Space seems to extend forever in all directions, but that is just a mental model that people have for the universe, which is not necessarily correct. In the past, humans believed the Earth was flat because Earth's curvature was too subtle to detect. But today, it is widely known that the Earth is a sphere.
That knowledge has given most scientists little thought about the universe. Some say that the universe is flat, but other 3D shapes also offer alternatives to infinite space. Now, a new study suggests that the universe could be a giant doughnut based on the strange patterns found in the leftover light from Big Bang.
Universe Could Be a Giant Doughnut Based on the Weird Patterns in Leftover Light From Big Bang, Study Suggests
Flat Geometry Explained
According to the University of Oregon, there are three possible shapes of the universe. It could be a flat universe also known as Euclidean or zero curvature, or it could be a hyperbolic or open universe described with negative curvature, or a spherical or closed universe with positive curvature.
But most of the observations so far of the cosmos are flat. As per Live Science, the geometry of "flatness" refers to the behavior of parallel lines as they move to infinity.
On the other hand, lines of longitude on the Earth begin perfectly parallel to each other at the equator and eventually converged at the north and south poles. Since the parallel lines intersect, it reveals that the Earth is indeed not flat.
A similar concept may apply to a 3D universe. For example, the cosmic microwave background (CMB), the light from the cosmos, is only 380,000 years old but sits over 42 billion light-years away with tiny fluctuations in temperatures.
Astronomers predicted the size of these fluctuations and compared it to observations in which they found that those rays flight changed directions over space-time, which indicates that the geometry of the universe is curved. However, similar measurements also reveal that, when small-scale deflections from galaxies and black holes are not accounted for, it would result in a flat universe.
But there are different kinds of flats. As per Quanta Magazine, flat shapes can be cut and taped at the edges to create a cylinder. Then, one needs to tape the right and left edges to create a doughnut shape or, as mathematicians call it, a torus.
More so, another flat shape could be a Morbius strip, which is just a thin strip connected in a circle. It is still geometrically flat since parallel lines stay parallel. Overall, mathematicians have found 18 possible geometrically flat 3D topologies. But if the universe is indeed a giant doughnut, scientists could look into two directions to see a different version of the Milky Way galaxy or any cosmic objects.
READ ALSO: Most Detailed 3D Map of the Universe Showcases 7.5 Million Galaxies Surveyed Using 5,000 Telescopes
Topology of the Universe
Astronomers have estimated the topology of the universe in many different ways. They have looked for duplicate patterns of galaxies to matching circles in the CMB, but the evidence just points to the universe as both geometrically flat.
But the paper, titled "The Search for the Topology of the Universe Has Just Begun" available in the preprint database arXiv, suggests that past measurements were limited. Also, CMB observations showed that some weird unexplained anomalies of patterns are appearing where they should not be.
The complicated topology of a universe could explain some of these strange anomalies in the CMB, according to Live Science. For now, researchers recommend additional studies of the CMB to confirm this concept, which suggests there could be a mirror image of the world somewhere in the universe.
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