Dr. Carl Sagan Speaks at IMSA

good afternoon and welcome to the first james r thompson leadership lecture at the illinois academy of sciences and mathematics my name is don nordland and I have the privilege of serving as executive vice president of the

imsa

fund for the advancement of education, headed by fun board governor thompson the

imsa

fund is a nonprofit corporation that recruits private sector investment in illinois mathematics and science academy, as most of you know, imsa is the nation's only three-year public residential high school for talented math and science students equally important the academy serves as an educational laboratory to develop and test innovative programs to share with other schools, school districts, teachers and students in illinois and the nation private sector donations provide a margin of excellence , Resources for IMSA Last year was our most successful fundraising year, corporate foundation and individual donors donated seven hundred and eighty thousand dollars to the IMSA fund, an increase of forty-two percent over the previous year.

The James R Thompson Leadership Lecture Series is just one example of the programs made possible by these private donations. At this time I have the privilege of introducing you to the talented and visionary leader of this pioneering educational institution, executive director of IMSA Dr. stephanie pace marshall stephanie thank you don and good afternoon this is a very special and proud day at the illinois math and science academy and on behalf of the board of directors imsa faculty and students welcome to the academy and the inaugural leadership conference by james r thompson 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 truly fitting that our first thompson leadership conference outside will focus on science and his contributions to human understanding and will feature one of the most prominent scientific academics in the world at this time.

I would like to recognize several very special friends of IMSA, first and foremost the man in whose name this conference was established and one of those in whose honor this school is 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 champions of imsam, senator forrest etheridge and representative suzanne deutschler, both of whom have been strong supporters of the academy and in fact, education throughout illinois we are delighted that they could be with us today forest suzanne is also It is a pleasure for me to bring you greetings from Governor Jim Edgar who could not be with us today but sent a letter and I would like to read it, my friends, as governor of the state of Illinois, I am very pleased to extend a personal greeting to all those attending the first james r thompson leadership lecture presented by dr.

Carl Sagan Illinois. Illinois' most valuable resource is our young people, and I commend the vital role Dr. Sagan plays in fostering that source. I am sure that this enriching and rewarding experience will result in new ideas and developments. Education is a lifelong process and I hope you continue to take advantage of all future educational possibilities like you, our stars. of tomorrow strive for excellence with my best wishes jim edgar governor we are also very pleased to have with us members of the board of directors of imsa the board of directors of the imsa fund the alliance council and local government officials and we are finally delighted to give you Welcome our corporate foundation and individual IMSA fund donors, we thank you for your generous support and look forward to forging even stronger partnerships with you at this time.

Now it is my great pleasure to introduce walter lee, the president of the imsa student council, thank you dr. marshall good. afternoon, on behalf of the student body, faculty and staff of the illinois math and science academy, it is my pleasure to welcome our special guests from several illinois schools. We are truly delighted to have with us student representatives from our neighboring high schools in Aurora and to welcome our 1991 IMSA juniors who come from various schools in Illinois, in addition, I would like to welcome teachers from all over the state participating in the imsa summer adventures and the 2 impact programs that each teacher was invited to bring their principal and a student and we are pleased to have you with us as well, it is also a pleasure to welcome some very specials from the imsa community, those alumni parents and alumni parents who are with us here today and last but not least, welcome to the members of the media we appreciate your interest in the science of education and dimsa again welcome everyone our guests i hope you enjoy james r thompson's first leadership lecture thank you walter now it is my privilege and pleasure to introduce you to our speaker today dr.

Carl Sagan is David Duncan, professor of astronomy and space science and director of the Laboratory for Planetary Studies at Cornell University, is president of the Planetary Society, the world's largest space interest group, and is a distinguished visiting scientist of the laboratory Caltech jet propulsion system. Dr. Sagan As you know, he has played a leading role in the expeditions of bicycle sailors and travelers to the planets. His scientific research has improved our understanding of the greenhouse effect in Venusian dust storms on Mars, organic haze on Titan, the origin of life, and the search for life elsewhere. For 12 years he was editor-in-chief of Akeras, the leading professional journal dedicated to planetary research, in addition to publishing more than 600 scientific articles and popular articles.

The doctor. Sagan is the author, co-author or editor of more than 20 books, his Emmy and Peabody awards. The award-winning television series Cosmos has been watched in 60 countries by more than 400 million people. The accompanying book, also called Cosmos, was on the New York Times bestseller list for 70 weeks. Dr. Sagan and his colleagues have been involved in long-term research. consequences of nuclear war and in part for this work received the annual public service awards from the Federation of American Scientists and Physicians for Social Responsibility. He has received many other awards among 18 honorary doctorates from American universities. We feel honored and very lucky. that dr.

