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

#121

Post by ricksunny » Sat, Oct 04, 2025, 7:10 PM UTC

Panzerschrek wrote: post #114

ricksunny wrote: post #106

Earlier quoted context omitted.

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.

Yes I was being a bit too glib in relegating atmospheric escape mechanisms exclusively to action by the solar wind. Lot of proposed mechanisms, uncertain how many of them are verified and quantified to what magnitude.

https://en.wikipedia.org/wiki/Atmospheric_escape

https://en.wikipedia.org/wiki/Hydrodynamic_escape

As a layperson I see our current epistemological state as long on models, and short on empirical verification (because we're talking about a difficult phenomenon to verify).

I think I mostly wanted to offer counterpoint to the original comment that 'this atmosphere can't stay long' i.e. even under elevated temperatures.

(I'll probably update my prev comment with those wikipedia links.)

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

#122

Post by erickf1 » Sat, Oct 04, 2025, 7:11 PM UTC

From a purely mathematical, scientific, and logical standpoint, I must regard this article as entirely speculative. The scientific claims it presents are extraordinarily improbable, and sound reasoning compels their complete dismissal.

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

#123

Post by ElFitz » Sat, Oct 04, 2025, 7:13 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?)

Andy Weir’s Project Hail Mary had an interesting take on that.

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

#124

Post by HarHarVeryFunny » Sat, Oct 04, 2025, 7:23 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!

Intelligence evolved at least three times on earth - dinosaurs (leading to corvids, but a raptors already intelligent), mammals and cephalopods (e.g. octopus).

I suspect that any evolutionary environment will eventually create enough variety and instability that some generalists emerge, creating a reward for intelligence. The rise in intelligence from early water-bound life to later forms was likely all driven by more complex and diverse environments.

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

#125

Post by LeifCarrotson » Sat, Oct 04, 2025, 7:26 PM UTC

dotancohen wrote: post #115

scarmig wrote: post #76

Earlier quoted context omitted.

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…

That's "Dragon's Egg" by Robert L. Forward, a classic Sci-fi story:

https://annas-archive.org/md5/4c381ac344506d10037fc8e7747098...

The cheela lived on the surface of a neutron star, and they lived faster because the nuclear physics that powered their metabolism are far faster than the chemical and mechanical physics that power our own.

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

#126

Post by eep_social » Sat, Oct 04, 2025, 7:31 PM UTC

ricksunny wrote: post #110

>was rich in volatile elements essential for life, such as hydrogen, carbon and sulphur. Today years old on learning that 'carbon' is a 'volatile element'. (I come to learn that astrogeology has a unique definition of volatile). • The summary's own source article points makes no reference to carbon being volatile. • The wikipedia article for 'volatiles' in the astrogeological sense makes no reference to carbon being…

I take this as “volatile” in the sense that it bonds easily with other molecules

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

#127

Post by quotemstr » Sat, Oct 04, 2025, 7:37 PM UTC

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…

Planetary collisions happen all the time. All of Mercury, Venus, Earth, and Mars in our solar system had them. We can see their signatures in other solar systems too: see https://en.wikipedia.org/wiki/List_of_extrasolar_planetary_c...

Whatever the great filter is, it's not planetary-scale collisions during the accretion phase of solar system formation.

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

#128

Post by QuantumGood » Sat, Oct 04, 2025, 7:37 PM UTC

erickf1 wrote: post #122

From a purely mathematical, scientific, and logical standpoint, I must regard this article as entirely speculative. The scientific claims it presents are extraordinarily improbable, and sound reasoning compels their complete dismissal.

History repeatedly shows that the popular: "extraordinary claims demand extraordinary evidence" is often dependent on the frame of reference.

What is thought to be likely is used to frame conventional wisdom as truth, making the new viewpoint "extraordinary, until, over and over again, the new viewpoint becomes conventional wisdom. So "extraordinarily improbable" is really just an overton window framing (what we accept/don't accept), rather than a statement based in logic. Though your overall framing reminds me so much of historical phrases that I wonder if you are being intentionally ironic.

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

#129

Post by HarHarVeryFunny » Sat, Oct 04, 2025, 7:38 PM UTC

mattmaroon wrote: post #117

HarHarVeryFunny wrote: post #40

Earlier quoted context omitted.

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.

Huh? Even in the 1-in-a-trillion case, there's still maybe 1 trillion galaxies each with one planet that was struck by a water bearing comet, so even if only 1/1000 of those are otherwise habitable, that still leaves a billion habitable planets in the universe with water.

I doubt water (H2O) is actually that rare. The most common elements by far, both in our own galaxy and the universe as a whole, are Hydrogen and Helium, but the next two most common are Oxygen and Carbon.

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

#130

Post by corimaith » Sat, Oct 04, 2025, 7:52 PM UTC

JamesLeonis wrote: post #35

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 Drake Equation is filled with assumptions, like life must appear on a planet in the Goldilocks zone of a star. The whole equation has only one datapoint to extrapolate from. Tweak the equation's parameters and it will predict universes that only have one civilization per galaxy or worse! We have no way of knowing what those parameters are because we haven't seen other examples. A major reason we are interested in…

Even if you only had a handful of civilizations, the sheer time that has passed and size of the universe should mean that life should still be alot more apparent.

With sublight velocities achievable today, I recall it would only take around a million years for a Von Newmann probe to cover the entire galaxy. Such a probe is quite conceivable, so why isn't there more evidence of such probes everywhere?

Another point I feel is that proliferation of life should be an self-reinforcing affair, for intelligent life even more so. A spacefaring nation may terraform or just seed planets, and these in time will replicate similar behaviors. At a certain point, a galaxy teeming with life should be very hard to reverse given all the activity. A life itself isn't necessarily evolved from biology, AI machine lifeforms should also well suited to proliferate, yet we don't see them anyways.