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The search for extraterrestrial life as we don’t know it

scientificamerican.com

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Re: The search for extraterrestrial life as we don’t know it

#31

Post by narag »

akiselev wrote: post #26
perihelions wrote: post #13

Question for people up to date with modern biochemistry: if there were extraterrestrial microbes on Earth right now, with totally unique chemical origins unrelated to proteins, nucleic acids, saccharides, etc., how likely would we be to notice them? And which analytic method would find them first? Is there a systemic search for this kind of crazy stuff, and where are the review papers for them? I don't know the keywo…

Very, very unlikely like astronomically so. Most microorganisms are so small they're practically transparent so we have to exploit biochemistry to "stain" them - hence why you'll often hear of bacteria classified as either Gram positive or negative, because of the Gram stain. If the biochemistry is unique or even slightly different i.e. right handed chirality, we'd basically have zero of our usual tools at our dispos…

There's already a whole world of terrestrial microbes that we expect or even know for certain to exist but can't culture, let alone stain, which means we can't really study them.

I'm going to bookmark this for the case someone asks: what piece of information that seems basic did you ignore until very recently?

A question that often arises is: if current life evolved from chemistry that's simpler than DNA, why has that one disappeared? Maybe it hasn't.

Re: The search for extraterrestrial life as we don’t know it

#32

Post by bsder »

pfdietz wrote: post #16
bsder wrote: post #14

Life may not look like us, but it sure seems like it's going to have nucleic acids just like us. The building blocks are extremely common, they seem to have fairly broad initial conditions, and it seems like they are practically inevitable once those conditions exist.

> it seems like they are practically inevitable once those conditions exist Given that we have exactly one occurrence of Origin of Life, how did you conclude this? From life originating quickly on Earth once it had cooled enough? That could be explained by the conditions in which life might originate not persisting for very long after a planet forms.

My comment is about the building blocks.

We seem to find amino acids everywhere. It seems like once conditions exist that they can form, they DO form.

We don't have any equivalent building block which is anywhere nearly so ubiquitous.

In addition, these building blocks are reversible within 3kcal/mol. Life requires reversibility. http://wavefunction.fieldofscience.com/2008/10/unbearable-he...

We have no other building blocks with this kind of versatility. None.

So, life may not be based on DNA/RNA, but it's almost certain to be based around amino acids.

Re: The search for extraterrestrial life as we don’t know it

#33

Post by infradig »

likeabbas wrote: post #2

For those who don't know, there's a very significant movement happening within factions of the US government to push disclosure on potential non-human intelligence visiting earth. This 15 minute guide is worth the read https://www.uap.guide Other significant efforts searching for alien life include the Galileo Project by Dr. Avi Loeb of Harvard https://projects.iq.harvard.edu/galileo/home Edit: For those who don't kn…

Disclosure == Rapture for the #ufotwitter crowd. It's basically a religious cult.

Re: The search for extraterrestrial life as we don’t know it

#34

Post by jcfrei »

cactusplant7374 wrote: post #30
jcfrei wrote: post #25

Earlier quoted context omitted.

Counterpoint: Alien life will probably look very similar to life on earth. If you look at evolution then countless species have evolved into something crab-like: https://www.youtube.com/watch?v=wvfR3XLXPvw Turns out that their form is pretty good for survival. While biology can take on a myriad of forms, the competitive nature of life will weed out a lot of them. And since the rules for biochemistry are the same acro…

I agree with this but would the intelligent beings on other planets be the same size as humans? Could there be giant creatures that are just as intelligent as us?

There's a natural limit to size due to the square-cube law. An increase in height leads to a cubed increase in mass which means they are pretty quickly too large and require too much energy to sustain themselves.

Re: The search for extraterrestrial life as we don’t know it

#35

Post by dmurray »

cactusplant7374 wrote: post #30
jcfrei wrote: post #25

Earlier quoted context omitted.

Counterpoint: Alien life will probably look very similar to life on earth. If you look at evolution then countless species have evolved into something crab-like: https://www.youtube.com/watch?v=wvfR3XLXPvw Turns out that their form is pretty good for survival. While biology can take on a myriad of forms, the competitive nature of life will weed out a lot of them. And since the rules for biochemistry are the same acro…

I agree with this but would the intelligent beings on other planets be the same size as humans? Could there be giant creatures that are just as intelligent as us?

There are some square/cube laws that put a rough cap on how big an efficient animal can be with Earth biology. But if you change some parameters (lower gravity, energy-rich environment, stronger building materials than bone) you could get hundreds of times bigger than humans. Even on Earth, intelligent dinosaurs would have been completely possible.

