The Copernicus Complex: Are We Special in the Cosmos?

you good evening everyone my name is Andrew frack no I'm the Astronomy instructor here at Foothill College in Los Altos Hills and it's a great pleasure for me to welcome everyone here in the Smithwick auditorium and everyone watching us at home on your computer to this the first lecture in the 15th annual Silicon Valley astronomy lecture series this series is co-sponsored by NASA's Ames Research Center one of the premier NASA centers in the United States for both science and education by the Foothill College astronomy program we offer astronomy classes both in the day and evening and what we call our astronomy for poets program we are we offer classes for people who are not technically inclined but just have a romantic interest in the universe also the program is co-sponsored by the Astronomical Society of the Pacific which is an organization just celebrating its one hundred and twenty-fifth anniversary bringing news about astronomy to teachers students amateur astronomers and the public at large and last but not least we are co-sponsored by the SETI the search for extraterrestrial intelligence Institute are the leading organization scientific organization in the u.s. searching for signs of extraterrestrial intelligence and we're very grateful for the help of all these organizations tonight's speaker is dr. Caleb Scharf who is the director of astrobiology at Columbia University in New York City he's one of the leading scholars at the interface of astronomy and biology in this relatively new field that we call Astro biology he's the author of a widely praised book called gravity's engines which was the basis of a BBC documentary called swallowed by a black hole his textbook extrasolar planets and astrobiology won the 2011 Chambliss prize for the best astronomy textbook in addition to over 100 scientific research papers dr. Scharff has written non-technical articles for such magazines as Scientific American The New Yorker science and many other publications and he's been frequently interviewed on television and radio his latest book the Copernicus complex was just published by Scientific American Farrar Straus and Giroux and it is that book which is the topic of his talk tonight then looking in the largest of scales at our place in the universe it's a great pleasure for me to present dr. Caleb Scharf thank you very much for that introduction it's a great pleasure to be here this evening it's wonderful to see so many faces in the audience thank you for coming out to to have an evening that may be a little different than the usual evening sitting around watching television or drinking beer at least that's what I do usually because tonight we're going to talk a little bit about some very big questions big questions that are not only ancient but they're very deep the questions that speak to the most fundamental aspect of our existence so what do I mean by this let me start with just a little little taster of where we're going to go let me talk a little bit about significance or insignificance and a good place to begin is with me this is me I think I was around one-year-old and let's let's think about my place in the universe there I am I was born here in the city some of you may recognize it from some of the artifacts in this this image it's the City of London and city of London is of course on a small island in a great ocean on a planet which is a rocky sphere covered in a thin veneer of atmosphere and water and that planet has a companion shown to scale here the earth is at the lower left of this image the moon is up there at the top right and around the time that picture of me was taken you can gauge how old I am from this humans went there and we came back again a total round-trip of about half a million miles and that's all we did which is perhaps not surprising because all of that is in that little dot where the blue arrow is on the lower right hand side there that little dot is orbiting a fairly ordinary star the Sun showing up there at a distance of about 93 million miles that star the Sun is merely one of several hundred billion stars in a great swirl of matter that we call the Milky Way galaxy and the Milky Way galaxy has some companions its companion to a galaxy called Andromeda and it's more grouping of galaxies but these are not the only galaxies because across the universe there are some 300 to 400 billion galaxies within the region at the universe that we call the observable universe that we have mapped out to a certain distance this is a map where each little tiny dot is a known galaxy if we could see the entire observable universe it might look something like this the observable universe is the place from which light has had time to reach us in the last 30 13.8 billion years so it's a big place but we now have reasons some reason to believe that this may not be the only universe there may be other universes out there separated in space and time and dimension with different properties in fact there may be 10 to the 10 to the 16 distinguishable universes out there and this is a number determined solely by the information carrying capacity of the human brain of a human lifetime the actual potential number of other universes out there that we couldn't tell the difference between is about 10 to the 10 to the 10 to the 7 so are we special or unique are we at all significant in light of all this it can seem pretty obvious that the answer has to be how can we be significant how can I be how can me and my little baby pram back in the late 1960s possibly be at all significant and it's an important question to ask though because the interesting thing is that the answer isn't quite as simple as you might be led to believe from what I just showed you and this is what we're going to talk about this evening because the answer to these sorts of questions can be yes/no and of course it's not so simple that's really the story of science it's never quite so simple so where do we begin well I'm going to do during the course of the next 50 minutes or so is try to discuss both sides of this equation to talk about things that suggest that yeah we're not special with insignificant and things that suggest well maybe there is something a little unusual about us about life on Earth so where do we begin well let's begin with this guy this is actually a 19th century picture of Copernicus portraying him as he might have been in the 1500s so it's a rather romanticized view of him having sudden enlightenment on some rooftop somewhere surrounded by suitably placed maps and tools Copernicus some 500 years ago really took what we would recognize to be the tools of modern science and applied them to understand the mechanics of our solar system and in doing so he removed the earth from the center of existence he was trying to explain the movements of the Sun the Moon the planets and the stars in the sky was a very mechanistic problem he was trying to solve in a more elegant way than had been done before to do that he put the Sun at the center but he also thought more deeply about the implications of this and he even said and this is an almost exact quote from Copernicus's writings there is no one center in the universe now this is an astonishing thing to say five hundred years ago of course his conception of the universe was rather different than ours he was really thinking about essentially the solar system he wasn't even really thinking about what the Stars might truly be and where they truly were but this notion that there is no centrality there's no special place in the universe was incredibly important and over the decades and centuries that followed Copernicus it it like a snowball roll rolling down the hill it gathered momentum and it turned into a very important and central piece of Western science this notion in fact when Einstein and others were trying to apply the tools of general relativity to understand the dynamics of the universe as a whole this was a critically important idea that there is no particular spatial center to the universe the universe is expanding everywhere at the same time and this has given rise to what we might now call the principle of cosmic mediocrity which is to say that we are definitely not special but no place