The Problem With "The Rare Earth Hypothesis"

[@zrebbesh]

Something I rarely see in these discussions is the probability that a planet REMAINS habitable for long enough for something like us to emerge. People tend to assume that once life exists it remains. But how many servings of primordial soup were overcooked or frozen or poisoned or irradiated? How many places got an 'oxygen crisis' without a last-minute rescue by mutants able to breathe the stuff? How many were orbiting unstable stars or had their atmospheres leached away by magnetic storms? We don't get as far as multicellular organisms without a few billion years to work, and the universe is under no obligation to give a planet a few billion years to work.

[@WaxPaper]

I think that's one of the facets of the REH; another condition that makes a rare earth rare, or even rarer. It's a good point, imo. Are we just super lucky? How many times did we escape extinction? Were we lucky with evolution, too? Did multicellular life emerge and then die out, and then through some unimaginably small chance, emerge again? And then you take the rarest instance of any one of these things, and you have to plug that in to the equation of all these other conditions... It really wouldn't surprise me at all if we were the only life in the galaxy right now. We don't have any reason to think that's true, but it wouldn't surprise me if that's what we learned.

[@rolandthethompsongunner64]

Indeed !

[@todgerx]

Absolutely, also even if all of the above doesn't happen. How many blow themselves up. Wasn't it a factor in the equation that wmds go hand in hand with intelligence? I mean let's take current events on earth. Earth could be a very very different place in 1yr time right?

[@rolandthethompsongunner64]

@@todgerx Seems humans rely more on hope and faith and ignore facts. Yes absolutely, intelligence means war and destruction. Imagine anti matter bombs and teleportation. The universe is probably littered with dead civilizations. We’re just on borrowed time.

[@todgerx]

@@rolandthethompsongunner64 yeah and I actually believe we are on borrowed time. We are wayyy to destructive to last long term. And according to some, one of these hug events isn't far off. Some claim our megnetic field is getting very very weak indeed. Down to 28% I believe, some are pointing to events like extreme fires, earthquakes, strange animal behaviour (like all those whales and dolphins beeching themselves, on mass) I they do happen, but some claim the frequency of events now are unprecedented. Even Google the angler fishes that have been coming to surface around the east coast, no one knows why they are coming to surface. They have never been seen like this, as they normally reside in the depths. Even world events form last 2yrs. I honestly don't buy, my gut is telling me that was governments buying time to prepare for what's coming. Theres also evidence like many has pointed out, that the sun rises more soutb these days. Its been observed by many people. Idk, I'm no expert. One of the channels I follweia called "suspicions observers" what crazy is many of the claim they were making 2-4 yrs ago are coming through. Even the direction the poles are moving towards. They called out 4 yrs where they where headed, and they were right, all using the information provided by government stations. After a few yr of their predicted paths. What u think?

[@matthewtheobald1231]

Evolution teaches us that the Earth isn't finely tuned to life, but in fact the opposite is true. Life is finely tuned to Earth, not the other way around. It only appears to us that Earth is perfect because evolution insures that organisms function within the environment they find themselves in.

[@MCsCreations]

Precisely!

[@nishd7161]

So there's life that's finely tuned for the other 7 planets and all the moons in our solar system? Yes, I am aware that there could be life elsewhere in our solar system, but you are making it seem like it should be everywhere since it can just tune itself to exist in all environments.

[@nishd7161]

@Jo Jo Of course. This seems axiomatic to me. We see it on earth itself with life adapted to different environments. This doesn't do much to answer the first part of the statement which is what conditions (or different sets of conditions) are required to produce life. This is the question at hand in the video.

[@garethdean6382]

The problem there is that due to evolution, ANY life will be fine tuned to its environment given time. That can lead to false confidence. I can state, for example, that kiwi birds are fragile and can only live in specific environments. This is true. The counterargument would state that this is how evolution works, their fine tuning is nothing special. This is also true. But then it could be taken a step further to state that kiwi birds must exist everywhere. *This* is false. If evolution teaches us anything it is that there is no grand design, not everything possible will be, only that which blind selection stumbles upon. And to start it may need very specific conditions indeed, whatever might happen once the ball is rolling.

[@MachineGunX2]

Yes but that basically brings us back to square one. It would mean that there's no reason why life couldn't exist on other planets but there's also no reason why it should. After all, we haven't found any complex life or life at all on the planets near to us, which seem to be how most of planets in the universe are. So, life could exist out there but there's still nothing telling us that it does. For now we just can't know

[@christophercrowder872]

"I'm not a skeptic; I'm not an advocate. I just await the result with keen interest." I love this *so* much.

[@lionelmessisburner7393]

I’m an advocate, and I think we all have good reason to be.

[@itsathing3369]

@@lionelmessisburner7393 That is an example of not ineffective claim: in order for a claim to be effective you have to give evidence for your claim.

[@xXxSNIP3RGUYxXx]

@@itsathing3369 it is actually an example of a youtube comment, which does not require you to be such a weird nerd

[@itsathing3369]

@@xXxSNIP3RGUYxXx This is an example of me realizing that yes, you are correct.

[@thalmoragent9344]

Amen

[@jeschinstad]

One fascinating fact is when people say life started very quickly after the Earth was formed, they're all ignoring the birth of the moon. If the Theia hypothesis is correct, then we live on a second generation planet. Who's to say life didn't start on Earth 1.0, which was then hit by Theia and then life could eventually rain back on Earth 2.0? I think that's a fun idea, because it may be that planets that are suitable to _create_ life, is therefore not suitable to _sustain_ life and vice versa. For instance, a water world would be great to sustain early life that hasn't learned survival yet, because water is such fantastic protection from from radiation. But if you need radiation for abiogenesis, then what makes a planet suitable for life, is also what makes it infertile. The same is true for evolution, where an ocean can nurture life and make it multiply, while some of it get washed up on dry land where it can be exposed to high levels of radiation to accelerate mutation before it gets washed back into the ocean. But if Earth started out as suitable for abiogenesis and was then completely transformed into a planet suitable for evolution - with existing life waiting in orbit - then it's easy to see how that could be an extremely fine balance, perhaps unlikely to ever happen twice. This would also explain why life appears to have started really quickly, while we have still not been able to figure out how it got started to begin with. It is possible that abiogenesis simply isn't possible on Earth 2, but only on Earth 1. It would explain a lot.

[@CoolWorldsLab]

That’s an interesting idea! Of course the impact basically wiped the record of any such life so likely not a testable hypothesis sadly

[@jeschinstad]

@@CoolWorldsLab: Thanks! :) All evidence of abiogenesis is wiped out anyway, but for all I know, it's easier to figure out what Earth 1 must've been like in order for Earth 2 to form. Knowing the difference might bring new ideas to a future Miller-Urey experiment and if that experiment was an instant success, then I'd say we'd be onto something. :) But I think I mostly like thinking about rare Earth almost out of spite. It's really frustrating to see these celebrity scientists proclaiming that life _must_ be everywhere. I find it deeply unscientific, knowing that one clap is not a rhythm. It's almost like they're saying "religion says we're special and therefore we are not", but that's no better than religion. :)

[@paulm749]

Along that line, there's the theory that life may have originated first on Mars, and then was seeded to Earth via asteroid impacts, thus making us all Martians in a sense. For no particular reason I find that hypothesis rather pleasing...

[@Sadeeq]

It would also be a weird form of panspermia where microbes came from earth 1.0 to start life over on earth 2.0 and those microbes would be our LUCA

[@nickscurvy8635]

The problem with this is earth is 4.5 billion years old. The theia impact was 4.5 billion years ago. If earth started BEFORE the impact it would have had to start within a few hundred million years, before it even had water on its surface. This would lead one to conclude that not only are the conditions of life rare but the conditions of life are highly transient as well, meaning its even less likely the rare earth hypothesis would indicate. I do sorta think the ideas cool tho.

[@robotaholic]

I love your intellectual honesty where you don't claim to know things you don't.

[@TheHeadincharge]

As a teacher in university, the thing I always warn my students of is to be wary of an over-confident scientist who does not present ambiguity in their arguments. At best they’re not telling the whole story, and at worst they’re simply spreading pseudoscience for personal gain.

[@grahamtrudinger7690]

Yes I like David's objectivity too.

[@MrWolfheart111]

I know hey :)

[@csquared4538]

Outside of actually smart, educated people, I feel like I've been the target audience for this channel for years and I'm somehow just discovering it. Going to binge through some of these today!

[@Derektaylor1983]

I still can't get over the first civilization to emerge in our galaxy video, i've listened to it 5 or 6 times and not a day gone by that i haven't thought deeply about it.

[@nursemark447]

I enjoyed that one a lot too. I viewed it from a filter of it being discriptive of humanity. Did you get that too?

[@nicholaskenneth113]

My favorite video by them for sure

[@ami_gourav]

That one really got me

[@EventHorizon31]

We might be them.

