[HN Gopher] Earth was born dry until a cosmic collision made it ...
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Earth was born dry until a cosmic collision made it a blue planet
Author : amichail
Score : 183 points
Date : 2025-09-30 16:54 UTC (4 days ago)
(HTM) web link (www.sciencedaily.com)
(TXT) w3m dump (www.sciencedaily.com)
| alexey-salmin wrote:
| Ah the First Impact
| rd07 wrote:
| I know this reference lol
| zkmon wrote:
| All life on Earth is illegal immigrants from another planet.
| ReptileMan wrote:
| Only if the earth was seeded with life.
| pfdietz wrote:
| Which is possible, at least from sites elsewhere in the young
| solar system. Life might have originated on Mars, for
| example, or perhaps in one of many small, warm, wet
| asteroids. These early asteroids were kept from freezing up
| by the presence of short lived radioisotopes, the decay
| products of which are detectable today in parts of
| meteorites.
| subscribed wrote:
| Which seems to be quite possible. This is what we have from
| just one mission: https://www.esa.int/Science_Exploration/Spa
| ce_Science/Rosett...
| zkmon wrote:
| Sorry, I was only joking. Someone got busy seriously down
| voting! Maybe wrong times to utter the phrase "illegal
| immigrants". I get it.
| prerok wrote:
| Well, I for the count of one, didn't think it bad, but
| thought provoking. We're all immigrants, when you get deep
| into it (speaking from Europe, where we usurped previously
| native folk some 1500 years ago), and we all came from Africa
| anyway.
|
| But, yeah, political implications nowadays are a slippery
| slope.
| shireboy wrote:
| 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 hampering life.
| OgsyedIE wrote:
| Unless collisions like the article suggests are a statistical
| inevitability, that is.
| dotancohen wrote:
| Hydrogen is the most common element in the universe. So long
| as you have elemental oxygen, it will react with things and
| hydrogen is the thing it will react with the most. So having
| water is almost a given for any Star system. Additionally,
| protoplanet and cometary collisions are in fact statistically
| inevitable. The real question is if water can be delivered at
| a point after enough gravity has amassed to ensure the water
| stays there.
| jug wrote:
| Right, that's the sticky point? The likelihood of a planet in
| the Goldilocks zone to be too hot in the early stage of
| stabilizing its chemistry that it requires seeding with
| "post-formation" chemistry? Is that likelihood close to 100%,
| or maybe not even near and we were just set up for a funny
| cosmic event.
| xbmcuser wrote:
| Your assumption we need water for life to exist is in my
| opinion wrong. We only know Earth so assume that is what is
| needed for life to exist.
| yosefk wrote:
| What's the chemistry of life without water? Do you refer to
| the promising Russian studies of life sustained by alcohol?
| joshuahedlund wrote:
| There is a hard limit on the number of atomic elements, and
| an even smaller limit on the number of soluble compounds that
| facilitate chemical reactions, and water is demonstrably both
| the best and the most common in the universe.
|
| So while it may be possible for life to exist without water,
| any alternatives should be reasonably expected to be even
| more rare than water-based life
| caymanjim wrote:
| There's a reason life is carbon-based, and it's not random.
| It's the only element that works, due to abundance; ability
| to form many bonds; bonds that are just durable enough but
| not too durable. There's plenty of sci-fi about silicon-based
| life, but that's infeasible fantasy. And no other elements
| have any hope. If you have carbon-based life, you need water
| as solvent and medium.
|
| It's a pretty safe assumption that all life requires water.
| marcosdumay wrote:
| > due to abundance; ability to form many bonds; bonds that
| are just durable enough but not too durable
|
| Well, the thing is that all of those are environment-
| dependent.
|
| We do have data on a somewhat diverse set of environments,
| and it's enough to confirm what we knew about the
| flexibility of carbon. But it's not enough to disprove the
| alternatives.
| Animats wrote:
| > There's plenty of sci-fi about silicon-based life, but
| that's infeasible fantasy.
|
| Right. Silicon dioxide is quartz.
|
| Longer analysis.[1]
|
| [1] https://www.the-ies.org/analysis/does-silicon-based-
| life-exi...
| warent wrote:
| You're getting a lot of negative feedback for whatever
| reason, but you're absolutely right.
|
| I for one remember reading about possible silicon/methane
| based life, etc. Actually, here's a whole wikipedia article
| on what you're talking about.
|
| https://en.m.wikipedia.org/wiki/Hypothetical_types_of_bioche.
| ..
|
| Perhaps HN folks will lose your scent now and direct their
| snark there
| Mistletoe wrote:
| But when you dig down deep on theories like that it just
| doesn't make sense from a chemistry or physics standpoint.
| Everyone saw that Star Trek episode about silicon based
| life and ran with it as being possible. It's just a show.
|
| https://en.wikipedia.org/wiki/The_Devil_in_the_Dark
|
| https://lweb.cfa.harvard.edu/~ejchaisson/cosmic_evolution/d
| o...
