Dr. Carl Sagan Speaks at IMSA

[Music] you [Music] good afternoon and welcome to the first james r thompson leadership lecture at the illinois mathematics and science academy my name is dawn Nordland and i have the privilege of serving as executive vice-president of the MC fund for the Advancement of Education which fund board is headed by governor Thompson the MC fund is a not-for-profit corporation that enlists private sector investments in the illinois mathematics and science academy as most of you know EMSA is the nation's only three year public residential high school for talented mathematics and science students equally important the academy serves as an educational laboratory for developing and testing innovative programs to share with other schools school districts teachers and students in Illinois and in the nation private sector gifts provide margin of excellence resources for M sub last year was our most successful fundraising year corporate foundation and individual donors gave seven hundred and eighty thousand dollars to the M sub fund a 42 percent increase over the previous year the James R Thompson Leadership lecture series is just one example of programs made possible by these private gifts at this time it is my privilege to introduce the talented and visionary leader of this pioneering educational institution M TSA's executive director dr. Stephanie pace Marshall Stephanie [Music] Thank You Don in good afternoon this is a very special and proud day at the Illinois mathematics and Science Academy and on behalf of the Board of Trustees the faculty staff and students of EMSA welcome to the Academy and to the inaugural James R Thompson Leadership lecture at a time in our nation's history when national and international attention is once again focused on achievement in mathematics and science it is indeed fitting that our first Thomson Leadership lecture would focus on science and its contributions to human understanding and would feature one of the world's foremost science scholars at this time I would like to recognize several very special friends of EMSA first and foremost the man in whose name this lecture was established and one of those in whose honor this school was dedicated please join me in extending a very warm welcome to governor jim thompson and his wife jane I would also like to recognize two special advocates of M sub senator Forrest Etheridge and representative Susan Deutsch lair both have been strong supporters of the Academy and indeed education in all of Illinois we are delighted that they could be with us today Forrest [Applause] it is also my pleasure to bring you greetings from Governor Jim Edgar who was not able to be with us today but he has sent a letter and I would like to read it to you my friends as governor of the state of Illinois I am very pleased to extend a personal greeting to everyone attending the first James R Thompson leadership lecture presented by dr. Carl Sagan Illinois's most valuable resource is our young people and I commend the vital role dr. Sagan is playing in nurturing that source I am certain this enriching rewarding experience will result in new ideas and developments education is a lifelong process and it is my hope that you will continue to take advantage of all future educational possibilities as you our stars of tomorrow strive for excellence with best wishes Jim Edgar governor [Applause] we are also very pleased to have with us members of the EMSA Board of Trustees the Imps of fun Board of Directors the Alliance Council and local government officials and finally we are delighted to welcome our corporate foundation and individual donors to the EMSA fund we thank you for your generous support and we look forward to forging even stronger partnerships with you at this point it is now my great pleasure to introduce Walter Lee the president of the EMSA Student Council Thank You dr. Marshall good afternoon on behalf of the student body faculty and staff of the Illinois mathematics and Science Academy it is my pleasure to welcome our special guests from various schools of Illinois we are truly delighted to have with us student representatives from our neighboring high schools in Aurora and to welcome our 1991 EMSA jr. scholars who come from various schools in Illinois in addition I would like to welcome those teachers from throughout the state who are participants in M says summer adventures and impact two programs each teacher was invited to bring his or her principal and a student and we are pleased to have you with us as well it is also my pleasure to welcome some very special members of the MC community those parents alumni and alumnae parents who are with us here today and finally last but not least welcome to the members of the media we appreciate your interest in Education Science and EMSA again welcome to all of our guests I hope you enjoy the first James R Thompson Leadership lecture Thank You Walter it is now a privilege and pleasure for me to introduce our speaker today dr. Carl Sagan is the David Duncan professor of astronomy and space science and director of the laboratory for planetary studies at Cornell University he is president of the Planetary Society the largest space interest group in the world and is a distinguished visiting scientist with the Jet Propulsion Laboratory at Caltech dr. Sagan as you know has played a leading role in the Mariner Viking and Voyager expeditions to the planets his scientific research has enhanced our understanding of the greenhouse effect on Venus dust storms on Mars the organic haze on Titan the origin of life and the search for life elsewhere for 12 years he was editor in chief of Icarus the leading professional journal devoted to planetary research in addition to more than 600 published scientific papers and popular articles dr. Sagan is author co-author or editor of more than 20 books his Emmy and Peabody award-winning television series cosmos has been seen in 60 countries by more than 400 million people his accompanying book also called cosmos was on the New York Times bestseller list for 70 weeks dr. Sagan and his colleagues have been engaged in research on the long-term consequences of nuclear war and partly for this work he was given the annual awards for public service of the Federation of American scientists and of physicians for Social Responsibility he has received numerous other awards among those 18 honorary doctorates from American universities we are honoured and most fortunate that dr. Sagan also serves as a member of the Illinois mathematics and science academies national advisory board and it is that reason that he is with us today several years ago in speaking about the importance of emphasis mission dr. Sagan said the following and I whoa the need to understand how the universe works is fundamental to human nature it is also essential for safely managing the human