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[Egan_BW]

The moon is only really relevant to animals and their navigation, not really a vital part of life.

[Starver]

I personally think that if there's a lot of chattering going on around the galaxy, it's probably just nothing like we can (or can be expected to) detect. Yet.

Even if it's mundane EM, then broadcasting means more limited discernable range for a given power¹, and narrow-casting rules out detection unless (incidentally or purposefully) aimed at. And, either way, we also need to be listening at the right time, in the right direction. Which is something we can improve.

Any dialogues (or single sides of a dialogue) that we can listen in on are probably far from "most logical speculative transmission style" and has probably developed into a more sophisticated protocol developed through a completely alien idea regarding information theory, or even two completely alien idea-sets that have then set about to mutually uplift each other into a hybrid system of the more advanced and practically-tested theory...


That's if they're even chatting with each other, or soliloquising to get attention/etc.  That's if intelligence is a given on planets with suitably advanced biology. That's if suitably advanced biology is a given on a planet with any biology at all. That's if any biology at all is...  But those aspects (plus the longevity of otherwise qualifying civilisations) are in the Equation.  Whereas I'm looking at f_c alone and asking that further nuances be tacked on.


((Ninja moon question: hard to say. It is said that the stabilising influence of the Moon helps keep our planet's spin and inclination fairly predictable over long stretches of Earth's attempt to develop life, whilst also that the fluctuations of the lunar tides (noting that there is also the solar tidal component) might have encouraged the evolution of amphibious and eventually terrestrial capabilities. There is probably a range (whether wide or narrow) of constancy+periodicity of conditions,, for various sizes (or absences, or maybe even surragacies) of moons that gives life the same help and hinderences...

And a planet that was never smacked into by a Mars-sized companion and never created a moon? Well, maybe that also didn't develop sustain the core magnetohydrodynamics also necessary, for various very good reasons...))

((@Egan_EW: See above for the reasons why it might be... In, so far, a sample of one - so somewhat speculative.))


¹ Plus would they actually use the natural frequency of hydrogen, given its ubiquity and easy possible confusion with comet comas? I think they'd be cleverer than that.

[origamiscienceguy]

I meant more along the tides. Are tides important for developing life?

[sluissa]

I meant more along the tides. Are tides important for developing life?

Probably on some level. It would help water borne life transition up onto land easier. But there are also more minor tides provided by the sun alone that would probably do about as much for developing life as the moon tide does. I'd be surprised if there wasn't something that the moon did to influence, but I'm not thinking of anything vital in general.

[Starver]

There are arguments that the moment Moon's phasing is very useful.  Daily cycles (and, in the absence of something like the Moon, strict 12-hourly or 24-hourly¹ solar-only tides) are useful, and annual (seasonal, whether Winter/Spring/Summer/Autumn or (Very)Wet/Dry) is obviously used in many lifecycles, but the lunar-monthly cycle, and the (perhaps also keyed into the tracking process) drifting of the tides' peakings and troughings across the clock, between one day and the next gives the identifiable unit of time that is not only usefully administrative in a human sense (albeit artificially aligned to the year) but also for other creature life-cycles.

But until we get to ask the residents of a differently-configured planet how/if their life works with equivalent timespans... It's a little up in the air.


(But it is assumed that tides are, quite littorally, the best way to get things to start living out of the water.)

¹ For complex reasons, it's not so simple to say "two high and two low tides per (roughly) daily cycle, as we currently have it, even though you'd mostly expect this.

[Max™]

The WOW! signal has a plausible source which was recently discovered to be a funky interaction between comet debris and the solar wind, as I recall. Using hyperaccelerated protons to communicate would be silly anyways, and they'd still get slowed down by the mush of interstellar space being much denser when you're whizzing through it at high fractions of c.

Why would other races want to talk to other races, though?

We're still a long way from reaching the bottom on the miniaturization ladder, accordingly distant from the realistic peak computing capability, and haven't even begun dismantling the solar system to build a matrioshka brain around our star.

In a simverse you can fly around at enormous multiples of c, or straight up teleport to visit an entirely plausible permutation of any given local stellar environment, at which point you could have a chunk of brainstar work out what may live there, how they would have evolved, and if they are sapient you could then have it work through a conversation with you about what it is like to live there.

