r/interestingasfuck • u/howimetyourcakeshop • 10h ago

Our moon being formed.

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u/ShaggyCan 10h ago edited 10h 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 8h 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/hikerguy555 7h ago

Wait what. What do you mean "allow" for escape v? Like if the planet had more gravity couldn't it be escaped with more force? Is it because the curvature also increases (decreases?)? I'd still feel like saying it'd be impossible for life to escape it doesn't feel right while simultaneously acknowledging that science doesn't care what "feels right"

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u/KingDudeMan 7h ago

If their was too massive, gravity would make escape velocity less feasible, so smart species could still remain “trapped” on their planet. Is it possible? Probably, but it’s dramatically harder and becomes less “worth it”.