Science
Related: About this forumOur universe might be a giant three-dimensional donut, really.
By Paul Sutter - Astrophysicist about 17 hours ago
(Image credit: wacomka/iStock/Getty Images Plus)
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.
A tasty problem
Physicists use the language of Einstein's general relativity to explain the universe. That language connects the contents of spacetime to the bending and warping of spacetime, which then tells those contents how to interact. This is how we experience the force of gravity. In a cosmological context, that language connects the contents of the entire universe dark matter, dark energy, regular matter, radiation and all the rest to its overall geometric shape. For decades, astronomers had debated the nature of that shape: whether our universe is "flat" (meaning that imaginary parallel lines would stay parallel forever), "closed" (parallel lines would eventually intersect) or "open" (those lines would diverge).
More:
https://www.livescience.com/universe-three-dimensional-donut.html
TomDaisy
(1,860 posts)Blue Owl
(50,291 posts)Was when the late great Stephen Hawking acknowledged Homer's donut theory of the universe...
brush
(53,743 posts)Didn't "the universe" once mean everythingour tiny solar system tucked away in a spiral arm of the Milky Way galaxy, our nearest neighbor galaxy, Andromeda, and all the other galaxies, black holes, undiscovered entities and whatever else and the space beyond?
Which still makes me wonder what is the area beyond the new donut theory called infinity? There's that word finally, which we used to hear all the time about space/distance and time somehow being the same
multigraincracker
(32,641 posts)number of such universe may not be finite.
Javaman
(62,504 posts)BlueWavePsych
(2,635 posts)muriel_volestrangler
(101,271 posts)This does not appear to be about donuts, which are solid objects where the interior matters; this seems to be about tori, which are only concerned with the surface of a donut.
https://en.wikipedia.org/wiki/Torus
https://en.wikipedia.org/wiki/Three-torus
This is talking about what you could get if in any of three dimensions you could go round in a circle. My first thought of "how close are we to the surface, how big is the inner radius, and how big the outer" turned out to have no meaning, because it's not about a donut after all.