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Dynamical origin of Theia, the last giant impactor on Earth

(arxiv.org)
92 points bikenaga | 6 comments | 08 Jul 25 18:10 UTC | HN request time: 0s | source | bottom
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echelon ◴[08 Jul 25 19:36 UTC] No.44503282[source]▶
Imagine if life had evolved on Earth or Theia prior to impact. Imagine if it was intelligent and played witness to the giant cataclysm.

Given that intelligence took an awfully long time to emerge from LUCA, that seems implausible. But it's fun to imagine pre-Theia "Silurians". That sort of impact would have scorched earth of any trace or remnant of their existence. It feels as though there must be sufficiently advanced civilizations out there witnessing this exact scenario play out without the necessary technology to stop it. Though that fate would be horrifying.

Another thing to think about is that shortly after the Big Bang (if there was one, Lamda-CDM or similar models holding up), was that shortly after the Big Bang the temperature of the early universe was uniformly 0-100 degrees Celsius. It may have been possible for life to originated in this primordial interstellar medium without even so much as needing a host planet or star! Just life coalescing in space itself.

That early primordial soup, if it existed, could have seeded the whole universe. Most aliens might have matching molecules and chirality if those decisions predate our galaxy.

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1. andrewflnr ◴[08 Jul 25 21:37 UTC] No.44504282[source]▶
> It feels as though there must be sufficiently advanced civilizations out there witnessing this exact scenario play out without the necessary technology to stop it. Though that fate would be horrifying.

I suspect this is not actually that common. Giant impacts are more common in early solar systems; things eventually settle into nice circular orbits like we have now. Whereas intelligent life does seem to take a while to evolve, so probably more common later in a solar system's life cycle.

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2. echelon ◴[08 Jul 25 23:28 UTC] No.44504943[source]▶
Uncommon for sure.

Our sun and earth won't last long enough, but Mercury's orbit is potentially unstable.

A red dwarf might harbor live bearing planets long enough to see its long-lived orbits eventually destabilize. Or perhaps witness the even rarer interstellar collision or destabilization from rogue planets, etc.

3. dylan604 ◴[09 Jul 25 00:50 UTC] No.44505339[source]▶
> Whereas intelligent life does seem to take a while to evolve

basing that theory on an anecdotal story of 1.

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4. kaliqt ◴[09 Jul 25 01:31 UTC] No.44505538[source]▶
While true, the opposite is true that we have zero evidence of any life whatsoever, anywhere, ever, except with us.
5. nkrisc ◴[09 Jul 25 02:12 UTC] No.44505756[source]▶
You got better evidence?
6. andrewflnr ◴[09 Jul 25 03:51 UTC] No.44506185[source]▶
Depends how you count it. One planet, but a solid handful of mass extinctions with big adaptive radiations, most with several million years of development, and tons of reasonably intelligent social animals, only one of which produced industrial civilization. But yes, working with the best evidence we have...