| modius2025 wrote:
| 1. xbmcuser's point: They challenge the anthropocentric
| (Earth-centric) assumption -- "we only know life as we know
| it." Philosophically valid, but scientifically weak without
| proposing a viable alternative chemistry.
|
| 2. joshuahedlund's reply: Grounds the argument in chemistry
| and probability.
|
| There are only ~90 stable elements - a finite combinatorial
| chemistry space.
|
| Among possible solvents, water is the most abundant and
| chemically versatile (dipolar, wide liquid range, high heat
| capacity, good at dissolving ions and organics). - So even if
| other solvents can work (like ammonia, methane, formamide),
| the odds heavily favor water-based life.
|
| 3. caymanjim's addition: Brings in carbon's unique valence
| behavior:
|
| 4 valence electrons - can form stable, complex chains and
| rings.
|
| Bonds are strong but not too strong - dynamic yet stable
| biochemistry.
|
| Silicon (next best candidate) forms brittle, static lattices
| and poorly soluble oxides - bad for metabolism. - Therefore:
| if life is carbon-based, water is the only sensible solvent.
| adverbly wrote:
| No kidding... This would probably resolve the Fermi paradox if
| proven true...
| frankohn wrote:
| I agree. In addition to the chemical elements like water, as
| mentioned in the article, the impact with Theia also enabled
| strong magmatic activity at the core of the planet, and that
| was a critical element as well to sustain life.
|
| Probably the strong magnetic activity of the Earth's core was
| key to maintaining the atmosphere, but also, the magmatic heat
| contributed to keeping the planet at a good temperature to
| support life when a young Sun provided significantly less
| radiation.
|
| All these elements may suggest that the collision is needed to
| satisfy the very strict requirements about where the planet is
| located and about the size and composition of the colliding
| planet. This makes the probability for life-sustaining planets
| in the Drake equation extremely low.
|
| As an indirect proof of the tightness of the condition is the
| fact that the Earth in its history had periods of climate
| extremes hostile to life, like the Snowball Earth when the
| planet was completely covered by ice and snow, or at the
| opposite extreme, the very hot periods when the greenhouse
| effect was dominating the climate.
| JamesLeonis wrote:
| 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 Europa is because it might
| have underground oceans. Hypothetically, through tidal forces
| with Jupiter, the moon's core is hot enough to create oceans
| under the ice crust. Combined with hydrothermal vents you have
| the possibility for deep sea life similar to our own deep
| oceans. The Drake Equation does not predict this possibility.
| mr_mitm wrote:
| The Goldilocks zone doesn't enter the Drake equation at all.
|
| As a reminder, this is the equation:
| https://en.wikipedia.org/wiki/Drake_equation#Equation
|
| It makes very few assumptions.
| crazygringo wrote:
| I'm assuming they were referring to this term:
|
| > _n_e = the average number of planets that can potentially
| support life per star that has planets._
|
| The fact that the planet is neither too hot nor too cold
| would seem to be a major component of this term:
|
| https://en.wikipedia.org/wiki/Habitable_zone
| mr_mitm wrote:
| That's just your interpretation. Take the equation at its
| face value and it does allow for life originating around
| some deep sea vents, like JamesLeonis speculated.
| acestus5 wrote:
| yeah you are right the Drake equation does not assume
| Goldilocks zone.
| stouset wrote:
| It goes the other way around. The Goldilocks zone is a
| shorthand attempt at helping us guess how many planets
| out there are capable of supporting life.
| DennisP wrote:
| It does seem unlikely that such life forms would ever
| become spacefaring.
| rowanG077 wrote:
| That's a separate term in the equation.
| DennisP wrote:
| Yes, but we should consider these linkages when setting
| values. If we assume that volcanic vent life is very
| unlikely to become spacefaring, we should either leave it
| out of the "life" term, or leave it in but lower the
| probability of the "becomes spacefaring" term.
| buran77 wrote:
| 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
| point. fi = the fraction of planets with life that go
| on to develop intelligent life (civilizations). fc =
| the fraction of civilizations that develop a technology
| that releases detectable signs of their existence into
| space. L = the length of time for which such
| civilizations release detectable signals into space.
|
| Can you define any one of those without assumptions, in a
| scientifically proven way?
| mr_mitm wrote:
| Thanks, I read that part before I shared it. It's pretty
| clear to me, these are pretty well defined quantities,
| just hard to measure. What is unclear is perhaps the
| definition of life. But at no point does it assume a
| planet must be in the Goldilocks zone. So perhaps you
| want to point out those assumptions you are talking about
| to me, because I don't see them.
|
| Edit: the parent post has been edited substantially after
| I replied.
| the_af wrote:
| How can you extrapolate those terms from a single planet
| with known life without making assumptions?
| mr_mitm wrote:
| I can't, but the equation itself doesn't to that. The
| assumptions are up to the reader to make. That's why I
| think that the equation isn't particularly useful.
| buran77 wrote:
| > these are pretty well defined quantities, just hard to
| measure.
