Science magazines have been publishing articles in the past 2 days after a paper in Nature Astronomy suggesting the Universe is not flat but spherical.
What current laws of physics point to this and if true which established laws of Physics will have to be binned?
A link with the claims would be nice.
Huh. I’ve always just assumed the universe is spherical.
I recall from a very long time ago that a “flat” universe does not mean two-dimensional, but rather that if you got in a spaceship and went in a particular direction, you could go on forever. But a “spherical” universe means you would eventually return to your starting point, just like if you flew all the way around Earth. Is that what is being referred to here?
Current measurements are heavily in favour of a flat universe - WMAP- Shape of the Universe
Looks like this article, or something like it, are at the root of the question - Wild New Study Suggests The Universe Is a Closed Sphere, Not Flat : ScienceAlert
The articles look to be based on Planck evidence for a closed Universe and a possible crisis for cosmology | Nature Astronomy where the authors argue that anomalies in the gravitational lensing of the cosmic microwave background radiation can be explained by a curved/closed spacetime geometry.
The laws of physics are perfectly fine with either possibility (or with a hyperbolic universe, which is the opposite of spherical, sort of like the shape of a Pringle). It’s not consistency with the laws that’s the issue; it’s observations. And even there, it’s complicated by the fact that a spherical (or hyperbolic) universe with a very large radius looks an awful lot like a flat one, so even if our observations suggest that the Universe is flat, we can never actually rule out the possibility that it’s spherical but just really big.
Basically, yes.
If I understand this correctly, some guys basically were looking at the latest and greatest data for the cosmic background radiation and came to some interesting conclusions. One problem we have with our current understanding of physics is that there is more gravitational lensing in the cosmic background than there should be if the universe is flat. We can correct that mathematically by adding in a “lensing factor” of sorts, but then we don’t understand what that lensing factor actually means from a real world point of view. It’s just a fudge factor in the math.
What this paper says is that if you look at the best numbers we have now and assume a curved universe, we can actually get rid of the lensing fudge factor.
And that’s all that the paper says. It’s only looking at background radiation and lensing and stuff related to that.
Others have pointed out that while the curved universe gets rid of this mysterious lensing fudge factor that we have been using, it breaks other things. So either way, whether the universe is flat or curved, there are things going on that don’t match up with our models of how we think they should behave.
Still, it is interesting that, according to this study, the lensing factor does go away if you assume a curved universe.
Some of the terminology here may confuse laymen. Since I am often a confused layman myself, let me try to help.
For laymen, “sphere” is often used to denote what mathematicians call a “3-ball” (three-dimensional ball). Technically a “sphere” "or “2-sphere” is the shape that corresponds just to the surface of a 3-ball. (Flatlanders living on a 2-sphere, e.g. the surface of the Earth, would think about only two dimensions. The 3rd dimension arises for us when we contemplate a 2-sphere because it is convenient for us to imagine it as the surface of a 3-ball.)
But in this thread, “sphere” refers not to 2-sphere but to 3-sphere — the (3-D) boundary of an imaginary 4-dimensional ball.
One way to understand a 2-sphere is to cut two disks out of thin sheets of plastic, glue their edges together and then pull on and stretch the plastic till you get the desired spherical shape. To do something similar to get a 3-sphere, you’d start with two 3-balls, glue the complete surface of one, point-by-point, to the complete surface of the other () and continue from there. ( - This will be impossible, although you might imagine a 4-D creature doing this in 4-D space.)
Is this new? I always heard the universe is curved so that if you go forward long enough you’ll end up back where you started.
Until around 1999, it was an open question whether the Universe was closed, flat, or open. Some may have preferred one model over another, but without any real evidence.
Since then, the evidence has all been that the Universe is flat, or very close to it (and had some surprises that we didn’t expect in 1999).
There may be something to this new study, but it’ll face a serious uphill climb if it disagrees with two decades of evidence.
No, that was always just one possibility, and the recent evidence (until this study, at least) has pointed against it.
Originally this is what I thought as well. Starting from a single point and moving out in all directions. I had to revise that idea due to the fact that there was not an equal amount of matter and anti-matter - leading me to assume that the universe is actually asymmetrical.
Well consider there’s no space for the point to expand into; it is its own space. So why would it have to be radially symmetrical like an explosion?
Yeah, it’s equally awful no matter what angle you look at it from.
One reason folks might have thought the Universe was closed, when its shape was still undetermined, was the expanding-balloon analogy. It’s only an analogy, and no analogy is perfect, but it’s a lot closer analogy for a closed universe than it is for an open one.
On rare occasions, I, like many others, sometimes have trouble visualizing a universe with 4 dimensions of space. The depictions of the different universe geometries seem to always use a 2D plane in our 3D space and show how it deforms when placed into a different geometry. Trying to scale that slice up to a full 3D space in a new geometry hurts the head.
I wonder what various objects, like a cube, would look like in a saddle universe. Or, what would a cube constructed in a saddle universe would look like after it has undergone a transformation into our presumed-flat universe.
4 dimensions of space? I guess you could visualize that with some effort, but there are lots more videos showing what things look like near a black hole, or in variously shaped 3-d spaces
What do you mean by a cube? In a curved space, there exists no object with all of the same properties as a cube. You can pick and choose some of them, but depending on what you pick, you’ll get different shapes.
Kind of like the old video game Asteroids…you leave off one side of the screen and re-enter the opposite side.
https://boards.straightdope.com/sdmb/showthread.php?t=448155&highlight=asteroids
Well, the “Big Bang Theory” has held prominence for ages. If the universe did indeed come into being in that manner, the explosion would send matter in all directions from a central point. It would have to expand as an ever growing spherically shaped entity. How could it possibly be flat? I’ve never heard of any serious theory maintaining that the universe is flat