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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

#211

Post by andrewflnr »

II2II wrote: post #201
andrewflnr wrote: post #59

Earlier quoted context omitted.

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.

Multiple impacts is the standard hypothesis for a source of Earth's water. If I recall correctly, outgassing from volcanos is another source. Keep in mind, the solar system formed from a relatively homogenous nebula. It was the formation of the sun that forced lighter elements to migrate outwards, and that only happens if the lighter elements aren't already part of a larger object. There isn't much of a difference be…

> Multiple impacts is the standard hypothesis for a source of Earth's water.

Right, which is why it's baffling to me that everyone in this thread seems to be losing their mind over this result, thinking it affects the Drake equation and rewrites solar system dynamics. The multiple impacts thing might not have actually happened to earth, but there's still no reason to believe it wouldn't work.

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

#212

Post by WalterBright »

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…

Especially in the context of this, I am baffled by people who go to great lengths to prevent life from Earth arriving on other solar system bodies. Such as all the efforts to sterilize the probes.

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

#213

Post by dleeftink »

WalterBright wrote: post #212
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…

Especially in the context of this, I am baffled by people who go to great lengths to prevent life from Earth arriving on other solar system bodies. Such as all the efforts to sterilize the probes.

Historically to prevent pre-contamination and erroneous biosignature readings. This may ease once we have some solid pointers or confidence there may be none (caution is likely warranted due to the gravity of such a discovery).

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

#214

Post by Animats »

Kerrick wrote: post #156
Animats wrote: post #139

Earlier quoted context omitted.

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] http…

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.

Probably not the only host, but habitable planets are sparse. If Einstein was right and faster than light travel is impossible, the number of planets we can even talk to is not that large. There are only 94 stellar systems within twenty light years.

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

#215

Post by WalterBright »

dleeftink wrote: post #213
WalterBright wrote: post #212

Earlier quoted context omitted.

Especially in the context of this, I am baffled by people who go to great lengths to prevent life from Earth arriving on other solar system bodies. Such as all the efforts to sterilize the probes.

Historically to prevent pre-contamination and erroneous biosignature readings. This may ease once we have some solid pointers or confidence there may be none (caution is likely warranted due to the gravity of such a discovery).

But we also lose opportunity.

Consider Mars. Endless probes for 50 years going to Mars looking for life. No clue of life has ever been found. At what point do we face the fact that Mars is a dead rock?

What we should be doing is collecting samples of extremophiles from the Earth, and attaching a few packets of them to every probe going to Mars, and see what happens. Probably nothing will happen, but it's worth a try.

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

#216

Post by pinkmuffinere »

3oil3 wrote: post #205
pinkmuffinere wrote: post #166

Earlier quoted context omitted.

You heard the man! Monkey us from?

Hey that bit was for the lols, although it is quite valid to say, just missing plural and a comma. Innacurate in some ways -mainstream theory is not about coming from apes, rather is about sharing a, yet undiscovered, common ancestor. I mentionned the pigs because of promising advancement in organ transplantation, notably kidneys that reached a milesone recently, and I mentionned the hips because human hips and ape h…

I really appreciate your open response! Your writing style is so fascinating, it reminds me of how my dad used to talk (he was Persian, not a native English speaker). What’s your background? How did you end up with these beliefs?

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

#217

Post by runarberg »

hdgvhicv wrote: post #203
runarberg wrote: post #176

Earlier quoted context omitted.

Permanent exponential growth is very rare in nature, and even rarer in biological systems. What we observe as exponential growth is usually only a partial observation of a logistical curve or is missing a system collapse at the end of the curve. We have no reason to believe alien (or even human) civilization will continue to grow and expand forever. Heck even the human population curve has started to slow down and is…

Unless some means of communicating faster than light is found a galactic colonisations is not a civilisation, its multiple ones. A colony ship heading in one direction at 0.1c will never interact with one heading the other way at the same speed. After 10,000 years the civilisations will be very different, after 100,000 years they will barely be the same species. Even if 99% stop and fail, the 1% will continue and con…

Yes, I think that will never happen. My prediction is that generational ships are super rare in the universe, and may only happen ones or twice in the entire history of a civilization, and for a tiny portion of civilizations. Meaning by far majority of all civilization will have zero generational ships. Maybe a single civilization somewhere in a distant galaxy will have hundreds, but nowhere near enough to cover an entire galaxy, not even if we count decedent civilizations.

