4 ms·

But won't they burn earlier in the atmosphere due to exposing bigger surface to it? AFAIU small asteroids burn in the atmosphere and thus don't reach the surfac

by akavel 3y ago

But won't they burn earlier in the atmosphere due to exposing bigger surface to it? AFAIU small asteroids burn in the atmosphere and thus don't reach the surface or reach it in very small pieces (and presumably more distributed if a bunch of them at once), vs. big ones burning less in total and hitting more concentrated; do I have it wrong?

icegreentea2 3y ago
Yes, but planet killers can be mind boggling large. The 'dinosaur killer' was estimated to be 72 teratonnes of TNT equivalent. Even if you spread that perfectly evenly over 10 days, that's a 83 MT nuke going off every second. Or taken another way, the dinosaur killer had an total estimated energy of 300ZJ - 3x10^24J. Total solar energy is 44 quadrillion W (4.4x10^16 J/s). Even spread over 10 days (864000 seconds), that results in an excess 3.5x10^18 J/s. Which is why I said it depends on what your threshold is. Certainly somewhere between city buster and dinosaur killer lies the tipping point.
- LorenPechtel 3y ago
  But you're not going to meaningfully spread the energy over time. If the bits are going to hit that means they didn't move more than 4000km after the strike. Assuming they're distributed in a sphere that means none hits more than 4000km early, either (and likewise 4000km late)--and since we are talking about objects with a relative velocity of a few km/sec that means it's dispersed over at most a couple of hours. By the back of the envelope you're looking at about a megasun. Once again, a scenario where letting the rock just hit is not as bad--energy spent gouging a huge crater is energy not spend blasting civilization.
  - LargoLasskhyfv 3y ago
    Since you're discussing Teratonnes, I'll link a discussion from X which is about what a 10GT nuclear warhead ignited at 80km altitude would do just thermally. Crossed my timeline just recently and has a link to https:// https:// apps.dtic.mil/sti/tr/pdf/ADA 383988.pdf if you don't like https://twitter.com/ToughSf/status/1689305541422575623 https://twitter.com/ToughSf/status/1689305541422575623

by akavel 3y ago

icegreentea2 3y ago

Yes, but planet killers can be mind boggling large. The 'dinosaur killer' was estimated to be 72 teratonnes of TNT equivalent. Even if you spread that perfectly evenly over 10 days, that's a 83 MT nuke going off every second. Or taken another way, the dinosaur killer had an total estimated energy of 300ZJ - 3x10^24J. Total solar energy is 44 quadrillion W (4.4x10^16 J/s). Even spread over 10 days (864000 seconds), that results in an excess 3.5x10^18 J/s. Which is why I said it depends on what your threshold is. Certainly somewhere between city buster and dinosaur killer lies the tipping point.

LorenPechtel 3y ago
But you're not going to meaningfully spread the energy over time. If the bits are going to hit that means they didn't move more than 4000km after the strike. Assuming they're distributed in a sphere that means none hits more than 4000km early, either (and likewise 4000km late)--and since we are talking about objects with a relative velocity of a few km/sec that means it's dispersed over at most a couple of hours. By the back of the envelope you're looking at about a megasun. Once again, a scenario where letting the rock just hit is not as bad--energy spent gouging a huge crater is energy not spend blasting civilization.
- LargoLasskhyfv 3y ago
  Since you're discussing Teratonnes, I'll link a discussion from X which is about what a 10GT nuclear warhead ignited at 80km altitude would do just thermally. Crossed my timeline just recently and has a link to https:// https:// apps.dtic.mil/sti/tr/pdf/ADA 383988.pdf if you don't like https://twitter.com/ToughSf/status/1689305541422575623 https://twitter.com/ToughSf/status/1689305541422575623