We are alone in the Universe, unless we guess otherwise.

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We are alone in the Universe, unless we guess otherwise.

Post by rainbow » Mon May 25, 2020 9:42 am

Given that excess of exoplanets – and given how we emerged here on Earth – then surely other life-forms will similarly spring up on other orbs too, right?

Well, maybe not. At least, we don't yet have any real data to know one way or the other.

The only firm evidence we have that life exists anywhere, in fact, is Earth, and even life on Earth may not have been destined to thrive, let alone evolve to the point where you can read these words.

"Despite having no observational data concerning non-terrestrial life, we are in possession of stronger constraints when it comes to life on Earth," Kipping writes in his paper.

"Until this situation changes, inferences concerning the existence of life elsewhere in the Universe must unfortunately rely heavily on this single data point."
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Re: We are alone in the Universe, unless we guess otherwise.

Post by Woodbutcher » Mon May 25, 2020 11:55 pm

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Re: We are alone in the Universe, unless we guess otherwise.

Post by JimC » Tue May 26, 2020 12:04 am

Ah, but we have definitive evidence from Galaxian! :tea:
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Re: We are alone in the Universe, unless we guess otherwise.

Post by pErvinalia » Tue May 26, 2020 1:49 am

I reckon we'll find life on titan (or is it enceladus?) . And maybe mars too if there's underground water.
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Re: We are alone in the Universe, unless we guess otherwise.

Post by Hermit » Tue May 26, 2020 2:20 am

As the number of discovered exoplanets grows bigger, the probability of discovering intelligent extraterrestrial life approaches 1.

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Re: We are alone in the Universe, unless we guess otherwise.

Post by L'Emmerdeur » Tue May 26, 2020 3:06 am

This is all if, of course, but as I understand it the results of the model indicate that life is likely to emerge on a planet closely similar to Earth. It seems unlikely that Earth is unique in the Universe. Not just in the Universe, but elsewhere in our own galaxy.

The chances that a given planet with life will also develop what we might recognise as an intelligent species is disfavored in the model (3 to 2 against) but that means that approximately one third of planets that are as hospitable to life as Earth will also give rise to a species with intelligence.

Mind, intelligence does not inevitably entail something like human civilization. Going by the present example, civilization is a risky route for intelligence to follow. The human species right now resembles a child playing with fire in the family house.

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Re: We are alone in the Universe, unless we guess otherwise.

Post by NineBerry » Tue May 26, 2020 11:43 am

Even if there are other planets with conscious life forms, even the idea of getting there in a reasonable amount of time seems impossible.

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Re: We are alone in the Universe, unless we guess otherwise.

Post by rainbow » Tue May 26, 2020 1:49 pm

L'Emmerdeur wrote:
Tue May 26, 2020 3:06 am
This is all if, of course, but as I understand it the results of the model indicate that life is likely to emerge on a planet closely similar to Earth. It seems unlikely that Earth is unique in the Universe. Not just in the Universe, but elsewhere in our own galaxy.
Does this planet need to have a moon the size about of the Earth's Moon?

That would make the chances of finding another planet closely similar to Earth to be quite unlikely, wouldn't you say?
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Re: We are alone in the Universe, unless we guess otherwise.

Post by L'Emmerdeur » Tue May 26, 2020 3:33 pm

rainbow wrote:
Tue May 26, 2020 1:49 pm
L'Emmerdeur wrote:
Tue May 26, 2020 3:06 am
This is all if, of course, but as I understand it the results of the model indicate that life is likely to emerge on a planet closely similar to Earth. It seems unlikely that Earth is unique in the Universe. Not just in the Universe, but elsewhere in our own galaxy.
Does this planet need to have a moon the size about of the Earth's Moon?

That would make the chances of finding another planet closely similar to Earth to be quite unlikely, wouldn't you say?
'Quite unlikely' in the British sense of somewhat unlikely, yes. I wouldn't go so far as to agree that the American sense of that phrase, very unlikely, is applicable though I agree it decreases the odds to add an unusually large moon as a necessary component of the system.