I also think fast space travel (like 0.1c) is rare among civilizations, and may only happen in the order of hundreds of time in the history of some civilizations. And most of these fast space travel will scientific instruments for curiosity and exploration, not for colonization. And that a technologically advanced civilization would favor doing their explorations with telescopes, not probes. So probes would only be sent long distance for rare occasions.

This would mean that almost no civilizations will be expand beyond their solar system, and those that do, will only do it a handful of times, and the expansion will finally stop.

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

#218

Post by hdgvhicv »

runarberg wrote: post #217
hdgvhicv wrote: post #203

Earlier quoted context omitted.

Unless some means of communicating faster than light is found a galactic colonisations is not a civilisation, its multiple ones. A colony ship heading in one direction at 0.1c will never interact with one heading the other way at the same speed. After 10,000 years the civilisations will be very different, after 100,000 years they will barely be the same species. Even if 99% stop and fail, the 1% will continue and con…

Yes, I think that will never happen. My prediction is that generational ships are super rare in the universe, and may only happen ones or twice in the entire history of a civilization, and for a tiny portion of civilizations. Meaning by far majority of all civilization will have zero generational ships. Maybe a single civilization somewhere in a distant galaxy will have hundreds, but nowhere near enough to cover an e…

It doesn’t matter how rare it is to get started once it starts. Every ship is a new civilisation that is created, one predisposed culturally and perhaps genetically to spreading out.

Especially once you reach the “hundreds” level then given the technology exists and the people exist why would it stop, until there’s nowhere else to go.

There is the light cage issue where a civilisation can only spread so far with exponential growth before internal pressures overwhelm it (the leading edge never gets a chance to continue as it is overwhelmed by trailing edges)

Even in that situation though you’d still have self replicating probes - likely at a far lower tech level than biological. Once you reach the tech to send one probe which can duplicate itself more than once using resources in a new system then its game over.

Send 50 probes to each of the 50 stars within 15 light years at 0.01c. If 10% make it they then use local materials and send 50 more, that’s 250 out in 1500 years. Then it’s 1250 out in 3000 years. Within a few millennia years you’ve got millions of probes spreading in an unstoppable way. The ones heading back “inwards” will fail, but those heading outwards will reach each new star dozens of times, only one will need to get there. Within 10 million years you’ve reached the entire galaxy.

To stop it you’d have to make a self replicating probe which was faster and did exactly the same thing and caught the earlier probe, but then when would that probe itself stop, it would have no way of knowing if there were any other “bad” probes to find without becoming the bad probe itself.

Living beings are the same. Once a few dozen have made it and passed on, it’s inevitable it will continue. It may leave out a hollowed husk in the origin point with all resources having being consumed in the centre, but that doesn’t matter as the centre has no way of affecting what happens on the edge, and one edge has no way of affecting another edge.

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

#219

Post by snorbleck »

nebula8804 wrote: post #208
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…

I recently became addicted to the SpaceSimsx and SimulaVerse. My takeaway is that so many just slight deviations can extinguish life on earth. I used to think of possibility of life in other worlds just in the lens of statistics. There are so many combinations and possibilities that it seems inevitable. But seeing just how perfectly aligned our solar system is makes me really reduce the probable number of chances of…

Could a tardigrade withstand these scenarios? If the answer to any of those is yes, could we then say that even with the parameters skewed a bit, there is a chance life exists elsewhere, and under completely different and extreme or (not "normal") conditions? Is the tardigrade here as a "clue" to tell us that life could form potentially anywhere?
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