|
| They are "defined" conceptually, in words, not in
| physical quantities. It assumes we can assign a known
| value to any of that when we don't and likely never will.
| It's like saying "Let X answer the unanswerable question.
| X is the answer".
|
| > at no point does it assume a planet must be in the
| Goldilocks zone
|
| You could say it implies it with _fl_.
|
| > Edit: the parent post has been edited substantially
| after I replied.
|
| Only for legibility.
| howieburger wrote:
| Those variables come with embedded assumptions they are
| essential and meaningful to discovery of life and
| civilization elsewhere in the universe.
|
| For all we know civilization exists inside our car
| battery. Why assume it only exists on planets.
|
| It's not explicit in it's assumption but implicit
| assumption the equation is meaningful.
| scarmig wrote:
| 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?)
| dotancohen wrote:
| 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.
| LeifCarrotson wrote:
| 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.
| DennisP wrote:
| There's also _Sundiver_ by David Brin, which has plasma
| life forms in our sun.
| ElFitz wrote:
| Andy Weir's Project Hail Mary had an interesting take on
| that.
| DennisP wrote:
| One approach is to give each variable a probability
| distribution. The greater our uncertainty about possible
| values, the wider the bell curve.
|
| Drexler and colleagues did that, and found "a substantial
| probability that we are alone in our galaxy, and perhaps
| even in our observable universe (53%-99.6% and 39%-85%
| respectively). 'Where are they?' -- probably extremely
| far away, and quite possibly beyond the cosmological
| horizon and forever unreachable."
|
| https://arxiv.org/abs/1806.02404
| lordnacho wrote:
| It actually adds excessive structure.
|
| The underlying model is just:
|
| N*f
|
| How many planets are there, and what proportion of them
| have detectable life?
|
| The f does not have to be structured as fl->fi->fc,
| although we can see why you'd assume that kind of
| structure. It's simple to calculate the PI(series) when
| the model is just a funnel. Like the Million Dollar Money
| Drop gameshow.
|
| But you could imagine a more complex model of
| probabilities that branches and merges. There could be
| events on the bayesian tree that amplify downstream
| events. For instance, suppose there is some pathway that
| if reached will leave certain minerals that future
| civilizations could use. This has happened already on
| earth at least once: lignin bearing plants could not be
| easily digested for a long time, and that led to coal
| formation during the carboniferous period.
|
| You could imagine many such potential trees, but we only
| have one iteration.
| bethekidyouwant wrote:
| Not really there's always gonna be water comets in the frost
| zone.
| corimaith wrote:
| 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.
| fooker wrote:
| > Such a probe is quite conceivable, so why isn't there
| more evidence of such probes everywhere?
|
| Time, not space, is your answer here.
|
| Two reasons -
|
| (1) civilizations might not survive long enough to do this.
|
| (2) 13 billion years is a long time. So you have the
| reciprocal of that as the chances to be in the right year
| to see such a probe. And with results from the new
| telescope we now have hints that the 13 billion number is
| bogus, the universe is likely far older.
| mr_toad wrote:
| At some point replicative drift will set in. How many
| replications is two million years? How long before the
| probes evolve? How long before they speciate? How long
| before a species turns on itself?
| littlestymaar wrote:
| > 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?
|
| What are the incentives to build and deploy such a thing
| though? We as a civilization fail to fund things that have
| a ROI of more than a few years, how are you going to fund
| something that pays off after a million year?
| HarHarVeryFunny wrote:
| 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 100B - 1T galaxies out there and
| therefore a similar number of such events.
| pavlov wrote:
| Do other galaxies matter here? A civilization would need to
| be incredibly powerful to be detectable from another galaxy.
| ben_w wrote:
| At the moment, rapid and massive expansion seems likely
| with tech only just on the horizon.
|
| Enough AI and robotics for an autonomous factory may be a
| mirage (such mirages have (metaphorically) happened
| before), but it seems like it's on the horizon.
|
| Even with relatively mundane growth assumptions, that can
| go from "species inventing writing" to "Dyson sphere
| completed, is now sending out seeds to every accessible
| galaxy" on significantly less than the timescale of light
| crossing a spiral galaxy's disk.
| kingkawn wrote:
| Cmon the number of hypothetical extrapolations based on
| no data in these statements is beyond superstition to
| something like delusion
| ben_w wrote:
| If I put citations into everything I write, I'd be a
| Wikipedia article, and people would still criticise the
| conclusions without reading any of them.
|
| But contrawise, I do have data, they're broadly
| categorised as "history", "biology", and "all the stuff
| cited by Stuart Armstrong that time".
| pfdietz wrote:
| Galactic colonization, carried to saturation, would
| detectably modify the appearance of a galaxy. So called
| "type 3 civilizations" would convert a significant fraction
| of starlight to lower grade heat, which would be radiated.
| Searches have been conducted for this signature, with the
| result that no more than 1 in 100,000 galaxies has such a
| civilization, and with the result being consistent with
| none.
