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

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

#91

Post by gus_massa »

blindriver wrote: post #49

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.

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

#92

Post by stouset »

acestus5 wrote: post #46
mr_mitm wrote: post #44

Earlier quoted context omitted.

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.

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

#93

Post by o11c »

andrewflnr wrote: post #75
o11c wrote: post #70

Earlier quoted context omitted.

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 rel…

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

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

#94

Post by modius2025 »

xbmcuser wrote: post #18
shireboy wrote: post #4

This could mean in the Drake equation ne -number of planets capable of life- is very small. A planet has to be hit with a comet big enough to deliver a large amount of water but not so big or fast to destroy it. And be in the Goldilocks zone of the star. Also the mass of the planet would play a part - gravity of more massive ones would be more likely to capture a comet. But again, too massive and I could see that ham…

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.

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.

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

#95

Post by [deleted] »

o11c wrote: post #63
indigodaddy wrote: post #56

Earlier quoted context omitted.

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 (n…

[deleted]

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

#96

Post by TuringTest »

leoedin wrote: post #74
echelon wrote: post #68

Earlier quoted context omitted.

And you have to have multiple low probability events. These probabilities multiply. We had a good start. A Jupiter to clear the debris, a Theia impact to create tides and contribute to tectonics, a magnetic core, a shielded atmosphere. We had water delivered to us. Maybe even panspermia. Maybe cell walls and mitochondria are hard. Maybe multicellular is hard. Maybe life on land is hard. Building lungs, rebuilding eye…

Even on Earth, the only reason humans exist is because the “local maximum” of the dinosaurs was wiped out by a meteor. Perhaps comparably intelligent dinosaurs would have eventually evolved - but it’s not a given!

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.

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

#97

Post by Qem »

leoedin wrote: post #74
echelon wrote: post #68

Earlier quoted context omitted.

And you have to have multiple low probability events. These probabilities multiply. We had a good start. A Jupiter to clear the debris, a Theia impact to create tides and contribute to tectonics, a magnetic core, a shielded atmosphere. We had water delivered to us. Maybe even panspermia. Maybe cell walls and mitochondria are hard. Maybe multicellular is hard. Maybe life on land is hard. Building lungs, rebuilding eye…

Even on Earth, the only reason humans exist is because the “local maximum” of the dinosaurs was wiped out by a meteor. Perhaps comparably intelligent dinosaurs would have eventually evolved - but it’s not a given!

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

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

#98

Post by andrewflnr »

o11c wrote: post #93
andrewflnr wrote: post #75

Earlier quoted context omitted.

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.

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

#99

Post by andrewflnr »

the_af wrote: post #65
blindriver wrote: post #49

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.

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.
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