[@Derektaylor1983]

@@EventHorizon31 I think we may well be, at least advanced enough to think of these types of ideas. Its really hard to try to get your head around existence 5 billion years from now or more. If we never left our star but lasted long enough to put a project like that into effect, i would consider humans a success.

[@violetlight1548]

As an aspiring science fiction writer, I tend to discount the Rare Earth Hypothesis because if I took it seriously, I wouldn't have much to write about. However, it's refreshing to see a mathematical argument against it, as opposed to "just" philosophical or "wishful thinking". Thank you!

[@gravoc857]

I take it seriously. I think it’s because I can’t get enough of the Fermi Paradox. I deep dive into all the theories. My problem is I’ve gotten to the point that I can argue so strongly for all of them, that I no longer know where I actually stand.

[@robertshort9487]

Or you explore what happens when humans diverge from each other

[@gustavopaez2444]

I believe this is the case. And I also write sci fi and it's amazing to give an Universe to a single species. Asimov did it and Herbert and they wrote the most amazing tales

[@rizkyadiyanto7922]

considering there are like millions of stars in our galaxy alone, even 100 earth-like planets is still rare, isnt it?

[@gravoc857]

@@rizkyadiyanto7922 Depends on what perspective you’re considering. Earth sized exoplanets around Goldilocks planets are common. Planets with intelligent civilizations observed: zero beyond us.

[@asa9528]

I’ve been utterly addicted to your videos lately. So many great questions posed and discussed. I love your content so much.

[@paulm749]

So, the "rare earth" hypothesis may be true... but it may not account for all the ways intelligent life might arise in the universe. This seems reasonable.

[@nickscurvy8635]

The problem is lack of data. We have to assume that the factors are favorable to us because we exist but we have absolutely no data on any other intelligent species. It's possible that in the swirling gasses of the early universe, there emerged intelligent species of life who feeds off the the stars. But until we find the C'Tan I'm not gonna hold my breath on it.

[@chuckschillingvideos]

@@nickscurvy8635 That's right. We just don't know if we're drawing the correct conclusions from what we actually DO know, because we have no idea how it fits into the vastness of what we don't know.

[@nickscurvy8635]

@@chuckschillingvideos but we gotta draw some sort of conclusions or make some sort of predictions because we have to focus our search somehow. Space is vast. We can't check under every rock and inside every crevice. There's just too many

[@chuckschillingvideos]

@@nickscurvy8635 We do? We HAVE to search something we have no idea what we're searching for or how we would even know where it is or what it would look like if we did stumble upon it? This is metaphysics, not science.

[@danschneider7531]

It may be rare to make humanoids but humanoids could be a fleeting fraction of a % of intell life.

[@absolutelyreel8795]

Prof, I truly love and appreciate your unbiased, scientifically backed opinions or lack thereof them, based on the data available. Please do not stop sharing.

[@slevinchannel7589]

Hi.

[@user-ri8ps6cl4w]

@@slevinchannel7589 hi.

[@tonyisnotdead]

all opinions are biased

[@TheSpearkan]

I'm in the rare earth camp, but the main factor I'm considering is multicellularity. The process that drove life on earth to move beyond single celled organisms is not fully understood, with one theory suggesting that it emerged as a survival mechanism during a Snowball Earth event. If this is true, then we only got complex organisms as a result of a set of specific circumstances to both be made and unmade. Remember, of the 3 billion years life has existed on Earth, only a sixth of that time has complex life existed, couple that with the fact the numerous traits needed to make a civilisation crating species (tool use, lifespans, intelligence etc...) And the odds go small again. It is in my opinion that while life is somewhat common in the universe, complex life is rare while actual civilisations are almost an impossibility, probably only a handful in the entire galaxy.

[@zibbitybibbitybop]

I think the fact that it took life as long as it did to develop intelligence on Earth in spite of having such favorable conditions for life overall is solid evidence that even if Earth-like planets are common, intelligent life will still be rare, anyway. That, combined with sheer cosmic distance and the rapid degradation of radio signals across that distance, means that we'll almost certainly never see any direct evidence of intelligent alien life, even if it does exist. It's simply too far removed from us in space and time.

[@Hooyahfish]

Yep. Agreed. It’s still fun to look though. Maybe we’ll see some traces of it through spectroscopy.

[@julieeichler691]

@@Hooyahfish yes, while spectroscopy looks back at the observer, so to speak, as quantum mechanics is something that we have to leave in the foundation of what we're studying. I have been studying as an amateur for over 30 years and I believe that it is almost impossible for us to actually obtain a visual of what actually is. However we can know that all is relative to everything else and that there has to be interconnected dimensions. So as this looking like the only life in the universe we have been able to observe, so far, how do we know dimensionally theorizing, that there aren't many other versions of this Earth 1.0 concept. Just this morning I was thinking about the Thea planetoid hitting the Earth concept. Also the fascinating reminder that water which can start life but perhaps not sustain it, is what protects us from radiation, which can cause diseases and mutable conditions. Next thing I'm on to studying: if radiation causes cancer, why is it also used to cure it?!

[@raygeorge9325]

We first need to define what is intelligent life to me I believe humans are ignorant rash violent murderers genocidal people inherently we are quick to conclude so many things and we are narcissistic from the moment we looked up at the stars we wanted to destiny not of a man but I’m a god so we like to think we are rare and special signs process because even if you have a perfect environment in habitable planets it doesn’t mean life flourishes Vitas was one is the twin the earth now it’s in a greenhouse and now we are leaving this planet to a greenhouse perhaps life started on Venus and they do that for mass exodus would be impossible they sent the seas of life to this planet

[@steveburke1519]

Where is it written that conditions here are so favorable? Maybe the reason it took 4 billion yrs for us to evolve is because conditions here aren't so favorable. Maybe on some worlds 2 billion are enough. We just don't know. We're a sample size of one. Not enough data.

[@storksforever2000]

People always assume that intelligent life arose once in this planet. I don’t really understand why. Human beings most likely were almost wiped off the face of the Earth at least once, down to a population of a couple thousand. That could’ve happened multiple times throughout Earth’s history. I feel like anthopocentric assumption underlies that viewpoint. Also the idea that alien civilizations would utilize radio signals to communicate in general is becoming increasingly outdated. Even human beings are doing it less as compared to decades ago when SETI was formed. And they basically operate under the assumption that a civilization would be directly beaming insanely powered radio waves directly at our system on purpose, for possibly millions of years. You’re better off looking for local evidence like ancient probes. I don’t think the arguments for humans being special are particularly strong.

[@dravendavis8338]

Don’t forget the rare sun hypothesis, ours is a really nice star, most stars flare up much more than ours which may strip atmospheres quicker, or they may die to fast, or the solar activity makes it impossible to properly develop technology

[@z-beeblebrox]

But we have a great catalogue of stars. We don't need a hypothesis because we already know exactly how many sun-like stars there are in the galaxy. So there's nothing to speculate about

[@dravendavis8338]

@@z-beeblebrox I should change to rare sun filter than? Even if we aren’t calling it a hypothesis most starts are still very active and aren’t very conducive to live, especially life like us, even most stars in our size range are probably too active to host technological civilizations because they’re planets would have too many Carrington events…or no atmosphere lol

[@z-beeblebrox]

@@dravendavis8338 There are 4 billion sun-like stars in the Milky Way dude. Take your pick.

[@ontheruntonowhere]

@@z-beeblebrox They are 'sun-like' only in the sense that they fall within the main sequence; we know absolutely nothing of their volatility. It has been further estimated that only 300 million 'sun-like' stars possess a habitable planet, which must be figured into your argument. If a great many of these 300 million 'sun-like' stars are hostile to life, as the OP suggests, this is indeed a huge filter, and more so when other limiting factors are taken into account. Dude.

[@pineapplepenumbra]

"ours is a really nice star," Well you say that, but you wouldn't want it dropping round for tea.

[@godessesque]

Its so rare I love a video so completely that I subscribe to a channel without watching more of the content, but this was one! Brilliantly made and reminds me of the educational shows that was on TLC, PBS, and Discovery when I was a kid! Moreover, those last 3 Minutes were inspiring and wow if only every kid in grade school heard those words at the right age. Might help fight the pandemic of cognitive dissonance we face geopolitically. I'm sending this to every teacher friend I know.

[@Darnell]

Great video as always. I am in the rare earth camp due to how hostile the universe is towards life. I usually say that I think carbon-based life forms are rare. For all we know there could be energy based life forms.

[@mamavswild]

There could be both. There could be more than just the both.

[@Nitidus]

@@mamavswild There could be an old man with a long, white beard creating our universe and reality. "Could......."

