Bringing the alien life debate back to reality

[Dutch Uncle]

Before I leap to the conclusion that life is inevitable in the presence of liquid water, I'd like to see evidence that life emerged more than once in four billion years on earth.

Once in four billion years almost sounds like a fluke or an extremely rare occurrence to me.

In the last decade we have become aware of a vast deep biosphere in the Earth's crust, miles below the surface. I think it would be one of the great scientific discoveries of the century to find life forms there which have a separate genetic legacy from all the known life that descended from LUCA.

While life may, indeed, be inevitable, it appears to be extremely rare. As such, there may not be any previous life forms to LUCA.

One thing that does seem clear is that once life takes hold, it's very difficult to eradicate.

 

[Cypress]

While life may, indeed, be inevitable, it appears to be extremely rare. As such, there may not be any previous life forms to LUCA.

One thing that does seem clear is that once life takes hold, it's very difficult to eradicate.

Agree. for existing life, descent with modification by natural selection and gene drift is robust and nearly impervious to any kind of fatal knock out blow.

 

[Dutch Uncle]

Agree. for existing life, descent with modification by natural selection and gene drift is robust and nearly impervious to any kind of fatal knock out blow.

Finding life off planet keeps running into the Fermi Paradox. If life is inevitable, where is it?

Based upon the results, there seem to be two main conclusions: Life is rare and the interstellar distances between lifeforms is vast.

Have you ever visited a "The Voyage" display? I saw the one in Corpus Christi. It really nails the vastness of "Space".

http://voyagesolarsystem.org/

http://voyagesolarsystem.org/the-experience/

 

[BartenderElite]

That is my contention. Prove me wrong snowflake.

I'm not going to prove you wrong - but you can't prove me wrong, either.

It's odd to ridicule the mere idea that there could be other life in a universe where there are over a trillion galaxies, each with roughly 100 billions stars. I don't know how someone could believe - without any doubt at all - that earth is the only planet with life in all of that vastness.

I'm curious - is it a religious thing? Does it threaten anyone's beliefs to think (quite logically) that there could not only be life elsewhere in the universe, but that it might be pretty abundant?

 

[Dutch Uncle]

I'm not going to prove you wrong - but you can't prove me wrong, either.

It's odd to ridicule the mere idea that there could be other life in a universe where there are over a trillion galaxies, each with roughly 100 billions stars. I don't know how someone could believe - without any doubt at all - that earth is the only planet with life in all of that vastness.

I'm curious - is it a religious thing? Does it threaten anyone's beliefs to think (quite logically) that there could not only be life elsewhere in the universe, but that it might be pretty abundant?

The religion thing has an inherent problem: If they go strictly by the Bible, then life only exists on Earth. If they truly believe that God is all powerful, then they can't deny God could put life on every planet in the Universe.

There's also the problem of Jesus; did Jesus die for all the space alien's sins too? Or did he have to be executed on every planet with life?

 

[Cypress]

Finding life off planet keeps running into the Fermi Paradox. If life is inevitable, where is it?

Based upon the results, there seem to be two main conclusions: Life is rare and the interstellar distances between lifeforms is vast.

Have you ever visited a "The Voyage" display? I saw the one in Corpus Christi. It really nails the vastness of "Space".

http://voyagesolarsystem.org/

http://voyagesolarsystem.org/the-experience/

Nice. I don't think the human mind evolved to be able to intuitively comprehend distances like that.

The Fermi paradox seems to boil down to a couple simple questions:

Is life a chemical law of the universe; does it inevitably emerge in the presence of liquid water?

Or is life almost a fluke, something which required a perfect storm of chemical, physical, and cosmological events which are only very rarely replicated.

 

[Dutch Uncle]

Nice. I don't think the human mind evolved to be able to intuitively comprehend distances like that.

The Fermi paradox seems to boil down to a couple simple questions:

Is life a chemical law of the universe; does it inevitably emerge in the presence of liquid water?

Or is life almost a fluke, something which required a perfect storm of chemical, physical, and cosmological events which are only very rarely replicated.

Agreed on the inability of the human mind to fully grasp the distances involved.

Fluke appears to be the best candidate, IMO. Life is a very rare event.