I would say that it's rather unlikely that Earth is the only planet of its size in the Universe with a large moon, orbiting in what we consider the habitable zone. Given that there are probably billions of planets in our own galaxy, I expect that many planets exist in the Milky Way that are similar to Earth in these details.

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Re: We are alone in the Universe, unless we guess otherwise.

Post by Brian Peacock » Wed May 27, 2020 7:22 am

Even if the mere possibility of life is so unlikely as to be negligible, the Universe is so staggeringly huge, like really really big, like so massive that it breaks our concept of scale, then that's still an awful lot of possibility. I mean, if Earth is the only planet with life in the Galaxy there's still an incalculable number of Galaxies out there.

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Re: We are alone in the Universe, unless we guess otherwise.

Post by rainbow » Wed May 27, 2020 7:59 am

L'Emmerdeur wrote:
Tue May 26, 2020 3:33 pm

I would say that it's rather unlikely that Earth is the only planet of its size in the Universe with a large moon, orbiting in what we consider the habitable zone. Given that there are probably billions of planets in our own galaxy, I expect that many planets exist in the Milky Way that are similar to Earth in these details.
It would probably be a bit beyond me to calculate the probability of a planet being hit by another object, so that they don't break into little bits, but collide at just the right angle and velocity to form a binary planet system like the Earth - Moon.
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Re: We are alone in the Universe, unless we guess otherwise.

Post by rainbow » Wed May 27, 2020 8:21 am

Giant impact hypothesis

The prevailing theory supported by the scientific community, the giant impact hypothesis suggests that the moon formed when an object smashed into early Earth. Like the other planets, Earth formed from the leftover cloud of dust and gas orbiting the young sun. The early solar system was a violent place, and a number of bodies were created that never made it to full planetary status. One of these could have crashed into Earth not long after the young planet was created.

Known as Theia, the Mars-sized body collided with Earth, throwing vaporized chunks of the young planet's crust into space. Gravity bound the ejected particles together, creating a moon that is the largest in the solar system in relation to its host planet. This sort of formation would explain why the moon is made up predominantly of lighter elements, making it less dense than Earth — the material that formed it came from the crust, while leaving the planet's rocky core untouched. As the material drew together around what was left of Theia's core, it would have centered near Earth's ecliptic plane, the path the sun travels through the sky, which is where the moon orbits today.
https://www.space.com/19275-moon-formation.html
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Re: We are alone in the Universe, unless we guess otherwise.

Post by JimC » Wed May 27, 2020 8:50 am

The Moon thing is only important if having large tides (and therefore a big, dynamic intertidal zone) is a useful feature for the invasion of land by terrestrial animals. Perhaps it is so, but not having a large moon would not be a total deal-breaker for evolution, I would suggest...
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Re: We are alone in the Universe, unless we guess otherwise.

Post by L'Emmerdeur » Wed May 27, 2020 5:20 pm

I recall reading about ideas on intertidal zones being a likely environment for the very first life to form. Of course there are other candidates, including oceanic hydrothermal vents.

We don't know that an impact is the only way for a binary planet system to form, nor do we have an accurate idea of how common or uncommon such binary planets are.

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Re: We are alone in the Universe, unless we guess otherwise.

Post by LucidFlight » Wed May 27, 2020 8:57 pm

rainbow wrote:
Wed May 27, 2020 7:59 am
L'Emmerdeur wrote:
Tue May 26, 2020 3:33 pm

I would say that it's rather unlikely that Earth is the only planet of its size in the Universe with a large moon, orbiting in what we consider the habitable zone. Given that there are probably billions of planets in our own galaxy, I expect that many planets exist in the Milky Way that are similar to Earth in these details.
It would probably be a bit beyond me to calculate the probability of a planet being hit by another object, so that they don't break into little bits, but collide at just the right angle and velocity to form a binary planet system like the Earth - Moon.

I'm sure if we fed all the parameters into a giant computer and waited for a while, it would tell us the answer.
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