future but foolishly we have designed a society based on science and technology and which hardly anyone understands Science and Technology this is a clear prescription for disaster our future depends on producing and encouraging highly competent ethically responsible young scientists as well as much greater scientific literacy in the general public the illinois mathematics and Science Academy in Aurora Illinois is dedicated to meeting this challenge it is a gift from the people of Illinois to the human future today I am honored to introduce a man who has dedicated his life to advancing scientific knowledge promoting the ethical applications of science and increasing the general public's understanding and appreciation of the beauty Wonder and mystery of science I don't know how technical and detailed dr. Sagan will be in his remarks but just in case you cannot comprehend or recall all that he will tell us today about comets and the Oren's of origins of life I came across a crystal clear explanation that should assist us it was in the Sunday comics two weeks ago in the comic strip mr. buffo proudly displayed on mr. burrows t-shirt was the following statement on the creation of the universe attributed to Carl Sagan it was late it was dark things happened fast [Applause] would you please join me in welcoming one of the world's premier astrophysicists dr. Carl Sagan excuse me on the lights yeah all these lights on all of these organs don't cause a sound problem there mercury vapor can cause that little band buzz because of it magnetic field vector Thank You dr. Marshall for that generous introduction what we've been talking about here is with the lights a lot of lights on me and only a little bit of light on you you can see me which you may or may not be happy about but I can see you which I'm unhappy about because I like some feedback loop with the audience so I'm hoping that we can have a little more light in the audience and these lights on me off that's good I'm really pleased to be here with you I will not spend any time explaining to you why it's important for people to understand science for one thing dr. Marshall quoted me on it and for another thing you wouldn't be here if you didn't understand that yourself what I'd like to do is to talk about a subject which in a way is extremely fundamental is wonderfully interdisciplinary and about which we are actually beginning to learn something that you know it might not have been true we might have been wholly ignorant about this fundamental subject but we've been lucky and the subject is the origin of life now what are we talking about when we talk about the origin of life we look at life around us and I don't just mean the students at this institution but all the life on earth we see what seems to be a wonderful diversity all the beasts and vegetables and microbes and if the earth were only a few thousand years old as people believed for a long time by adding up the begats in the book of Genesis um then the idea that that some organisms evolved from other organisms evolving from very simple organisms that was just a silly idea and hardly anybody believed it and for good reasons but if as we now know the world is four-and-a-half billion years old as we know beyond the shadow of a doubt from radioactive dating among other other methods then there is time and the critical insight into what was possible if the world was very old happened in the epical publication in 1859 of Charles Darwin's book the Origin of Species and their Darwin proposed a mechanism by which evolution could occur it's at once ruthless and heartless and at the same time subtle intricate beautiful he called it natural selection the idea is extremely simple and all you have to do is just think about it for a few minutes and it's clear something like that has to be true and it goes like this if children resemble their parents in their hereditary characteristics if young animals and plants resemble their parents if there is a hereditary transmission of information and if that information is subject to any kind of variation of the sort that we today would call mutations then there will be slightly different organisms in each generation from the previous generation some of those organisms by accident will be better adapted to the environment some will be less adapted and the differences might be very tiny the differences might have to do with the biochemistry or length of the bones or ability to run faster breathe air or resist disease or anything if also organisms reproduce rapidly so that under the best conditions there get to be huge numbers and therefore competition between organisms is established then natural selection will favor certain organisms and do the opposite for other organisms there will be a steady progression of change certain mutations will be selected for certain other mutations will be selected against and this winnowing the organ organism selected against die or don't live as long or at least need fewer offspring and so working in this way small changes every generation over an enormous period of time major changes in life can happen and if you think about the lifetime of human beings compared to the lifetime of the planet maybe the average person is a few decades old the earth is a few billion years old so the average person lives for 100 million the age of the planet and therefore how could we possibly understand from what we ourselves see in our own lifetime the progression of evolutionary change to understand that you must go to the fossil record and so Darwin not only recognized the principle mechanism for evolution and its power but also proposed rather diffidently he before he got into that line of work he had intended to be a minister a preacher in the Church of England he proposed that humans as well as all the other beasts and vegetables had evolved the humans came from a nonhuman primate ancestor who would look certainly something like an ape to us if we were introduced to him or her that our primate ancestors evolved from other mammal ancestors the mammals from reptiles the reptiles from amphibia amphibia from fishes and so on back to some very simple organism that was the ancestor of everybody on earth and in that sense incidentally stressing a deep kinship of all the plants and animals on earth were all cousins and it was Darwin who first explicitly stated this by a mechanism which actually makes sense but you might think this doesn't explain explain some things but it doesn't explain the fundamental question because we're did that first ancestor come from and there Darwin was stumped or almost stumped there is one curious line he wrote in a letter to his friend Joseph Hooker who was the president of the Royal Society of London which went something like this if only Darwin said we could imagine a warm little pond somewhere in the ancient