Bringing the alien life debate back to reality

C

Cypress

Well-known member
If there is any chance of humans encountering alien life, at least two extremely unlikely things must be true:

Life evolves easily. Decades of research have yielded little in the way of identifying the mechanism of abiogenesis — the formation of life from non-living matter. There are several different theories on the origin of life, and none of them are any good. In the laboratory, we have had some success in creating biomolecules such as amino acids from gaseous precursors; the Miller-Urey experiment is the most famous of these. But scientists have yet to come even close to reproducing life in the laboratory. This strongly implies that life does not evolve easily.

But even if we were to cede the point that life can evolve easily given enough time, there is another problem: the vast majority of exoplanets are inhospitable to life. New research suggests that most stars are incapable of supporting plant life via photosynthesis. Harvesting a star’s energy is the first step for the evolution of life, but evolution cannot even get started if there is not enough of it.

Interstellar travel is possible and practical. This, in my opinion, is even more unlikely than the easy evolution of life. We know life evolved at least once (here on Earth), but we have no idea if interstellar travel is possible. Sure, we could get on a spaceship today and head for a planet orbiting the nearest star, Proxima Centauri, but we better pack a lot of fun-sized bags of pretzels because it will take about 6,300 years to get there.

The notion that we will develop (or that some advanced alien civilization has already developed) the ability to easily traverse the galaxy is pure speculation. It is physically impossible to travel at the speed of light, though it may be possible to travel at a substantial fraction of the speed of light. Still, even if light speed was possible, the distances between stars is nearly unfathomable. Traveling at the speed of light, Proxima Centauri is still more than four years away; the other side of the galaxy is over 100,000 years away.

“Theoretically possible” does not mean “probable”

Sci-fi enthusiasts note that unknown technologies may develop, such as the ability to warp the fabric of spacetime or to travel through a wormhole. But again, these suggestions are purely speculative. Other than some fancy math that suggests such maneuvers could theoretically be possible, we have no idea if either can actually happen. Just because unicorns and mermaids are theoretically possible does not mean that they exist.

Continued
https://bigthink.com/hard-science/we-are-effectively-alone-universe/
 
I think the writer is wrong that photosynthesis is a requirement to jump start life.

Chemosynthetic microbes can and do exist, and they harvest energy for metabolism from chemical energy.
 
Cypress said:
If there is any chance of humans encountering alien life, at least two extremely unlikely things must be true:

Life evolves easily. Decades of research have yielded little in the way of identifying the mechanism of abiogenesis — the formation of life from non-living matter. There are several different theories on the origin of life, and none of them are any good. In the laboratory, we have had some success in creating biomolecules such as amino acids from gaseous precursors; the Miller-Urey experiment is the most famous of these. But scientists have yet to come even close to reproducing life in the laboratory. This strongly implies that life does not evolve easily.

But even if we were to cede the point that life can evolve easily given enough time, there is another problem: the vast majority of exoplanets are inhospitable to life. New research suggests that most stars are incapable of supporting plant life via photosynthesis. Harvesting a star’s energy is the first step for the evolution of life, but evolution cannot even get started if there is not enough of it.

Interstellar travel is possible and practical. This, in my opinion, is even more unlikely than the easy evolution of life. We know life evolved at least once (here on Earth), but we have no idea if interstellar travel is possible. Sure, we could get on a spaceship today and head for a planet orbiting the nearest star, Proxima Centauri, but we better pack a lot of fun-sized bags of pretzels because it will take about 6,300 years to get there.

The notion that we will develop (or that some advanced alien civilization has already developed) the ability to easily traverse the galaxy is pure speculation. It is physically impossible to travel at the speed of light, though it may be possible to travel at a substantial fraction of the speed of light. Still, even if light speed was possible, the distances between stars is nearly unfathomable. Traveling at the speed of light, Proxima Centauri is still more than four years away; the other side of the galaxy is over 100,000 years away.

“Theoretically possible” does not mean “probable”

Sci-fi enthusiasts note that unknown technologies may develop, such as the ability to warp the fabric of spacetime or to travel through a wormhole. But again, these suggestions are purely speculative. Other than some fancy math that suggests such maneuvers could theoretically be possible, we have no idea if either can actually happen. Just because unicorns and mermaids are theoretically possible does not mean that they exist.

Continued
https://bigthink.com/hard-science/we-are-effectively-alone-universe/
Click to expand...

There is no alien life except in the minds of loons and hacks.
 
I've read some theories that say that life arose on earth multiple times - some think MANY times. It kept getting destroyed w/ the early bombardment of meteors that the primordial earth experienced, and kept happening again & again.

I tend to believe that. There are definitely many exoplanets where it can't exist, and there are whole swaths of the galaxy where it can't exist. But I think the mistake we make is that we base everything on our perspective, and on how life evolved on earth - since it's the only life we know. We always assume there needs to be carbon, or water, or whatever it is. Some alien life may be radically different from what we know. "It's life, captain - but not as we know it."

