How can the universe be flat?

Most astronomers think the universe is spherical; others claim it resembles a soccer ball more often than not, with several flattened sides rather than a perfect round shape.

A lack of a "unified field" illustrates one of the mysteries and paradoxes that bedevil astronomy, astrophysics, and quantum physics. According to unified field theory, one set of mathematics ought to function in both the vast and tiny realms of astrophysics and quanta, but this isn't the case at the moment.

Additionally, keep in mind that dark matter accounts for 95% of the universe's total mass, which is "missing." This means that the amount of mass required to produce the known gravity cannot be explained by the visible universe alone; what is visible accounts for 5% of the universe's total mass.

Although it is difficult to answer your question with any degree of certainty, it is unlikely to be addressed anytime soon.

If the density of the universe is exactly equal to the critical density, then parallel light rays will continue to be parallel, indicating a flat geometry. This idea comes from general relativity, a theory that explains how mass and energy cause spacetime to curve.