| pavlov wrote:
| This is interesting speculation, but it adds one more
| completely unknown variable to the Drake equation.
|
| What's the probability that a radio-capable civilization
| becomes a galactic type 3 one? Looking at the only
| example we have, it appears very unlikely. It seems much
| more probable that we'll destroy ourselves within the
| next centuries.
| runarberg wrote:
| I am not an astrophysicist but I have a hunch any
| speculations of galactic colonization fails to entertain
| just how big space actually is. I feel like there is
| ample reason to suspect the probability of galactic (or
| even interstellar) colonization is exactly 0, and no
| civilization in the history of the entire universe will
| ever colonize an entire galaxy (and probably not even
| more than a handful of solar systems outside their home
| world; if any).
| HarHarVeryFunny wrote:
| I guess it depends what question are we trying to ask. It
| may well be that there is no other intelligent life close
| enough to us, or coexisting with us in time, that we will
| ever be aware of it, but yet the universe may still be
| teeming with intelligent life.
|
| In either case it's a statistical question of how common is
| life, and intelligent life, but of course there's the human
| interest in potential contact with another intelligent life
| form.
| tshaddox wrote:
| > 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.
|
| But numbers can go arbitrarily low.
| echelon wrote:
| 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 eyes, having actual energetic gasses on
| land...
|
| Maybe life is easy, but intelligence is hard. Maybe
| civilization is hard.
|
| Maybe technology development can only happen on dry land,
| because aqueous chemistry is hard in water. Sorry mollusks
| and cetaceans: you'll probably never be able to do
| chemistry or materials science.
|
| Maybe you need water and carbon and other chemistries
| aren't robust enough.
|
| Maybe you need lots of fossil fuel deposits to develop
| industry. And that requires growth without bacteria and
| decomposers for millions of years, implying a certain order
| to evolution.
|
| Maybe you need a certain sized gravity well to escape.
|
| Maybe surviving the great filter is hard and still ahead of
| us. Maybe every species can build tech where a kid in their
| garage can extinct the entire species by 3d printing grey
| goo.
|
| There's just so much we don't know about how life could
| happen. Let alone intelligent life. We don't even know
| where we're headed.
| leoedin wrote:
| 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!
| TuringTest wrote:
| It took several environment-changing events to get our
| unique kind of intelligence; mammals had to thrive in
| place of saurs; and then, Africa needed to be split by
| the Rift and to create the dry savannah.
|
| This forced some apes to climb down the trees and depend
| on a diet of scavenging for meat, which happened to both
| increase brain size AND require improved intellect to
| survive, forcing the evolution of our hypertrophied
| symbolic brain.
|
| Had this not happened however, other intelligent species
| could have filled the niche. There's no shortage of other
| intelligent species in our planet, not just other mammals
| but octopus and some birds. And then you get hive
| intelligence, which could equally be forced to evolve
| into a high problem-solving organism.
| Qem wrote:
| Maybe they didn't produce an intelligent species just
| because they had not the luck of living in the
| unprecended time in the history of Earth with both high
| atmospheric O2 and very low atmospheric CO2 we enjoyed
| for a while, before we started to burn fossil fuels by
| the gigaton. See https://www.qeios.com/read/IKNUZU
| 3eb7988a1663 wrote:
| 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...
| HarHarVeryFunny wrote:
| 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.
| macintux wrote:
| 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.
| Qem wrote:
| > ...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
| HarHarVeryFunny wrote:
| 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).
| macintux wrote:
| None of which are, I assume, as easy/efficient/effective
| to integrate into a new civilization's tech tree as coal
| & oil.
| HarHarVeryFunny wrote:
| What has that got to do with energy dense rocket fuels
| for getting to orbit ?!
| macintux wrote:
| The key phrase was "successor civilization".
| crazygringo wrote:
| So? We build nuclear power plants and it's not exactly
| easy/efficient to extract uranium. Hard things are done
| all the time.
|
| Having coal/oil is pretty irrelevant in terms of whether
| a civilization can build spacecraft.
| GWBullshit wrote:
| You're not wrong, but you're in the wrong place to talk
| to people about low-probability events and how they
| multiply. Most Hacker News can't into elementary-school-
| level probability equations and will instead take the
| ostrich approach; there was some behavioral scientist
| dude from Cambridge Analytica who wrote about this and
| the TL;DR is that most "adults" have infantile minds that
| prefer various safety blanket mechanisms that society is
| more than ready to offer them just to do anything to have
| an excuse to not face the truth of what basic math
| reveals to more likely than not be true.
| HarHarVeryFunny wrote:
| > Maybe life is easy, but intelligence is hard
|
| Intelligence has evolved three times independently on
| earth - dinosaurs/birds (raptors, covids), mammals, and
| cephalopods (Octopus)
|
| > Maybe you need water and carbon
|
| Maybe so, but Oxygen and Carbon are only behind (albeit
| far behind) Hydrogen and Helium as the most abundant
| elements in the universe
| mr_toad wrote:
| > But numbers can go arbitrarily low.
