Earth was born dry until a cosmic collision made it a blue planet • Hacker News Board

Re: Earth was born dry until a cosmic collision made it a blue planet

#111

Post by 3eb7988a1663 » Sat, Oct 04, 2025, 6:13 PM UTC

leoedin wrote: post #74

echelon wrote: post #68

Earlier quoted context omitted.

And you have to have multiple low probability events. These probabilities multiply. We had a good start. A Jupiter to clear the debris, a Theia impact to create tides and contribute to tectonics, a magnetic core, a shielded atmosphere. We had water delivered to us. Maybe even panspermia. Maybe cell walls and mitochondria are hard. Maybe multicellular is hard. Maybe life on land is hard. Building lungs, rebuilding eye…

Even on Earth, the only reason humans exist is because the “local maximum” of the dinosaurs was wiped out by a meteor. Perhaps comparably intelligent dinosaurs would have eventually evolved - but it’s not a given!

Dinosaurs existed for some 200 million years with no detectable signs of technology development[0]. Presumably, the steady state did not produce a scenario in which the intelligence niche would develop without some other less catastrophic global change event.

[0] Unless that episode of Voyager was right on the mark https://memory-alpha.fandom.com/wiki/Distant_Origin_(episode...

Re: Earth was born dry until a cosmic collision made it a blue planet

#112

Post by alganet » Sat, Oct 04, 2025, 6:17 PM UTC

stared wrote: post #6

Imagine this sci-fi plot twist: Aliens make live habitable by hitting proto-Earth with a planet, so life can sprout there. They calibrated it such a way that angular size of Moon is the same as of Sun.

Imagine the real twist being that complex intelligent life on a planet only goes past some critical development point if there's some sort of weird coincidence in the sky that pushes its inhabitants to understand the mystery.

It's the weirdest filter: you need a giant sign that points you where to look for answers. Without it, you're less likely to find what the universe is all about.

Re: Earth was born dry until a cosmic collision made it a blue planet

#113

Post by ahazred8ta » Sat, Oct 04, 2025, 6:20 PM UTC

praptak wrote: post #28

So we're not only made of elements which formed inside star(s) but also ones merged from two different planets. This is weird.

There was a giant incandescent donut involved, too. https://en.wikipedia.org/wiki/Synestia

Re: Earth was born dry until a cosmic collision made it a blue planet

#114

Post by Panzerschrek » Sat, Oct 04, 2025, 6:21 PM UTC

ricksunny wrote: post #106

Panzerschrek wrote: post #104

I don't understand why all these volatiles (hydrogen, nitrogen) didn't evaporate during such huge collision, which likely melt the whole Earth's crust. Even if a temporary atmosphere was formed, with high post-impact temperatures this atmosphere can't stay long.

As far as we know, molecules and atoms escaping into space comes due to the solar wind. Somehow the solar wind activates these atoms and carries them off into the distant vacuum, ad infinitum presumably though (I would imagine) limited by the heliopause. [edit, benefiting from convo: mechanisms on atmospheric escape, to varying degrees of verification) • https://en.wikipedia.org/wiki/Atmospheric_escape • https://en.w…

With high enough temperature some molecules may achieve velocities enough to escape. The question is - how hot was it really? The initial collision happened at least with escape velocity, so there was roughly enough energy for volatiles an non-volatiles to escape. But non-volatiles condensed presumably pretty quickly (but were still hot) in comparison to volatiles.

Re: Earth was born dry until a cosmic collision made it a blue planet

#115

Post by dotancohen » Sat, Oct 04, 2025, 6:28 PM UTC

scarmig wrote: post #76

buran77 wrote: post #45

Earlier quoted context omitted.

The equation itself makes no assumptions. But anyone trying to calculate something with it must. The last five factors in the equation will be filled in by assumptions based entirely on one data point, life on Earth. From your link: ne = the average number of planets that can potentially support life per star that has planets. fl = the fraction of planets that could support life that actually develop life at some poi…

It does assume that life must be associatable with a planet. It's a plausible assumption, but you could also hypothetically have life develop on a star itself or its remnants, comets, clouds of interstellar gas. Maybe even something more exotic than that (dark matter? some weird correlated statistical properties of the quantum foam?)

About forty years ago I read a terrific book about life forms that live on a star. Maybe Starquake was it called? Did to the abundance of energy on the surface of a star, they live their lives a million times faster than humans. Thus for both them and the humans who discover them, communication is difficult. I think the humans push these life forms to develop civilization, which from the human's perspective had them go from primitive animals into sophisticated beings of technology past their own in something like a day.