in the universe is special that's the principle of cosmic mediocrity and it applies certainly when we're trying to understand the dynamics of the universe but it's also a very comfortable thing in terms of modern science and the interesting thing about the principle of cosmic mediocrity is that it also suggests that the circumstances of the earth and of life on Earth are also not special then that has to be true if we believe in cosmic mediocrity but that kind of implies that there should be life everywhere because if we're cosmically mediocre there has to be lots of other cosmically mediocre out there that's equivalent in some way so on the face of it this suggests we're not significant of course we're not special we're mediocre but it's also saying there should be life everywhere that's interesting because add something we might be able to test so let's think a little further about this let's go to the other side of the equation because a lot of the modern discussion of maybe life is special maybe there is something special about the earth actually came out of physics and in particular something that has become known as the anthropic principle so I'm just going to talk about that a little bit here also show why it may not be correct or at least it may be more complicated so in the late 20th century actually round about the 1970s we had learned that the universe was finite in age was expanding but a number of physicists were also seeing that there were central properties of the universe central features of the universe and I'll put up a list here this looks kind of complicated so don't worry don't panic we'll talk about a couple of these very briefly I'm just putting the lists up there to for completeness number physicists had noticed that if you looked at certain fundamental characteristics of the universe which were otherwise completely independent of each other and for which there was no deeper underlying predictive theory to say what they should be so things like the relative strength of gravity to electromagnetic forces for example or the amount of energy that you get out when you fuse two nuclei together some of those fundamental properties or fundamental constants of nature I all sort of lined up in such a way that life can exist what do I mean well take for example the strength of gravity compared to the strength of electromagnetic forces if you changed that relationship just a little bit you might not make stars in the universe and stars make heavy elements like carbon and we're made of carbon chemistry so if you change something a little bit in the fundamental underpinnings of the universe you've subvert the whole pathway to life like us and there are other things for example the size of quantum variations in the early universe what does that mean well tiny imperfections in the very very young universe that have actually grown into all the structure that we see in the cosmos change that a bit the universe turns out different and we wouldn't be here so these physicists said well this is kind of interesting this says that that the existence of life itself is telling us something about fundamental physics it's telling us about the fundamental characteristics the universe that means life is kind of special you only need one instance of life in the universe for this to be true now you may be sitting there and I hope you're sitting here going wait a minute wait a minute because if it weren't like this if things weren't finely tuned in this way we wouldn't be here to make the observation in the first place so it has to be like this that's true except if this is the once and only universe why did it turn out this way that's a disquieting thought it's an uncomfortable thought well is this true is is this the once and only universe now this comes back to something I mentioned just a few slides again there's a way out of this there's a way to get back to some cosmic mediocrity which is say well maybe this isn't the totality it's just a tiny piece of this multiverse okay that we're one of 10 to the 10 to the 16 distinguishable universes and so it's not surprising that we find ourselves in a universe that is suitable for life it just happens to be one of those many many universes is suitable for life it's just got the right to fertility so of course we find ourselves here so that seemingly solves this notion of being special but there's something in there that's a little tricky because it doesn't actually help us with the question of our significance within this universe because it only requires the idea of the anthropic principle only requires one instance of life having occurred in the universe to be true and multiverse theories and they are theories they're very compelling very some of them but they are there is there is no experimental verification yet they don't say anything about how much life you might expect anyway now you might say well why should there just physics theories and that's true but yeah we want to know the answer to this we want to evaluate our place in the universe and we'd certainly like to know whether it's just us or there are others and I'll come back to this right at the end of the talk there's some connection is a deep connection between how much life there might be in a universe in other words how fertile a universe is the abundance of life and some of this deeper physics so it's an easier way to to get to the answers to begin to evaluate our place and universe properly to evaluate our significance whether a special or not well yes of course there is it's around us we just have to look out into the cosmos to begin to understand these things so let's do that and what I'm going to do first is just to take a tiny little trip to the side to think a bit about the passage of time because in all these discussions about how much life there is in the universe and whether we're special not we often leave out the piece of it that is actually very very important which is that things change in the universe so let me just do a quick three-minute history of us our entire 10 billion year history now we've only got through about four and a bit billion four-and-a-half billion years of that history we have a bit more to come so let's do it all so where do we come from well we come from a place like this this is a picture of the Triffids emulous it's about 5,000 light years away from us in our galaxy it's a great collection of gas and dust this image is about a hundred and fifty trillion miles across and it's places like these in our galaxy where gas and dust in interstellar space is beginning to condense together pull together by its own weight and pulled together because able to cool down it's beginning to condensed out of interstellar space and if we look deep in images like these peering inside this is a Hubble Space Telescope image we see all these extraordinary structures and increasingly dense accumulations of gas and dust and if we compare really really deeply in we see these almost egg like regions very very dense regions where material is falling together very rapidly on cosmic timescales rapidly enough that it begins to form new stars and a new star on the next image will be a computer animation a rendition you start as we think form in this sort of situation they form as matter condenses out of the interstellar medium at the center of this image is a forming star a protostar matter falling onto its getting hotter and hotter and it's squeezing itself down to the point where it begins nuclear fusion surrounding it is a great swirling disk of material primarily gas with some dust mixed in it's about 20 billion miles across give or take if we're looking back at the history of our own solar system and in that disk of swirling material around this growing star matter begins to clump together into solids there is dust that clumps with other dust there are ices that form and these pieces begin to accumulate and fit together to make larger and larger objects while it's happening though the central star is getting hotter and hotter and it's boiling everything away so in fact this all takes place very rapidly and in merely for our solar system 95 million years or so give or take I'm sure it's more certain than that let's say in 95 million years after we take that egg