[@terrykrugii5652]

We know very precious little about the universe, so as silly as the idea of energy based life forms sounds... I can't personally rule it out

[@jettmthebluedragon]

@@terrykrugii5652 their is no energy based life forms 😑energy runs and ATP our cells 😐and if their was other life then the chances of you living again are higher then 1% but truth is we are alone depending if the universe is finite or not will give us the the odds of this planet being created again 😐after all 1 you *the odds of a planet having or created life 1 * 1 universe finite or not * infinite time *infinte space = the odd of life being created 😐so regardless DNA is made of matter and matter can be created and distroyed and based on the odds of a planet having life is 1 it means we have a higher then 0% chance this planet will be created again 😐after all a true death does not mean it no longer exits a true death means their is a 100% guarantee of something NEVER being created ever Beacuse 0* infinity=0:😑but since dissipate all odds the chances of a planet ever having life is 1 witch means we have a higher then 0% chance we will be reborn again 😐and however long until this planet was created is how long we shall remain dead.,.again 😑

[@terrykrugii5652]

@@jettmthebluedragon k

[@JSkitt]

I think when we think of "intelligent" life, we think too much of civilizations far more advanced than humans. There are so many factors involved in our existence, but the problem with the Rare Earth Hypothesis is that it blueprints our process of existence as the universal determinant. As stated in the video, there's other factors that can build up to life, which I agree on that take. I do believe there's intelligent life somewhere in the universe, but the observable universe is so large that finding us is essentially finding a diamond earring in the pacific ocean. Ruling out other civilizations is a hasty assumption, but being realistic about the scaling of our universe is important. It took billions of years before Earth became home to intelligence, so for a civilization far enough forward to locate us with ease would be with odds far greater than any of those equations.

[@slevinchannel7589]

No Way theres only ONE livable Planet in all of Existence. No way.

[@JSkitt]

@@slevinchannel7589 I believe there's a bunch of Earthlike planets, possibly even with regular life forms. Its just advanced civilizations are a lot more rare. Our universe is so large even with one in trillion odds, there would still be at least 100 other civilizations.

[@slevinchannel7589]

@@JSkitt Yeah, even if this Universe is the Only One, i bet theres no way only 1 Planet has Life.

[@juiceoverflow]

I said girl why are you calling I said girl why are you calling yeah she said I need a new whip yeah cuz I know that you still ballin she just wanna go back to the future so I brought that girl a DeLorean

[@Nitidus]

In my book, saying, "there might be so many ways we don't know yet," is like saying there might be a god who created the universe. We can only take into consideration what we know or what is probable, or at least plausible. That's why we're looking for planets like ours. We don't know of anything completely different that could support any sort of intelligent life; you need water, carbon (or possibly silicate), a starter and loads and loads of time for evolution to happen. This might very well only happen under such extremely special circumstances that we're a fluke. There might be sentient rocks out there but since there is no evidence at all, neither practical nor hypothetical, it doesn't matter. Of course this might be completely wrong but that's the same for ALL things in existence. Nothing might be how we portray it today when someday out of nowhere, completely new information surfaces. Until then, things are how they are. Everything we think of is just a model to describe something else to ourselves, anyway. But you can't have a rational debate when "maybe there is something magical that changes everything" counts as an argument.

[@oredk]

This channel makes me feel more informed than my entire university. I feel more happy and educated from watching this chanel compared to 3-4 days a week at university. If my teachers would have same passion like this amazing creator things would be so different for me and many others.

[@themealena817]

Awesome. The fact we consider ourselves lucky for having survived through so many "filters" might just mean we didn't come by the easiest way. Imagine you reach the top of a mountain, it was long, difficult, you are the only one left from the thousands who started to climb with you. Once at the top you could look at the other moutains tops around thinking it is much likely nobody sits there. But these other mount might have a cable car. None the less, having only your mountain as reference, you will assume that the chances of reaching the top of a mountain are few in millions when it is reaching the top of YOUR mountain you are estimating. I like to think that life is just a common organisation of matter such as crystals.

[@rolandthethompsongunner64]

Crystals are minerals not life.

[@themealena817]

@@rolandthethompsongunner64 For sure, I guess we all get that. It was a metaphor to point out that matter is somehow able to arganize itself in wonderful ways, and maybe (maybe) it takes no more effort to organize as amino acid than to shape a snow flake as far as the conditions are here. And by saying "I like to think that", I mean just that I like this idea, not that it is my conviction. I like to think I'll win the lottery some day...

[@rolandthethompsongunner64]

@@themealena817 Of course. The issue isn’t matter becoming life. It’s the where, why, and when, and how often. We think it’s common like say crystalline structures. Or like to believe it is. But I don’t see the evidence for it. Hate to be one of these people, but I believe we’re alone at least in our part of the galaxy. My reasoning is our star is so unusually stable it would have drawn attention to itself by some advanced civilizations by now. Or, they’re already here. Just may opinion.

[@pansepot1490]

@@themealena817 I agree with your comparison between life and crystals. When you look at it at a fundamental level life is nothing but highly complex chemistry. There’s not even a well defined line between life and non life so this mystical ideas of a switch that goes off and life appears is completely wrong (and I am sorry to see that prof. Kipping contributes to perpetuating it). The most recent research on abiogenesis has shown for instance that there’s chemicals that (in the right conditions) can replicate and undergo natural selection, which is something we believed only life could do. Obviously, gathering evidence that these phenomenon occur spontaneously and are more common than previously thought tells us very little about how common the right conditions are in the universe and in our galaxy more specifically. It’s however more data that can help us refine our guess. In case someone is interested I highly recommend the two Prof. Dave Explains videos debunking creationist James Tour. Yeah, the format is entertaining debunk videos but they also are a good survey on the latest developments of abiogenesis research, and besides providing all the references they also include interviews to scientists. They are heavy on the chemistry stuff but even if most of the details go over normal people’s head still one comes out with a better understanding of what origin of life is about.

[@danschneider7531]

The Great Filter analogy is also a troubling one. It cd very well be that there are Great Accelerators to life.

[@motherbrain2000]

I never felt that the rare earth hypothesis was saying earth is the only place where something like this could’ve happened. I think the rare earth hypothesis was saying a whole bunch of things have to go just right and therefore it probably happens once per local group (Milky Way, Andromeda, and triangulum and all of their satellite galaxies: 1 trillion stars are so )per billion years. or something like that-you know: “rare “

[@TimoSt3v]

I love these videos and the message they carry. Especially the last part about staying open towards the possibility or maybe probability that we all got it wrong got me thinking. What all humans share is their desire to beliefe in something, whether it's a higher power, love or purpose. I myself believe in curiosity.

[@benjaminbeard3736]

What a great channel... It amazes me that one KZbin channel has challenged me more intellectually than several years of secondary education. Keep it up!

[@slevinchannel7589]

Know Sci Man Dan, another great science-youtube-channel?

[@rodeoclownobama5796]

did college teach you not to hate blm, and accept them ruining towns and selling drugs?

[@lionelmessisburner7393]

I mean dr kipping is a genius and an educator himself

[@IndigenousUndergroundPrimate]

So, Google says we`ve studied over 200 large asteroids, moons and planets around our Sun. And so far they`ve found that no two are alike. No two have the same chemical make-up nor impact history. Each Planet in the Milky Way is _bizarrely_ different. I`ve got a gut feeling this is universal for our type of galaxy.

[@MaloPiloto]

Fascinating video. Thank you once again, Dr. Kipping. I think that intelligent life is, if not unique, then exceedingly rare. One must also factor into the equation the fact that, at about 13.8 billion years old, the universe is actually quite young compared to its expected life span. If life is to evolve elsewhere , it may just be that it takes a lot longer for it to do so at all and certainly to a higher level. As such, we may really be alone because, in great part, we are the first!

[@mlc2200]

I always thought about that hypothesis! I feel like maybe we are indeed one of the first civilizations

[@lennartbjorksten707]

I believe our own planet's history indicates that intelligent life is rare. Dinosaurs ruled the Earth for two hundred million years, and in all that time, not a single critter evolved that was capable of producing even stone age technology. I wouldn't be surprised if it turns out that life is fairly commonplace in the universe, but intelligent life is rare.

[@jettmthebluedragon]

Yea but how can the entire universe only be 14 billion years old ?😐and ok time just starts with the Big Bang and now it will expand forever heat death forever happy ?😐I don’t think the entire universe is over 14 billion years old if earth is 4.6 billion also we say EVERYTHING is expanding so how can you explain that gravity can pull things together?😐 I just think the entire universe would have to be MUCH older then we realize 😐for every atom every galaxy black hole etc and besides it’s not like we would ever know this planet would ever happen in the first place 😑so how can the entire universe only be 14 billion years old ? It does not make since 😓even IF the universe has a end that does not explain how everything got their in the first place 😐

[@lionelmessisburner7393]

We are definitely not alone. We could be an early civilization though. Imagine what some galaxies will look like in billions of years. Probably much more filled with life

[@michaelandrew677]

If I had to guess, I'd say we should expect to find evidence of microbial life pretty much anywhere the basic conditions were favorable (liquid water, an energy source, protection from ionizing radiation). Making the leap to advanced multi-cellular life may be exponentially more problematic.