Still, in a galaxy with 100B stars and a Universe with over 100B galaxies, the odds seem good that the fluke has occurred elsewhere.

https://solarsystem.nasa.gov/solar-system/beyond/overview/

Our Milky Way galaxy is just one of the billions of galaxies in the universe. Within it, there are at least 100 billion stars, and on average, each star has at least one planet orbiting it. This means there are potentially thousands of planetary systems like our solar system within the galaxy!...

...Our Sun is one of at least 100 billion stars in the Milky Way, a spiral galaxy about 100,000 light-years across. And where are we in the Milky Way? Our Sun lies near a small, partial arm called the Orion Arm, or Orion Spur, located between the Sagittarius and Perseus arms.

https://www.skyatnightmagazine.com/space-science/how-many-galaxies-in-universe/

One such estimate says that there are between 100 and 200 billion galaxies in the observable universe.

Other astronomers have tried to estimate the number of ‘missed’ galaxies in previous studies and come up with a total number of 2 trillion galaxies in the universe.

However, based on recent measurements of the darkness of the night sky, this may be an overestimate.

 

[Cypress]

Agreed on the inability of the human mind to fully grasp the distances involved.

Fluke appears to be the best candidate, IMO. Life is a very rare event.

Still, in a galaxy with 100B stars and a Universe with over 100B galaxies, the odds seem good that the fluke has occurred elsewhere.

https://solarsystem.nasa.gov/solar-system/beyond/overview/


https://www.skyatnightmagazine.com/space-science/how-many-galaxies-in-universe/

Absent any compelling evidence, I am on Team rare life myself.

I've never been that impressed with the math of a hundred billion stars in the Milky Way and a hundred million galaxies.

It's not the sheer number that matter.

We live in a very large and complex galaxy. If we can't find evidence of life in this galaxy, I see no reason to expect it to be in other galaxies.

Many galaxies and many stars are depleted in heavy elements, which are required for life.

None of the blue giants or Red supergiant stars would be expected to have planets with life, those stars don't live very long.

The white dwarfs are the dead embers of sun-like stars, I wouldn't expect life there.

As for the red dwarfs and G type stars, how many of them are depleted in heavy elements, and how many are in potentially gravitationally unstable binary and trinary systems? Solo stars like our sun tend to be the exception rather than the rule. And of those, how many have rocky planets with a magnetic field in the Goldilocks habitable zone of it's star's orbit?

So the number of potentially habitable star systems in our galaxy probably gets whittled way down from 100 billion. And the percentage of those that have intelligent life probably whittled it way down from there.

 

[Saint Guinefort]

Absent any compelling evidence, I am on Team rare life myself.

I've never been that impressed with the math of a hundred billion stars in the Milky Way and a hundred million galaxies.

It's not the sheer number that matter.

We live in a very large and complex galaxy. If we can't find evidence of life in this galaxy, I see no reason to expect it to be in other galaxies.

Many galaxies and many stars are depleted in heavy elements, which are required for life.

None of the blue giants or Red supergiant stars would be expected to have planets with life, those stars don't live very long.

The white dwarfs are the dead embers of sun-like stars, I wouldn't expect life there.

As for the red dwarfs and G type stars, how many of them are depleted in heavy elements, and how many are in potentially gravitationally unstable binary and trinary systems? Solo stars like our sun tend to be the exception rather than the rule. And of those, how many have rocky planets with a magnetic field in the Goldilocks habitable zone of it's star's orbit?

So the number of potentially habitable star systems in our galaxy probably gets whittled way down from 100 billion. And the percentage of those that have intelligent life probably whittled it way down from there.

In the Milky Way NASA guesses there are something like 4.1billion sun-like stars and they further estimate that of these stars 300 million of them have "habitable" planets (MIT). I would think that advanced life would definitely have been detectable by this point assuming they could generate a signal we could receive. Maybe advanced life is super rare but simple life is really common.

The probabilities are multiplicative and going from development of simple life to development of advanced technological life is what makes it much more rare. Maybe we share the galaxy with 300million planets that look like the Earth when stromatolites ruled.

 

[Cypress]

In the Milky Way NASA guesses there are something like 4.1billion sun-like stars and they further estimate that of these stars 300 million of them have "habitable" planets (MIT). I would think that advanced life would definitely have been detectable by this point assuming they could generate a signal we could receive. Maybe advanced life is super rare but simple life is really common.

The probabilities are multiplicative and going from development of simple life to development of advanced technological life is what makes it much more rare. Maybe we share the galaxy with 300million planets that look like the Earth when stromatolites ruled.

