The universe expands from the Big Bang and it grows faster and faster. There are galaxies that move away from us faster than the speed of light. But it is not a problem for physics.
There is a curious relationship in the universe known as Hubble’s law that tells us that the further away a galaxy is, the faster it gets away from us. This was the first empirical demonstration that the Universe expands and impressed the physicists of the 1920s. Since then, much research has been done about it until in 2005 a group of researchers received the Nobel Prize for discovering that the universe is expanding faster and faster.
Yes one think of Hubble’s law as an equation, one can find the distance at which the galaxies that stray from us do so at the speed of light, this distance is called the Hubble radius. Any galaxy that is farther from us will move in the opposite direction from us faster than light. Surely more than one is shocked that something may violate Einstein’s theory of relativity, but the reality is that it is not violated; never.
Reconciling relativity with galaxies moving away from us faster than light
Let’s get to the heart of the matter, Why can something go faster than light in a vacuum? To do this, we will begin by remembering a correct way of enunciating that postulate of the theory of relativity: Nothing can travel through space faster than light in a vacuum And it’s just the part of through space where the key is that allows these galaxies to drift apart so quickly. Galaxies do not move through space, but the space between the galaxies and us expands, resulting in each other getting further and further apart.
It is not something easy to understand, but we will explain it little by little so that it is clear. Let’s imagine an elastic fabric on which we draw two points with a marker. Next we stretch the fabric, so that the distance between the points increases, but none of the points has moved from their place on the fabric, the drawings are still in the same area of the fabric that we did, although now the distance between both have increased. Now imagine that one of those points is Earth and the other is a galaxy that we are observing. From Earth that point-galaxy has moved away from us, although none of us have moved by the cloth.
This is what happens with the Universe, the space (space-time if we want to be precise) expands, and although at small distances we cannot see it, at great distances the effect is more than remarkable. In this way a galaxy that is moving away from us can do it faster than light without violating the theory of relativity, since with respect to space itself its movement is null or very small. But wait, there are still more chicha, those galaxies that move away from us faster than light we can see! Yes exactly despite moving faster than light, its light reaches us
Space expands, and it will forever
Although it is a very active field and it is not considered that there is any certainty to affirm it, the consensus among physicists is that the universe expands faster and faster and will never stop. In other words, the galaxies that move away from us will continue to do so faster and faster so that more and more galaxies will move away from us faster than light. This leaves us various possible scenarios for the end of the Universe, none of them anything encouraging, as we are going to see now.
The first is cooling death, which is a scenario in which the galaxies, which move away from each other, stop interacting with each other, then the stars of each galaxy begin to separate until they stop interacting and in the end we end up with a very dispersed, very cold universe, and very very empty. On the other hand we have the Big Rip that reaches the stretch of space to the extreme in which the predictions speak of all the atoms being torn and we ended up with isolated subatomic particles floating in an empty space.
Luckily for us, we won’t be here to see any of these endings. As always if you have any questions about what we have explained, do not hesitate to use the comments and we will respond as soon as possible.