[@Agnemons]

If you have liquid water you have protection from ionizing radiation. And life on Earth started in liquid water.

[@michaelandrew677]

@@Agnemons You're not going to have liquid water on the surface for very long without a magnetic field. The solar wind would strip away any atmosphere. And shallow tidal pools wouldn't be deep enough to protect against dangerous solar radiation. A magnetic field is pretty much a must unless life was underground.

[@papaclanc]

Cannot thank you enough for not having distracting background noise/music. You keep it very low volume (actually you don’t need it at all for me, as the content itself is mesmerizing). At any rate, your presentation is on par with Matt on PBS Spacetime. Thank you for your work.

[@michaelhorning6014]

I am in the Rare Earth camp, mostly. So many odd characteristics of Earth combined to make life possible. And the magnetosphere doesn't just shield us from radiation, without it the atmosphere would have been blasted away by the solar wind. Both complex life and intelligent life are narrower funnels than Fermi Paradox advocates seem to think. We may be the only, or one of very few so far apart in time and space that we will never meet, or we may be the first.

[@grantdillon3420]

Definitely, for beings like us, an atmosphere is necessary. However,It could definitely happen that evolution takes place purely under water under a thick ice sheet with no atmosphere.

[@DrRyan82994]

@@grantdillon3420 i think that’s likely, that there is life underwater on other worlds, maybe even common, but they would never develop intelligence. they could be clever like a dolphin or an octopus, without fire, i don’t see how they go further than that actually scratch dolphins. i’m dumb, they breathe air. their’s much higher concentration of oxygen in air than water by the way, that’s also a factor limiting intelligence

[@michaeledwards2251]

The question is, How difficult is fusion ? Coal is good for a few centuries, nuclear for tens of millennia, fusion is needed for millions to billions years.

[@CubicApocalypse128]

"...carbon stars with ancient satellites, colonized by sentient fungi. Gas giants, inhabited by vast meteorological intelligences. Worlds stretched thin across the membrane where the dimensions intersect... impossible to describe with our limited vocabulary!"

[@sharksareneat8723]

I really appreciate that he acknowledged this new wave of UFO/UAP reports coming from the US military. There's nowhere near enough evidence to say these bizarre UAP pilots have been seeing constitute alien intelligence, but at this point (especially with the classified version of the 2021 UAP report released) there's enough to say there's SOMETHING weird going on there. As someone who used to be quite skeptical of it, I'm very interested in the subject now.

[@TheHeadincharge]

Certainly something weird, but certainly not something alien. The logic of it inevitably breaks down the moment you start to question through all the other factors at play. For example, it’s an awfully interesting coincidence that UFO sightings have increased drastically with the proliferation of flying objects in the air, especially drones which are easily accessible. It’s also interesting that there’s a history of people faking UFO videos. With modern technology, this has never been easier for anyone to create. Also, why is it that aliens always appear in round ships? It’s easier to believe the possibility of something maybe existing with absolutely zero proof than simply acknowledging the unknowns within the realm of what we do know.

[@asherstribe5695]

These are the videos I love from this channel. I wish David had more time to make more content. I sometimes forget he’s doing actual research. What I wouldn’t give for a couple videos a week, heck even a video a week would be awesome.

[@slevinchannel7589]

I could recommed you some epic Sci Channel, if you like.

[@rossicourvosi218]

@@slevinchannel7589 yes please

[@slevinchannel7589]

@@rossicourvosi218 Sci Show, Sci Man Dan, Joe Scott, Tom Scott, Hbomberguy and many others come to mind, so if you want more, just say it.

[@slevinchannel7589]

@David Nash Oh, i never heard of Parallax Nick, so many thx!

[@slevinchannel7589]

@David Nash Im watching Second-Thought this very moment.

[@iannewman3641]

This has very quickly become one of my favorite channels. Love the content and the narration is sooooo good 🧡🧡🧡

[@joshuamccaulley7040]

Great video, when I was in high school. My Earth Science's teacher had asked. " What are the building blocks for life " he hadn't asked specifically, so I had answered we do not know. Naturally I was told I was wrong and the correct answer was Oxygen and Liquid water. So being me I challenged this answer. Asking then why we search for these elements on other planets thinking that other life develops in the same way. Just because it worked for our planet and life on our planet does not mean that alien life requires the same elements. He told me that was ridiculous. I say he was and likely still is Naive to think that just bc it worked for us that it is the only way. So in the words of one Jeff Goldblum. " Life will find a way "

[@gama5942]

Awesome, keep that trait!

[@VelociraptorsOfSkyrim]

Great thought process, but slightly flawed conclusion. We can only search for what we know, and most other hypotheses on how life could develop do tend to fall flat. For example, Earth is mostly made up of Silicates, so if a Silicone based lifeform was possible, Earth would most likely be containing Silicone based life instead of Carbon based life. Until we have evidence of life based on something other than carbon, we shouldn't speculate wildly. Otherwise, we won't get anywhere in the search for life elsewhere in the Universe.

[@iluvrolaz]

I actually agree with you n have always been confused by the assumption that life in all places requires oxygen n water etc... our definition of life is only OURS, but there can absolutely be other forms of life defined in ways we can't even comprehend.... we may know quite a bit about life on our planet, but we know NOTHING of life in the universe.

[@RenegadeShepTheSpacer]

@@iluvrolaz The reason we have to work from that hypothesis is that we need to follow our understanding of science, and science tells us that life is only possible in the forms we already know of. We need more data points in order to re-evaluate that position.

[@daveschere918]

I think molecular machines not the cell are the start of life, the cell along with biochemistry is product of the environment on Earth. We are in a position to discount nothing since we have no evidence beyond our own world.

[@philosophyforum4668]

I think I read somewhere that out of all the exo-planets we have discovered so far, none are more hospitable to life than Mars. I wouldn't be considering whether a planet has a moon or a Jupiter companion. Just stick to rocky, temperature, size, water, atmosphere, and EM field.

[@slevinchannel7589]

Know Sci Show, Joe Scott and Veritasium?

[@DrRyan82994]

size, mars is too small

[@EzraB123]

Not really true, we've found exoplanets more ideal than Mars. The problem is distance so some things have to be assumed.

[@philosophyforum4668]

@@EzraB123 What's the star, and what do we have to assume?

[@philosophyforum4668]

@@salem353 If it's smaller than the earth, the gravity will be weaker, and men will end up looking like little girly-men. That's what happens when people go into space

[@dougsinthailand7176]

I believe Brownlee made a careful distinction between microbial life and complex life.

[@xhanmalo6440]

The most eloquently put way of saying "We don't know"! Loved the video.

[@wizzardofpaws2420]

Out of the dozens of space channels I subscribed to, Cool World's is by far my favorite!

[@peadarmurray7994]

What other channels do you follow, I'm looking for new space channels to watch

[@greyowl3787]

Cool worlds + PBS Space Time + Sabine Hossenfelder justify the very existence of youtube

[@gregor-samsa]

@@greyowl3787 Sternengeschichten (german) kurzgesagt (english and german)

[@greyowl3787]

@@gregor-samsa thx I’d never heard of Sternengeschichten, I’ll check it out (although I hope they have subtitles coz my german is very very rusty)

[@gregor-samsa]

@@greyowl3787 its an austrian guy (Freistetter) speaking very, very slow and clear and everything ist typed , too. this year he will have his 500th podcast.... if nothing happens!

[@danielluna7648]

Always exciting when a new episode drops. Love the work you're doing and the messages you constantly express. Thank you for all you do. It means a lot to many of us out here. Your videos make me feel like there's still child-like wonder in the world.

[@johnstrawb3521]

For the love of god, replace this narrator. His self-importance and newsreader's cadence are painful. --Worse, this channel has gotten far less interesting over time, seeming bent on popularizing rather than exploring.

[@Freak80MC]

Honestly the idea that life emerging is actually the easy part, but that it's life SUSTAINING for billions of years to develop intelligence that's the hard part, is kinda fascinating to me. That life originating can be happening everywhere across the universe but it's also mostly everywhere that it dies out super fast, and we're one of the rare exceptions there.

[@ungmd21]

They are both very hard. As a physician I understand the life sustaining part, but starting life from inorganic chemicals is far beyond our scope.

[@thomasappleby4212]

I love the journey cool worlds takes us on. I can't wait until we find some real findings. I will be coming straight here to see what cool worlds has to say.

[@newdefsys]

Yes, I agree that the search for intelligent life in the universe shouldn't be a search for our doppelgangers, but, there are hopes and expectations attached to that search, especially in the sense of 'making contact'. Finding a planet with only single-celled microbial life, while profound, would ultimately not make any lasting impression on humanity. Mold slime on an exoplanet is barely more exciting than mold slime in a bath tub. At the other end of the spectrum is finding a civilization so advanced and so alien that we cannot distinguish them or their technology. In that case, we are the mold slime. The search for intelligent life does have a priorities list and an alien civilization that we can relate to and communicate with is at the very top.