That corroborates precisely what I wrote.

Rather than tossing around the admitedly impressive 100 billion number, the actual amount of possibly habitable stars is only a tiny fraction of one percent of those.

And that doesn't even include estimates for how many of those actually have rocky planets with magnetic fields or a large lunar companion, and within the Goldilocks zone which are critical to all life on earth .

 

[Dutch Uncle]

That corroborates precisely what I wrote.

Rather than tossing around the admitedly impressive 100 billion number, the actual amount of possibly habitable stars is only a tiny fraction of one percent of those.

And that doesn't even include estimates for how many of those actually have rocky planets with magnetic fields or a large lunar companion, and within the Goldilocks zone which are critical to all life on earth .

All of which reduces the possibility of extraterrestrial life making life of Earth very rare.

 

[Dutch Uncle]

Absent any compelling evidence, I am on Team rare life myself.

I've never been that impressed with the math of a hundred billion stars in the Milky Way and a hundred million galaxies.

It's not the sheer number that matter.

We live in a very large and complex galaxy. If we can't find evidence of life in this galaxy, I see no reason to expect it to be in other galaxies.

Many galaxies and many stars are depleted in heavy elements, which are required for life.

None of the blue giants or Red supergiant stars would be expected to have planets with life, those stars don't live very long.

The white dwarfs are the dead embers of sun-like stars, I wouldn't expect life there.

As for the red dwarfs and G type stars, how many of them are depleted in heavy elements, and how many are in potentially gravitationally unstable binary and trinary systems? Solo stars like our sun tend to be the exception rather than the rule. And of those, how many have rocky planets with a magnetic field in the Goldilocks habitable zone of it's star's orbit?

So the number of potentially habitable star systems in our galaxy probably gets whittled way down from 100 billion. And the percentage of those that have intelligent life probably whittled it way down from there.

In statistics, the higher the number, the more likely a rare event will occur. It doesn't matter if the odds of life are low, the more opportunities, the more likely life will develop.

Our Sun will eventually become a white dwarf. It's too small to nova. After a few billion years, it'll become a red giant and smoke the Earth, but warming the gas giants where life could develop (or move to) their moons. Eventually the Sun will shrink to a white dwarf.

https://www.nasa.gov/image-feature/goddard/2019/why-the-sun-wont-become-a-black-hole

Will the Sun become a black hole? No, it's too small for that!

The Sun would need to be about 20 times more massive to end its life as a black hole. Stars that are born this size or larger can explode into a supernova at the end of their lifetimes before collapsing back into a black hole, an object with a gravitational pull so strong that nothing, not even light, can escape. Some smaller stars are big enough to go supernova, but too small to become black holes — they'll collapse into super-dense structures called neutron stars after exploding as a supernova. But the Sun's not big enough for this fate, either: It has only about one-tenth of the mass needed to eventually become a neutron star.

So what will happen to the Sun? In some 6 billion years it will end up as a white dwarf — a small, dense remnant of a star that glows from leftover heat. The process will start about 5 billion years from now when the Sun begins to run out of fuel.

Like most stars, during the main phase of its lifetime, the Sun creates energy by fusing hydrogen atoms in its core. In about 5 billion years, the Sun will start to run out of hydrogen in its core to fuse, and it will begin to collapse. This will let the Sun start to fuse heavier elements in the core, along with fusing hydrogen in a shell wrapped around the core. When this happens, the Sun's temperature will increase, and the outer layers of the Sun's atmosphere will expand so far out into space that they'll engulf Earth. (This would make Earth uninhabitable for life as we know it — though other factors in planetary evolution might make it uninhabitable before that point.) This is the red giant phase, and it will last about a billion years, before the Sun collapses into a white dwarf.

 

[Cypress]

In statistics, the higher the number, the more likely a rare event will occur. It doesn't matter if the odds of life are low, the more opportunities, the more likely life will develop.

Our Sun will eventually become a white dwarf. It's too small to nova. After a few billion years, it'll become a red giant and smoke the Earth, but warming the gas giants where life could develop (or move to) their moons. Eventually the Sun will shrink to a white dwarf.

https://www.nasa.gov/image-feature/goddard/2019/why-the-sun-wont-become-a-black-hole

Before our sun becomes a white dwarf it will vaporize our oceans and incinerate our atmosphere. So we aren't going to be looking to white dwarfs as candidates for habitable systems.