history of the earth in which certain molecules were interacting and then dot dot dot uh and he even said what some of those molecules might be and they are what we call organic molecules plus he explicitly said ammonia plus phosphates for 1870 or so this is a remarkably good insight even though it was something he never actually published just in private correspondence so Darwin had the idea that the origin of life was connected with the origin of certain organic chemicals now all of life today on this planet at least is based upon one category of molecules called the nucleic acids and the nucleic acids encode supervise the construction of another category of molecules called proteins and certainly life on Earth is mainly the business of nucleic acids and proteins if we could understand the origin of nucleic acids and proteins without pre-existing life we would certainly be making a substantial step forward towards understanding the origin of life it's not the same thing if you have the building blocks just lying around that doesn't mean you have a living thing but if you look more closely you see that the nucleic acids are in a way self-replicating molecular systems under the right conditions they make identical copies in themselves if you could imagine an early organism which was no more than a molecule that could make copies of itself then you might be there or pretty close if you had a molecule which could crudely make copies of itself then there would be mutations the replication would not be perfect cosmic rays would produce changes in the molecule and so then the next generation that that molecule would copy would be changed in that direction well that's all you need if you have replication and mutation natural selection is working and since we know that the nucleic acids are self-replicating it's a very major step towards understanding the origin of life if we can understand the origin of these particular molecules so I want to stress it's not the same thing but it's a major step there so okay where did this stuff come from four billion years ago I say four billion years ago because we know the epoch of the origin of life pretty well better than 10% accuracy and the argument goes like this the earliest fossils we know are about three-and-a-half billion years ago although the carbon isotope chemistry from sediments that a 3.8 billion years ago maybe indicate the presence of life even then it's hard to find fossils back then because there's hardly any pieces of continents that they back that far so there's a paucity of the geological record and it might be that there are fossils a little bit earlier than that the earliest fossils we have are of colonial microorganisms and so that's that's fairly advanced they could not have been the first organisms and so there had to be a substantial period of time before that for the first organism then running the other way the earth at the time of its formation was a very inhospitable environment because the earth fell together pieces from the sky and in the process was melted and produced a steam atmosphere and the pieces that made the earth continued to fall and in a certain sense they're still falling today every impact of a comet or an asteroid which I'll come to shortly is in a way the very tail end of the distribution function of the falling together of the earth and in the early days before the solar system was cleaned up by collision stuff was falling from the sky all the time and big things falling from the sky you can see might make the earth an unpleasant place especially if it would melt large areas of the earth and even by 4 billion years ago there were occasional massive impact by 4.1 and 4.2 billion years ago sterilizing impacts that we just sterilized the whole ocean or or vaporize the whole ocean and send it off into space we're still occurring so you can see the time of the origin of life is bounded and it's maybe between 4.2 and 3.8 billion years ago roughly speaking would call it four billion years ago and there's some people who think that if the origin of life happened quickly in terms of the geological timescale at least that maybe it's a probable event maybe you just set the conditions right and pow life arises now nobody has ever done an experiment in which you I don't know mix together the gases and waters of the early Earth and have stuff falling from the outside maybe and shine an ultraviolet light and zap it with electrical discharges for a while and then at the end of the experiment somebody crawls out of the reaction vessel nobody's managed to do that we're very far from that but in the other hand making the building blocks of the proteins and nucleic acids there as I will explain we've been very successful you know I sense you have lecturing here and that is every time you wave your hands there's a bright light that goes off it's it most remarkable correlation and and when I leave here I'm gonna have this disappointed sense of a sort of superpower lost you know William Huggins was a mild-mannered 19th century astronomer who scared the world he didn't mean to who's just minding his own business which was spectroscopy but one thing led to another you can never tell what's gonna happen if you're a scientist you're you're very arcane mm-hmm abstruse work may suddenly have all sorts of social relevance and you better be ready for it so here's what happened he was a pioneer I'm gonna take off my jacket he was a pioneer in looking at astronomical objects having their the light from them passed through a telescope and then a spectrometer which dispersed the light into its constituent colors and then recognizing the signature the pattern of absorption lines which gave you some idea of the chemistry of the source often of reflected sunlight off a solar system object or emitted light from a distant star he succeeded in in recognizing the some of the atoms and distant stars he looked unsuccessfully at planets and sort of as a fluke he looked at comets and he found a set of absorption lines and comets which were different from those in Stars and couldn't figure it out for a long time what it was and then he and some French scientists the French scientists must have been especially good at this thought to look at the absorption spectrum of olive oil which I imagine was sitting around more in the French labs than in the English lab of William Huggins and to their amazement Olive Oyl looked like comets now if only it were true we would have an economic motivation for space flight that is missing today but what it turned out was not that there was aa Lavoie 'el there but that if you vaporize and dissociate olive oil you produce a molecular fragment C - two carbon atoms attached to each other which is also up there in the comments and so although they didn't use this word exactly this was evidence for organic matter in comets Organic