I remember as a kid hearing Carl Sagan talk about the billion upon billion of stars in the universe and the probability that somewhere out there, there has to be life around one of those other stars. According to the European Space Agency’s scientists, there are 1 times 10 to the 12 (a 1 with 12 zeros trailing) stars in our galaxy, and perhaps 1 times 10 to the 11 or 12 galaxies in the universe. That means there are 1 times 10 to the 23 or 24 (1 with 24 zeros trailing) stars in our universe. That is a vast amount of places that could have a planet like ours. But now we have to think small, like in chance and probabilities, and this got me postulating.
Earth is pretty rare and the conditions for making life on Earth are even rarer as coincidence after long shot coincidence happened to make Earth the perfect place for life. So, I did a little estimating and came to the possibility that the conditions that made Earth are rare enough that we MIGHT be all alone. Here are my estimates:
Everyone now knows how the Earth and moon were formed, but not everyone talks about the probabilities of the results happening just right. Here are my estimates and remember, as you multiply probabilities together, it becomes more difficult to do. So say you have a 1 in 5 chance of something happening, but when you are doing two things that have a 1 in 5 chance of happening, you now have a 1 in 25 chance of that thing happening together.
Here is my list of probabilities on Life on Earth Occurring:
- Chance of Asteroid Becoming a Moon after collision: 1 in 1,000,000
- Chance of collision tilting the Earth exactly 7 degrees: 1 in 40,000
- Chance of Sun Being the right size / giving right about of energy: 1 in 5,000
- Chance of amino acids hitting earth to begin life: 1 in 1,000
- Chance of enough water forming on earth for life to begin: 1 in 400
- Chance of Earth having enough iron to create a magnetic field to protect us from radiation: 1 in 50
- Chance of Earth being the right distance from the sun: 1 in 25
- Change of Earth being the correct size for life to form as it did: 1 in 10
Individually, all of these do not look too farfetched from what we are discovering about other worlds and stars, but taken together, the probability of life forming on Earth is EXACTLY 1 in 10 times to the 24th! The same number of stars there are in the universe, so if you multiply both numbers together, you get 1. I am NOT saying there cannot be life elsewhere, just that an Earth-like planet might be a lot rarer than we think.