[@sandal_thong8631]

We can look in 3 directions simultaneously: microscopic life in our solar system (Mars, Europa, etc.), radio and laser signals from an extraterrestrial civilization, and future telescopes that could detect exo-planet atmospheres for oxygen and pollution. A positive response in any of the three will dispatch the idea that we or our world are unique.

[@MercurialRed9]

Finding a planet with microbial life could be the start of that planet’s journey toward more complex lifeforms, so discounting it wouldn’t be the best idea. We can’t assume that every planet with lifeforms is the same age as our planet, or that it’ll take the same journey, and that in itself makes it very interesting.

[@alexgibbons2188]

It's beautiful how this guy explains this. Intelligent life can be created in so many different ways, the universe has an amazing talent for have complex symmetry and evergrowing amounts of facets. Once we think we know something it has without question been completely flipped inside out and proven to be completely different from what we thought. Why can't we all just believe that anything is possible and we will never be able to not be wrong or even incomplete about our narrative of how the universe works.

[@bubz4994]

this is an interesting take! i still believe that, regardless of whether the focus is anthropocentric, the process is going to be incredibly complex and therefore occur relatively rarely. i prefer to refer to my belief as the “rare intelligence” hypothesis so as to minimize the anthropocentrism of it. whether or not the variables are specific to our development, whatever the path taken will require a great deal of variables, especially if you accept that evolution is objectively factual and must be what governs the development of biological life (i find it hard to argue that evolution shouldn’t be applied to the entire universe). it seems to me that whatever the paths are, the probability on the scale of our galaxy, for example, is not likely to be filled with numerous advanced civilizations. that’s just my interpretation of things though. i do imagine the paths would have to be relatively similar in their fundamentals considering the physics that governs all processes in the universe must be identical.

[@Chris.Davies]

I can think of several other aspects of Earth which contribute to it being almost unique. I tend to think The Great Filter is behind us, and not in front of us. Only because the opposite is depressing.

[@MojoIglesias]

I do hope there will be a book published by Cool Worlds Lab eventually on these matters, like a 'Rare Earth Revisited' or something, with up-to-date knowledge, tackling all these questions on this channel's videos, and more of course! So thought provoking!

[@CoolWorldsLab]

I’ve been thinking something similar

[@calvingrondahl1011]

When Einstein was wrong he admitted it. Rare Earth?… Rare Scientist?

[@stephenlogsdon8266]

This was an excellent video! Very thought provoking. Next, maybe you can explore the kind of biology is needed to make intelligence, because in my opinion, there are a bunch of “rare” needs for this as well. In my “first-contact gone wrong” Sci-Fi books, I try to explore these subjects in the hypothetical. My question to you: how does biology take single-celled life to tool using, successfully? Not that humanity is out of the woods, so to speak, since we do seem to be so self-centered in not seeing we will be the authors of our own destruction if we don’t change course.

[@etherealawakening7720]

Brilliant video!!! There's a world of truth in simply being open to reality as it is and not how it seems, is portrayed or wished as being. Starting by also leaving emotional attachment to information supporting or denying our beliefs is helpful, not always the case but helpful nonetheless. Great info and nice perspective!

[@itsallfunandgames723]

The more I learn about this, the more it seems everyone who doesn't have an interesting emotional attachment to the idea of aliens being around, and perhaps a strong belief that they visit us and that they themselves may have even met them, tends to be rather impressed by the notion that the Drake equation is less than or equal to one. The idea that life only arises with exacting conditions certainly matches the universe I know.

[@andrewberdahl9922]

Who exactly would be impressed by that?

[@gasdive]

I'm thinking that if life is common, we should find ourselves on a very typical planet, orbiting a very typical star. But we don't. Red dwarves are the most common by a large margin. So it's surprising that we find ourself orbiting a yellow dwarf. There seem to be other things that are surprising. It doesn't tell us for sure that the right conditions are rare, but it's an indication. Big moons seem rare, it's surprising we have one. Surprise after surprise stacks up. Like if you were only allowed to see one basketball professional and know for sure that they're a basketball professional, but you could see lots and lots of people. They might be 2m tall. One sample doesn't tell you that it's a requirement to be very tall to be a basketball professional, but they are surprisingly tall. It's a hint that height might be related to the chance of being a basketball professional.

[@Sky_Guy]

The curse of having only one sample size. Imagine if you saw a 5'4" (162cm) basketball player; you'd be immediately sent down the exact wrong direction by assuming basketball requires you to be short! Exactly how Jupiter makes it _seem_ like a habitable planet needs a gas giant to shepherd comets and asteroids, while it may really knock more out of stable orbits than it helps.

[@absolutelyreel8795]

I think someone wasn't paying attention 🤔

[@gasdive]

@@Sky_Guy Yes and no. A 5 foot 4 inch person isn't the most common, but they're not particularly rare. A 2m tall or taller person is about 1 in 1500. A 5 foot 4 "short or shorter" is about 1 in 30. So it would indicate that shortness is a factor, but not strongly indicate it. To get the same indication that shortness is required the sample would have to be 4 foot 10, which also is about 1 in 1500.

[@Sky_Guy]

​@@gasdive The shortest basketball player ever was 5'3", or I would've tried to be more mathematically precise. Regardless, the example works. We have no way of discerning exactly how off our understandings of the moon/Jupiter/magnetic pole are in relation to the actual prerequisites for life.

[@gasdive]

@@Sky_Guy no, your example doesn't work. Having a sample that's completely ordinary in some aspect doesn't tell you anything. A 5,4 sample doesn't tell you that you need to be near 5,4. If you were given a single sample of an accountant, and they were 5,4, it wouldn't indicate that height is in any way related to accountancy. It's a perfectly normal height. If you were given one sample of accountants and they were 2m tall, that would indicate that height is in some way related. You wouldn't be certain, but it's a strong indication. It would be wrong, which is the real issue with single samples. They don't give certainty, but they do give indications. All you know for certain is that 5,4 or 2m, or whatever you observe in your single sample is within the allowable range. The fact that we orbit a yellow star doesn't mean we know for sure that a yellow star is required. However the fact that only 3% of stars are yellow, and we have one anyway, is a hint that they might be important.

[@ianhopcraft9894]

The Rare Earth Hypothesis was a great read. Until reading it I believed life must be common simply because of the number of stars but it altered my assumptions a lot. Lets not forget that a conclusion of that book is that the universe may be acrawl with bacteria but that civilizations could be vanishingly rare. I love these videos - they always address the best questions.

[@sentientflower7891]

The Universe "may" be filled with bacteria planets but it actually is sterile with only one exception and that is the Earth.

[@Overcaffenated]

Based on numbers, life should be common in the Universe. Intelligent life, however, again based on numbers, is uncommon. Look at Earth, there have been millions and millions of species on Earth. How many had creative intelligence? Only one.

[@sentientflower7891]

@@Overcaffenated no, based on numbers the Universe is fine Tuned only for sterility and therefore finding one living planet exceeds expectations.

[@adamplentl5588]

@@sentientflower7891 no. There no indication of fine tuning.

[@sentientflower7891]

@@adamplentl5588 the Universe is ideally designed for lone hydrogen atoms in the vacuum. Not so well designed for life of any sort.

[@Steve_P_B]

Problem with the question of the conditions required for life is, even on earth there is no hard and fast rule, especially when we look at micro-organisms. Some require oxygen rich atmosphere, some require CO2 rich atmosphere, some need a lack of oxygen, we even have found life in the intensely toxic and hot environment of a volcano. Life evolves to the conditions, not the other way around

[@jettmthebluedragon]

It’s not just co2 😐it’s all about many factors Beacuse is climate change and different habitats 😐it’s not just about co2 after all we are rising co2 levels it’s only getting to get worse 😑we say it will be a long road yea what about climate change or global warming 😐? our governments won’t change and things will just get worse from here😑now all of us will face extinction and theirs nothing we can do about it 😑even the planets core will run out we will all die at some point 😐however it all depends on what we do 😐as a species continue to use fossil fuels ? Or chnage ? 😐nature does not care that all comes down to choice 😑we kill animals for sport we experiment on them making them feel pain we rize animals just to kill them all for money 😑what you think will happen when you die you think you will have all that money ?😐no your dead wrong 😑

[@Steve_P_B]

@@jettmthebluedragon That's kind of what I was getting at. We have found that there's such a diversity of life with such widely various requirements for survival, even in our one planet, that there are no absolute rules for requirements for life

[@Pebphiz]

I love the awe-struck, almost melancholic vibe of this video. He seems like a true admirer or the universe's wonders. Personally, I don't expect intelligent life, or any alien life, to be found any time soon, if at all. We know that our planet had the right conditions for life yet it seems to have only happened once. And then out of all the millions and millions of species that sprung from that common ancestor, only one has even begun to conquer its nature. The Earth looks like a great success at first glance, but inspires more doubt than confidence the more you think about it.