of course merely means a molecule based on carbon it doesn't mean of biological origin there are astronomers who refuse to use the word organic because they're worried that people will misunderstand that it means a biological origin and a colleague of mine calls it the O word you find all sorts of of circumlocutions that astronomers use including they say carbonaceous carbon containing and then after the experimental results on Halley's Comet a new phrase was introduced tuned particles c h o and carbon hydrogen oxygen nitrogen it made your effort to avoid saying the word organic but I hope it won't offend anybody I'm gonna just use the word organic as chemists routinely do well so Huggins discovered some organic matter in comets big deal but he continued over the years and then in the 1880s he found evidence for not the molecular fragments EC but the molecular fragments see em the night trial radical except it has another name names count in this business the other name is cyanide and but nobody paid much attention to that until just before 1910 because in the year 1910 first slide please the earth was predicted to pass through the tale of how is common I'll of course need the lights down with the slider thank you the small intelligence test posed to be here turning off the light this life I failed the test so this is the idea the tail of the comet pointing away from the Sun the earth thank you passing through the tail of the comet and then people suddenly thought my goodness there's cyanide in the tail of the comet prussic acid is potassium attached to the cyanide radical and a single grain of prussic acid on your tongue can kill you so the idea of enormous quantities of cyanide in the tail the comet the earth passing through it scared lots of people there were sustained national Penix in Japan and Russia a hundred thousand people in Constantinople ran to the rooftops in their night clothes people in Chicago stuffed rags and newspapers under their doors the Pope banned the birdie hoarding of cylinders of oxygen in Rome a smattering of people all over the world committed suicide because they they didn't want to die by poison gas and poor William Huggins was responsible for all this and he never talked to a reporter in his life now what's more there were lots of scientists he said wait a minute it's not even clear that the earth is actually going to pass through the tail of the comet and if it does we can calculate what the density of cyanide radical is and it'll be at the very most one part per trillion of stuff in the air and you can breathe that amount of cyanide it's not that one atom of cyanide will kill you and people said it's less dangerous than breathing the noxious atmosphere of London um but that did no good once the idea was in the public mind people got tremendously worried well except for the people who committed suicide nobody died in 1910 because of Halley's Comet except for the fact that William Huggins died in 1910 but not from cyanide he was 85 years old well the curious fact is that the molecule in question hydrogen cyanide is a key precursor for the synthesis of amino acids the building blocks of proteins and the nucleotide bases the building blocks of nucleic acids it's a really strange fact that this molecule which can kill you if you happen to be an oxygen breather might in fact have been central for the origin of your distant ancestors I'll come back to that shortly what I'd like to do now is to give just a quick sense about what comets are and talk about their involvement in the origin of life next slide please this is a montage of the views in various cultures of what they saw when a comet came by except for the last two before the era of the telescope and you can see that that people had quite different views including this as you might guess medieval rendition which was that a comet looked like a sword even here comets are psychological projective tests there's a few other representation of comets I haven't included here people see what they're sort of interested in but what was it most people thought that either was something was a sign sent by God to warn us of impending disaster that's always been sitting on the edge of scientific interest in comets or Aristotle's view that it was a sort of meteorological fire in the upper atmosphere an exhalation from the interior of the earth that stayed fiery in the air so the question is is this something in the Earth's atmosphere as almost everybody thought or is it something astronomical in the 16th century the Danish astronomer Tycho Brahe he Johannes Kepler's teacher realized that there was a way to answer that question next slide please if you had two widely separated observing stations on the earth and the comet was low close to the earth in the atmosphere then this guy looks at it and will see it against one background set of stars one constellation and this guy looks at it and sees it against a different background and therefore there's an excellent way to see if it's down low if on the other hand is far away next slide please then two widely separated stations will see it more or less against the same and this method which is known as parallax in which many of you probably know about not only works qualitatively but it works quantitatively by the relative shift against the background stars you can tell in fact how far away it was well brah he organized a cooperative international program to examine a comet and found beyond any doubt that the comet was beyond the moon trans lunar distances which everybody thought really bizarre especially because the prevailing religious doctrine was that nothing could change in the heavens that was one of the main reasons people wanted comets to be down in the atmosphere but it's mathematics hard to say no to what a comet in fact was was not frittata brought he to figure out and this was I'll come to it in a moment the a and insight provided by Edmund Halley but let me let me show you what the contemporary context of comets is next one so here's a schematic of the inner planets of the solar system Mercury Venus Earth Mars and this scale is one astronomical unit there's something pathetically chauvinistic but astronomer is deciding that the Earth's distance from the Sun is an astronomical unit you measure the whole universe by our distance from the Sun but it's a kind of conceit that we have to live with well the earth is one astronomical unit from the Sun by definition and here is a so-called short-period comet which you can see lives more or less in the inner part of the solar system next slide this scale is a hundred astronomical units so everything we saw in the last picture is within this little square and so here's the orbits of Jupiter Saturn Uranus Neptune and Pluto and this highly eccentric or elliptical orbit is the orbit of Halley's Comet which as you see lives part