shape piece out of a nebula watch it collapse under its own weight we end up with well a star the Sun and some fossils here are the fossils and we're that fossil but rather we live on that fault edge we are that fossil because the material we are composed of have come from that fossil this is what you get after 95 million years and arguably the most interesting piece of the history the solar system happened 4.5 7 billion years ago when the star started to form 95 million years after that it was all over with boring it's been downhill ever since and of course where we exist some 4.5 7 billion years after that initial period of formation it's kind of an in-between time and it's not going to stay this way for too long in another billion years or so our Sun will have gotten sufficiently bright that the surface temperature of the earth no matter how you how you do it how you change the atmosphere will not be able to sustain liquid water probably be the end of life as we know it now of course in a billion years time we're pretty unlikely to be around even if our descendants still are they will be different from us ok that evolution will force that to happen and if we go a little bit further another four billion years after that what's going to happen well basically the Sun is going to inflate its outer layers it will finish burning nuclear fuel the hydrogen nuclear fuel and its core it will go through a period of transformation over another few hundred million years it will end up as a giant crystallizing ball of carbon and oxygen the earth may or may not still exist and that's it ten billion years and it's over and done but during that ten billion year span another 10 billion or so stars have formed in the Milky Way galaxy so we really exist in a sliver of a sliver of a sliver of time and during the rest that time the galaxy continues to produce stars and other things now one thing that we have not known until recently is whether or not those other stars either the ten billion that formed during the the sun's the solar system's ten billion year life span or that have already formed whether those other stars also have planets around them and it's difficult to find planets planets are small and dark and still is a big and bright and if you put the two of them together on the sky enormous ly difficult to see planets because the light with the star swamps them however this has all changed and it started about twenty years ago we now know through a variety of incredibly clever technological tricks to detect this or sense the presence of planets around other stars I won't go into any detail on this but it's I'm sure you can read about it and if you haven't already read about it we now know of over 4,000 planets we have robust detections of the presence of more than 4,000 planets around other stars one of the ways in which this has been done has involved the NASA Kepler mission which was a space telescope that monitored the tiny dips in light of about a hundred and fifty thousand stars due to planet orbiting around them and occasionally passing between us and those parent stars you can monitor those tiny dips in light the point is that we've discovered many many planets out there and we simply did not know if this was going to be the case more than twenty years ago we might have speculated that planets might be fairly common but we didn't know we really didn't know and it's now got to the point where you can have headlines like this it's New York Times it must be correct far-off planets like the earth dot the galaxy and it's true because we've detected enough planets to begin to make statistical extrapolations that mean something so we know that universe makes planets in great abundance there are hundreds of billions of other planets in our galaxy the Milky Way in fact there are roughly 1.4 planets for every start and we'll QA galaxies probably more than that we can also begin to make statements about planets that could conceivably resemble the earth in some way so for example we can take our measurements and make statistical extrapolations to say that we're pretty confident that within about 20 light-years of us which is really pretty nearby that's a nearly 120 trillion miles of us there is at least one candidate earth-like planet well what does that mean well me it really just means a planet of about the same size as the earth orbiting its parent star at a distance that could allow for the presence of liquid water on the surface so called Goldilocks zone or habitable zone and that means that there are at least something like fifteen billion such worlds just in our galaxy so this kind of gets us back to feeling mediocre perhaps at least in terms of planets like this however there's a twist to the story the twist is to do some extent with the incredible diversity of these other worlds let me just run through this this is going to be a quick laundry list of some of the diversity that we see in other planets for example there are things called hot Jupiters these are gas giant planets like Jupiter that orbit their parent stars incredibly closely some of them go around their parent stars in less than 24 hours it's still a bit of a mystery how they end up there there are planets that we think are ocean planets plants that have a much larger water abundance than the earth so there may be oceans hundreds of miles deep covering these planets there are super-earths planets that are essentially rocky worlds but they are more massive than the earth but not quite as massive as Neptune and there isn't one of those in our solar system something I'll come back to in a moment there are planets with hydrogen envelopes now some of you may not be very excited by that okay but I can assure you astronomers and planetary scientists are excited by that because these planets with hydrogen envelopes hydrogen atmospheres are otherwise small rocky planets but they have these enormous hydrogen and probably helium atmospheres we have really no idea how they got those but they're out there there are planets that are incredibly carbon rich we can already make that deduction and those planets would have fundamentally different geophysics and geochemistry not dominated by silicates but dominated by carbon instead there are where are we rogue planets okay so this really just throws it out the window these are planets that have no parent star what are they doing these are planets that we think used to have a parent star formed around the parents are in that great swirl of material that I showed you the animation off but have somehow been flung out into interstellar space and there are a lot of them that could be as many of these planets as there are stars there are planets doing the most perverse things imaginable in our own solar system all the planets orbit in the same sense that the Sun spins that kind of makes sense if you look at that picture of the swirling disk of material forming planets and stars but then we find planets going in the wrong direction what are they doing we have ideas but we still don't know for sure there are planets that probably have great layers of diamonds inside them there are so-called patched systems or systems where planets seem to have formed to a maximal amount as if nature couldn't get enough of making planets and it put them all closely together in orbits where if they were a little bit closer together it would all disrupt so for example there are places where we think there may be nine planets all within the equivalent orbit of the earth there are planets going around twin suns this is a fabulous piece of science fiction made real there are binary stars twins does that have planets not just orbiting one of those stars but orbiting around both of them at the same time there are Icarus world planets on orbits that are so elongated that during the course of one orbit their temperature can change by a thousand degrees they plant on hugely elliptical orbits our own solar system has orbits that are relatively circular and spread out there are many systems in fact the majority of systems have strongly elliptical orbits that relates we think to the deeper dynamical history of planetary systems and the last one up here pitchblack worlds I like these pitchblack worlds these are gas rich planets