Is the universe really infinite?

(Dan Tri) - It is one of the most profound questions we can ask, and here is the short answer: We don't know.

Is the universe infinite or finite?

Despite great strides in exploring the observable universe, scientists still cannot come up with a final answer to the question of whether space is infinite or has some strange shape.

Current theories fall into two main streams: some believe that the universe is truly infinite, with no boundaries, while others believe that the universe is finite but has no "boundaries" in the usual sense.

Researchers stress that the ultimate answer may be beyond human reach, despite increasingly detailed observations and theoretical advances.

However, what we know about the observable universe and the most distant galaxies can provide important hints.

The dense and active star field at the center of the Milky Way (photo: Triff/Shutterstock).

What we know about the universe

The part of the universe we can observe is definitely finite. Since light travels at a finite speed and the universe is expanding (confirmed by black hole collisions), we can only see a certain “horizon”.

The universe has been expanding since the Big Bang, causing galaxies to move farther and farther apart. The greater the distance between two galaxies, the faster they drift apart.

This can be visualized by inflating a balloon with dots drawn on its surface; as the balloon inflates, the dots move away from each other, simulating the expansion of space.

However, the shape of the universe, as well as whether it has "edges" or stretches on forever, remains a mystery. Current measurements of cosmic curvature suggest that the universe is spatially flat.

This does not mean that the universe is a flat disk, but rather that if two laser beams were shot parallel through space, they would never intersect or separate, even after billions of years.

The flatness of the universe opens up two obvious possibilities: If the universe were flat like an infinitely long sheet of paper, it would be infinite. But it could also be flat in the shape of a torus (a doughnut), in which case it would be finite but have no boundary.

The planar geometry we observe still allows for a finite global topological structure but without boundaries, and current observational precision is not sufficient to clearly distinguish these two cases.

Why the truth can forever remain a mystery

Illustration of the multiverse theory. This theory suggests that beyond our observable universe, there could be an infinite number of other universes, sometimes called parallel universes or "bubble" universes (photo: Vchal/Getty Images).

Despite great advances in observation, the ability to determine whether the universe is truly infinite or just vast still faces major limitations.

Astrophysicists have different views, some leaning towards an infinite universe, others believing in a finite universe with a special topology. The multiverse theory further complicates the issue, emphasizing the speculative nature of this question.

Because we only observe a fraction of the universe, any conclusion about the entire universe requires an extrapolation that may never be testable.

We cannot “rewind” the universe or perform controlled experiments on a cosmic scale. We rely entirely on passive observations. This means that questions about what lies beyond our observational horizon, how space is connected, whether there is a boundary, or whether time and space stretch on indefinitely, may remain unanswerable.

Ultimately, the universe may be so vast that even if it were finite, distinguishing it from the "infinite" may forever be beyond our reach.

If it were infinite, we might never observe evidence of a boundary. Either way, the question may be beyond the scope of human empirical understanding.

Source: https://dantri.com.vn/khoa-hoc/vu-tru-co-thuc-su-vo-han-20251126015148568.htm