of its time out beyond the orbit of Pluto the next slide increases the scale to a thousand astronomical units everything we saw in the last one is in this little square and here is the orbit of a not unusual longer period comet called comet mirko's and it mainly lives far beyond the planet and it intersects a very interesting regime into which no spacecraft has yet ventured in which the cometary nuclei silently frozen orbit the Sun and if we go out to the next step of 10 next slide to a 10,000 astronomical unit scale then we find ourselves in what is called the Oort cloud of cometary nuclei a spherical cloud of maybe a trillion comets typical size of one maybe a kilometer across that orbits the Sun every now and then a passing star or a passing interstellar gas and dust cloud shakes up the Oort cloud makes a ripple and occasionally a comet will be redirected in the new orbit down into the inner solar system and there's a new comet in our skies what's more of the short period comets were probably captured by the planets in the inner solar system from original long-period orbits so the Comets come from halfway to the nearest star by and large they are visitors from the interstellar dark they're not the same as the stuff in the solar system the fact that they might be carrying organic matter is made doubly interesting by the distance of their origin next slide here is now for the inner solar systems the orbit of Jupiter a small fraction of the set of orbits of comets look how many there are look how the orbits all intersect each other and it's very clear that if the earth is orbiting something like this once a year and these guys are bopping in and out once every few years and the earth lives for four-and-a-half billion years that you can't avoid some of these guys bumping into the earth collisions with comets just unavoidable and as you go back earlier in the history of the solar system it's much more unavoidable next wide comment is made mostly of ice every time the comet comes close to the Sun about a meter thickness of the ice evaporates and eventually after enough perihelion passages all the ice is gone and so all that's left is the non icy stuff mainly rocky material and organics and some of that becomes fragmented and so what you have is the orbit of the comet begins to be filled up with these fine particles the whole orbit each spine particle is a separate little comet or planet circling the Sun well if the earth plows through that orbit these fine particles is gonna enter the Earth's atmosphere within a certain size range the small guys burn up a blade away in the upper atmosphere mainly about 100 kilometres up and so when you're outside walking on a clear moonless night maybe at the time of the Perseid meteor shower and you look up and you see a lovely little flash that is a piece of a dead comet in its last moments before being dissipated into atoms and I think that's a much more poignant and lovely and realistic view than the other view which is that it's something the size of the Sun falling into the Earth's atmosphere right a falling star think of how that phrase is built into the language and into poetry and what an erroneous view of nature it carries with it in the same sense that the word sunrise and sunset are pre Copernican they are words that come from a time when everybody imagined the earth was stationary and the Sun was moving rather than the other way around the language has fossils in it as well as the geological record the next slide shows that bigger objects entering the Earth's atmosphere also burn up this is called a fireball and a number of UFO reports are due to pieces of comets larger than the dust sized or pea-sized objects that make me yours very little particles float down like a fine ring they are slowed down so quickly that they do not burn up and very big particles massive objects boulders city sized objects will traverse the Earth's atmosphere and make it to the surface without much burning up there will be an ablation crust on the side that will burn up but the body of the thing will make it to the surface of the earth I'll come back to that as well next slide now pieces of comet come to us as I've been saying but they mainly burn up it's hard to get a piece of a comet we also fly airplanes at stratospheric altitudes a message is being sent to me of it we also fly airplanes at stratospheric altitudes with the kind of flypaper on their wings to catch dust particles from comets it's very hard to grab a piece of a comet so in addition to the Comets coming to us we can go to the Comets in 1986 Halley's Comet made it next return to the earth after the Huggins 1910 apparition it it orbits the Sun every 76 years so 10 plus 76 is 86 just like clockwork it was back but by 1986 for the first time the human species had invented a means to go and greet Halley's Comet and find out what it was so there were two Soviet spacecraft this is a representation of one of them called Vega that carried a set of instruments from 17 European nations plus the one American instrument which got a board despite the best efforts of the Department of Defense to prevent it a European spacecraft called Giotto which had contributions from 13 European nations and the first two interplanetary spacecraft of Japan they were more elementary spacecraft and they flew by at a greater distance conspicuous by its absence was a spacecraft from the United States it was it was voted down in the White House because it was too expensive it would have cost as much as a single b-1 bomber of which we were then committed to purchase 199 would have compromised national security so as a result there are no American spacecraft why Halley's Comet and this may be a chauvinistic remark as a result of that there are missed scientific opportunities about understanding Halley's Comet the Soviet spacecraft and especially the European spacecraft Giotto get very close Giotto got within a few hundred kilometers of the nucleus of the comet see there's a solid object in there and then there is a fuzzy cloud of gas and dust called the coma and then the gas and dust is blown back by radiation pressure in the solar wind to form the long and lovely tails of comets and what we see from the earth is a little bit of coma and mainly tail and the nucleus hiding in there that nobody has seen what these European and Soviet spacecraft did is fly through the coma almost colliding with the nucleus to see what the nucleus of a comet looks like and the next slide shows you this dark shadowy peanut shaped object it's about ten kilometers across long dimension is the nucleus of Halley's Comet it's very dark the amount of sunlight that it reflects back is something like three or four or five percent that's very dark that's as dark as black velvet and that is in fact one piece of evidence for what organic matter and what you're seeing here