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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.

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.

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.

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.

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.

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.

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

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.

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.

> 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.

How can you extrapolate those terms from a single planet with known life without making assumptions?

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

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.

yeah you are right the Drake equation does not assume Goldilocks zone.

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.

Not really there’s always gonna be water comets in the frost zone.

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.

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.

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.

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.

> 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.

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.

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).

> ...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

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.

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...

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

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.

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

Do other galaxies matter here? A civilization would need to be incredibly powerful to be detectable from another galaxy.

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.

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.

Cmon the number of hypothetical extrapolations based on no data in these statements is beyond superstition to something like delusion

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".

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.

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.

Unless collisions like the article suggests are a statistical inevitability, that is.

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.

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.

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.

The likelihood of those criteria might be vastly different in a younger universe than in this one, no?

No kidding... This would probably resolve the Fermi paradox if proven true...

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.

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

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.

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.

> 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.

What's the chemistry of life without water? Do you refer to the promising Russian studies of life sustained by alcohol?

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

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/do...

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.

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

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?")

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.

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

...no, I don't think it makes either of those assumptions.

All at once is what explains the isotopic homogeneity (e.g. in oxygen) between the earth and the moon

Meaning not just all the water but all the oxygen came in with Theia?

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.

>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]

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

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.)

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.)

> 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").

How does this square with the fact that we have solid evidence of water on Mars as well?

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.)

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.

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.

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.

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)

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.

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?

> 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

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.

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.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.

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.)

I wonder how much adenine, guanine, thymine, and cytosine was present in that water.

Is this the same collision theorized to have created the moon?

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 ...

Yes

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

And the remnants of two neutron stars colliding.

As above, so below. Two humans colliding, too.

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.

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

Original paper: https://www.science.org/doi/10.1126/sciadv.adw1280

Not buying it, Mars had water with no major collision.

Ah the First Impact

I know this reference lol

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.

> 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.

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?

This guy thinks he's smarter than all those scientists. Consider his opinion accordingly.

This makes some sense actually. Does anyone have a counterargument to this?

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.

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.

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.

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.

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...

What if they miscalculated and intelligence evolved when the moon drifted too far to cover the sun?

They regularly smashed asteroids onto earth until intelligent life emerged.

Smashing will continue until morale improves…

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.

All life on Earth is illegal immigrants from another planet.

Sorry, I was only joking. Someone got busy seriously down voting! Maybe wrong times to utter the phrase "illegal immigrants". I get it.

Only if the earth was seeded with life.

Which seems to be quite possible. This is what we have from just one mission: https://www.esa.int/Science_Exploration/Space_Science/Rosett...

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.

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> but please trust the science!

If you're going to disparage the best idea humanity has ever had, you are required to commit and explicitly suggest your preferred alternative.

Your attempt at clever irony is a negative contribution to the world.

It is precisely the tendency of scientists to qualify their certainty that makes them worthy of our trust.

Reading comprehension: The collision with Theia likely had a large effect on Earth once it occurred, but the collision might still have been unlikely to occur in the first place.

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.