|
| Which begs the question, why 1, and not zero? I can buy
| zero, or a very large number. But 1 exactly? Nature doesn't
| do that.
| soVeryTired wrote:
| Simeon Denis Poisson would like a word with you.
|
| But in seriousness, I agree.
| tshaddox wrote:
| There's not a huge difference between zero and one, other
| than whether someone's around to comment about it on HN.
| And even a second wouldn't really tell us more about the
| probabilities.
| rdtsc wrote:
| Just as easily as we can multiply planets times systems times
| galaxies times cluster groups we can multiply multiple small
| probabilities of each chemical being present at the right
| time and right type, temperature ranges, gravity ranges, etc
| mattmaroon wrote:
| 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.
| HarHarVeryFunny wrote:
| 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.
| andrewflnr wrote:
| I don't see any reason to believe that giant impact is the
| _only_ way to get life-supporting amounts of water. We know
| Mars had liquid water. We know Titan has lots of ice. We 're
| pretty sure Venus at least had noticeable amounts of water. Did
| all of these come from Theia-type impacts? I don't think we
| have any evidence of that.
| GWBullshit wrote:
| Speaking of Drake equations, you should (1) see the other
| comment here with this account name (2) check out the top
| Pirate Bay rip of Dark City (which predated that other movie)
| and turn on the English subtitles and count the number of times
| the characters look at or make gestures pointing to certain
| alignments of the text in the subtitles and, if you're true
| "hackers", try to figure out the encrypted messages in the text
| alignments that the characters are looking at/pointing to at
| key moments - and then when/if you figure out what the
| encrypted messages mean, try to figure out how the director
| worked together backwards so that they could have a script that
| aligns a certain way using subtitles and then make the scenes
| so that the actors are looking/pointing to key spots at just
| the right time.
|
| If you appreciate technical things, you'd be in for a treat.
| ctrlp wrote:
| The likelihood of those criteria might be vastly different in a
| younger universe than in this one, no?
| quotemstr wrote:
| 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.
| mr_toad wrote:
| A couple of dozen collisions out of 6000+ known exoplanets.
| Not exactly common, but not freakishly rare either.
| kulahan wrote:
| Don't forget this can only happen once, really. You need it to
| be such a rare event that it doesn't keep sanitizing the planet
| with repeated impacts, but one really perfect strike will bring
| what you need and allow life to form.
|
| The number of instances where this (something unreasonably
| unlikely) happened in our cosmological history is kinda
| surprisingly high. I'm absolutely convinced there's no advanced
| life (and CERTAINLY no technological civilizations) outside of
| earth.
|
| One other example: we gained most of our adaptability,
| curiosity, and problem solving skills as very tiny mammals
| while dinos ruled the earth. The only way we ever took over the
| planet was thanks to an asteroid wiping out all those huge
| creatures. Suddenly, high adaptability and intelligence and
| resilience was what mattered, and being big and strong suddenly
| was a massive disadvantage.
|
| Our intelligence exploded largely because that extinction event
| removed almost all major predators, turning earth into a giant
| survival puzzle sandbox for mammals to grow in.
|
| Edit: our brains only grew big because it was the best means of
| survival - they're crazy expensive, so without this "sandbox
| puzzle" effect, we probably never would've grown them.
| tastyfreeze wrote:
| Earth has been struck by large comets many times killing the
| majority of life on the planet each time. In an early solar
| system it would be more frequent. Once a comet impacts there
| is one less comet out there. The solar system cleans up over
| time making impacts less likely over time.
| kulahan wrote:
| There isn't that much of a difference in the number of
| comets in space across just 5 billion years.
| mr_toad wrote:
| > Suddenly, high adaptability and intelligence and resilience
| was what mattered, and being big and strong suddenly was a
| massive disadvantage.
|
| Maybe it was just being small, puny, and having a tendency to
| cower in burrows was what saved us. Our ancestors may not
| have been much smarter than squirrels, and squirrels aren't
| very bright.
|
| Hominids brains didn't get big until long, long after the KT
| extinction. A Tigers brain is not that much smaller than that
| of an an Australopithecus.
| kulahan wrote:
| Correct - that's what SAVED us. What allowed us to thrive
| and dominate the planet was what I mentioned.
|
| It may be more correct to say that growing a larger brain
| (larger than a lizard's, I mean) was only realistically
| possible because of the sudden loss of predators.
| Animats wrote:
| Right. It's discouraging. We now know that many stars have
| planets, and some of them are even in the Goldilocks zone. But
| if it takes a planetary collision to get water... And only one
| planetary collision, because each one wipes out essentially all
| life.
|
| Look at the rest of the solar system. Mars - almost no water.
| Luna - almost no water. Venus, maybe water[1], but as steam.
| Too close to the sun and too hot.
|
| [1] https://phys.org/news/2025-10-venus-clouds-reanalyzed.html
| Kerrick wrote:
| I find it incredibly encouraging. I fear aliens existing in
| sufficient enough quantity to find us more than I fear Earth
| being the only host to intelligent life until we escape it.