are jets of ice blowing off the comet heated by sunlight vaporizing carrying dust in it and that will later form the tail next slide is maybe you can see a little bit better I recognize people in the back some of this may be hard I apologize for that but you can see maybe more clearly here the nucleus he's coming now there were instruments onboard the spacecraft to look for chemistry something like a mass spectrometer and what is very clear is that Halley's Comet is rich in organic matter it's made in fact about 25% of a variety of organic molecules the trouble is for technical reasons which if anybody's interested I can outline in the question period the reliability of specific identification particular organic molecules is weak but that their organic is clear okay so if comets are loaded with organic matter if comets hit the earth today there was a little one that hit hit Siberia in 1908 and if they hit the earth with much greater frequency at the time of the origin of life maybe your organic matter played a role in delivering to the earth the stuff from which life emerged next slide so here is an artist's conception this is the Japanese artists Kazuaki yo Socky a lovely picture of the earth around 4 billion years ago the moon is closer to the earth then so it looks bigger in this guy what is represented here is that this stuff falling from the outside exogenous material and stuff generated in this case from lightning on the inside down here endogenous organic matter right exogenous the X Oh is the same root as exit meaning out and endogenous the endo root is the same as entrance so molecules from up there molecules from down here what is the relative contribution of these two next one um this is a schematic representation of a mechanism of the production of amino acids the building blocks of proteins as fully demonstrated in the laboratory if the earth were hydrogen rich the universe is hydrogen rich the giant planets are hydrogen rich hydrogen rapidly escapes from the earth it is plausible that the early atmosphere of the earth had a lot more hydrogen than it does today so up there is water this guy and this guy is methane this is ammonia if such molecules are struck by ultraviolet light or charged particles they fall to pieces the radicals recombined you can see the pieces here and to the principal products are guess what hydrogen cyanide HCN and there's an atom right there you can't see very well formaldehyde and these two materials cyanides and aldehydes together with the ammonia in the air and the water in the oceans readily form with high-yield amino acids so there's something quite remarkable you take very common stuff very simple molecules apply any energy that breaks them into pieces and then they recombine and form some of the molecules of life wouldn't have to be that way and we are we learn something from the fact that the laws of physics and chemistry permit this 'ready synthesis of the building blocks of life next slide well you can calculate how much ultraviolet light there was in the early environment of the earth measure in the laboratory the efficiency of production of organic molecules and then integrate and get the total amount that must have fallen of course molecules fall to pieces as well as being synthesized and so you calculate what the steady-state abundance of organic matter could have been in this case from ultraviolet light and endogenous source next slide endogenous production of organic matter is happening today it's not on the earth because we have an oxygen atmosphere but on Titan the big moon of Saturn where the Voyager spacecraft found gas phase simple organic molecules including HCM and this pinkish impenetrable cloud layer is made of complex organic solids and those solids if you drop them in water make lots of amino acids and in similar experiments the building blocks of the nucleic acids are also produced so it may be that on Titan in a frozen state is an enormous amount of the products of pre biological organic chemistry the stuff that four billion years ago on the earth led to the origin of life maybe not gone very far on Titan because ordinarily it should be very little liquid water their surface temperature is 95 degrees above absolute zero but on the other hand through cometary impacts and maybe through some tectonic activity there may be episodic melting of ice and maybe there is a little liquid water chemistry there we don't know we hope to land there sometime early in the next century back to earth next slide so that was about endogenous now about exogenous this is a picture of course of the moon you can see Aurora Illinois right there and as you well know the Highlands the uplands of the Moon are cratered but saturation cratered so craters fall on top of craters and the whole surface is full of craters and there's no erosional processes on the moon are almost none so we are looking back to very early times the moon is an impact counter and since the moon is close to the earth it's very likely that the moon would have received all these impacts and the earth not we have very few craters today but that's because we have running water which erodes the craters so from the lunar crater in record you might be able to figure out how much stuff fell on the earth four billion years ago next slide and here is a curve of the number of craters larger than a certain amount per unit area on the moon as a function of the age of the surface how do we know the age of the surface the Apollo astronauts and the Soviet robotic lunar vehicles brought samples of the moon back from different places got a sample measure its age by radioactive dating compare it with the crater count and there is a correlation and so four billion years ago you know roughly speaking you can see the arrow bars how many craters were falling per unit time per unit area on the earth or the moon and if that stuff was mainly or half or 10% comets you can figure out how much organic matter was produced next slide well I don't want to spend any time on this but just to indicate that both from exogenous sources and from endogenous sources you could calculate how much organic matter per year fell on the earth at each epoch from different sources in the next slide likewise and so then it's possible to do an inventory and see how much of the stuff there was can I have the lights please no no the lights there Yeah right thank you so what it looks like is that there's certainly fair room for uncertainty here but with even within the range of uncertainty there looks like there was a huge amount of organic matter on the early on the early Earth so much that in the most optimistic case if you mixed it into oceans of contemporary extent and depth you would have a solution of organic matter with about the constituency of Campbell's beef broth now that's that's a good medium for the origin of life few