whose atmospheric chemistry is such that it absorbs almost all that light that falls on them they are darker than the darkest piece of coal it's a lot of diversity the interesting thing is that all of this information now gives us a way in which to gauge our solar system against others gives us a set of fingerprints if you will so let's just do that how does our solar system actually stack up against these others in terms of is it common or is it not common well I'm going to do this very crudely but just to show you some of the things we can look at so for example if we look at the types of orbits of the planets in our solar system the architecture of our solar system and the stability of these orbits not just now but in the past and in the future we find that we kind of belong to a 25% Club most systems are somewhat different if we look at the fact that we don't have one of those super-earth planets 60% of stars we think have a super-earth around them yet that type of plant does not exist in our solar system so it puts us in a sort of 40% Club and then something that's kind of staring us in the face all along but we didn't know until we found out that the words planets around other stars the Sun while an ordinary star is not the most common type of star in the galaxy most stars are less massive than the Sun in fact 75% of all star less than half the mass of the Sun and this kind of puts us in a slightly unusual Club because those lower mass stars also have planets around them and of course we have this planet that we're sitting on in this habitable or Goldilocks zone it's orbiting at a distance from its parent star that allows for the existence of liquid water on the surface of liquid water we think may be a requisite a prerequisite for life so take them all together very crudely this is very very crude kind suggests our solar system is a bit of a one in a hundred type plate it's not completely rare but it's kind of unusual that's interesting whenever you see something like this a flag goes up but we don't know how that relates to the existence of life here at least not yet but it's interesting it is a check in the column for perhaps or something special here so to go to the next piece of this and this is where you know as astronomy related talks go I'm going way left field okay because to understand some of that we also have to think about life itself we have to go to the inner verse I'm not sure that's a particularly good word but it sounded kind of cool and the universe is to do with the nature of life so let's have a little think about the nature of life on the earth so let's look at life on Earth I'm pretty sure this is the only astronomy talk you ever see that has a picture of a cow in it maybe I don't know maybe there's a cow trend not so long ago 50 hundred years ago if you asked someone you stopped someone on the street and you said what's life on Earth tell me what is it what what does cut what constitutes life on Earth then I say well maybe cows and animals and grass and trees and insects stuff like that is what dominates life well not exactly so let's consider a cow so a cow consists of about 10 trillion cow cells and cow cells like our cells are quite complex have a lot of complex structures and they're all glued together literally glued together so a cow is 10 to the 13 complex cells glued together but that's not all that a cow is because a cow is also about a hundred trillion simple microbial cells microbial meaning single-celled organisms the bacteria or the other great branch of single-cell organisms the archaea like us we're the same large multicellular life on this planet carries around an enormous micro bio it carries around microbes bacteria archaea and we can't exist without them they help us I jest our food they related to our immune system they're to do with our biochemistry they're part of us in fact a typical adult human and if you're squeamish I apologize carries around roughly two pounds in weight of pure microbial life that's kind of a blob like this sort of squishy blob like well you can use your imagination now it's very interesting it's become a central piece or at the forefront of medical research biological research understand the interplay between this microbial life and creatures like us and the cow and other things because we can't exist without each other some of these microbes we are their habitat take us away and they won't be able to survive the reason for bringing this up is that the same pattern extends to the planet as a whole the majority of life on Earth is microbial it's single celled organisms they are in numbers at least 10 to the 30 individuals living any one moment they are extremely genetically diverse far more genetically diverse than the larger creatures and they're everywhere they're not just on this remote or on my skin in my stomach or out here in the lecture room they're in the atmosphere there oceans that in the soil that in the rock they've been found kilometers down in the sub structure of the Earth's crust they are everywhere they are ubiquitous and that is very important because the environment that we live in today and the environment of the earth over the last 4 billion years or so has been fully intertwined with these organisms the microbes were the first recognizable life that we know of on the planet and they have remained the dominant type of life on the planet and they have essentially engineered and re-engineered the planet over time depending on what was thrown at them from other things other events they have manipulated and shaped the planetary environment for the last 4 billion years and we are proof of that the oxygen we breathe is proof of that the production of oxygen through photosynthesis was invented by microbes probably at least 3.5 3.8 billion years ago now you'll see where I'm going with this I hope it's complicated it's all biology is complicated I'm sorry I'm a poor astronomer biology is complicated but it's fascinating one of the ways in which we can conceptualize what they've done to the environment is to think about the biological processes that are particularly relevant for altering the environment these are processes that we call metabolism and all life on Earth uses a finite set of metabolic tools okay so metabolic tools are ways in which organisms extract energy from the environment ways which they extract energy and raw materials from the environment so for example we are oxygen respirators that's our primary metabolic process there are organisms whose primary primary metabolic process is fermentation something near and dear to my heart perhaps some of you too things like nitrogen fixation ok the more exotic sounding metabolic processes like iron respiration or manganese respiration and taken by certain microbes some of which live on the surface of desert rocks altogether they're about ten metabolic processes that life uses all together most of life is is microbial the genetic code that describes the molecular machinery that organisms use to carry out these particular metabolic processes it's relatively small it's about 1,500 genes key genes these are become known as the core planetary gene set in certain circles so what is interesting about the core planetary gene set well the really extraordinary thing is that this set of genes is widely dispersed across microbial life individual microbes may operate for example by doing fermentation that's how they survive but they may carry other parts of the core planetary gene set genes that for example might do oxygenate photosynthesis or something else they just just don't use those genes and because microbes are everywhere and have been everywhere for a long time over time they are essentially the guardians of this core planetary gene set which is the if in a way you could look at it as the the solution that life has found for surviving on this planet the interesting thing about that is if an asteroid comes along and hits the earth and destroys 99.9 percent of life it's okay doesn't matter it really doesn't it really doesn't because somewhere the core planet regime set will be preserved they may be shared across a number of microbes summer but it only takes a handful of these things working under a rock somewhere and you haven't lost that