| akk0 wrote:
| How does this square with the fact that we have solid evidence of
| water on Mars as well?
| lukan wrote:
| Having some water and having lots of water is a slight
| difference. The most arid dessert on earth is a jungle compared
| to Mars.
|
| (Also Mars could have been also hit.)
| oceanplexian wrote:
| Except Titan likely has more water on it than Earth.
| Therefore unless we're a fluke of a solar system planetary
| bodies with water on them should be extremely common.
| addaon wrote:
| Titan is outside the frost line. There's no question that
| there's a huge amount of water in solar systems, the
| question is if there's a consistent transport system
| (comets, in this case) that moves it inside the frost line
| to where liquid water can, given an atmosphere and gravity,
| exist in conditions that match our familiar conditions for
| life.
| lukan wrote:
| Titan is interesting, but much further away from the sun,
| so different conditions. We want earthlike conditions, life
| that can sustain on anything else, is just hypothesis so
| far.
|
| (As is the claim from the article)
| munchler wrote:
| The article mentions that the inner planets were initially
| too hot to retain water, but presumably Titan didn't have
| that problem, being much farther from the sun.
| hn_throwaway_99 wrote:
| Mars is further out in the solar system, and I'm assuming it
| was further out than Theia when the collision occurred.
|
| The article doesn't say no planets can have water, but just
| that originally Earth was too close to the Sun to have liquid
| water. Theia, according to this hypothesis, was not.
| stared wrote:
| 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.
| WillAdams wrote:
| That is pretty much the premise of Hal Clement's short story
| "Halo", which I read in _Space Lash_ (originally published as
| _Small Changes_), but now available in:
|
| https://www.goodreads.com/book/show/939760.Music_of_Many_Sph...
|
| I recommend folks read it in reverse chronological order,
| starting at the back, then working to the front and bailing
| when things get too quaint/old-school/golden-age.
| aitchnyu wrote:
| What if they miscalculated and intelligence evolved when the
| moon drifted too far to cover the sun?
| layer8 wrote:
| They regularly smashed asteroids onto earth until intelligent
| life emerged.
| rstillwell wrote:
| Smashing will continue until morale improves...
| shagie wrote:
| I would say "spoilers" ... but it's the title of the story.
| _The Fermi Paradox Is Our Business Model_
|
| https://en.wikipedia.org/wiki/The_Fermi_Paradox_Is_Our_Busin...
|
| https://www.tor.com/2010/08/11/the-fermi-paradox-is-our-busi...
| vardump wrote:
| 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.
| stared wrote:
| I know that. But in this scenario, aliens know the timescale
| of appearance of life intelligent enough it can appreciate
| solar eclipse.
| dotancohen wrote:
| 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.
| alganet wrote:
| 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.
| pfdietz wrote:
| Original paper:
| https://www.science.org/doi/10.1126/sciadv.adw1280
| praptak wrote:
| So we're not only made of elements which formed inside star(s)
| but also ones merged from two different planets. This is weird.
| aeonik wrote:
| And the remnants of two neutron stars colliding.
| alchemism wrote:
| As above, so below. Two humans colliding, too.
| neuronic wrote:
| In the scale of the universe this is bound to happen, likely
| infinite times anyway and _this_ is what feels rather weird to
| me. Not just the perceived "special circumstances" but that
| independent of the rarity it will still happen many many times
| and then any conscious lifeform developing technology to
| realize this be subject to the definition of survivorship bias.
| ahazred8ta wrote:
| There was a giant incandescent donut involved, too.
| https://en.wikipedia.org/wiki/Synestia
| timbowhite wrote:
| Is this the same collision theorized to have created the moon?
| wvbdmp wrote:
| Yes
| rcostin2k2 wrote:
| That's what is suggested here but according to the Giant Impact
| Hypothesis the impact happened about 4.5 billion years ago and
| formed the Moon from debris, and it likely vaporized much of
| any existing water on proto-Earth rather than delivering it...
| More investigations needed ...
| blindriver wrote:
| Absolute garbage.
|
| The Earth has a nearly perfect circular orbit. Any collision with
| another planet would have pushed it off its orbit and caused it
| to at the very least created a more elliptical orbit that likely
| would have made the swings in temperature more deadly for life on
| Earth.
|
| This entire article is science fiction.
| indigodaddy wrote:
| This makes some sense actually. Does anyone have a
| counterargument to this?
| o11c wrote:
| It's backwards. Highly eccentric orbits are the default;
| near-circular orbits are the inevitable result of averaging
| out a large number of orbits after they collide.
|
| It's also ignoring the fact that we likely _did_ have
| additional planets, but after interactions with other planets
| with nearby orbits, they would have been either ejected out
| of the solar system entirely, caused to collide, or herded
| into more circular (non-overlapping) orbits.
|
| This is why Pluto is not a planet.
| prerok wrote:
| While I agree with you on most points, that is not why
| Pluto is not a planet.