hundred million years of that amino acids nucleotide bases um you might make a lot of progress for the origin of life there's a lot of other work on the origin of life that is being done including stuff on self-replicating RNA a kind of nucleic acid molecule which has the magical property of also being able to catalyze to act as enzymes which are otherwise all proteins and there are experiments in which amino acids link up into things like proteins there are experiments in which nucleotides linked up into things like very short nucleic acids in the 35 or 40 years since such experiments were first done at the University of Chicago by the way enormous progress has been made but we can hardly say that we're there at the origin of life but it it seems very likely that through some mix of up there and down here of exogenous and endogenous huge amounts of organic matter of the right kind we're on the earth at the right time and so in this sense we are the beneficiaries of the Commons but this is not the only way in which comets have influenced our evolutionary history and I'd like to end with another way in which we are beholden to the comments in what follows I will say comets but it's possible that what I mean is big asteroid suppose you were an extraterrestrial visitor extraterrestrial survey biologists drop down onto the earth for just a brief period of time look around examine the biology but swiftly make a brief report and then on to some other planet there are so many planets the Milky Way galaxy you can spend a huge amount of time on any given one and you will leave it to graduate students to fill in the details later suppose you were dropped down on the earth not today but a hundred million years ago let's say you would find on earth rich amazingly rich in life but it would not be life of the sort that we are familiar with today or at least not at first glance next slide please instead it would be an earth with guys like this animals bigger than trees this is the earth of the dinosaurs they were on the land in the water in the air they had filled every ecological niche they had been there for something like a hundred million years before this time compare that with our species who has been here for only a few hundred thousand years they were a thousand year a thousand times longer lived than we are up to now this was their planet next slide and some of them were fearsome hunters note all the little sharp teeth right there now where were we 100 million years ago well we weren't humans hadn't evolved yet we were at most a possibility our direct ancestors were little mouse sized timorous cowering nocturnal insectivorous malice insectivorous means we ate bugs nocturnal means we came out at night why do we only come out at night that's why now part of your job as the survey biologist of the earth 100 million years ago is to predict the future course of evolution on this planet who would you bet your money on the mouth the mouth sighs guys who eat bugs and come out at night or these guys who'd been around for a hundred million years I mean not this exact species because the dinosaur is also revolving I think there's no question you would bet on the dinosaurs and yet 65 million years ago something happened which in a very short period of time geologically speaking wiped out all the dinosaurs every last one of them was killed all over the earth every environmental niche and not just the dancer but most of the species of life on Earth most of the species of plants most of the species of animals supposed to the species of oceanic as well as land-based organisms some terrible colossal catastrophe happened to the earth what was it next one the American physicist Luis Alvarez had the nice idea let's examine the atomic chemistry of the layer in the rocks corresponding to the time when the dinosaurs got wiped out so here is a section from a famous part of the Earth's sedimentary calm from Gubbio Italy down here this white stuff is chalk generated by the microscopic calcareous foraminifera that lived in the Cretaceous sea at the time the dinosaurs were flourishing right these guys took carbon dioxide from the air and made calcium carbonate shells and then they died in the calcium carbonate felt to the ocean bottom and were huge numbers of them and over millions of years a big amount of chalk build up most of the chalk that you use on your blackboards comes from these little guys who are contemporaries of the dinosaurs the White Cliffs of Dover are made of in england are made of the remains of these microbes these sub microscopic guys okay so here we are and here it stops this is time of dinosaurs this is not no dinosaur fossils up here and as you can see there's a transition layer look at that right there and it's made of clay and it corresponds to the time that all those organisms including the dinosaurs got wiped out so naturally we would be interested in seeing if there's anything strange about that layer what Alvarez found is that there was a an anomalously high abundance of certain atoms of which the chief one is iridium which is not a household word or at least wasn't until this discovery chemical elements whose names are unfamiliar are most likely rare because they were abundant there would be names for them that everybody heard of the reason there isn't a lot of iridium at the Earth's surface is that it likes it has an affinity for iron and when most of the iron in the earth segregated out to form the core of the earth the iridium was carried with it whereas in objects like comets and asteroids which we're not big enough to melt and do core formation the iridium remains distributed so meteorites that come from asteroids have lots more iridium than the surface of the earth so the Alvarez contention was that the reason there's a lot of iridium in here is because an extraterrestrial object hit the earth and splashed its iridium all over the earth from the fraction of iridium in meteorites you could calculate how big an object did it have to be to distribute that amount of iridium all over the earth and this is all over the earth not just in Gubbio Italy dozens of places you dig down in the sedimentary column there and you find accessory diem the impacting object had to be Alvarez calculated about ten kilometres across that is the size of Halley's comet and therefore the berkeley group proposed that 65 million years ago a comet or asteroid hit the earth and that made lots of guys die how next slide so here's an artist's view of this comet hitting the earth if the Comets ten kilometers in size and the Earth's oceans are only three kilometres thick then the impactor doesn't care about the oceans it's just the same situation as if there was no ocean it's like one of the big impact craters on the moon hits the earth carves out a huge impact crater the impactor fragments the material it is excavated