The Fermi Paradox Asks Where All The Aliens Are


The part of the universe that we can see is actually a teeny tiny bit of the whole thing. So there comes the age-old question: Where is everybody? Or more importantly, is there anyone at all? Here’s how the Fermi paradox theorizes these questions.

First of all, it’s useful to remember how much of the universe we can observe.

When we look at the night sky, we can’t help but think how enormous the universe is. In fact, what you can see is nothing compared to what you can’t. We can only see about 2500 stars if we’re lucky, and these stars are all closer to us than 1000 light years. In the picture above, you can see how little we can see with our naked eyes.

It’s estimated that there should be around 100-400 million stars in our galaxy.

Also, this number should be the number of galaxies in the whole universe. Then the number of stars in the universe should be 10^22-10^24.

Now let's look a little farther away.

Scientists don’t know how many of these stars resemble our Sun in terms of their size or radiance, but the estimated probability is 5%-10%. Even if only 5% of them are like our Sun, it means there should be 500 quintillion stars in the universe that are pretty much like our Sun.

What about planets?

According to scientists, planets orbiting around stars that have necessary conditions to enable life on them should be around 22%-50% of the whole number. Again even if we take the smallest number to make predictions, at least 1% of the stars should have planets orbiting around them that are similar to the Earth, which means there should be 100 quintillion planets like ours in the universe.

There comes the question of life...

Even if intelligent life occurs on only a minuscule percentage of planets around these stars, there might still be a great number of extant civilizations, and if the percentage were high enough it would produce a significant number of extant civilizations in the Milky Way. This assumes the mediocrity principle, by which the Earth is a typical planet.

Physicist Enrico Fermi asks: “Where is everybody?”

According to the line of reasoning, Earth should have already been visited by extraterrestrial aliens. But why haven't they contacted us yet?

There are a few theoretical answers to this question. Here are some of them…

They haven’t contacted us because we are the only advanced civilization in the universe.

They may have visited Earth before human life existed.

Or perhaps there are others out there, but we are too primitive to talk to them, or they have chosen not to reveal themselves to us yet.

Or they actually exist, and they have already contacted us, but the authorities haven’t make it public yet. (Conspiracy theorists like this one the best, I guess.)

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