There is one question that has marveled scientists and the field of astronomy since the beginning of time is: How big is the universe? I’ve always been fascinated by such inquiries as well. This is an extremely loaded question, but I think it’s possible to break it down into relatively understandable chunks. These chunks are things like the number of stars, solar systems galaxies, universes, and more. But to compare the sheer magnitude of such things we also must measure in time, mass, volume, and many other variables. Let’s get into it.
To start, we can begin by looking at our solar system. We have eight planets (9 if you include Pluto and one star in the center of it all. Earth has a circumference of almost 25,000 miles which is nearly twice as big as mars and is already a huge mass. Think of all the places you have ever been and can think of which on our planet. Earth is a huge place. However, it isn’t anything compared to Jupiter which is roughly 2.5 the size of ALL the planets in the solar system combined. And the sun is ten times bigger than Jupiter. The end of just our solar system is about 122 astronomical units (AU) away from the sun, where one AU is 93 million miles. Next, there are roughly 100 billion solar systems in the milky way galaxy which means there are about 200 – 400 billion stars and 100 billion planets just in our galaxy. There is also a black hole in the center of each galaxy which will be important for later. Some of these galaxies have two stars called a binary star, or 3 stars called a trinary. Star. We also have 100 billion galaxies in our universe which mean we have 100 billion trillion stars in our universe. Okay, we need to pause because I just hit you with a bunch of numbers and if you are anything like me you are probably struggling to comprehend the exact size of all this. We can stop with the numbers and move on (sort of).
So the next question is how many universes are there? What if I told you the answer is infinity? Our universe is continuously expanding, and the expansion is getting faster which makes no sense considering the universe one day will collapse in on itself or be torn to bits. But are there other universes? Remember when I said the black holes in the center of galaxies would come in handy? Well, nows that time. One extremely compelling theory being studied right now suggests that each black hole leads to another universe in which there are hundreds of billions of galaxies, and in each galaxy, there is a black hole which leads to a different universe, etc. This is one concept of infinity. If you want to continue this level of far-fetched thinking, then ponder this. Some are believing that it might be possible that each one of these universes holds earth with a version of you that is the same with minute differences. This is where the concept loses me completely. But back to the size of the universe.
If the universe has around 100 billion trillion stars and we probably have about 10^24 planets in the known universe, how many are potentially habitable? It’s hard to tell how many could be potentially habitable in the universe, but in the galaxy, about 70 billion look earth sized, and 11 billion looks like they are surrounding a sun-like star. This gives me tremendous hope about being a potential multi-planetary species because the numbers give humans tremendous odds of being able to find another habitable planet. Getting to another habitable planet is another animal though. If we did get to other planets and wormholes did potentially exist as we think they do then time could be completely different. Earth could be completely gone, and people on other planets could be hundreds of years older in comparison thanks to Einstein’s theory of relativity. Stars and planets get destroyed and reborn so often (relatively) that there is so much universe that we have not been alive for and will never be able to see or know in the future.
Even right now we know so little about the universe and are so small it is hard to grasp what we are missing. The only thing we can do is live to strive for more information on the universe to keep the human race alive, become a multi-planetary species, make life easier, and try to enjoy the process of living.