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Comment by mtlmtlmtlmtl | Hacker News Reader

I'll chime in with gamma ray bursts from a very nearby supernova, and I suppose a black hole passing through the solar system messing up the orbits. Some simulations have suggested a small chance that Mercury's orbit will at some point be destablised by the influence of Jupiter, and that it might end up colliding with the Earth.

There's also alien invasions, pandemics, etc.

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gamma ray burst is a fun one (though unlikely thankfully!) -- a similar one that gets me excited is "false vacuum collapse" whereby the "energy" of the fabric of space itself is at a local but not global minimum. So in some unspecified conditions it drops to a lower/lowest minima and a destructive wavefront expands through the universe at the speed of light. Since the universe is so large, maybe one is already expanding right now, you'd never know (since speed of light). The upside is you'd never know it happened since death would take nanoseconds. Last I read about it, we don't know whether it's a local minima "false vacuum" versus global minimum.

I saw something about that one recently, maybe it was on Spacetime. At first it bothered me, but then I sort of made my peace with it since like you said, it's physically impossible to see it coming and we'd all die instantly. It's almost like the civilisation equivalent of going in your sleep. I could drop dead from an aneurysm 5 minutes from now. No point worrying about it though. There's sort of a morbid comfort in that.

The good news is that since the universe on the whole is expanding faster than the speed of light due to dark energy, as long as it happens far enough away the universe will be expanding too quickly for it to ever reach us.

Do any of those events have recent precedents (say in the last 5k years) apart from pandemics?

the earth has cycles, the sun has cycles, the galaxy has cycles.

Last event was 6k years, half harmonic of the main 12k years cycle. The carrington event signed the arrival of the galatic current sheet (a rippling magnetic wave emitted by the core of the milky way) which, among other things, causes the earth magnetic field to decrease.

There was no "very nearby supernova", it's just the sun and the event is much smaller but still a kind of nova (called micronova).

The induced current from the micronova is believed to be able to unlock the crust from the mantle which adds to the magnetic pole shift a physical pole shift.

The younger dryas impact theory is wrong in the way that the impact was just a proxy of the micronova (full coronal mass ejection) and not the cause.

Civilization has cycles too, I guess.

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