Bringing the alien life debate back to reality

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.
 
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/
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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.
 
Guille said:
I think you're wrong on both points.

Life evolved easily here, why not elsewhere?
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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?.
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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.
 
Cypress said:
Bringing the alien life debate back to reality
https://bigthink.com/hard-science/we-are-effectively-alone-universe/
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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.
 
Guille said:
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.
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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.
 
Doc Dutch said:
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.
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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.
 
Cypress said:
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.
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Not a biochemist, but your previous posts about the origin of life back up the conclusion that photosynthesis is not a requirement.
 
Cypress said:
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
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why assume alien life would require amino acids, peptides or organic compounds?......
 
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......
 
I would find it difficult to believe that in an infinite universe,
there aren't an infinite number of planets so similar to our earth
that the life forms living on them would be pretty much the same a well.

The real issue is that it can't possibly matter to us.
If they're similar to us, they can't survive the interstellar travel any more than we can.
We'll never interact, so we're completely irrelevant to one another.
 
NiftyNiblick said:
I would find it difficult to believe that in an infinite universe,
there aren't an infinite number of planets so similar to our earth
that the life forms living on them would be pretty much the same a well.

The real issue is that it can't possibly matter to us.
If they're similar to us, they can't survive the interstellar travel any more than we can.
We'll never interact, so we're completely irrelevant to one another.
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An infinite universe is an assumption that requires several mathmatical constructs to be true, first and foremost that spacetime has zero curvature beyond our field of vision. It seems to have zero curvature, but that inference is limited to our field of vision and the precision of our instrumentation.

My second comment is that we will never be able to surmise if there is life in other galaxies, due to the distances involved.

But I'm not sure that matters.

By the standards of the cosmos, we live in a very large and complex galaxy of almost infinite variety. If we can't find life in this galaxy, I'm not sure why we would conclude if must exist in other galaxies.
 
Cypress said:
An infinite universe is an assumption that requires several mathmatical constructs to be true, first and foremost that spacetime has zero curvature beyond our field of vision. It seems to have zero curvature, but that inference is limited to our field of vision and the precision of our instrumentation.

My second comment is that we will never be able to surmise if there is life in other galaxies, due to the distances involved.

But I'm not sure that matters.

By the standards of the cosmos, we live in a very large and complex galaxy of almost infinite variety. If we can't find life in this galaxy, I'm not sure why we would conclude if must exist in other galaxies.
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How can the universe not be infinite?

if it has boundaries, what exists beyond them?

Since universe means everything, that would have to be part of the universe as well.
 
NiftyNiblick said:
How can the universe not be infinite?

if it has boundaries, what exists beyond them?

Since universe means everything, that would have to be part of the universe as well.
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Sooooo.....you don't accept the Big Bang theory nor see the Universe as a bubble?
 
NiftyNiblick said:
How can the universe not be infinite?

if it has boundaries, what exists beyond them?

Since universe means everything, that would have to be part of the universe as well.
Click to expand...

If spacetime has positive curvature, then space maintains a spherical shape, and if you set off in one direction, trillions of years later you would end up back where you started from.

The universe isn't expanding into anything, into any preexisting void. It is the space itself between the galaxies which is expanding.
 
PostmodernProphet said:
why assume alien life would require amino acids, peptides or organic compounds?......
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Because it's a good conservative scientific assumption to focus our search on carbon based life that at least loosely followed the known laws of biology.

The Earth had has four billion years for silicon based life or other exotic forms of life to emerge. But we've never seen anything other than the one lineage of carbon based life all descended with modification from the same microbe which existed 3.8 billion years ago.
 
Cypress said:
If spacetime has positive curvature, then space maintains a spherical shape, and if you set off in one direction, trillions of years later you would end up back where you started from.

The universe isn't expanding into anything, into any preexisting void. It is the space itself between the galaxies which is expanding.
Click to expand...

I don't understand the concept of the spherical shape of space
as a sphere always exists in whatever is outside it's circumference.

What's outside of the sphere would be part of the same infinite universe the way I can imagine it.
 
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