from the crater fragments and these fine particles are blown up into the high atmosphere and indeed off there some of it off the earth all together into an orbit that the earth gradually sweeps up Andrea Crete's from it's in fact now thought that it fell not in the ocean but on the land near the Yucatan Peninsula in Mexico the next slide shows the result darken skies all over the earth lowered temperatures both of which caused much but not all vegetation to die herbivores have no plans to eat and also are probably not well adapted to the cold they die carnivores have no herbivores to eat they die you can see a forlorn Triceratops extremely unhappy you can tell from the facial expression to say nothing of the remains of other nine asuras littering the landscape he has a lot to worry about on the other hand I don't know if many of you can see it but there is an extremely happy animal in this picture right there see that little guy four legs and a tail his head is up and there's a little smile on his face right there that guy is our great great great great great and a large number more grades grand parent the death of the dinosaurs removed the principal predators the principal enemies of the mammals suddenly the world was theirs the competition had been removed and so there got to be a fantastic efflorescence of the mammals filling lots of ecological niches and this so-called adaptive radiation of the mammals we are the beneficiary of let me have the lights for a moment please it's impossible not to have this thought suppose the comet that hit the earth 65 million years ago missed it by a little bit I mean after all the comets are are jetting know these these great Jets of vaporized ice come off and just like you know a blown up balloon you let it go and and then the balloon does all this weird coursing about it's essentially the same was a rocket engine so if there were a slightly different distribution of pockets of ice it would have been different jetting and slightly different non Newtonian motion of the comet and it could have missed the earth could easily have missed the earth suppose the comet hadn't hit the earth 65 million years ago suppose that happened then the dinosaurs continued to evolve so what would it be like today so maybe in that case there would be a room at a school devoted to Science and Mathematics and there'd be a lecturer up here on the platform and we would all be about nine feet tall with lots of green slimy scales and sharp teeth and we would all think we're extremely handsome and the lecturer would be imagine what if a comet had hit the earth 65 million years ago a lot of our ancestors were cold blooded and we would have had a lot of trouble and maybe we would all us dinosaurs would have been rendered extinct and then the lecturer would say and then the lecturer would say maybe under those circumstances the mammals we've taken over the little mouse sighs guys who hide from us you know the vermin in the woodwork it would have been their planet and then as a few people just did there'd be a little snicker running through the audience at such an absurd idea that mammals could have taken over and then the lecture would continue on to something else which I will now do the next slide is a symbolic representation of a kind of dinosaur that was in fact around then with a much larger brain for its body size than most of the extremely feeble-minded dinosaurs and that's sort of the guy from whom the if the dinosaurs had not been wiped out the smart dinosaurs of today filling this room and on the stage might have evolved from but the one thing you can say about the dinosaur is of course they were wiped out is that their extinction was not their fault the human connection with comets therefore is very deep we are as I said several times the beneficiary of the comets we owe our lives to the comments we will of course continue studying them we are alive in the sense that the stuff from which we came we evolved was partly of cometary origin and that humans perhaps would not have evolved if not for cometary impact we will continue studying them Halley's Comet will be back again in 2065 we will by then next slide please I hope substantially improved our spacecraft capability and maybe we will have astronauts who will land on how its Comet and take samples back you see she's grabbing a extremely important collection of complex organic molecules from the comet to bring it back to earth and I think in the next century some of you will almost certainly be around in 2065 so check it out um how much more we learned about comets then the last slide I showed just four I forgot there is no last line I was about to say aesthetic reasons can I have a lights please a last thought I'd like to leave you with is this if you take a look just think back on this talk which is a you know an attempt to to describe one single subject look how it involved astronomy geology physics chemistry even some atmospheric sciences having to do with the climate change from the dust any time you look at a subject like this you find that it's wildly interdisciplinary the boundaries between the subject matter like chemistry and physics and so on are made by people they're not part of nature the boundaries are man and woman made what nature knows is a continuum everything connected you learn subjects by disciplines for the convenience of the teachers and sometimes of yourself but nature isn't like that nature mixes all the sciences together and so it's a very good thing whatever science you're going to go into to learn lots of different areas of science I think it's a wonderful thing that there is an institution like this in the state of Illinois or anywhere I think it's terrific that you have made the commitment to leave your homes at a very young age to come to a place where you can learn at a high level Science and Mathematics and much else I hope the much else includes a deep awareness of the social responsibility of scientists and I wish you all the best luck so no time for blessed thank you Thank You dr. Sagan your comments have been fascinating and humbling I might add on a personal note you have dispelled a myth I always thought it was chicken soup not be fraud we will indeed remember the first James R Thompson inaugural lecture at this time I would like to prevent you with a commemorative picture which also contains your quote and we hope that you will display it proudly on your wall in your office or wherever as a remembrance of your time at the Illinois mathematics and Science Academy thank [Applause] [Music]

Channel: Illinois Mathematics and Science Academy (IMSA)

Views: 77,960

Rating: 4.866426 out of 5

Keywords: Illinois Mathematics and Science Academy, IMSA, James R. Thompson, Leadership, Lecture Series, Dr. Carl Sagan

Id: hF1VDUsmzu0

Length: 86min 32sec (5192 seconds)

Published: Mon Jul 15 2013