r/interestingasfuck • u/howimetyourcakeshop • 9h ago

Our moon being formed.

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u/ShaggyCan 9h ago edited 9h ago

Earth is a strange planet for this reason. Because Earth's core is so large in proportion to it's diameter it has a stronger magnetic field at the surface and is denser than a planet formed through normal gravitational accretion. If Earth was any lighter, it would have ended up like Mars, unable to hold it's atmosphere. Earth is probably at the very low end of habitability due to its size. Most exobiologists look at what we call super Earth's because they are more likely to have complex life. Another cool fact is that the further you go back in time the shorter the day lasted on Earth and the closer the moon was. 65 million years ago a day was around 23 to 23.5 hours long and the moon was 2 to 3 thousand km closer.

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u/daou0782 7h ago

And do you know there’s a very narrow window where planets have the right mass/density to allow for escape velocity?

So maybe larger worlds are more habitable but life on it is trapped in their gravity wells. And lighter planets don’t normally have cores large enough to allow for magnetic fields strong enough to protect their atmospheres.

Truly a rare earth.

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u/ShaggyCan 7h ago

I'm pretty sure it's in Asimov's Foundation series where a character is actively looking for Earth, which has long been abandoned and lost, and the character sees Earth's statistics ie moons, size, density etc and exclaims that there is no such planet, no planet that small has a moon that big etc. it very much highlights how rare our planet could be.

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u/Your_New_Overlord 5h ago

Rare, yes, but with billions of solar systems there’s still a hell of a lot of others just like us.

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u/zindorsky 3h ago

Maybe. We don’t actually know the probabilities involved. What if they’re 1 in a quadrillion?

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u/traevyn 2h ago

One in a quadrillion in the entire universe is still at LEAST a few of them

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u/Your_New_Overlord 1h ago

Two sentient lifeforms are never going to meet each other, so what’s the difference? It’s just a nice thought that we’re not alone.

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u/castlite 3h ago

Not necessarily