The following is a reader’s comment on yesterday’s piece about the likelihood of finding alien life in the galaxy.
I’m a proponent of the rare earth hypothesis myself. I would be surprised if there were more than 10 carbon copies of Earth in the Milky way, but I wouldn’t be surprised if we were the only Earth in the galaxy. I think normies, and even a lot of higher IQ people are way, way, way too optimistic about the odds of intelligent alien life. Allow me to enumerate all the intricacies that make Earth so special:
Firstly, an Earthlike planet has to have a long lasting molten core. Earth is the only rocky planet in the solar system, including all known dwarf planets, which has a molten core. Which is hypothesized to have arisen as a result of two proto-planets colliding in the primordial solar system. The heavier of the two protoplanets absorbed the core of the lighter planet, and much of the debris from the second planet; the millions of shards that began orbiting the what became proto-Earth coalesced into the proto-moon. Earth’s molten supercore provides our magnetosphere which deflects solar wind, preserving the atmosphere and ocean. Without the magnetosphere, Earth would be as sterile as Venus or Mars. The molten core also provides long lived hypervulcanism which has emitted green house gas over the eons preventing the Earth from freezing over during severe ice ages; volcanic eruptions provided many essential heavier metals found in our soil and crust crucial for life and tool making.
Secondly, and of course the most basic bitch of them all, the Earth like planet has to lie in the star’s “goldilocks zone.” Too close, and it’s a perpetual hell on Earth. Too distant, and it’s a perpetual winter wonderland.
You need a giant moon relative to the Earth, which stabilizes Earth’s rotation on a reliable axial tilt. Otherwise you do not have stable long lasting climates, and prevailing winds can reach hundreds of miles per hour.p A binary, tertiary, etc. solar system with multiple stars reduces the chances of life. Planets are hotter, and the orbits are not as stable. You also often have stars of different masses in these systems. So you could have a parent star with an Earth that was the same size and as stable as our sun, which shared a solar system with a larger star that goes supernova after a couple billion years, and blows up the Earth. All stars larger than G-type main sequence stars burn out within 3 billion years or less. Cellular life took 3 billion years to develop on Earth. M-type main sequence stars, aka Red Dwarfs, are also ill suited for life. Because the goldilocks zone for M-types is so close to the star, that the star’s gravity would tidally lock the Earth, as the moon is tidally locked to Earth, so one side of the planet would be eternal day, the other eternal night. Red dwarfs also produce very little blue light, crucial for photosynthesis. Without photosynthesis, you do not have oxygen
You ideally want a series of outer gas giants behind your Earth 2.0 similar to Jupiter, Saturn, Uranus and Neptune, whose gravity sucks up the majority of asteroids from the fringes of the solar system and beyond
You need to have the right galaxy. If you have an unorganized, irregular galaxy like the large magellanic cloud, you’re going to have too much radiation, and too little metallicity to A) sustain life, B) form rocky Earth like planets. Also, even if you have the right galaxy, if that galaxy then collides with another, it can upset the equilibrium and reorient the solar system into a bad place in the course of a few million years.
There is a galactic goldilocks zone, similar to the solar goldilocks zone. If the solar system is too close to the center of a spiral galaxy, there is too much background radiation for life to evolve into complex forms. If the star is too far away from the center, there is again, too little metallicity to form rocky planets.
Even if you have all these predicates, Earth is 4.5 Billion years old. We’ve only had radio contact for 100 years. So records of our existence beyond Earth only extend out 100 light years from Earth. And of course radio waves become more diffuse and unintelligible as they expand out into space. So odds are, assuming there are a few to even a few thousand other Earths out there, intelligent civilizations capable of detecting radio waves evolved on those Earths and then went extinct, or intelligent civilizations capable of detecting radio waves have yet to evolve on those Earths, if they ever do. And if by some fluke there is another contemporary civilization capable of detecting radio waves right now out there somewhere, the odds are again, it exists too far from Earth to detect our radio waves.