information life doesn't need to reinvent the metabolic tools to exist which may be pointing towards something Universal it's a way in which life can survive for billions of years on a planet and those same metabolic processes are tied into chemistry carbon chemistry that we see the build blocks of everywhere in the universe we see carbon chemistry on planets asteroids interstellar gas you name it it is ubiquitous if you look out into interstellar space 70 to 80% of all molecules that are floating out there are carbon-based molecules and they're kind of things we would recognize they are the precursors to things like amino acids so what am i trying to say well and this is kind of this was the most complicated part of this talk it's suggestive that all of this together is a plausible blueprint for how planetary life may have to operate anywhere and how it can operate incredibly successfully irrespective of the biochemical details because what life seems to have figured out is cloud storage yeah no it is it has and it got there four billion years before us because so okay cloud storage just in case is anyone in Silicon Valley who doesn't know what that is if I take a picture on my cell phone of my cat doing something that is only interesting to me and I dropped my phone in the in the toilet it's okay because the picture has gone and been stored in multiple copies somewhere else out in the cloud on other computer service well microbes kind of invented that first the core planetary gene set is in the cloud it's in the cloud of 10 to the 30 individual organisms you can't kill all 10 to the 30 way you probably could if you had a black hole or something in the ER but that's another story so it's a very interesting thing that I think suggests it brings us back to the idea of cosmic mediocrity because it's sort of suggesting a possible universe or mechanism by which life gets going and preserves its critical information by the way this this animation is an animation of chlorophyll and vegetation on the earth with passing seasons and I like to say this is gene expression this is the largest version of gene expression you'll ever see it's try to it's the core planetary gene set expressing itself so that's one other piece here given all of that and I'm trying to argue that this this would suggest that life may be abundant out there there are tools mechanism systems that life could latch onto that will make it much easier for it to survive and it's all based on the same chemistry but how diverse could that life be I mean is there going to be anything else like us because that's question we often come back to can the pathways or trajectories be very diverse well let's think about that because that speaks to something that comes up again and again if any of you have read around this topic your your perhaps recognize this this is the idea that microbes simple things like bacteria and archaea might be the sort of organisms you'd find everywhere in the universe but what about complex celled life what about cows and us our cells are different they're much bigger much more complicated and we are in some ways much more vulnerable than microbes so there's an argument that says perhaps complex celled life and a corollary to that is intelligent life it's very unlikely very rare now what how these arguments may well the arguments tend to go along the lines are saying look if you go back through earth's history you can point to many features of earth's history which all have to line up it's a little bit like the anthropic principle had to line up just right us to be here the complex celled life to be here for example we have a planet with a particularly large moon compared to the planetary size and that moon helped stabilize the spin axis of the earth actually it prevents it from falling into resonances with the gravitational pull of Jupiter and Saturn but that's a whole other story it basically prevents the spin axes the earth from changing dramatically if the moon wasn't here the Earth's spin axis were changed by 50 60 degrees over time spans of tens of thousands hundreds of thousand years which would profoundly impact the climate of the plan it would change it severely again and again and again and complex life like us might have a hard time evolving in that situation the configuration of the continents and the oceans on our planet the nature of plate tectonics all helps stabilize climate again that's something that could have been critical for us to eventually come along there have been mass extinctions and mass extinctions whether it's an asteroid or something else often allow once it's wiped out a bunch of organisms it opens up opportunities for evolution opens up opportunities for diversification of species and then and so all of these things if they were different complex life might not have happened here and the argument is that these things individually are quite unlikely if you just pick a random planet around a star quite unlikely to have any one of these things let alone all of them together and there's a piece of evidence as well in this argument that comes from biology it's a central one it's perhaps the strongest argument for this notion of a rare Earth and it's to do with a thing called mitochondria - gaining may well have heard of mitochondria these structures inside our cells in the cells of any large multicellular organism that basically act like little power generators for ourselves they produce chemical energy forms bacteria and archaea don't have them because of mitochondria our cells can express something like 200,000 times more genes than can a bacteria and it's how we get to be big and an energy intensive however biologists some biologists have argued that the existence of mitochondria which is so critical for us being here for any large multicellular complex life happen because of a single incredibly unlikely merger of two simple organisms two billion years ago two little things got together and entered into some kind of symbiotic relationship to form essentially the ancestor to our types of cells but it was a very unlikely merger and that means that while it clearly happened here it's very unlikely that it's going to happen in many other places now I'm going to try to tear that down a little bit this is a sort of maybe a little brief interlude because I'm going to talk about baseball it's because these rare earth arguments rest on saying that if this hadn't happened if this hadn't happened if this hadn't happened we wouldn't be here and those things that happened were each quite unlikely so the net result is an incredibly unlikely event but is that a good enough basis to say that life like us has to be rare in universe what I'm going to argue is maybe not so let's let me tell you a story okay so I'm sitting at home the phone rings on the other end of the line is someone I haven't spoken to in a long time a long-lost friend they've tracked me down their family is great we have a wonderful conversation they say to me hey you know what I've got a ticket to this incredible baseball game tonight do you want to come sure we meet up we get stuck in traffic we're late to the game we get there we can't get to our original seats we have to walk around the stadium as we're walking around the stadium we stopped because there's a great batter on the field and we want to watch the batter hits the ball it sails into the air and guess what it lands in my hand so I say to myself that's incredible that's so unlikely because if my friend hadn't called me if we hadn't got stuck in traffic if we hadn't be walking through the stadium we haven't stopped at that moment if the batter hadn't been on the field just then I wouldn't have caught the ball it's incredibly unlikely to have happened but is it because in a big stadium full of spectators and a great batter on the field a big baseball game it's essentially inevitable that some spectators going to catch the ball at some point during the game and they too are going to be going through the same reactions they say if I hadn't eaten that bagel if I hadn't flushed my cat down the toilet if I hadn't tripped over my shoelaces I wouldn't be standing here during the ball it's unbelievable so the point is the point I'm trying to make is that the rare-earth