NASA's estimate of 300 million systems with rocky planets that potentially could host life is only based on being located in the Goldilocks zone, and even the authors admitted this was a weakness of their paper since there are other criteria that make a planet habitable.

This is my thought experiment on other potentially neccessary criteria for a planet to possibly host life:

Probability liquid water exists - 50% (p50). Our system has two near-Earth sized rocky planets in the Goldilocks zone, only one of which has liquid water. So p50 seems like a reasonable guess.

Probability of a strong magnetic field - 33% (p33). Of three rocky planets in the Goldilocks zone of our system, only one has a strong magnetic field. So p33 seems like a reasonable guess.

Probability of permanent stable orbital mechanics - 50% (p50). In the absence of tangible information, an even chance seems like a reasonable guess.

Probability of large gas giant in outer system to clear out any frequent incoming asteroids of a lethal size - 50% (p50). In the absence of tangible information, an even chance seems like a reasonable guess

Probability abiogenesis will actually take place, even if all conditions are met: if we assume the emergence of cellular life for prebiotic materials is difficult to achieve and something of a fluke, assume probability of 1%. If we assume life readily emerges in the presence of liquid water, assume probability 50%.

Water = p50.
Magnetic field = p33
Stable orbital mechanics = p50
Gas giant clearing asteroids = p50.
Abiogenesis, low confidence = p1
Abiogenesis, high confidence = p50

High end estimate: 6.25 million planets in Milky Way host life.

Low end estimate: 125,000 planets in Milky Way host life.

Either way, that is less than 0.00001 percent of star systems in Milky Way that would host life.

And that is without further culling for the probability intelligent life would emerge on a planet that happens to have a biosphere.

 

[Dutch Uncle]

Before our sun becomes a white dwarf it will vaporize our oceans and incinerate our atmosphere. So we aren't going to be looking to white dwarfs as candidates for habitable systems.

NASA's estimate of 300 million systems with rocky planets that potentially could host life is only based on being located in the Goldilocks zone, and even the authors admitted this was a weakness of their paper since there are other criteria that make a planet habitable.

This is my thought experiment on other potentially neccessary criteria for a planet to possibly host life:

Probability liquid water exists - 50% (p50). Our system has two near-Earth sized rocky planets in the Goldilocks zone, only one of which has liquid water. So p50 seems like a reasonable guess.

Probability of a strong magnetic field - 33% (p33). Of three rocky planets in the Goldilocks zone of our system, only one has a strong magnetic field. So p33 seems like a reasonable guess.

Probability of permanent stable orbital mechanics - 50% (p50). In the absence of tangible information, an even chance seems like a reasonable guess.

Probability of large gas giant in outer system to clear out any frequent incoming asteroids of a lethal size - 50% (p50). In the absence of tangible information, an even chance seems like a reasonable guess

Probability abiogenesis will actually take place, even if all conditions are met: if we assume the emergence of cellular life for prebiotic materials is difficult to achieve and something of a fluke, assume probability of 1%. If we assume life readily emerges in the presence of liquid water, assume probability 50%.



High end estimate: 6.25 million planets in Milky Way host life.

Low end estimate: 125,000 planets in Milky Way host life.

Either way, that is less than 0.00001 percent of star systems in Milky Way that would host life.

And that is without further culling for the probability intelligent life would emerge on a planet that happens to have a biosphere.

By that time that happens to our Sun, life would have either moved off planet or destroyed itself. I think white dwarfs are an excellent place to look for ancient life.

Looking for planets in the Goldilock Zone are a great way to find planets for colonization.

 

[Cypress]

The JWT found no evidence of an atmosphere at the near Earth-sized rocky planet Trappist-1.
But there are other near Earth-sized rocky exoplanets in the Trappist system which haven't been examined for atmospheres yet.

https://www.space.com/james-webb-space-telescope-no-atmosphere-trappist-1-exoplanet

 

[Truth Detector]

I'm not going to prove you wrong - but you can't prove me wrong, either.

I can prove YOU wrong. Is there any evidence there is alien life out there? Answer; NO.

It's odd to ridicule the mere idea that there could be other life in a universe where there are over a trillion galaxies, each with roughly 100 billions stars. I don't know how someone could believe - without any doubt at all - that earth is the only planet with life in all of that vastness.

