The Fermi Paradox

Things that go BOOM

Greetings from the Couch
Oct 15 · 3 min read

The great filter is a theoretical barrier that species must overcome to survive and evolve. It’s a part of a paradox Italian physicist Enrico Fermi proposed in 1950 to explain why we have yet to hear from intersteallar civilizations, basically asking “where are all the little green aliens?”.

I need to explain some bits about the universe before I can get to the aliens because Life (as we know it) Is Complicated and can only occur after stars explode. No, really.

Things that go BOOM

A few stars need to explode before we can get anywhere near life as we know it, because we’re made up of a bunch of different elements, none of which were available in the early universe, which started with a sudden expansion, transitioned into a soup of energy, then cooled and condensed into the first atoms, starting with Hydrogen, which condensed slowly into stars.

Put another way, when you have a lot of anything close together, sooner or later bits of it clump together. When they clump together, the weight (mass) increases and more stuff clumps together. It’s like adding marbles to a trampoline. Sooner or later some will clump together, which increases the weight on the surface, creating a distortion. At which point anything on the edge of that distortion heads down to the centre. Keep doing that long enough and sooner or later there’ll be a big mass of marbles sitting together. Which helps with cleanup because sooner or later, someone’s going to want to use the trampoline for something else.

Stars work because their mass (weight) holds a lot of hydrogen in one place through gravity. And we know stars are made of Hydrogen and Helium because of Cecelia Payne’s doctoral thesis, published in 1925.

Now you need a truly enormous amount of Hydrogen to form a star. Here’s a size comparison of our sun compared to the planets just to give an idea of how much we’re talking about.

Image by Roberto Zinche at

If you zoom in, you’ll see me waving at you, third from left.

The combined weight of the sun is 1,988,500 x 10²⁴kg. That’s this number:


And ours is not particularly noteworthy.

By comparison, The Earth is a piddly 5.9724 x10²⁴ kg, or 5,972,400,000,000,000,000,000,000kg.

When you’ve got that much mass things get very very hot at the centre. And when there’s a temperature of, say, 4,000,000 Kelvin, or 3999726.85 Celsius, a bunch of complicated reactions occur that Ethan Siegel clarifies in “The Sun’s Energy Doesn’t Come From Fusing Hydrogen into Helium (Mostly)”. But to summarize, nuclear fusion occurs where Hydrogen becomes a bunch of other elements and an enormous amount of energy is thrown outwards, the same as in a nuclear explosion.

But the process doesn’t last forever, the fuel runs out and the fusion gets complicated. When you run out of Hydrogen, the Helium forms Carbon, next on the periodic table. As these heavier molecules are drawn into the core by gravity, temperatures increase again, creating more elements and running out of others. The size of star determines how far this process goes and how much is thrown out into the cosmos through expansion, throwing off layers and even explosion.

What’s this mean for us? Every element in DNA is produced in exploding stars. All life on this planet originated in the core of a star that then exploded, throwing the elements outward.

Next up

Organisms and the Fermi Paradox

Disorderly Instruct

Sharing knowledge and making things clear

Greetings from the Couch

Written by

Really not a neural network enhanced instabot from the nastiest burrows of the darknet. (also do chai reviews on @melbournechai )

Disorderly Instruct

Sharing knowledge and making things clear

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