|
| The reason is that it was observed "too soon" because of
| its interaction with Neptune's orbit. Once we realized
| there were plenty of such objects in the range of Neptune's
| orbit but we also realized that these were not fully formed
| planets, we invented the term of dwarf planet, so Pluto was
| demoted to that status, which it shares with many other
| objects in the far out orbit.
|
| So, it was just a classification thing. We could have also
| said all those others are also planets.
| the_af wrote:
| Isn't the most common _scientific_ theory about the origin of
| the Moon that a big body collided with Earth?
|
| How can it be science fiction if most scientists currently
| believe this?
| andrewflnr wrote:
| This guy thinks he's smarter than all those scientists.
| Consider his opinion accordingly.
| gus_massa wrote:
| > _The Earth has a nearly perfect circular orbit. Any collision
| with another planet would have pushed it off its orbit and
| caused it to at the very least created a more elliptical orbit
| that likely would have made the swings in temperature more
| deadly for life on Earth._
|
| There is a lot of evidence of a big collision, but that's a
| very good question anyway!
|
| I guess the interactions with other planets and asteroids
| change the orbit to a more circular one. I couldn't find a
| serious source that confirm, and not even a non-serious, so I'm
| still curious, very curious.
|
| Anyway, there is a good theory that Jupiter formed at 3 AU and
| moved later to 5 AU and (very slowly) caused havoc in all the
| outer solar system
| https://en.wikipedia.org/wiki/Formation_and_evolution_of_the...
| So the initial orbits are not fixed in stone.
| sethammons wrote:
| Related, a recent study suggests up to 1% of our mantle is water
| trapped within rock that gets released as subduction increases to
| higher heat and pressure. This water could account for three
| times the amount of water on the surface and may represent a
| whole-Earth water cycle.
|
| https://www.bnl.gov/newsroom/news.php?a=111648
|
| I wonder how this ties in with the submitted link about Theia.
| And it will be interesting if we ever get similar trapped water
| discovered in martian rock.
| mcswell wrote:
| The article says the light elements hydrogen, carbon and sulfur
| (and oxygen?) were only able to condense on the outer planets
| (and their moons). And the original article specifically says
| "the inner Solar System planets Venus and Mercury are largely
| devoid of volatile elements". If that's the case, why does Venus
| have so much carbon dioxide?
|
| (I'm not saying the article is wrong, just trying to understand.)
| o11c wrote:
| Keep in mind that carbon dioxide is almost 3x heavier than
| methane. Part of the reason Venus has "so much" CO2 is because
| all the lighter gasses _have_ been depleted.
|
| (But yes, Venus is hard to satisfactorily explain, regardless
| of whether you accept the article's conclusions at face value.)
| pfdietz wrote:
| > why does Venus have so much carbon dioxide?
|
| Venus doesn't have liquid water, which is needed for the
| reaction of silicates with CO2 ("weathering"). Without that
| reaction, CO2 just accumulates in the atmosphere. Most of the
| carbon on Earth (and there's a lot) is locked up in rocks.
|
| There's also a biological effect. Here on Earth, silica in the
| ocean is scrubbed out by microorganisms that create silica
| shells; these tiny shells fall out into sediments, where (in
| deep ocean) they eventually form a kind of biogenic rock called
| "chert". Elsewhere, typically in shallow water, carbonate rocks
| are formed from the remains of other kinds of animals. Without
| these effects, the dissolved silicon concentration in seawater
| would be orders of magnitude higher, and the silica would react
| to form clays. This reaction would acidify the ocean and
| prevent carbonate formation.
|
| Just such "reverse weathering" has been hypothesized to occur
| after the Permian-Triassic boundary, where CO2 levels stayed
| elevated for 5 million years. The extinction event was so
| severe it disrupted chert formation (a "chert gap").
| andrewflnr wrote:
| I've tried reading the paper, which is obviously less hand wavy
| than this mess of a blog post but pretty tough going for a
| layman. I still don't see how they conclude that the water
| arrived all at once instead of in a bunch of comets...
| https://www.science.org/doi/10.1126/sciadv.adw1280
| hammock wrote:
| All at once is what explains the isotopic homogeneity (e.g. in
| oxygen) between the earth and the moon
| andrewflnr wrote:
| Meaning not just all the water but all the oxygen came in
| with Theia?
| o11c wrote:
| I also don't see how they disprove the contribution of gravity.
| Remember that Earth is composed of _fifty_ Titan-sized bodies.
|
| Titan, and probably Uranus and Neptune, probably have their
| methane etc. as a result of outgassing - initially, the
| volatiles are embedded in the inner rocks, but as they
| gravitationally differentiate and heat - and are subject to
| tide-like interactions with other bodies - the volatiles are
| released.
|
| (The real questions are "Why does Ganymede _not_ have an
| atmosphere? " and "What's up with Venus, really?")
| andrewflnr wrote:
| I believe the idea is that the water was all cooked out of
| Earth's protoplanetary disk material before it even formed
| large chunks. So gravity never got a chance to "contribute"
| on that front.