Yet, I don't know how anyone, particularly those who refuse to acknowledge the possibility that there is a God, can ridicule the idea there is no alien life out there based on facts.

I'm curious - is it a religious thing? Does it threaten anyone's beliefs to think (quite logically) that there could not only be life elsewhere in the universe, but that it might be pretty abundant?

It's a REALITY thing. There has been ZERO evidence of alien life except for Hollywood's versions of it.

 

[BartenderElite]

I can prove YOU wrong. Is there any evidence there is alien life out there? Answer; NO.

Yet, I don't know how anyone, particularly those who refuse to acknowledge the possibility that there is a God, can ridicule the idea there is no alien life out there based on facts.

It's a REALITY thing. There has been ZERO evidence of alien life except for Hollywood's versions of it.

That didn't prove me wrong. I never said there was DEFINITELY life in elsewhere in the universe. Just that scientifically, it's a very logical proposition. I personally can't imagine trillions of other suns, and ours is the only one that has a planet w/ life.

Are you referring to me w/ that 2nd line? I never said there isn't the possibility of a God.

And back to the 1st line: You have NO IDEA if there is or isn't evidence of alien life "out there." No idea whatsoever. There could be a HUGE amount of evidence. We just haven't discovered it yet. You know - there is the whole "don't have the technology to travel many light years" issue.

 

[Saint Guinefort]

Yet, I don't know how anyone, particularly those who refuse to acknowledge the possibility that there is a God, can ridicule the idea there is no alien life out there based on facts.

You know there is a form of atheism that basically just fails to believe in God as opposed to "refusing the acknowledge the possibility". I'm that kind of atheist. While I accept that I COULD BE WRONG right now I fail to see sufficient evidence for God. But if more information comes to me that proves to be compelling I will hopefully change my mind.

Sounds like that is what you are in relation to alien life. You simply fail to see any evidence for it, so you assume it likely doesn't exist. If such evidence comes to the fore you'll change your mind. Fair enough.

As the other poster noted, however, no one on here is saying for sure there's alien life. Just that all things considered the likelihood is non-zero. But it's all a guess anyway.

 

[Cypress]

That didn't prove me wrong. I never said there was DEFINITELY life in elsewhere in the universe. Just that scientifically, it's a very logical proposition. I personally can't imagine trillions of other suns, and ours is the only one that has a planet w/ life.

Are you referring to me w/ that 2nd line? I never said there isn't the possibility of a God.

And back to the 1st line: You have NO IDEA if there is or isn't evidence of alien life "out there." No idea whatsoever. There could be a HUGE amount of evidence. We just haven't discovered it yet. You know - there is the whole "don't have the technology to travel many light years" issue.

I tend towards being agnostic about alien life or supreme dieties.

But, the universe itself seems primed for life. Carbon and water are almost uniquely adapted to provide the scaffolding for the emergence of life.

We can't categorically discount that this planet has the only life in the galaxy. But the fact that pre-biotic amino acids are ubiquitous in the universe is at least circumstantial evidence that the universe is primed for life.

On the flip side, I don't think there's any direct evidence of a Christian God who became incarnate as Jesus. But I am prepared to accept the possibility there is some higher organizing principle underlying the cosmos and all of reality, the the fine tuning of the cosmos may be circumstantial evidence of it.

 

[Dutch Uncle]

I tend towards being agnostic about alien life or supreme dieties.

But, the universe itself seems primed for life. Carbon and water are almost uniquely adapted to provide the scaffolding for the emergence of life.

We can't categorically discount that this planet has the only life in the galaxy. But the fact that pre-biotic amino acids are ubiquitous in the universe is at least circumstantial evidence that the universe is primed for life.

On the flip side, I don't think there's any direct evidence of a Christian God who became incarnate as Jesus. But I am prepared to accept the possibility there is some higher organizing principle underlying the cosmos and all of reality, the the fine tuning of the cosmos may be circumstantial evidence of it.

Primed? The elements are there. The only thing missing is life itself. It's like prepping a garden; pick a nice sunny spot, till the soil, add fertilizer, install a watering system. So what's missing? Seeds of life.

While it's possible, that the seeds could spontaneously generate, the odds of doing so seem a bit long. LOL

FWIW, I do believe, given enough attempts, the seeds could self-generate, but it would take billions of years and trillions of attempts. The current results bear this out.