For starters, let’s talk about how many stars there are just in our own galaxy. The reason I want to start with stars is an obvious one: they all have potential to have their own solar system full of planets.
The Milky Way galaxy has an estimated 100 billion stars; that’s a lot. It is just an estimation, but still. Check out how they estimate this on space.com. Anyways, for the purposes of this post, we will assume 100 billion stars exist in our very own galaxy.
If our own back yard has 100 billion stars, how many of those stars do you think support at least one planet? The answer is: the majority do. Actually, pretty much all of them do, according to space.com. To keep the math simple, we will put that number at 10%, just for kicks!
If we have 100 billion stars in our own backyard, and if just 10% host only one planet, that means 10,000,000,000 planets exist just in the Milky Way. 10 billion; that’s a LOT! Now, let’s pick another number for how many of those planets are in the Goldilock zone, which is simply the habitable zone of a planet orbiting its star. The Goldilock Zone is based on our own needs for survival and intelligence here on Earth. It is highly possible that other civilizations do not require the same things we do, like oxygen, or even water. But, for sake of argument, we will use the Goldilock Zone and the percentage of .1%. Notice that I did not use 1, as in a whole number, I used .1, a tenth of a percent.
If just a tenth of a percent of the 10,000,000 stars have planets in the Goldilock zone, that means 10,000 habitable planets exist in our galaxy. That’s just 10,000, so the odds are still real low that there is intelligent life out there. But, and a big BUT, what about the other galaxies in the Universe? How many galaxies are there in the Universe? The answer, according to physics.org, is 100,000,000,000; the same number of stars in our own galaxy.
So, if there are 100 billion galaxies in the Universe, and if we assume each of them have 10,000 planets in the habitable zone, then there is potentially 1,000,000,000,000,000 planets that can support life as we know it here on Earth. WOW! MIND BLOWN! Do you still think we are the only intelligent life in the Universe?
Notice, I did not include all planets that are thought to exist in the Milky Way. I also did not consider the possibility that our limited number of stars with planets had multiple planets; I, for the sake of easy math assumed it was just one planet per star, out of the very low number of 10,000,000 planets in the Milky Way. I did not consider the possibility that other life forms might not require what we require here on Earth to thrive: water, oxygen, etc. etc. Lastly, some galaxies have trillions of stars. Yes, no joke- some have trillions with a ‘T’, not a ‘B’. I used a nice easy number of 100 billion stars for every galaxy.
This is an age-old question: are we alone? I don’t think we are, and I think sheer odds back me on this. The odds are just to enormous that other life exists. There is something called the Drake Equation. Dr. Frank Drake set out to find the odds that other life exists in our Universe. Although highly controversial (his equation), it is still pretty much the only thing we have to guesstimate. The equation is only controversial because different numbers can be plugged in for different parts of the equation. The Universe is observable ONLY, it is not like we can run out there and count all that we see. So, check out the Drake Equation, and do a little research, and decide for yourself if alien life exists.