[@DW-10]

How does one species conquer it’s nature?

[@docsavage8640]

Is ruining your own habitat really a conquest of anything but common sense?

[@gwugluud]

I think there eventually will be a time that possums are as commonly domesticated as dogs and cats are. I'll sometimes sleep on a cot (a nice bed-like one which actually has a mattress) outdoors during winter, and my rural locale has many possums, and they're out at night. I hear possums coming through when I do this backyard camping. I sleep deliciously out in air which is moving, and hearing ambient sounds, such as distant trains. Possums are attracted to people. I've awakened to discover a possum was sleeping on top of me across the blanket. I slide them gently off of me; I can't get past their rat-like tails. I have the impression that possums want to be taken care of my humans.

[@Blate1]

As a man who has read The Three Body Problem, I am really, REALLY rooting for the Rare Earth hypothesis being true.

[@bmoraesarqueo]

Well, I'm a scientist too. A different kind: an archaeologist. In the last 20 years I've seen a gap growing stronger between humanities and the "hard sciences", even though I work with earth sciences myself, with a background on humanities. It felt awesome when someone acknowledge that Drake's equation (and it's variants) are very anthropocentric, showing that no matter the field of knowledge you're in, they are all intersected, as latent in many scientific works nowadays. It's time to bridge that gap! Congrats for the video.

[@exoplanets]

Very interesting. Great video.

[@DARKLYLIT]

Such a rare, humble argument for Agnosticism, regarding....well...anything! Let the actual data show us what actually IS. If only the world operated in this fashion. We likely wouldn't be so crazy in our anthropocentric beliefs. Thank you David. You're an inspiration! :)

[@freespirit995]

Another exciting and thought-provoking presentation! You have a remarkable gift for explaining complex scientific ideas to the lay person - i.e. someone like me, as I have no science education worth speaking of but just a general interest... Many thanks for these videos!

[@erictaylor5462]

2:50 To be fair, that bar is set extremely high. If the bar were a pole vault we are talking Olympic world record setting high. I doubt Percival Lowell lied about the canals on Mars. I think he truly believed that what he was seeing was both quite clear and obvious, yet no one else could see them, even when they used his own equipment. It must have been incredibly frustrating, and I would not be surprised if he believed these other scientists were being dishonest when they said they saw nothing. Today we know that our senses and our memory are not quite as faithful to reality as we would like to think. Lowell *WANTED* to see the canals so badly that his brain just said, "Okay, mate. There you go" and filled in the blanks. I can't imagine how disappointed he would be in the data from the probes we have collected over the last 57 years. "You mean I just imagined the canals?" I wonder if he could have gotten over that disappointment and appreciated the amazing data and discoveries we have made.

[@Perfxnizm]

A true scientist would. I’m not a scientist but I do enjoy learning and that’s a huge part of science. When I’m proven wrong I know that I know more than I did before being proven wrong. Our bodies and brains are tools for us and everything that benefits is an upgrade 🤙

[@JoeE37]

One thing I would add. General Relativity tells us that if the geometry of the universe is flat then it should be infinitely large and our experiments thus far are consistent with that being the case. If the universe is infinite then every possible Hubble volume is bound to be realized. Thus if we can eliminate any reasonable doubt from that measurement then we must conclude there are infinite civilizations.

[@QualityQuad]

Yes exactly dude. You can’t just use one form of conditional probability for life. You nailed it on the last section. I remember thinking the same thing about needing parallel conditional probabilities when I learned about the Drake equation in school. Well done. There can be more than one way.

[@phoule76]

My name is Luca. I lived on the ocean floor...

[@OkSid300]

My name is Bob and I wish you never crawled out of the ocean.

[@Miniweet9167]

We are fully capable of appreciating the preciousness and unbelievable chance that we have to be here once we fathom the unique elements that had to happen in succession over billions of years. No religion can explain it but the simple fact we are here and have managed to accomplish so much should fill us with awe and reverence. Not to God, but to probability.

[@metaparcel]

Your resentment towards God is quite obvious.

[@bassem500]

Thank you very much for this inspiring presentation! My problems with the rare earth hypnosis are the following: - Putting factors in a multiplied chain is a shallow approach. Some factors are major while other factors might automatically follow if a major factor is reached. - As far as I remember learning, there were several mass instinction events on earth ( not a reset to zero, but still ) . Life came back each time. - There could be alternative origins to life, some we could imagine ( like possible life in the oceans of Europa ) and some we could not fathom or even detect. - The coding of information for life could be based on something very different to DNA. - Even if life in the universe most probably is best based on some similar complex form of organic molecule as DNA, Amino Acids which are a major building block of such structures are abundant in space. - Last but not least: the universe is on a trajectory from simple to ever more complex structures. It is therefore more likely than not that life evolves at a certain stage, since it is at a higher level of complexity. And since the universe is at the same age all over ( not observation wise ), it follows that it must have reached similar levels of complexity all around.

[@themanofshadows]

I agree.

[@macht4turbo]

When considering how on earth we can observe co evolution, the independent evolution of the same trait, i think we can assume, that the evolution of life is very probable once the building blocks are available. That being said, we don't know in how many ways life can form, we only know carbon life forms. There is research into other pathways of evolution and i think, if we can achieve any progress in that, we can reassess the question whether life in the universe is plenty or rare. Until then it seems like we are limiting the scope way too much by only looking for similar earth like condition. It is our best bad, but at the same time the worst possible. That being said, the question will probably remain academic, because the probability of any life being in range of human civilization are essentially zero.

[@teugene5850]

this video really moved me... fundamentally and existentially... thank you... thank you....

[@audio_boys]

bruh really just used "punctilious" in a sentence and expected me not to pause

[@johnstjohn4705]

Impressive! One of the most well-reasoned and well-presented videos I've watched in a long time. It seems that the farther out we can see, the more homogeneous the cosmos appears to be. For instance, we now know that it's quite common for stars to have planets. Even though I think the Rare Earth Hypothesis is probably wrong, I agree that we should be agnostic. We don't know enough yet.

[@mikedl1105]

So far we have only found 1 Earth. I think, until we have more data, the null hypothesis should be that Earth is extremely rare

[@211212112]

The most important thing I learned at university was to freely admit to myself and others that “I don’t know.” And “I’ll find out.” I thought earth sized planets around sun like stars are hard to detect. How do we know the percentage of rocky planets at the right distance? I know we are a single data point, but in a way we are not. How many species originated on earth? How many of those were intelligent enough to have language? Also maybe plate tectonics isn’t a deal breaker and neither is a magnetosphere or a nice moon, etc, but maybe missing two, three, etc of those makes things much more unlikely. The great resets were important, but also could of ended life. Without volcanic activity mostly driven by plate tectonics Snowball Earth very possibly would of stayed planet Hoth like.

[@shantiescovedo4361]

I do believe in the rare earth hypothesis, and I will plant my flag here in the comments section, but I also hope that I am wrong.

[@logansmith2703]

Same. Hopefully we find life somewhere and manage to disprove it but frankly I just don't believe Rare Earth is wrong.

[@prototropo]

I love the conversation around this question-Rare Earth-but I think there’s another question nearly as forbidding in scale: Rare Encephalon. How rare is a volitional sentient being? The requisite factors may be as numerous, and even more subject to temporal sequence and stochastic uncertainty, like serendipity and synergy, constraints and contingencies, gear-trains of emergent integrities unimaginable by simple or even compound mathematical operations. Not the least of these is the astonishing power of one individual of one intelligent species to launch a series of events that might obliterate the 3.5-billion year journey of intelligence on one habitable planet.

[@reginaldgruenenberg4462]

Very cool and eloquent assessment of Rare Earth Hypothesis. I loved this book. Yet, I find David's disregard for plate tectonics as a crucial factor for the emergence of life (he simply leaves it out in the following equations) a mistake. But much more disturbing is that he doesn't factor in the most powerful argument for the uniqueness hypothesis, as I have coined it in 2008, namely that there is only ONE string of life on our own planet (all living beings being ancestors of LUCA, the lowest universal common ancestor) although we had and still have obviously all ingredients for life AS SUCH on our planet Earth. This is such a tremendously reducing factor for the probability of alien life, ESPECIALLY if you take it as the only example of such a success story. Because if you make hypothetically 1 million identical copies of our earth (as David did) and 10 or 100 or 1000 of them would spawn life that is identical to ours - which is highly probable because Earth has had only ONE biogenesis as far as we know - this reduces the probability of alien life to zero. I have read David's paper 'An Objective Bayesian Analysis of Life’s Early Start and Our Late Arrival' with great interest and its really enlightening on factoring in the time scales. But there again he does not mathematically address the ONENESS of life on Earth. How different would the calculation look if we had identified two or more strings of life on Earth! That would mean that life is a really robust and resilient feature of nature. But it isn't! This is not anthropocentric but a necessary element for the full awareness of the chances whether there is life outside of our terrestrial biosphere. And other than David Kipping I believe (and have proven in my way) that life on Earth is unique, enlarging this view to the Uniqueness Hypothesis that says that life on Earth is the only one in all of the history of the Universe, past and future. If life is to stay a factor in the history of our universe, we neccesarily will have to spread it. Otherwise it will die with Earth in a foreseeable future. And by this token it is our task as humans to be aware of our responsibility for life - instead of waiting and hoping that this sterile universe has other islands of life. There is a very good chance the the rest of the Universe is and will always remain dead without us.