Even if there are only a half dozen planets in a given galaxy that support & have life - that would still be trillions of planets in the universe that harbor life. I think it's probably a lot more than that, too, but just going w/ a conservative estimate. I mean, we might have life elsewhere in this solar system alone, with some of the moons of Saturn & Jupiter.
 
BartenderElite said:
I've read some theories that say that life arose on earth multiple times - some think MANY times. It kept getting destroyed w/ the early bombardment of meteors that the primordial earth experienced, and kept happening again & again.

I tend to believe that. There are definitely many exoplanets where it can't exist, and there are whole swaths of the galaxy where it can't exist. But I think the mistake we make is that we base everything on our perspective, and on how life evolved on earth - since it's the only life we know. We always assume there needs to be carbon, or water, or whatever it is. Some alien life may be radically different from what we know. "It's life, captain - but not as we know it."

Even if there are only a half dozen planets in a given galaxy that support & have life - that would still be trillions of planets in the universe that harbor life. I think it's probably a lot more than that, too, but just going w/ a conservative estimate. I mean, we might have life elsewhere in this solar system alone, with some of the moons of Saturn & Jupiter.
Click to expand...

My guess is that there is life elsewhere in the galaxy, though it might be rare.

But I think some questions are crying out for answers.

If life supposedly arose multiple times between 4 billion and 3.5 billion years ago, why did multiple clades of life suddenly stop appearing during the vast stretch of time between 3.5 and today?

If life so readily emerges, why don't we see other strands of life emerge in all of that time?

There are hundreds of amino acids, but only 20 are used by all life that has ever existed on earth. And all life that has ever existed in the last three billion years originates from the same last universal common ancestor.

If life that doesn't require carbon or water exists, I would think we might have found it here on earth. Earth has had ample time for other forms of life to exist, and earth has an enormous variety of localized geochemical and thermal environments which might breed exotic life unrelated to conventional Life
 
Cypress said:
My guess is that there is life elsewhere in the galaxy, though it might be rare.

But I think some questions are crying out for answers.

If life supposedly arose multiple times between 4 billion and 3.5 billion years ago, why did multiple clades of life suddenly stop appearing during the vast stretch of time between 3.5 and today?

If life so readily emerges, why don't we see other strands of life emerge in all of that time?

There are hundreds of amino acids, but only 20 are used by all life that has ever existed on earth. And all life that has ever existed in the last three billion years originates from the same last universal common ancestor.

If life that doesn't require carbon or water exists, I would think we might have found it here on earth. Earth has had ample time for other forms of life to exist, and earth has an enormous variety of localized geochemical and thermal environments which might breed exotic life unrelated to conventional Life
Click to expand...

I think it's easier for life to emerge in a more "pristine" environment. Every niche is now filled w/ predators and other obstacles - for a single-celled organism to establish ground? Life might be created & we might never know about it, because it would be almost imposslble for rudimentary life to survive on the planet today
 
BartenderElite said:
I've read some theories that say that life arose on earth multiple times - some think MANY times. It kept getting destroyed w/ the early bombardment of meteors that the primordial earth experienced, and kept happening again & again.

I tend to believe that. There are definitely many exoplanets where it can't exist, and there are whole swaths of the galaxy where it can't exist. But I think the mistake we make is that we base everything on our perspective, and on how life evolved on earth - since it's the only life we know. We always assume there needs to be carbon, or water, or whatever it is. Some alien life may be radically different from what we know. "It's life, captain - but not as we know it."

Even if there are only a half dozen planets in a given galaxy that support & have life - that would still be trillions of planets in the universe that harbor life. I think it's probably a lot more than that, too, but just going w/ a conservative estimate. I mean, we might have life elsewhere in this solar system alone, with some of the moons of Saturn & Jupiter.
Click to expand...

cuckoo-jack-black.gif
 
BartenderElite said:
I think it's easier for life to emerge in a more "pristine" environment. Every niche is now filled w/ predators and other obstacles - for a single-celled organism to establish ground? Life might be created & we might never know about it, because it would be almost imposslble for rudimentary life to survive on the planet today
Click to expand...

It seems to me what we are finding out that life on earth can thrive in the most extreme thermal and geochemical environmental conditions.

In rock strata miles below the surface, to superheated hot springs, to thermal vents deep on the abyssal ocean floor.
The tardigrade can live for months without oxygen or any kind of chemical energy, even surviving in outer space.

There seems to be plenty of places, and billions of years that other clades of life could have originated.

But wherever we have looked, even at the extremophiles in thermal pools or chemosynthetic bacteria at deep sea black smokers, these forms of life apparently have the same genetic legacy we do.
 
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