Astrophysicist Thomas Buchert, from the University of Lyon (France), said that, by examining the light of the ancient universe, he and his team have deduced that our cosmos can be connected in multiple ways, as well as closed on itself in all three dimensions. In other words, the scientist said that we may be in a kind of “giant 3D donut.”

Thus, if our universe were a finite donut, a spacecraft could be pointed in one direction and eventually returned to the starting point, making it possible for physicists to measure its size. “We could say: now we know the size of the universe,” he told *Live Science *astrophysicist Thomas Buchert.

If Buchert is right, our universe would be finite and, furthermore, it could be said that we know its size; According to their results, the entire cosmos could be only three or four times larger than the limits of the observable universe, some 45 billion light-years away.

**Debate on the geometry of the universe **

To explain the universe, physicists use Einstein’s language of general relativity. Broadly speaking, this language connects the contents of space-time with its bending and curvature, which in turn indicates to those contents how to interact. This is how, for example, we may experience the force of gravity

Whether our universe is “flat” (meaning that imaginary parallel lines would remain parallel forever), “closed” (parallel lines would eventually cross), or “open” (those lines would diverge) has been, for decades, a source of long debates between astronomers. And it is that the geometry of the universe would explain its future: the flat and open universes would continue to expand forever, while a closed universe, with a multi-connected topology, would end up collapsing on itself.

**Consider the topology **

To try to decipher this enigma, a team of astrophysicists from the University of Ulm (Germany) and the University of Lyon looked at the cosmic microwave background (CMB).

Observations that focus on the CMB, the flash of light released when the universe is only 380,000 years old, show that our universe is flat and that parallel lines will forever remain parallel to an ever-evolving universe. However, there is more than just geometry, and topology must be considered. The topology allows you to change the shapes while maintaining the same geometric rules.

When the CMB was issued, our universe was a million times smaller than it is today, so if our universe is actually multiply connected, then it was much more likely to wrap around itself within bounds. observables of the cosmos back then, according to *Live Science. *

However, today, the coverage of the universe is more likely to be on a scale far beyond observable limits, so the envelope would be much more difficult to detect. However, the CMB observations give us a better chance to see the distinctive features of a universe with multiple connections.

**CMB temperature disturbances **

The team looked specifically at disturbances in the CMB’s temperature. If one or more dimensions of our universe were to reconnect to themselves, the disturbances could not be greater than the distance around those loops. They just wouldn’t fit.

“In infinite space, the temperature perturbations of the CMB radiation exist on all scales. However, if space is finite, then those wavelengths larger than the size of space are lost,” Buchert explained to *Live Science.*

According to the scientific medium, this means that there would be a maximum space for disturbances, which could detail the topology of the universe.

**Computer simulations **

The team then ran a series of computer simulations to speculate on what the CMB would look like if the universe were really a “giant 3D donut,” in which the cosmos were connected to itself in all three dimensions. In these simulations, Buchert and his team found several large-scale missing disturbances.

“So we have to do simulations on a given topology and compare it with what is observed,” explains Buchert. “The properties of the observed CMB fluctuations then show ‘missing power’ on scales beyond the size of the Universe,” the researcher added. These fluctuations could mean that the universe is, in fact, multiply connected and of finite size.

“We found a much better match with the observed fluctuations compared to the standard cosmological model, which is considered infinite,” added Buchert. “We can vary the size of the space and repeat this analysis. The result is an ideal size of the universe that best fits the observations of the CMB,” concluded the professor.

While it’s fun to think that we live in a giant donut, Buchert emphasized that the results are still preliminary and that instrument effects may explain the missing large-scale fluctuations.

FEW (*Live Science, Futurism*)

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