| o11c wrote:
| Well, that seems to make 2 major assumptions (and several
| minor ones), both of which are probably false:
|
| * that the planetesimals that formed Earth had the same
| orbital characteristics (notably eccentricity), rather than
| being averaged out.
|
| * that planetesimals formed from dust in largely the same
| manner as planets form from planetesimals
| andrewflnr wrote:
| ...no, I don't think it makes either of those
| assumptions.
| animitronix wrote:
| Not buying it, Mars had water with no major collision.
| spenrose wrote:
| Claude Sonnet 4.5 summary of the original paper
| [https://www.science.org/doi/10.1126/sciadv.adw1280] for middle
| school students:
|
| How Earth Got Its Water: A Cosmic Detective Story
|
| The Big Question: How did Earth become a planet with oceans and
| life, when it formed so close to the hot Sun?
|
| What Scientists Did:
|
| - They used a "radioactive clock" made from two elements:
| manganese and chromium - Manganese-53 breaks down into
| chromium-53 over time (like ice melting at a steady rate) - By
| measuring these elements in meteorites and Earth rocks, they
| figured out WHEN Earth's basic chemistry was locked in
|
| Key Finding: Earth's chemical recipe was set within just 3
| million years after the Solar System formed (that's super fast in
| space terms!)
|
| The Problem: At that point, early Earth was missing the
| ingredients for life--especially water, carbon, and other
| "volatile elements" (stuff that evaporates easily when hot)
|
| Why Earth Was Dry: Close to the Sun, it was too hot for water and
| other volatile stuff to stick to the rocks that built Earth--they
| stayed as gas and floated away
|
| The Solution: About 70 million years later, another planet called
| Theia (which formed farther from the Sun where it was cooler)
| crashed into Earth:
|
| This collision created our Moon It also delivered water and other
| life-essential ingredients to Earth
|
| The Big Takeaway: Earth needed a cosmic accident to become
| livable. Without that lucky collision bringing water from the
| outer Solar System, we wouldn't be here!
|
| Why This Matters: If Earth needed such specific, lucky events to
| support life, habitable planets like ours might be much rarer in
| the universe than we thought.
| flufluflufluffy wrote:
| What I don't understand is how you define a single point (even if
| the point spans a million years) of "when the solar system
| formed." They say the chemical composition of the Earth
| solidified "only 3 million years after the solar system formed"
| -- isn't the formation of the planets itself part of the
| formation of the solar system? How does one define the moment of
| formation? Or does this mean that we know with certainty that
| there was no physically consistent body one could identify as
| "Earth" 3 million years prior, and then within those 3 million
| years, it coalesced and solidified?
| thangalin wrote:
| > How does one define the moment of formation?
|
| We don't. It's usually within a range. My illustrated book
| shows the timeline with more context and detail. Note that the
| events are provided on a timeline with some uncertainty (e.g.,
| +- 1 million years):
|
| https://impacts.to/downloads/lowres/impacts.pdf
| buildsjets wrote:
| I wonder how much adenine, guanine, thymine, and cytosine was
| present in that water.
| Panzerschrek wrote:
| 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.
| ricksunny wrote:
| 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.wikipedia.org/wiki/Hydrodynamic_escape ]
|
| Absent that, our treasured atmospheric molecules would have to
| autonomousy achieve escape velocity, some 22 km/sec , with no
| outside assistance. A difficult feat. And so, resident
| atmosphere.
| Panzerschrek wrote:
| 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.
| ricksunny wrote:
| 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.)
| ricksunny wrote:
| >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 volatile
| https://en.wikipedia.org/wiki/Volatile_(astrogeology) .
| Similarly, the wikipedia article for 'refractory', posed as the
| astrogeological opposite of volatile, does not place carbon at
| all in the spectrum of volatile to refractory.
|
| * Contra: at least two papers do refer to carbon being a volatile
| element. https://www.nature.com/articles/s41586-022-05276-x and
| https://arxiv.org/abs/2311.18262
|
| [shrug]
| eep_social wrote:
| I take this as "volatile" in the sense that it bonds easily
| with other molecules
| catigula wrote:
| Tough to gain any predictive information here due to the
| anthropic principle requiring a series of comical happenstance
| for observation to even occur.
| erickf1 wrote:
| 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.
| QuantumGood wrote:
| 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.
| cyberax wrote:
| I thought the consensus was that the water came from comet
| impacts?
| ctingom wrote:
| I don't believe this.
| 3oil3 wrote:
| We humans are not from Earth, what more signs need those who
| can't see? Humans,from all the species, the unique without a
| natural habitat. Humans, can not live on this planet unless we
| all get together and start adapting the environment. Otherwise,
| we can only survive and it's not fun. We have to wear clothing,
| cut downn trees. We get ill and stuff. Monkey us from? We closer
| to the pigs and not just the hips.
| poly2it wrote:
| What?
| pinkmuffinere wrote:
| You heard the man! Monkey us from?
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