[@SnootchieBootchies27]

What if the "oneness" of life is just the simple chemical/biological "way" that it can happen. What if there were thousands, or millions of LUCA that "spawned" independently, but they all took the same form because that's what chemistry and physics dictated was possible with the building blocks available at the time? I'm not saying this is what happened, just a thought experiment for you.

[@CoolWorldsLab]

Plate tectonics may be important, and we discussed it. You can put in the equation if you will, as I said swap out factors at your discretion. The point is that the number of factors is crucial, that’s what that segment of the video is really about, not arguing over individual terms. In terms of one abiogenesis event as important evidence, well I’d say that basically a big leap of faith you’re making. We don’t know that. There may have been trillions of abiogenesis events, even occurring right now on your fingertip. But they would be immediately out competed or consumed by extant life which has a sufficient evolutionary head start that new life cannot possibly compete. We know that at least one abiogenesis event occurred, but it may be much larger. So it’s again a case of “we don’t know”.

[@reginaldgruenenberg4462]

@@CoolWorldsLab Thank you for your detailed answer. But what I still don't understand is why one strain or string of life would inhibit another one to thrive. Why couldn't or wouldn't they coexist? Shouldn't this appear - if this hypothesis is accepted - as a strong limiting factor in probability calculations as yours? As you said, there might be other strings of life that we haven't observed. Thus it makes them even more improbable than alien life forms because we have our terrestrial biosphere very much under control. At least we can scrutinize it at will. In fact, we would certainly consider the offspring of a second or more biogenisises as alien life forms on our own planet, but even that doesn't seem to happen. There is an excellent German sci-fi novel on this topic, 'The Swarm' by Frank Schätzing. It will soon be turned into a television series, obviously by Netflix. It is exactly about such a second abiogenesis. But it's fiction.

[@Sr89hot]

After watching the Cool Worlds series I find myself becoming more scientifically agnostic. Being the top Astronerd at my place of employment, whenever I am asked about extraterrestrial life and I say ‘I don’t know’, my coworkers give me a unbelieving look. Almost as if I am hiding something from them.

[@CoolWorldsLab]

Spoken like a true scientist!

[@ami_gourav]

That is fundamental . Once raw data gets you love that

[@GilesMcRiker]

Wow your fellow McDonald's workers are so fortunate have such a thoughtful Astronerd as a colleague! I bet you're a real big fan of Astro-genius Neil DeGrase Tyson.too!

[@chuckschillingvideos]

The smartest person in the room is usually the quickest to acknowledge his/her ignorance.

[@chuckschillingvideos]

Agnosticism is wisdom. If you see anything being evangelized, you have EVERY reason to be skeptical - because agendas have entered the building.

[@DJDaveParks]

If the genesis of life was easy, with these perfect earth conditions, why did it only start once on earth, when there could have been other kinds of life evolving in parallel, from a seperate LUCA; silicone-based life for example, or another unrelated carbon-based LUCA - It seems we can infer something from that and place that into the equation.

[@100percentSNAFU]

My thought is that the perfect conditions here are perfect for us, but not so much for a non carbon-based life form, hence why we don't see such lifeforms here.

[@DJDaveParks]

@@100percentSNAFU maybe its the volume of the building block elements such as carbon that made carbon-based life more likely on earth, or just that carbon is the only element versatile enough that can, i think the other elements where here at the start too but maybe so low in volume that they didn’t combine or combine in the same conditions - but that still doesn’t explain why there issn’t more than one carbon-based common ancestor/LUCA. I realise you can’t prove a negative, but if you take a view that there should be other types of carbon-based life somewhere on the planet, but there issn’t, even with all the same building blocks and conditions available, it seems reasonable to infer something from this, where you can start to rule things out such as sun type, tectonic plates, planet or moon size, gravity, solar system objects, etc - where all things are considered equal. I realise this not an ideal way to approach the answer, and it doesn't get you one, but it might get you closer, and feed into the equation.

[@DJDaveParks]

@James Strawn im not sure i follow your metaphor..

[@akanjisekoni]

@@DJDaveParks he’s saying that just because you witness or discover something that you deem unnatural and you can form a logical explanation for how it came about, does not mean that your logical explanation is the correct answer for the unnatural thing that you’ve discovered/witnessed

[@ungmd21]

I am a physician and my job is to preserve and extend life with the training I have learned and continue to add. While the processes that occur in the universe to make stars and planets is amazing, they are quite simplistic by trillions of orders of magnitude of the processes in the most simple cell. I have to try to keep those processes running correctly and for many years. It is incomprehensive to me that these processes could easily come together

[@dougsinthailand7176]

How many times, I wonder, did single cell life arise on earth? Only once?

[@garethdean6382]

I mean, once it does it's probably going to alter the environment to prevent any recurrences. The first fish on land arrived unopposed, the second had stiff competition.

[@jssomewhere6740]

I think a open mind stance needs to be taken about what is truly requires to harbor life. I'm going back to the it's a dam big universe, and we have not yet started thinking or looking ( for lack of a better term ) outside the box. Too narrow it even a bit more the Galaxy we are in is fairly large also. There is sooooooo much out there we have not even considered yet. Life seems so fragile yet look at the catastrophic events it has survived on just this planet. To think it could not find a way in different conditions is in my eyes the thinking of a mind that does not want to find anything. Look I agree that we absolutely could be all alone in this universe. If so it is then our job to make our own aliens. Send people out and in a million or so years track them down and see if we recognize them. Until we can accomplish things such as that we must remain minds wide open, and recognize that our experience is probably a limiting feature of how we look and what we look for. Thanks for the shout out I'm honored. Please continue on this path it Is so fun to watch.

[@angryyoungman66]

How is your comment 1 day ago ?

[@riven5544]

Possibly a channel supporter. I think they get to see the bus a day ahead.

[@tms6660]

@@angryyoungman66 he’s a time traveler

[@pangaea5258]

@@tms6660 That's the only reasonable explanation.

[@ARWest-bp4yb]

Except that he's not using the drive-thru mic! 😁

[@truvc]

Something that is often forgotten: duration of habitability. To get intelligent life you need to have a habitable planet. And it needs to remain habitable for 5 billion years. Good luck with that!

[@TicTac2]

good point, evolution isn't quick

[@hallamhal]

19:22 This made me imagine super advanced life finding earth and thinking "They've managed to evolve with a large moon? No wonder they're so primitive, it's like they've been playing the game on hard difficulty!"

[@tylerdurden3722]

Evolution happens, everytime hard mode is switched on. E.g. If an environmet remained the same, a species tends to remain the same. Because there's nothing new it needs to adapt to. It's like humans, it's usually the few who endure and adapt to hard mode, that go on to thrive.

[@HugeGamma]

A disturbing scenario is that we go 500-1000 years into the future without ever finding any sign of life/ biosignature AND science is unable to recreate the process of abiogenesis LUCA in laboratory conditions. that's the astrobiology nightmare.

[@Apollo-zc2rj]

If Humans in the future both lack evidence of other life and are unable to artificially recreate abiogenesis, a lot of people are going to use that as definitive proof that not only is there a god, but they were directly involved in creating life on Earth.

[@CoolWorldsLab]

Ugh would be frustrating but certainly possible

[@infocat13]

@@CoolWorldsLab See bronze age collapse.......climate and crop failure this will happen again in less then 30 years

[@baddna9447]

@Da G That's in the Drake equation.

[@vulcan4d]

One thing for sure, complex life requires a stable environment.

[@awsumguy-bh9pz]

earthlike planets could be super rare but life could still be very common because there are other places out there that are not like earth but can still have life

[@hermask815]

Religion is when you hold onto your beliefs without data.

[@rodkeh]

Religion is when you believe what you find on the internet.

[@adamtedder1012]

Life has been in the past and is still on other bodies in our solar system. It's simply a matter of time until that becomes a simple fact that our descendants will know as common knowledge.

[@tylermoore4429]

The fact that all life on Earth has a single common ancestor says something I think. Assuming Earth has a decent distribution of all possible elements from the Periodic Table and offers a wide variety of atmospheric conditions (temperature, pressure, light, dark and so on), it has conducted a vast number of chemical experiments over its entire history. All that sampling of possibility space resulted in only one self-sustaining lifeform, LUCA. We don't know if there were other candidates before LUCA, but there are no LUCA-like phenomena happening today. That tells me LUCA was a vanishingly rare event in the universe.

