If you have an interest in astronomy or the cosmos

you’ve probably heard about the expanding universe theory. Basically, this means that the galaxies outside of our own are moving away from us and from each other, essentially creating a larger universe. And yet, the galaxies aren’t really moving through space. What is happening according to this theory is that space itself is moving.

One famous analogy has compared the universe to a loaf of raisin bread. The raisin bread starts out as a formless lump of dough with the raisins relatively close to each other. As the dough bakes and rises in an oven, the raisins become more spread out, yet they are still a part of the bread.

In the raisin bread analogy, the galaxies within the universe are the raisins, and space itself is the bread. The galaxies may be moving away from us and getting so far away that we cannot observe them, but gravity is still working to keep them confined within what appears to be a finite universe.

So, what does that mean for the future of the universe? Does it mean that there is a definite edge to the universe that will slowly spread out to infinity? Scientists don’t know, but they do have some theories. One theory is that the gravitational pull that holds the universe together will eventually give out, and the galaxies will spread out to infinity. The stars that make up these galaxies will eventually burn out, and the universe itself will cease to exist in several trillion years. Another fascinating theory is that the average density of the universe will eventually cause it to start contracting onto itself into one singularity in what scientists have dubbed the Big Crunch. According to this theory, the singularity that was once our universe could undergo another Big Bang and expand into a new universe. For all we know, this could have already happened countless times. Then again, it could be that the universe will simply expand and continue to exist for eternity, becoming infinitey large with no end in sight.

Of course, all of this is just speculation. There will always be things that we don’t know about the universe and cannot know, and the ultimate fate of the universe is just one of them.