4 ms·

Worth pointing out square/cube factors here. You can't have an ant the size of an elephant because while an animals strength goes up as its length squared its

Worth pointing out square/cube factors here. You can't have an ant the size of an elephant because while an animals strength goes up as its length squared its weight goes up with its length cubed. And a piece of rock the size of the moon doesn't shatter into seven pieces the way a piece of rock a meter across would. It splashes.

mncharity 2y ago
Yeah, planets are puddles. It's also easy to forget the brown-dwarf-hot body inside the Moon (and the star-hot one beneath our feet). Thanks to the rock insulators between us and them, and our universal heat sink. A disassembled Moon exposing mantle material... even with T^4 blackbody energy scaling, a bolide rain a year later very won't be a problem for humans. Comparing lunar mantle with Sun, say 6x cooler, 390x closer, and say <10x angular smaller - 390^2 beats 6^4, leaving what, a new 100x "Sun"?
- jchanimal 2y ago
  I liked your comment but then I "fact-checked" it. OT but curious how wrong this is: https://chat.openai.com/share/638e5461-7a4d-4c12-9103-da1b81172b51 https://chat.openai.com/share/638e5461-7a4d-4c12-9103-da1b81...
  - IntrepidWorm 2y ago
    Although curiously, most processes theoretically capable of exposing large amounts of lunar mantle would likely generate a decent fraction of that heat just on their own merit.
  - mncharity 2y ago
    Oops, estimation fail, thanks! Attempt to double spend "closer" - on both "smaller" and "cooler". A sun-hot Moon gets you only a second Sun. A lunar-mantle-hot Moon gets you merely an extra dim red dwarf "sun". The "100x" brighter was wrong. More like 1000x dimmer? The ChatGPT looks surprisingly ok. It struggled where textbooks and such are less than wonderful. So it raises the irrelevant Sun's core, and says "The Sun's energy output is vastly greater due to nuclear fusion reactions, emitting a massive amount of radiation across the electromagnetic spectrum. The Moon, lacking such reactions, emits no comparable energy.", perhaps reflecting the textbook "Sun shines because fusion" vs "Sun glows because hot, and hot things glow (with color and intensity proportional to temperature^4), and fusion is why it's still hot billions of years after forming". Though in a way it's true - "The Moon lacking such reactions, and being small, has cooled off and greatly dimmed since its last big formation impact". :) The "Brown dwarfs typically range between about 1,000 and 2,500 degrees Celsius at their surface, far hotter than the Moon's mantle." seems inconsistent with [1]. Thanks for the check! [1] graph: https://media.springernature.com/lw685/springer-static/image/art%3A10.1007%2Fs11214-019-0613-y/MediaObjects/11214_2019_613_Fig2_HTML.png https://media.springernature.com/lw685/springer-static/image... source: Fig 2 on page 9 of https://hal.science/hal-02863845/document https://hal.science/hal-02863845/document [PDF]

mncharity 2y ago

Yeah, planets are puddles. It's also easy to forget the brown-dwarf-hot body inside the Moon (and the star-hot one beneath our feet). Thanks to the rock insulators between us and them, and our universal heat sink. A disassembled Moon exposing mantle material... even with T^4 blackbody energy scaling, a bolide rain a year later very won't be a problem for humans. Comparing lunar mantle with Sun, say 6x cooler, 390x closer, and say <10x angular smaller - 390^2 beats 6^4, leaving what, a new 100x "Sun"?

jchanimal 2y ago
I liked your comment but then I "fact-checked" it. OT but curious how wrong this is: https://chat.openai.com/share/638e5461-7a4d-4c12-9103-da1b81172b51 https://chat.openai.com/share/638e5461-7a4d-4c12-9103-da1b81...
- IntrepidWorm 2y ago
  Although curiously, most processes theoretically capable of exposing large amounts of lunar mantle would likely generate a decent fraction of that heat just on their own merit.
- mncharity 2y ago
  Oops, estimation fail, thanks! Attempt to double spend "closer" - on both "smaller" and "cooler". A sun-hot Moon gets you only a second Sun. A lunar-mantle-hot Moon gets you merely an extra dim red dwarf "sun". The "100x" brighter was wrong. More like 1000x dimmer? The ChatGPT looks surprisingly ok. It struggled where textbooks and such are less than wonderful. So it raises the irrelevant Sun's core, and says "The Sun's energy output is vastly greater due to nuclear fusion reactions, emitting a massive amount of radiation across the electromagnetic spectrum. The Moon, lacking such reactions, emits no comparable energy.", perhaps reflecting the textbook "Sun shines because fusion" vs "Sun glows because hot, and hot things glow (with color and intensity proportional to temperature^4), and fusion is why it's still hot billions of years after forming". Though in a way it's true - "The Moon lacking such reactions, and being small, has cooled off and greatly dimmed since its last big formation impact". :) The "Brown dwarfs typically range between about 1,000 and 2,500 degrees Celsius at their surface, far hotter than the Moon's mantle." seems inconsistent with [1]. Thanks for the check! [1] graph: https://media.springernature.com/lw685/springer-static/image/art%3A10.1007%2Fs11214-019-0613-y/MediaObjects/11214_2019_613_Fig2_HTML.png https://media.springernature.com/lw685/springer-static/image... source: Fig 2 on page 9 of https://hal.science/hal-02863845/document https://hal.science/hal-02863845/document [PDF]