always curving towards itself.
-- and finally a shape we don't normally see - a hyperbolic surface with negative curvature. Like the flat plane it doesn't curve back on itself, but your laser beams are actually gong to get further apart the farther they travel, because space is curving away from itself. To compare it with a sphere - if you tried to lay out the the surface of a non-stretchy sphere (an orange peel for example) on to a flat surface, you'll have to cut it up into pieces first because the further you get from your central starting point, the less orange peel you have to go around. If you tried to do the same thing with a hyperbolic surface you'd have the opposite problem - the further you get from the center, the mo
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"a hyperbolic surface with negative curvature."
Pringles provide something of a familiar approximation.
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Sort of. But you need to keep in mind that the exact center "saddle point" of the chip is the shape of every point in space, not the overall shape of space itself. Personally I find it really hard to translate that visualization of a single infinitesimal region of space into a meaningful visualization of what a larger region of space would be shaped like.
The crocheted "hyperbolic planes" are by far the best visualization I've found - I'd highly recommend that anyone curious look for some decent Youtube
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The details are complicated, and if you're interested you can look at the Wikipedia page [wikipedia.org] for the mathematics, but you can actually simplify it down a lot. First you have to realize that mass and energy influences spacetime, and spacetime in turn influences mass and energy. That's kinda the foundation of general relativity: a large concentration of mass warps spacetime in such a way spacetime causes other mass to be attracted to the center of the concentration, and you get gravity. In fact, if the universe w
I think it's fluffy (Score:2)
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I think the entire universe is the other side of a massive black hole.
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Whether that is important, coincidence, or just plain wrong (after all, the observable universe is very unlikely to be the whole universe) probably keeps astrophysicists at the duty free booze on the last night of conferences.
Bye Bye dark-energy (Score:2)
This doesn't mean anything for "dark matter" as that's based on the movement of galaxies and galaxy-clusters
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Sphere-ish (Score:2)
Re:Sphere-ish (Score:4, Funny)
Hypersphere. It's like a sphere, but rounder.
Interesting - But Let's See If Others Can Confirm (Score:4, Insightful)
Announcements of revolutionary breakthroughs in cosmology are much more common than actual breakthroughs. This looks like serious work, but it needs to be scrutinized by other researchers before we can judge its significance.
Once again asking the question (Score:2)
What is the universe expanding into and/or sitting in?
I will now await the usual answers of how the universe has no edge, it keeps expanding outward, which doesn't answer the question.
If we assume the universe is like an expanding balloon, as the balloon expands it expands into the room. What is the universe expanding into? If there is no edge, how can it be described as round/flat/whatever?
Turtles all the way down?
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There is no "into" a deeper void that the universe is expanding into, if the universe is infinite; and if the universe is finite, spacetime is a closed manifold without an edge in the first place.
You may be wondering, isn't the Big Bang described as the universe being the size of a dust mote and expanding from that, so how could it now be infinite in size;
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If we assume the universe is like an expanding balloon, as the balloon expands it expands into the room.
You are assuming that there is a "room" without justification.
It would certainly be possible to imagine a physical reality that is entirely comprised of an expanding 2-D universe with a balloon-like topology. No room needed.
If you insist on having a room, in what is that room embedded? Turtles?
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If you insist on having a room, in what is that room embedded? Turtles?
Which is exactly my point. Every single response to my question has said the same then, more or less. The universe itself isn't expanding, it's the space between the stuff in the universe which is expanding. Which is a nonsensical statement because that implies there is an infinite amount of space for the stuff to expand into. Which goes back to my original question: what is the universe expanding into?
All I hear or am told is to rea
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that implies there is an infinite amount of space for the stuff to expand into
No, it doesn't imply anything of the sort.
You seem to be heavily biased by the fact that you yourself are embedded in a 4D spacetime, and you're trying to apply that same experience to the spacetime itself. Spacetime doesn't need to be embedded in anything, and it does not need to "expand into" anything.
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... be doing better than poor old Georg Cantor [wikipedia.org].
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It isn't sitting in or expanding into anything. Nothingness. Imagine a dark vacuum with no gravity, no light complete and total nothing. Then there is suddenly a massive explosion. Picture a slow motion reel of an m-80 going off in a dark room.
A super massive black hole somewhere in some universe broke physics and the other side of that black hole "created" our known universe.
I just made that up, hows it sound?
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The universe isn't expanding so much as the distance within space is expanding. There being nothing outside of space for us, it can expand as much as its little heart desires...that is unless there's some sort of new physics which after a point causes a phase change and all hell breaks loose.
Read some physics books and learn to stop assuming your implicit assumptions.
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As others have said, your question is based on false assumptions (or at least assumptions we have no reason to believe are true.)
Space and time themselves are expanding. Sort of like a sheet of graph paper that keeps adding new lines, without the squares getting any smaller, or the sheet getting any larger. Perhaps the simplest explanation I've heard boils down to this - if you were standing outside the universe, and tried to measure it, what would it's diameter be, and how old is it? And the answer to bo
Re: Once again asking the question (Score:2)
You obviously didn't get the memo: exactly 42 angels can dance on the head of a pin.
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Nope, "not even wrong".
That you try to project linguistic structures developed for counting sheep and ambushing mammoths onto mathematical concepts is where you're going wrong.
It is very arguable whether the universe is actually comprehensible. There is certainly no obligation on the universe to be comprehensible to a bald ape barely out of the trees, and used to measuring things on a less-than-planetary scale.
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Ah, the many worlds hypothesis....no evidence, nothing really behind it but it makes for good pseudo-science copy.
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[Bedivere, et al, 932 AD] (Score:2)
"And by that, my liege, is how we know the [Universe] to be banana-shaped..."
Hold it . . . hold it . . . hold it!!! (Score:2)
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Late 60's cosmology thought the universe was possibly flat, and all the data was consistent with that but not particularly constraining. "Flat" was perfectly plausible, but so were a whole lot of other shapes.
We already know (Score:2)
It's a Quarthex! [smbc-comics.com]
I don't think it can have a 'shape' (Score:2)
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OK, let the Universe be spherical. (Score:2)
But the Earth is *still* flat.
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4D (Score:2)
Every science show I've seen describes the sphere, in 4 dimensions, and if you traveled in a straight line long enough you'd end up where you started.
I must have missed this brief interlude of some other idea.
If the galaxy is in Orion's belt... (Score:2)
Distinction and difference (Score:2)
Isn't this a bitt of a distinction without a difference? The universe is expanding (and as far as I know, always has been expanding) at a rate such that you'll never get back where you started, even if the overall shape is closed. It may well be that the overall shape is so immense that we only need treat the observable universe as "flat, with a correction term".
Everything We Know About The Universe Wrong (Score:1)
Next up could be dark matter/Dark energy.
https://www.dailymotion.com/vi... [dailymotion.com]
BBC - Horizon - 2010 - Is Everything We Know About The Universe Wrong
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A Universe From Nothing' by Lawrence Krauss, AAI 2009
https://youtu.be/7ImvlS8PLIo?t... [youtu.be]
Can vi live in a closed universe and have a accelerated expansion at the same time, not according to the above video.
Why is this new? (Score:1)
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If you can have a sphere (Score:2)
Then you could also have a torus (donut)
And theres a few more complex shapes if you can have more dimensions (on the macro scale- I have heard that some people think its 11d in the micro scale)
Soap bubbles (Score:1)
Out universe was described as a multiverse of soap bubbles from an article I read almost 20 years ago.
Flat universe society (Score:2)