Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

Venus could have been habitable for billions of years (2019)

smithsonianmag.com

Post reply on HN
Print view View original

21–30 of 236 posts

Re: Venus could have been habitable for billions of years (2019)

#21

Post by selcuka »

samatman wrote: post #3
xwdv wrote: post #2

That’s enough time for a civilization to have been born, lived, and died. Unfortunately there’s probably no way to find evidence of their existence by now it seems? Some day they may say Earth could have been habitable for billions of years.

That's practically guaranteed. Eventually, the Sun will expand so much that Earth's atmosphere will boil clean off. A mega-civilization with enormous power could move Earth, buy some time, but nothing lasts forever.

> buy some time, but nothing lasts forever

That reminded me of The Last Question by Isaac Asimov. Quite enjoyable if you haven't read it already: https://www.multivax.com/last_question.html

Re: Venus could have been habitable for billions of years (2019)

#22

Post by stx »

elihu wrote: post #13

I wonder if one were to install a solar shade in front of Venus to block all light from the sun, how long would it take to cool to "normal" temperatures? The Earth cools pretty fast between day/night and seasonally, but Venus has a much thicker atmosphere, almost more like an ocean. And then the ground itself wouldn't cool instantly either. That's a lot of thermal mass.

Would cooling it help to reduce the amount of pressure the atmosphere has? Isn't the pressure on the surface something like 95 times that of earth.

Re: Venus could have been habitable for billions of years (2019)

#23

Post by virmundi »

stx wrote: post #22
elihu wrote: post #13

I wonder if one were to install a solar shade in front of Venus to block all light from the sun, how long would it take to cool to "normal" temperatures? The Earth cools pretty fast between day/night and seasonally, but Venus has a much thicker atmosphere, almost more like an ocean. And then the ground itself wouldn't cool instantly either. That's a lot of thermal mass.

Would cooling it help to reduce the amount of pressure the atmosphere has? Isn't the pressure on the surface something like 95 times that of earth.

Which is also largely why it’s hot.

Re: Venus could have been habitable for billions of years (2019)

#24

Post by mannerheim »

zabzonk wrote: post #12
andrewflnr wrote: post #10

Earlier quoted context omitted.

Complex multicellularity and cellular endosymbiosis have both occurred multiple times on earth. Those aren't the hard part. Further, there's no reason to assume that having mitochondria (rather than just having an intrinsically more efficient metabolism) is optimal, much less necessary, rather than a path-dependent accident of Earth eukaryotes.

> both occurred multiple times on earth Citation?

There are several kingdoms with multicellular life. Plants, animals, most fungi, some protists (many protists are more closely related to animals, fungi, or plants than they are to each other for that matter). See: https://en.wikipedia.org/wiki/Eukaryote#Five_supergroups

Note e.g. that animals and fungi are closely related on this diagram, but there are unicellular fungi (notably yeast). I would guess that this means the common ancestor between animals and fungi would have been unicellular. At any rate, both are far from plants, and other protist species unrelated to all of these are multicellular.

Endosymbiosis is generally accepted to also have occurred with chloroplasts. I believe there are also contemporary observed cases of protists consuming photosynthetic organisms and becoming immobile.

Re: Venus could have been habitable for billions of years (2019)

#25

Post by eggsome »

stx wrote: post #22
elihu wrote: post #13

I wonder if one were to install a solar shade in front of Venus to block all light from the sun, how long would it take to cool to "normal" temperatures? The Earth cools pretty fast between day/night and seasonally, but Venus has a much thicker atmosphere, almost more like an ocean. And then the ground itself wouldn't cool instantly either. That's a lot of thermal mass.

Would cooling it help to reduce the amount of pressure the atmosphere has? Isn't the pressure on the surface something like 95 times that of earth.

Surely it would cool below the point where Co2 becomes solid (most of the atmosphere is Co2).

Imagine walking around on fields of Co2 :)

Re: Venus could have been habitable for billions of years (2019)

#27

Post by meepmorp »

stx wrote: post #22
elihu wrote: post #13

I wonder if one were to install a solar shade in front of Venus to block all light from the sun, how long would it take to cool to "normal" temperatures? The Earth cools pretty fast between day/night and seasonally, but Venus has a much thicker atmosphere, almost more like an ocean. And then the ground itself wouldn't cool instantly either. That's a lot of thermal mass.

Would cooling it help to reduce the amount of pressure the atmosphere has? Isn't the pressure on the surface something like 95 times that of earth.

PV=nRT, so yes, reducing the temperature would reduce the atmospheric pressure.

Edit: wasn't thinking at all about the volume

Re: Venus could have been habitable for billions of years (2019)

#28

Post by eloff »

samatman wrote: post #3
xwdv wrote: post #2

That’s enough time for a civilization to have been born, lived, and died. Unfortunately there’s probably no way to find evidence of their existence by now it seems? Some day they may say Earth could have been habitable for billions of years.

That's practically guaranteed. Eventually, the Sun will expand so much that Earth's atmosphere will boil clean off. A mega-civilization with enormous power could move Earth, buy some time, but nothing lasts forever.

Why move earth when you could just throw up some shade?

By then things would be so different it's impossible to imagine what humans might do or be capable of our interested in - if we're still around.

Re: Venus could have been habitable for billions of years (2019)

#29

Post by andrewflnr »

zabzonk wrote: post #12
andrewflnr wrote: post #10

Earlier quoted context omitted.

Complex multicellularity and cellular endosymbiosis have both occurred multiple times on earth. Those aren't the hard part. Further, there's no reason to assume that having mitochondria (rather than just having an intrinsically more efficient metabolism) is optimal, much less necessary, rather than a path-dependent accident of Earth eukaryotes.

> both occurred multiple times on earth Citation?

Check out the abstract of this paper: https://www.pnas.org/content/99/18/11558 It takes for granted not only the long-established belief that chloroplasts were once free-living blue-green bacteria, but a number of eukaryote-within-eukaryote endosymbioses. As for multi-cellular life, plants, animals, fungi, and {brown,red,green} algae independently developed it: https://en.wikipedia.org/wiki/Multicellular_organism

This seems like a good article that describes the multicellularity problem in general, several interesting borderline cases, experiments in inducing the evolution of simple multicellularity (in one case, just by introducing predators into a culture), and ideas as to why it took as long as it did: https://www.sciencemag.org/news/2018/06/momentous-transition...

Re: Venus could have been habitable for billions of years (2019)

#30

Post by konjin »

whoisthemachine wrote: post #19

It's interesting that multi-cellular life developed on Earth around the same time these scientists hypothesize Venus would have become uninhabitable. Unrelated... still, fun to think about. https://en.wikipedia.org/wiki/Timeline_of_the_evolutionary_h...

Not overly. The Great Oxidation Event nearly destroyed all life on the planet. If it wasn't for a mutation that allowed life to live in an oxygen rich environment Earth could have gone the say way as Venus.
Post reply on HN