While it wouldn't exactly be the same as being at that star, without being informed what was going on you could quite easily live a simlife where you undertook a simjourney to a simworld full of simlife and never be able to tell it wasn't real, so what benefit outside of bragging rights/hard science research missions is there from hurling matter out into the universe from your star to drift through space for huge amounts of time just to wind up at another very similar star?

Direct overhead for an observer is "zenith".

That one I knew, but I was derping because I was seeing azimuth in my head but that's just the angle from north along the horizon, which I thought was called something besides just horizon, but I guess not.

[Starver]

The WOW! signal has a plausible source which was recently discovered to be a funky interaction between comet debris and the solar wind, as I recall. Using hyperaccelerated protons to communicate would be silly anyways, and they'd still get slowed down by the mush of interstellar space being much denser when you're whizzing through it at high fractions of c.

That would be silly. Not sure that's even ever going to be a thing, though.

Why would other races want to talk to other races, though?

If by (the second) "to" you mean "with", why would they, and we, not? It'd answer those questions raised about the necessity of the Moon, and all kinds of other stuff...   "Hey, you guys...  So you say your personal organic chemistey is based on Element 14, not Element 6...  So what's your environment like, to have that work out for you?"

[LordBaal]

Moon and tides necesary for life to develop, well perhaps_ maybe it makes it easier, perhaps other things could replace it.

I think maybe láser and óptic fibers become the standard com tech and then you lose the radio broadcasting where other civs could pick you up.

[Max™]

I meant to, with suggests a back and forth, and outside of implausibly similar tech level sapients reaching the same "hey is anybody out there" point within a few light years of each other within a few centuries of each other, there won't be much of that going on.

[LordBaal]

What about the mad chances of life developing un two planets on the same stellar system at the same time?

[wierd]

With the "Habitable moon(s)" scenario, that might happen frequently.  Multiple planets though? Not likely given the issues of orbital interactions, and the narrowness of goldilocks zones.


Habitable moons would all have similar composition, being formed from the same stellar debris field that their parent celestial body formed from. They would all be tightly confined within a narrow slice of the habitable zone of their star (assuming their planetary body occupies that zone. Some scenarios involving habitable moons use the mechanical actions on their cores to supply geothermal energy for supporting a biosphere, and dont need a star at all.), so it is possible for similar conditions to exist on many moons of a large celestial object, and that theoretically advanced life could form simultaneously on many close-by objects.

How often that happens in the universe?  Insufficient data.  It will likely remain insufficient for a very, very long time.

[LordBaal]

Well, perahps not to planets in the full sense of the word. But to intelligent life to emerge twice on the same system at the same time.

But wonder how eerie would be if it developed one after the other so xenoarcheology its the only connection.

I read once something (fiction I think) about how Mars had life but ran toó cold, now its earth turn's and eventualy it will be Venu's.

[Madman198237]

No. That was definitely sheer fiction.

Venus had a chance, but as the Sun got hotter the greenhouse effect went rampant and the planet died. Mars had a chance, but the lack of a magnetic field (No substantial iron core of a molten/solid combination) meant that the Sun's evolution and production of a solar wind killed it off. Eventually (5 billion years, don't sweat it. Yet.) the Sun will start to swell, and Earth's temperature will gradually increase until it becomes a blasted wasteland. Europa might actually some time as an ocean moon (Provided it doesn't constantly freeze as it passes behind Jupiter), when the Sun reaches roughly 1 AU in diameter.

The Earth will never become too cold. It will dissolve in the Sun before that. Or, if the predictions are off and the Earth is never engulfed, it might simply persist as a burned hulk, all water fried off, the surface a ruin of molten stone.

[martinuzz]

See? Solar energy is the future.

Does make me wonder. Would sufficient technology allow the conversion of the entire planet surface into a shell that would survive being engulfed by the sun going red giant, and harness the energy? (Not that it would be of much use on the timescales we are talking about. Once the red giant sun burns down into a dim dwarf the Earth would soon become a cold and dark place. It would be like buying a terminal patient a few extra months.

[MetalSlimeHunt]

If we're going to talk ridiculous planetary salvation measures, you could always build a shell that projects light with the same intensity and pattern as the Sun, power it with a giant fusion generator built inside the planet, and just jettison Earth into dark space.