Re: The search for extraterrestrial life as we don’t know it

#36

Post by cletus »

I'm not sure what the point of this is. In the last 60+ years we've obviously learned a lot and widened our definition of where life on Earth can live (eg subsea volcanic vents, in rocks in Antarctica). We obviously don't know the limits of biochemistry and thus in what environments life can evolve and where it can continue to live where it exists. We're certainly not going to be detecting a world full of microbes from light years away.

What we're primarily interested in is detecting tecnological life. At stellar distances this really means detecting evidence of spacefaring civilization. This means practially the same thing because the gap between initial technology and spacefaring technology is a cosmic blink of an eye.

And those signatures will transcend biochemistry and what type of world you originate on barring some major glaring error in our understanding of physics (eg thermodynamics being violated).

The reason is that life will ultimately come down to energy and mass. Both of these mean there is pressure to expand and to expand is to become visible. You can argue that expansion isn't inevitable in all cases and you might be correct but it doesn't matter. It matters only if all civilizations remain small and/or hidden. And the odds of that go down as the number of civilizations go up.

I am of course talking about Dyson Swarms, a cloud of orbitals around a star. To put this in perspective, a full Dyson Swarm around our Sun would give each of the 8 billion people on EArth living area roughly equivalent in size to Africa and each person would have a million times more energy than the entire of humanity currently uses.

Such megastructures would be very obvious from a great distance too (ie due to the IR signature of dissipating heat). Likewise, there would be no hiding from such a civilization.

Re: The search for extraterrestrial life as we don’t know it

#37

Post by sammalloy »

cactusplant7374 wrote: post #27
sammalloy wrote: post #8

Earlier quoted context omitted.

There is zero consensus that there is a "non-human intelligence visiting Earth". There is, one could argue, a phenomenon of some kind, either real or imagined, but nobody seems to know what it is. And yes, I’m familiar with the subject, and I’ve been following it for decades. Also, I think "disclosure" is somewhat of a misnomer. If people don’t know what it is, there’s nothing to disclose. People have been beating th…

The novelty factor is one reason. I can’t imagine being so advanced but not interested in other life forms.

Sure, the "show me what you got" factor, but what if it is only interesting to higher order primates? Maybe the aliens are too busy playing in infinite fun space or just have sublimed out of biology?

https://youtu.be/m1fZ7Ap6ebs

Re: The search for extraterrestrial life as we don’t know it

#38

Post by Jerrrry »

swayvil wrote: post #21

A hallucinogen is like a telescope. Many users of hallucinogens report meeting "machine elves". Maybe we should be looking there.

no, common hallucinogenic tropes are just remnants of our evolved collective unconscious; not any proto-communications from other dimensions.

i am plenty familiar with them and other characters, and their lessons always seemed terrestrial, subconsciously familiar.

Re: The search for extraterrestrial life as we don’t know it

#39

Post by marcosdumay »

narag wrote: post #31
akiselev wrote: post #26

Earlier quoted context omitted.

Very, very unlikely like astronomically so. Most microorganisms are so small they're practically transparent so we have to exploit biochemistry to "stain" them - hence why you'll often hear of bacteria classified as either Gram positive or negative, because of the Gram stain. If the biochemistry is unique or even slightly different i.e. right handed chirality, we'd basically have zero of our usual tools at our dispos…

There's already a whole world of terrestrial microbes that we expect or even know for certain to exist but can't culture, let alone stain, which means we can't really study them. I'm going to bookmark this for the case someone asks: what piece of information that seems basic did you ignore until very recently? A question that often arises is: if current life evolved from chemistry that's simpler than DNA, why has tha…

> A question that often arises is: if current life evolved from chemistry that's simpler than DNA, why has that one disappeared? Maybe it hasn't.

If that's the case, it was almost certainly because of the atmospheric oxygen.

Almost all of the chemical reactions that used to happen before it do not happen anymore on the wild.

Re: The search for extraterrestrial life as we don’t know it

#40

Post by pfdietz »

bsder wrote: post #32
pfdietz wrote: post #16

Earlier quoted context omitted.

> it seems like they are practically inevitable once those conditions exist Given that we have exactly one occurrence of Origin of Life, how did you conclude this? From life originating quickly on Earth once it had cooled enough? That could be explained by the conditions in which life might originate not persisting for very long after a planet forms.

My comment is about the building blocks . We seem to find amino acids everywhere . It seems like once conditions exist that they can form, they DO form. We don't have any equivalent building block which is anywhere nearly so ubiquitous. In addition, these building blocks are reversible within 3kcal/mol. Life requires reversibility. http://wavefunction.fieldofscience.com/2008/10/unbearable-he... We have no other build…

Ah, ok. You were talking about the small molecules, not life. That seems ok, although realize that the amino acids formed are a large superset of the ones life has ended up settling on. So it's conceivable another OoL event would settle on a different (if not disjoint) set.
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