Infinity is a mathematical concept that refers to an unlimited quantity within a magnitude. From our human point of view, it is impossible to conceive. always talks about infinite universe but it's kind of hard to understand. Every time we answer a question about the universe, hundreds of new questions arise. Is the universe infinite or does it have an end? This question, which mixes astronomy and philosophy, is undoubtedly the key question of science. The answer to this question, once found, will change everything. It is infinite and its implications will be amazing and terrifying at the same time.
In this article we are going to tell you about the infinite universe, the theories that exist and much more.
Is the universe infinite?
All current evidence shows that the universe has no borders. In other words, in principle, the universe is infinite. We know many things about the universe. We will know more in the future. But we were, are and will be limited by one aspect: the speed of light. As Einstein stated in his general theory of relativity, the only constant in the universe is the speed of light, which is 300.000 kilometers per second.
We also know that the universe was born in the big bang 13.800 billion years ago, which was the beginning of the expansion of the universe out of the space-time singularity. Since then, we know that it is expanding and it is doing so at an accelerated rate. In fact, it is expanding at a rate of 70 kilometers per second for every additional 3,26 million light-years of distance.
But what is the problem we run into when we try to determine if the universe has a limit? That is, when we try to determine if it is infinite or not. Well, we're limited by the amount of time light has to travel since the universe was born.
The farthest we can see in space is 13.800 billion light years. Well, technically, 13.799.620.000 million light years, because during the first 380.000 years of life of the universe, the energy was so high that atoms could not form, so subatomic particles were free, they formed to block photons. The truth is that light did not really emerge until 380.000 years after the Big Bang.
So that's our limit. We cannot see further. Since we can't see farther, we have no way of knowing if the universe really has an edge or, conversely, if it is infinite. So the only way to determine if the universe is eternal or finite is to rely on mathematical calculations and astronomical predictions.
The geometry of the universe and its eternity
One of the main ways to know if the universe is infinite is to determine its shape. It's an incredibly complex task, but mathematical measurements and predictions determine that the universe can only have four possible geometries: Euclidean (flat), spherical, hyperbolic (flat but curved), or toroidal (like a doughnut).
We ended up abandoning the open toroid, because the presence of two different curvatures (longitudinal and transverse) would make light travel differently in space. This violates the cosmological principle, which tells us that the universe is isotropic, that is, physical properties do not depend on the direction in which they are examined.
So we are left with three possible shapes: planar, spherical, or hyperbolic. The spherical hypothesis implies that the universe is closed. I mean, it's limited. If the universe is a sphere, it cannot be infinite. The flat and hyperbolic assumptions, since both assume an open universe, imply that the universe is infinite.
In this sense, determining the shape of the universe tells us if it is infinite or not. Can we know its geometry? Yes, at least approximately. Analyzing the cosmic microwave background. This is the radiation left over from the Big Bang. They were the first light echoes to appear in the universe 380.000 years after his birth. It is radiation that has traveled a great distance to reach us.
So it is this cosmic background radiation that is most affected by the curvature (or non-curvature) of the universe. If the universe is flat, its curvature is 0. If the universe is spherical, its curvature is positive (greater than 0) and if it is hyperbolic, its curvature is negative (less than 0).
In this case, what we do is calculate the distortion that the cosmic background radiation has undergone along its journey from the origin of the universe. We compare estimates of the size of the cosmic microwave background blob with the size of the mass that we actually see. If the curvature is positive (spherical geometry), we see larger spots than the mathematical model estimates.
If the curvature is negative (hyperbolic geometry), we see that the spots are smaller than the estimates of the mathematical model. Without curvature (flat geometry), we would see spots of the same size as estimated by the mathematical model.
What we see? No distortion. Or at least our curvature is very close to 0. The geometry of the universe appears to be flat. If the universe is flat, it means that it is open. If it is open, then it is infinite.
Its apparently flat geometry, combined with the fact that dark energy is not diluted in space no matter how much the universe expands, seems to suggest that the universe is indeed infinite. It does not have limits. You will discover new galaxies and new stars every time you travel through it. You will never find the limit or return to the same place. The universe is eternal.
So is the Universe really infinite?
Although studies of cosmic geometry and dark energy seem to suggest that the universe is indeed infinite, we can never be sure of that. This is basically because we cannot be 100% sure that the universe is flat.
We know that it has a curvature of about 0, but we're not entirely sure. The calculation can't be perfectly exact, so there may be a slight positive curvature that we can't measure (it doesn't matter much if it's negative, since it will be hyperbolic and still infinite).
The universe is flat or slightly spherical. But if it were slightly spherical, that would already mean that the universe would be a closed sphere, so this would make the universe a finite place. We may never be able to accurately measure its curvature. We would be totally blind if we didn't know if it really started from scratch. This small numerical difference will take us from the concept of an infinite universe to that of a finite universe. Not to mention, we still don't know the true size of the universe. We are limited by the parts of the universe that light allows us to see.
I hope that with this information you can learn more about the infinite universe and if it really is or not.