arguments are a little bit like this things take on new meaning after the fact except the difference with life being rare is it's like we're in the baseball stadium we don't know how many other spectators that there are we know we've caught the ball but we don't know how many other spectators could be out there right so the bottom line of this is if complex life is indeed rare in the universe well it's going to be sitting around thinking it's rare if complex life is common in the universe it's going to be sitting around thinking it's rare so it doesn't disprove the rare earth argument but it says I think that you have to be very cautious because it could be the polar opposite we would still think that our circumstances were very unusual and that things had to be lined up just right for us to be here so I know time is getting on I'm getting close to the end here so how do we pull this together what if any is the conclusion we've seen evidence for cosmic mediocrity that we're not special we've seen evidence on the other side that perhaps there is something unusual or special about our existence here well I'm just going to sort of take a shot at this I think that some of the key comes in examining the pathways that something like life can follow life is an extremely complex phenomena it may be the most complex phenomena in the universe and life much like planets on wobbly orbits and the the chaos of the formation of a solar system life seems to occupy a place somewhere between order and chaos chemistry that's not too harsh or not too all temperatures not too cold not too hot certain amount of order and disorder but somewhere in between is the right mix and that's kind of where life seems to pop out it's an emergent and dynamic phenomenon this idea of emergence is something that has been around for quite a while in physics that she's been around in philosophy for a long time but certainly in physics and emergence I'm going to show you just a very crude example of emergence just to get your of your mind thinking about this and think that life might be an emergent phenomenon so an emergent phenomena is something that happens when you have simpler things that follow simple rules but lots of them and they all interact together and then something new comes out of that that you could not easily predict so here just for fun is a picture of birds flying around now this is a flock of thousands of birds and you'll see as they fly around that yeah individual birds just flying around if you just saw one bird you wouldn't be very impressed you wouldn't see very much okay but put thousands of them together and something happens things emerge out of this new structures forms fronts shapes emerge and it's very dynamic they appear and disappear a little more disorder and you wouldn't see any of this you wouldn't see these shapes to much order and you wouldn't see these shapes it's something that happens at that border between order and chaos and it comes out of the net interaction of many smaller units things like chemistry things like molecules things even like simple life forms like bacteria can exhibit emergence so what does that do for us well what I'm trying to say is again it's to do with the possible diversity of life the possible pathways that life could take because a solution to this conundrum between the evidence for being something special mediocre about life here and about us is that as you Niq or as special as we are there may be enormous potential for other equally unique and special planets out there and for places for life to emerge in the universe in other words I'll argue that the logical conclusion to this this sort of paradoxes conundrum between these pieces of evidence is that we may be special but not exceptional so we can be unique but not significant yeah we're special but so are those guys so are those guys so are those guys we're surrounded by equally complex special interesting life perhaps because then you can have your Copernican cake and eat it too so I have two more sides an interesting thing here because obviously to really solve this problem we need to find other examples of life in the universe that's something I've not really talked about tonight but it's a a big piece of the science that many many people are pursuing today but let's take it a little bit further what if not just detect another instance of life independent from our somewhere whether it's on Mars or whether it's on a distant exoplanet what if we could really go out and begin to evaluate the total abundance of life in the universe never mind just the galaxies galaxies kind of local and boring let's do the universe let's suppose we could do that well how might we begin to try it well we're taking baby steps so for example right now we're beginning to find ways to look for things like the core planetary gene set on other planets this little graphic is meant to illustrate the idea of looking at the chemistry of planetary atmospheres as starlight is filtered through them so let's suppose we have a planet and it passes between us and its parent star the Starlight is shining through the atmosphere now if you saw the lunar eclipse 24 hours ago well less than 24 hours ago and we look kind of red that's because the light from the Sun was passing through the Earth's atmosphere being diffracted and reddened and yes and any of any upon the moon so it looked kind of red well the same kind of principle could be applied to looking at planets around other stars on the right-hand side is just a crude cartoon to illustrate that if you look at Venus Earth and Mars and look at the spectrum of white coming from them whether it's through the atmosphere or reflected from them there is a fingerprint as a fingerprint of the chemistry of those atmospheres the chemistry of the atmosphere of the earth is in part determined by the core planetary gene set this kind of tool is something that astronomers are trying to apply to exoplanets right now we can only do it for large planets that aren't very earth-like in any respect in the near future we may be able to do it for some a handful of planets that could perhaps resemble the earth in some way it's a way to look for bio signatures now here's the really ambitious bit suppose we managed to do this we figure out how to do this and we can begin to do it systematically we can actually have some confidence that we're finding all the life out there there are complications maybe life isn't always so easy to see what would we get if we could not only measure the total abundance of life in the universe because it's going to be a finite number within the observable universe right that's it if there's more life out there it's a finite number a finite amount what if we could tie that to the fundamental physics that determines that number right so this is like the anthropic principle but now instead of just saying life or no life we're saying how fertile is the universe and how is that related to deeper physics well they're really wild an ambitious thing it'll come up here is it we could determine our significance in the totality of all possible realities we or me off to stage left it's maybe not so crazy to be thinking in these ambitious terms because if we could figure out what it was that made our universe of a certain fertility well we could take those rules and we can ask about those 10 to the 10 to the 16 other universes and figure out how many of those might contain a certain amount of life now what does that get us well satisfaction um it gets us a certain satisfaction because we Gary's good a quantitative answer to this question of our significance final yes yes you know life is something that happens in you know one out of every ten to the ten universes or something like that I don't know what we would learn from that but that's the point why you would do actually don't know what you would learn all right my last slide if you allow me to try to be a little poetic for a minute because all of this question of significance or insignificance kind of assumes that we don't have any option but to accept what nature gives us we're either special we're not and I think it's maybe nice just to end on a slightly more open upbeat note because there's another simpler option available to us because