Re: Earth was born dry until a cosmic collision made it a blue planet

#116

Post by dotancohen » Sat, Oct 04, 2025, 6:32 PM UTC

stared wrote: post #107

vardump wrote: post #54

Earlier quoted context omitted.

The Moon was much closer to the Earth when it was formed. It's slowly becoming more distant. So the angular size has matched the Sun only for 450 million years. In 50 million years it's angular size will be smaller and total solar eclipses will be impossible. Note: Due to the Moon's orbit, the whole story is more complicated.

I know that. But in this scenario, aliens know the timescale of appearance of life intelligent enough it can appreciate solar eclipse.

It seems we only developed in the last 90% of time during which solar eclipses are possible. Perhaps we're slow compared to our galactic sisters and brothers.

Re: Earth was born dry until a cosmic collision made it a blue planet

#117

Post by mattmaroon » Sat, Oct 04, 2025, 6:42 PM UTC

HarHarVeryFunny wrote: post #40

shireboy wrote: post #4

This could mean in the Drake equation ne -number of planets capable of life- is very small. A planet has to be hit with a comet big enough to deliver a large amount of water but not so big or fast to destroy it. And be in the Goldilocks zone of the star. Also the mass of the planet would play a part - gravity of more massive ones would be more likely to capture a comet. But again, too massive and I could see that ham…

The thing is that even for a super low probability event, the size of the universe is so huge and such events must be happening all the time. e.g. Say chance of a random planet ever being hit by a water-carrying comet is one in a billion, then with 100B - 1T planets in the milky way it'd happen here 100-1000 times. If chances are only one in a trillion, and we're the one in the milky way, then there are still another…

If the numbers you propose turn out to be accurate then the odds of there being other life are near zero because even 1/1000 planets are not habitable likely.

Re: Earth was born dry until a cosmic collision made it a blue planet

#118

Post by Qem » Sat, Oct 04, 2025, 6:46 PM UTC

macintux wrote: post #109

echelon wrote: post #68

Earlier quoted context omitted.

And you have to have multiple low probability events. These probabilities multiply. We had a good start. A Jupiter to clear the debris, a Theia impact to create tides and contribute to tectonics, a magnetic core, a shielded atmosphere. We had water delivered to us. Maybe even panspermia. Maybe cell walls and mitochondria are hard. Maybe multicellular is hard. Maybe life on land is hard. Building lungs, rebuilding eye…

My pessimistic side says that the conditions for intelligent life are so implausible that we’re unique, and when we drain the planet dry of easily-accessible fossil fuels we’ve deprived any successor civilization of its opportunity to escape the planet. Basically I fear we’re the universe’s only shot of appreciating and populating the galaxy (or beyond) and we’re on the brink of throwing that away.

> ...when we drain the planet dry of easily-accessible fossil fuels we’ve deprived any successor civilization of its opportunity to escape the planet.

On the flip side, that could also be plausibly a blessing, avoiding them to fall into the same trap of becoming too powerful before they get wise. These comics illustrate it: https://www.badspacecomics.com/post/grounded

Re: Earth was born dry until a cosmic collision made it a blue planet

#119

Post by catigula » Sat, Oct 04, 2025, 6:57 PM UTC

Tough to gain any predictive information here due to the anthropic principle requiring a series of comical happenstance for observation to even occur.

Re: Earth was born dry until a cosmic collision made it a blue planet

#120

Post by HarHarVeryFunny » Sat, Oct 04, 2025, 7:01 PM UTC

macintux wrote: post #109

echelon wrote: post #68

Earlier quoted context omitted.

And you have to have multiple low probability events. These probabilities multiply. We had a good start. A Jupiter to clear the debris, a Theia impact to create tides and contribute to tectonics, a magnetic core, a shielded atmosphere. We had water delivered to us. Maybe even panspermia. Maybe cell walls and mitochondria are hard. Maybe multicellular is hard. Maybe life on land is hard. Building lungs, rebuilding eye…

My pessimistic side says that the conditions for intelligent life are so implausible that we’re unique, and when we drain the planet dry of easily-accessible fossil fuels we’ve deprived any successor civilization of its opportunity to escape the planet. Basically I fear we’re the universe’s only shot of appreciating and populating the galaxy (or beyond) and we’re on the brink of throwing that away.

As long as we have air and water (i.e. as long as we're alive), then we can make propellants such as Methane or Liquid Hydrogen and LOX, Hydrazine & Dinitrogen Tetroxide (or Hydrogen Peroxide).