[@whoff59]

We know of 1 self-sustaining lifeform, LUCA, yes. We don't know *if* there were other kinds of lifeforms and we don't know how many, we just know these other ones died out and LUCA had successors. That's like: there were dinosaurs and they died, only some of them developped to birds ... and today we don't see dinosaurs around us other than birds. So, this doesn't say anything about the plausibility of LUCA and/or other lifeforms at that time - or now. It is just the case that the successors of LUCA survived - and others did not.

[@MYNAME_ABC]

Factor in that universe was much smaller billions of years ago, therefore near supernovas roasting a planet was more likely than now. Then factor in that there is no universal "now" at all, at least in special relativity.

[@HeavyMetalMouse]

Unhelpfully, I think my lay-intuition of this issue, after encountering the limited data and the theorizing, is that it's probably a little more complicated than 'requirements for life'. Life, at its absolutely most basic, is 'simply' a self-replicating persistent pattern. A pattern that is not merely supported by happinstance of environment, but an active 'participant' in its own propigation (in that it does work on its environment to persist, rather than having work done on it to make it persist). Happenstance can get it started, and nudge it forward in interesting or useful directions, or crush it backwards towards extinction... and that is where the questions come in. It seems likely that the most basic simple 'life molecules' could happen to exist anywhere, simply because there's no way to know what kinds of molecules could even *be* life until we observe them. It seems likely, as well, that everything that comes after is, in its own way, a roll of the dice, and various large scale factors might weigh those dice rolls one way or the other, depending. Things like a large moon, or plate tectonics, or even liquid water itself, might just be thumbs on the scale - maybe life *can* happen without them, but having them helps quite a bit. Obviously, the more factors you have that help, the more likely you are to have life grow into something detectable with variety, but that isn't a sure thing either. Maybe you could run Earth simulation again and the dice simply don't end up falling that way, and the Oxygen Catastrophe wipes everything out because nothing managed to adapt the 'breathe Oxygen' option in time; or the first nucleic acids fold wrong and just end up only ever making a weird dead-end self-replicating protein that lasts a while then gets burned up in the next volcanic eruption. On the other hand, maybe you're looking at a hostile planet where everything is working against life, and against all odds the dice just keep coming up lucky - all the right adaptations end up falling into place just when they're needed and the engine of life starts and hangs on. The TL;DR is - maybe we're thinking about it wrong in terms of what is 'necessary' for life. Maybe it's more a matter of what makes it 'more likely' or 'less likely' at any given stage. Which isn't really all that helpful, but it definitely admits that the universe could end up being much stranger than we yet know. I also look forward to the result with keen interest. :)

[@JafoTHEgreat]

Your TLDR is TLDR. Ughh.

[@rphb5870]

Rare Earth only seems plausible due to the vastness of space until we start to realise how many criteria needs to fit perfectly in order for a planet like Earth to exist. 1) it have to be a G type star as any other star is too hot or too cold (4% of stars) 2) it have to be a single star system, as multiple stars screw up the equilibrium 3) it have to be at the right distance from the galaxy centre so there is neither too much activity nor to few rare (heavy) elements. 4) We need gas giants in the outer system to vacuum it for debris. 5) they have to stay in the outer system and not wander inwards. 6) The planet need a large moon to stabilise its axis. 7) the planet needs a solid iron core and a liquid outer core to create a magnetic field. 8) the planet needs water 9) the planet needs to be in just the right spot in the stars habitable zone. this is just the first 9 points, but there are over 200. We don't see anyone else because there is noone else. Life is just that incredibly rare. In a million years it wont be, as we would have been there and spread it, but as of now Earth is the only living organism in the universe, in all likelyhood.

[@whoff59]

as of 4) and 5) the gas planets: Currently many of the giant gas planets found in outer space are very near to their suns. This is fitting to the theory that giant gas planets are spiralling into their sun when created in a newborn star system and collecting the debris. So the current theory says: - Jupiter was needed to "vacuum the debris" and it wandered inwards - Saturn did the same and wandered inwards as well - it took Saturn to stop Jupiter wandering inwards - so, in a complicated dance the two of them they found their places of today So, in fact maybe 2 big gas planets are needed as condition for a habitable earth.

[@rphb5870]

@@whoff59 maybe, or maybe 4 is, as we have 4 not 2. But yes Saturn and Jupiter, Neptune and Uranus likely stopped each other from going in to the inner system, which again makes Earth so rare. I know many people despair over the fact that we haven't found any Earth 2 yet, but that is a good thing, because the rarer Earth is, and we know now that she is pretty damn rare, the more likelyhood it is that the great filter is behind us. I firmly believe that it is. The great filter is the difficulty life have to begin in the first place, because the condition for a planet like the Earth to form naturally are so specific so rare that it basically never happens, that it is rare to find just one Earth like planet in an entire galaxy, and we likely are the only life not just in the milky way, but in the local cluster as a whole. But where are we in a million years? Personally I think we are everywhere, in the galaxy at least. Life have a need to spread, it is one of the only traits that are shared by humans, turkeys, bacteria and everything in between.

[@TicTac2]

and even WITH all that, how exactly does abiogenesis work? either the Earth today is the wrong conditions or it's something incredibly rare as well

[@rphb5870]

@@TicTac2 the simple fact remains that we have never been able to produce life from non living matter. We have never observed it. We simply assume that it is something that just happened by chance. I don't want to use the G word but, but like many other things it seems like a miracle, an unexplained miracle. There are two goals that all life share: survive and multiply

[@AssassinsFear]

It depends on your definition of life. Other planets might have life in ways we cannot conceive. Or if you have a broader view of life, you could consider a planet or a star a form of life.

[@JT-ld5kh]

" It's ok to withhold belief until you see evidence either way. You don't have to plant a flag on issues with no data" I've been saying this for years. If only humans could be so inclined. The world would be much more peaceful, for one. But nope, people HAVE to have an answer. They have SUCH a hard time just saying "You know what?, I'm not sure." That's why people will believe anything. And they almost always stick with the first thing they hear and forever dismiss all other perspectives. Especially if it's instilled at a young enough age by their parents, my goodness it's so destructive to progress. Everyone thinks they are right, but hardly anyone agrees with each other. Now think about that.

[@precursors]

This man could talk about the inner workings of a mechanical swiss watch for hours and I would still listen

[@Gingnose]

I think the importance of magnetic field is that it keeps atmosphere remain intact If we see the current conditions on mars, almost all atmospheres are deprived of.

[@nilsqvis4337]

The plate tectonics is a particularly interesting point. Earth hasn't always had plate tectonic that function in the same way as today, being much more static in its nature. At the point it starts to resemble the current state is curiously enough when life starts becoming a lot more complex

[@shara7948]

Nevermind another earth. I don't even think there's 2 similar planets anywhere, even that cannot support life. That are just similar to each other, without the added question of whether it supports or is capable of supporting life.

[@timflatus]

You can't logically extrapolate from a single data point, absolutely. Even if we knew much more about how life began on this planet that still might not tell us anything about life anywhere else

[@BriarLeaf00]

"I await the result with keen interest" I don't think there's a better way of looking at such a profound question when there's so much still to discover.

[@rocwelledwards8942]

This world is such obvious proof of a creator. Anyone who dismisses that is trying so hard to be blind to the proof. And if God created us, he created others. We are not alone. We are part of a family.

[@rocwelledwards8942]

Though i dont intend that to mean that we shouldnt study everything and find out how it works. I love the discovery and the pondering. I just mean the lense that things evolved purposelessly verses created with purpose changes everything, and really helps us understand things better. We would stop dismissing so much as “leftover evolution baggage”

[@WokeandProud]

Yawn.

[@alexgarcia3610]

When you see a glass full of water, you dont think "ohh this glass has the same shape as the water inside. Must be finely tuned to water." Its the other way around.

[@MD-en3zm]

Perfect analogy - I love this. It expresses exactly what my thoughts are on this subject. Who knows what life might look like on other worlds?

[@shoam2103]

The problem with conditional probability equations is people often forget that one important assumption: the events or factors are mutually exclusive. To correct for that you need something like the exploration of parallel paths and summing them shown in the later chapters of the video

[@camilohiche4475]

My conclusion from this is that, if we assume that Earth-like life forming conditions are exceptionally rare in the universe (so much so that there is little hope of finding an Earth "twin" out there), then life probably needs exceptionally rare combinations of factors to form. So then we can make the bet / assumption that, if life formation is to be "common" in the universe, then every spontaneous life formation happens in its uniquely exceptional, singular set of improbable conditions, so then it must be "common" that there are multiple cases of planets with singular sets of particular conditions (completely different from Earth's) out there. So then, instead of looking out for planets with very similar Earh-like conditions (where the probability of all Earth-like factors coming together still remains overwhelmingly small, virtually non existent), we should focus on finding planets with very singular conditions, however different from Earth's they are.