instead of saying well let's try and measure our significance where were you actually we can cheat we can cheat we can change our cosmic significance we can and we've started that already we may not have realized it but we've already started it this is Voyager 1 launched in 1977 it's now some twelve billion miles from the Sun it's heading out into the beginnings of the interstellar space medium interstellar environment this same pattern is a way in which we could alter that equation of significance or mediocrity doesn't matter whether there's other life out there in the universe we could change our footprint we could do something about it now should we would we why would we well I don't know but it's something that is within our grasp it's within our capacity and that may be the one thing that makes us special that we have that option available to us we can cheat the universe we can make ourselves I'll stop there thank you we talked a little bit about habitable zones around stars where water could exist in liquid form I don't think I've ever been chilled without habitable zones around galaxies arguments have been made that the Centers of galaxies are going to be too violent they are likely to be nearby stellar explosions and maybe even gamma-ray bursts and the outskirts of galaxies the amount of heavy elements will be too low doesn't that significantly decrease although maybe not that much the likelihood of like what's the latest on Galactic habitable zones yes so it's a great question and I think right now we we just don't know what the impact of those differing galactic environments is truly going to be certainly a lack of heavy elements may profoundly influence how many small rocky planets you can produce however we also know that stellar systems do migrate around in our galaxy so it's not a totally clear clear-cut case that certain regions of the galaxy will be utterly devoid of planet bearing stars then the question of the center of the galaxy where there are many many more stars pack together and there may be supernovae and other things going on to create a more difficult environment maybe a violent a violent environment that either disrupts planetary systems or dumps radiation on to them again we we just don't know yet ability to detect pilots is still somewhat limited when it comes to looking that far away I think it's an interesting point I think it's something that would if we could get to the point where we could systematically look for bio signatures it would be very intriguing to see whether or not assuming there are only positive bio signatures whether there's a gradient there are regions of our galaxy where clearly something went wrong for life so yeah so not a great deal has been done about this because we're still in the taking the baby steps to making real measurements but it's definitely something interesting I actually think it would be it would be really interesting to be able to look at a entirely different type of galaxy for example an elliptical galaxy which is a great fuzzy ball of stars which typically has a different stellar population and a galaxy like ours what's happening there maybe it's very different maybe it's barren maybe it's not we don't know it's a good question so I'll be Democrat I'll flip back and forth so it'll go to this side next has the earth increased or decrease in mass since the earth first dates of existence ooh that's a good question so the earth I guess has increased a little bit in mass and it's increased because in some respects the process of planet formation still hasn't finished so every year something like 40,000 tons of material it's meteorites and it's cosmic dust rains down onto the earth and basically adds to the earth mass so over time that's a certain amount it's not a huge percentage of the Earth's mass but the earth has gained something now it's also probably lost something through its atmosphere so I don't know exactly how the equation balances out so the earth is also a bit like a leaky boat and the atmosphere is constantly leaking away into space some of the atmosphere includes stuff like water that directly evaporated from the oceans and also carbon dioxide that's come from volcanoes so that carbon dioxide was ultimately in rocks so there's going to be some balance to that equation which I don't actually know my guess is that the earth may have gained more than it's lost but it's not going to be a great deal it's a good question so I'll flip to the other side if a if a core planetary gene set in Earth can be strong enough to survive an asteroid cross gosh do you think that there's a way to use it to contort can share it to create a medicine that would make someone so-called invincible to diseases let's just say the last good again I didn't quite catch the is there a way to conjure the gene sets' to make a medicine that would make someone invincible to diseases oh I see okay so to basically take the the tricks of the core planetary gene set and to apply them to Wow that's a good question that's a very inventive question and an interesting one well you know I think there may be lessons to be learnt from it when we examine the human microbiome this this mass of microbes that live with us because obviously if we take an antibiotic that's a bit like taking an asteroid and throwing it at the planet as a whole and seeing how we recover and how a planet recovers may give us some clues about about the the medical things that you could do from that so it's yeah that's a terrific question it's a really good idea I can't give you a much better answer at the moment mine's not as good of a question as hers but have scientists discovered another planet suitable for human life like a block up back up planet and if so what is it called oh gosh is there a back up planet um well so I think it would be fair to say that right now there may be two or three exoplanets planets around other stars that we think could perhaps be capable of supporting life now I can't tell you what the names are because they all numbered if they have horrible numbers like GL 581 and stuff like that which you can never remember but we don't know for sure because we're basing that on simply measuring where the planets orbit and how big we think they are so we actually don't know whether they have things like water on whether they have a water content it's possible that the back up planet the best back up planet for us is in the solar system and it's Mars and people like L on musk have expressed this as maybe we should be thinking seriously about putting a million people on Mars as some kind of back-up plan now obviously that's only a back-up plan for a while because as you saw the solar system in a billion years time is not going to be so nice for life and in five billion years time it's all over so really going to a backup planet around another star would be a very good plan and I think in the next five to ten years we'll probably identify those planets so what do you think of the idea of panspermia that is non intelligence driven natural processes that can transport life from one solar system to another yeah so that's that's also a great question you know it's an interesting idea I think it's had a checkered history that idea it was originally brought up as a way to solve what was perceived to be a problem in explaining the origin of life here on earth because we couldn't quite see how chemistry could get itself together to make things like RNA and DNA and so on I think we now have a deeper appreciation of things like emergence that might encourage that and so people said well let's outsource the problem well we'll say that life here was started because it was seeded from something that came from space the practicalities of panspermia now that the trend transferral of living organisms between planets of our solar system may be much more feasible okay microbial life might be able to survive transit on a chunk of meteorite between Mars and Earth for example true panspermia that's between stars I think is a whole other order of magnitude difficulty and if you add to that perhaps to say that it's not accidental there's something out there that this is how it lives it spreads through the stars in it and it then seeds planets it's going to have to have some