Bringing the alien life debate back to reality

[T. A. Gardner]

Have you seen any evidence there is alien life dumbfuck?

I have, and it's right here on this board! There's plenty of evidence that there are posters here who have never been to Earth in their lives!

[Truth Detector]

LOL. Moron.

Indeed you are.

[Truth Detector]

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.

[Truth Detector]

I have, and it's right here on this board! There's plenty of evidence that there are posters here who have never been to Earth in their lives!

[Cypress]

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

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.

[Quincunx]

Just because we have the same genetic lineage as all the other life on earth doesn't mean life didn't arise multiple times. It could be that only one line survived. Remember in the End Permian, when about 95% of the ocean's biodiversity was wiped out where we could have lost many of those other strains. And that's only ONE of the many possible mass-extinctions that could have occurred. There's probably ample opportunity in the pre-Cambrian for multiple mass extinctions over and over again.

Yeah, life as we know it is pretty robust, but that doesn't mean it is impossible to destroy it. Especially early on when the environmental niches were not yet exploited. And what if the origin of life was the RNA-world hypothesis? Would we be able to clearly identify our "DNA lineage" back to that?

And finally: my favorite approach is that involving mineral surfaces as catalytic sites. Proto-life could have been little more than chemical adsorption features on clays or carbonates. Even the RNA-world article I cited above says: "It has been proposed that the first “biological” molecules on Earth were formed by metal-based catalysis on the crystalline surfaces of minerals. ". What if life started over and over and over as these mineral surface reactions? Finally when polynucleotides developed life took off in the form we know it.

This obviates the need for DNA-life to start multiple times. Once DNA was on the scene perhaps that is what finally gave a more robust system of reproduction and passing-on of heritable information and that is the lineage we share.

[Guille]

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...lone-universe/

I think you're wrong on both points.

Life evolved easily here, why not elsewhere?

As for interstellar travel, are we in a position to know that yet?

Best case scenario you lost one and tied one.

[Cypress]

I think you're wrong on both points.

Life evolved easily here, why not elsewhere?

I don't think that is correct to say.

Evolution by natural selection and gene drift occurs easily and readily.

But based on the evidence we have, life only originated once on Earth - in four billion years. All life we know of today and which has every lived traces a genetic legacy back to a last universal common ancestor.

If life is inevitable and easily originates, the question which has to be answered is why we don't see tangible evidence that different lineages of life emerged? Four billion years is more than enough time. The Earth is pregnant with a huge variety of localized thermal and chemical environmental variation. Any conjecture that life did supposedly originate multiple times is mere speculation.

As for interstellar travel, are we in a position to know that yet?.

We haven't ever seen any natural matter or energy which can travel faster than light.

Unless our laws of relativity are completely wrong, it requires infinite energy to accelerate mass to the speed of light. And the law of time dilation requires that even if you could go faster than light, you would travel backwards in time.

We've never seen any credible evidence of alien visitors or alien space travelers.

We've never seen an electromagnetic signal of technological civilization. Any advanced civilization would be expected to leave a footprint in the radio wave range of the EM spectrum, because they radio EM spectrum is the only form of energy which can be used for communication, navigation, transmission of information and data. The xray, gamma ray, and ultraviolet part of the EM spectrum is easily diffracted and scattered by atmospheres, dust, gas.


I am ready to believe that there is life in the galaxy, but that it might be rare and unusual. Absent any further evidence, I am not committed to saying life easily emerges and that the galaxy is pregnant with life.

[Doc Dutch]

How do you know?

Trump Dummy is able to read minds.

[Doc Dutch]

Bringing the alien life debate back to reality
https://bigthink.com/hard-science/we...lone-universe/

The author brings up two great points then leaps to a conclusion of "We are effectively alone in the universe
It does not matter if intelligent life exists elsewhere. We will never find each other."

Disagreed with his conclusion of "never". "Unlikely anytime soon" is a better fit.

Agreed life is rare. Agreed there is zero sign of life, much less intelligent life, off our own planet.

[Doc Dutch]

I think you're wrong on both points.

Life evolved easily here, why not elsewhere?

As for interstellar travel, are we in a position to know that yet?

Best case scenario you lost one and tied one.

The historical record indicates life originating is not easy. What it does indicate is that, once started, it's tenacious in how it takes over given enough time. Even when cataclysmic events such as super volcanoes and impact events destroy most life, it continues to spread.

Since life has only been found in one spot despite decades of searching, it's clear life isn't common in the Universe. Fermi's Paradox comes into play here.

The distances between stars is so great and the limitations of the physical universe, specifically the speed of light, make interstellar travel both difficult and time consuming.

[Cypress]

The author brings up two great points then leaps to a conclusion of "We are effectively alone in the universe
It does not matter if intelligent life exists elsewhere. We will never find each other."

Disagreed with his conclusion of "never". "Unlikely anytime soon" is a better fit.

Agreed life is rare. Agreed there is zero sign of life, much less intelligent life, off our own planet.

Good point. I think the author goes a bridge to far in several ways.

I don't agree with his insinuation that photosynthesis was required for life. The first prokaryotes were almost certainly not photosynthetic, and photosynthesis as a method of metabolism likely originated a billion years or so after the first chemosynthetic biological microbes.

[Doc Dutch]

Good point. I think the author goes a bridge to far in several ways.

I don't agree with his insinuation that photosynthesis was required for life. The first prokaryotes were almost certainly not photosynthetic, and photosynthesis as a method of metabolism likely originated a billion years or so after the first chemosynthetic biological microbes.

Not a biochemist, but your previous posts about the origin of life back up the conclusion that photosynthesis is not a requirement.

[PostmodernProphet]

The fact that amino acids, peptides, and organic compounds are ubiquitous in meteors and cosmic dust are clues suggesting it's worth looking for life elsewhere in the galaxy

why assume alien life would require amino acids, peptides or organic compounds?......

[PostmodernProphet]

I can imagine no reason why God would create galaxies so far away their light has still not reached us, for OUR benefit......I assume there are other creations of his enjoying other parts of the universe......