strange biochemistry in order to survive interstellar space there's a lot of radiation damage in out in space that temperatures are very low and so on so I think it's an interesting idea and I think it's still open an open question perhaps it would be helped if if we find life on Mars and we discover that we're related to it that would suggest that at least short-range panspermia does work and then maybe that will open up possibilities for considering further afield panspermia okay um so if light has been around since the Big Bang then what percent of the universe is the observable universe like what we can see sorry say at the very last piece what percent of the universe is the observer oh gosh is it like infinitely small or so yeah it's a great question so so the first bit of that you know we we don't know if life was around thirteen billion years ago maybe maybe there was some very early life so the observable universe is just defined by the distance from which light has managed to reach us after 13.8 billion years now how much more universe is there beyond that beyond that horizon some people have said physicists who try to understand that the deeper physics of the universe have said that the full universe may be a trillion or possibly a billion trillion times bigger than the edge we can see which would mean that we're still a tiny tiny thing our whole observable universe would just be a speck within just just this universe not even talking about other youth verses I know that does that answer your question so that actually still might under a little but so I've seen multiverse images of multiverses usually pictured as sort of distinct spheres of stuff and not as sort of one big thing and you know there should be nothing special about you know a particular sphere in that sense because you know with just a small part of a bigger University that's what makes sense to me why is that distinct imagery used you know distincts for lack of imagination I really I you know I I guess I guess it's used because well it's a representative of this observable universe which is where why it is managed to reach us and if there are universes that have a closed geometry so they have enough matter in them that they won't expand forever then at least mathematically you might conceptualize them as spherical although it's not really quite right because you know space is expanding if people always ask this so you know what's outside the universe well we're still sort of in the origin and we always will be and so is everything else right so yes I think that the depictions of and I was guilty of it too little bubbles or spheres is really more of a artistic convenience and lack of imagination than anything else Oh formal questions okay so you said that um there were planets that can orbit two suns right so how are they able to orbit two suns at the same time great question so they do it because they're orbiting way out here so the two stars are going around like this and the planet is out here sailing around safely and it's actually very interesting because people weren't sure we would see any planets orbiting two stars like that because when you have two stars are pretty big things and their their gravitational pull is still strong out here and that planet can still feel the fact that these two stars are going around each other so it's not a great stable place for a planet to really be so it was kind of surprising to find that planets had actually formed in those systems and orbiting but they have to do it a long way out you can't it would be nice if you could do it sort of figure of eight loop around the - and I'm sure there is a an orbital solution that allows that but it probably won't last for very long if microbial somehow became extinct with all life on Earth and I'm sorry if microbial life oh yeah probably is that I think okay so we cannot function without our microbes right we you know some people I've heard microbiologist refer to us as cruise ships for microbes we we live to serve our only purpose well no and there's something to be said for this our only purpose is to provide a specialized habitat for those microbes and in order for that to work we have to be completely reliant on them so I think yeah there might be viruses left but I don't know what they would do so that's a great Wow there's some really good out-of-the-box thinking here tonight that's a great question what would some signs be when the earth slowly dies off because of the sun's heat is this significant or insignificant to Earth's history say the very first part of that what would some signs be when the earth slowly dies off because of the sun's heat what would the some of the science be um yeah okay so uh what would happen yeah yeah so the Sun like any star that's burning hydrogen in its core gets brighter and brighter as it gets older okay so in fact three billion years ago the Sun was 30% fainter than it is today which is actually kind of a mystery how the earth managed to stay warm enough so what would happen is it's going to take a long time there are systems on the earth natural systems do with plate tectonics and all sorts of stuff greenhouse gases that try to stabilize the earth temperature but as the Sun gets brighter and brighter those systems are not gonna be able to respond and they some include life but you don't have to include life it's just geophysics and so basically the earth is going to really what's going to happen I guess yeah again a really good question because this is at the forefront of trying to understand the nature planet one possibility is as things get hotter and hotter more more water evaporates okay water evaporates it gets higher and higher up in the atmosphere it gets to the top of the Earth's atmosphere and then sunlight actually breaks the water apart into hydrogen and oxygen the hydrogen can escape because it's lighter it escapes to space that means you'll never make that water molecule again so the planet literally dries out okay it actually loses water into space effectively and so I think that would be one of the key things that would happen is the plant is going to dry out there are other things that would happen but actually the end state we were not entirely sure what that end state would be somewhere else affect the function of life on Earth how would finding life or how would how would like if we detected life somewhere else how it affect sorry that's also a good question you know let's suppose suppose we find life let's say it's on Mars or another planet and there's something odd about it let's say it works differently than us and we can see that you know that would have big implications for understanding of the nature of life here it would tell us something about the nature of life's origins here and say well it can happen differently in other places it might also also point to different fundamental biological processes and then we might be tempted to go and look to see whether those actually exist somewhere here on earth I think there's a there's a misconception that we understand everything there is to know about life on earth we have no idea we've seen this much we didn't know very long ago that microbes bacteria and stuff like that we're so so incredibly important so I think you know the biggest effect it wouldn't be necessarily that oh the aliens are going to come and get us but it would be shaking our deepest ideas about the nature of life here I hope that's a reasonable answer it's a good question well let's thank dr. and I'm sorry we had to cut off the questions we're going to continue the whole discussion and dr. sharp is going to sign books right across the way in appreciation Hall in just a couple of minutes so people will go over there we'll be there in a moment

Channel: SVAstronomyLectures

Views: 87,624

Keywords: astronomy, science, astrophysics, science news, Cosmology (Field Of Study), Exoplanet (Celestial Object Category), extrasolar planets, Astrobiology (Field Of Study), Caleb Scharf, origin of life, life on Earth, evolution of life, Anthropic Principle, Philosophy Of Science (Field Of Study), Copernican principle, Principle of Mediocrity, Cosmos, Nicolaus Copernicus (Astronomer)

Id: ERp0AHYRm_Q

Length: 78min 54sec (4734 seconds)

Published: Tue Oct 28 2014