Sagan is also a member of the National Advisory Board of the Illinois Academy of Sciences and Mathematics and it is for that reason that he is with us today several years ago speaking about the importance of the Imps' mission. The doctor. Sagan said the following and I quote the need to understand how the universe works is fundamental to human nature, it is also essential to safely manage the human future, but we have foolishly designed a society based on science and technology in which almost no one understands science and technology, this is a clear recipe for the disaster of our future. depends on producing and encouraging highly competent and ethically responsible young scientists, as well as increased 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 have the honor of introducing you to a man who has dedicated his life to advancing scientific knowledge by advancing the ethical applications of science and increasing the general public's understanding and appreciation of the wonder of the beauty and mystery of science. . I don't know how technical and detailed Dr. Sagan will be in his comments, but in case you can't understand or remember everything he will tell us today about comets and the origin of life orange, I found a very clear explanation that should help us.

It was in the Sunday comics two weeks ago. in the comic strip that mr buffo proudly displayed on his t-shirt was the following statement about the creation of the universe attributed to

carl

sagan

it was late, it was dark things happened fast could you join me in welcoming one of the astrophysicists Most important in the world? dr

carl

sagan

excuse me on the lights we have all these lights on all these oils do not cause a sound problem they are mercury vapor they will cause a very loud hum due to the magnetic field that is created thank you dr marshall for that generous introduction, of what we have been talking here is with the lights, a lot of lights on me and just a little light on you, you can see me, which you may or may not like, but I can see you, which I'm not happy about because I like the feedback loop with the audience so I hope we can get a little bit more light in the audience and these lights go out, that's good.

I am very happy to be here with you. I won't spend time explaining to you why it's important for people to understand science, for one thing, Dr. Marshall quoted me about it, and for another, you wouldn't be here if you didn't understand for yourself what I'd like to do. is to talk about a topic that in some ways is extremely fundamental, is wonderfully interdisciplinary, and about which we are actually beginning to learn something that you know might not have been true, we may have been completely ignorant about this fundamental topic, but, Uh, we. I have been lucky and the topic is the origin of life.

Now, what are we talking about when we talk about the origin of life? We look at the life around us and I don't just mean the students of this institution, but all life on Earth. see what appears to be a marvelous diversity of all beasts, vegetables and microbes, and if the earth were only a few thousand years old, as people long believed by adding up the births in the book of genesis, then the idea that some organisms evolved from other organisms evolved from very simple organisms, that was just a silly idea and almost no one believed it and for good reasons, but yes, as we know now, the world is four and a half billion years old, like We know without a doubt by radioactive dating, among other methods, then there is time and the critical vision of what would be possible if the world were very old occurred in the epic publication in 1859 of Charles Darwin's book The Origin of Species and there darwin proposed a mechanism by which evolution could occur, it is both ruthless and merciless 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 think about it for a few minutes and it's clear that something like this has to happen. true and says 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 some type of variation of the type that today we would call mutations then there will be slightly different organisms in each generation compared to the previous generation some of those organisms by accident will adapt better to the environment others will be less adapted and the differences may be very small the differences may have to do with the biochemistry or length of bones or the ability to run fast or breathe air or resist disease or anything else, if in addition the organisms reproduce rapidly so that under the best conditions there become large numbers and therefore competition between organisms is established, then natural selection will favor certain organisms and not the opposite, for other organisms, there will be a constant progression of changes, certain mutations will be selected for certain mutations, and this will reduce the selected organism, it will die or not live as long or at least leave fewer offspring and therefore it will work.

In this way, small changes in each generation over a huge period of time can occur major life changes and if you think about the lifespan of human beings compared to the lifespan 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 one hundred millionth as old as the planet, and therefore how could we understand, from what we see in our own lives? , the progression of evolutionary change to understand that you have to go to the fossil record and so on? Darwin not only recognized the main mechanism of evolution and its power, but he also proposed it quite timidly.

Before devoting himself to that line of work, he intended to be a minister and preacher in the Church of England, he proposed that both humans and all human beings. other beasts and plants had evolved humans came from a non-human primate ancestor that would surely look like something like an ape to us if we met it our primate ancestors evolved from other mammalian ancestors mammals from reptiles reptiles from amphibians, amphibians, fish and so on until some very simple organism that was the ancestor of all the inhabitants ofthe earth and, in that sense, incidentally emphasizing a deep kinship, all the plants and animals of the earth were all cousins ​​and it was Darwin who was the first to explicitly state this by a mechanism that actually makes sense, but one might think that This doesn't explain some things, but it doesn't explain the fundamental question because where did that first ancestor come from and Darwin was perplexed or almost perplexed?

There is a curious line. He wrote in a letter to his friend Joseph Hooker, president of the Royal Society of London, that it said something like Darwin saying that we can imagine a small warm pond somewhere in the Earth's ancient history in which certain molecules. interacting and then dot dot dot uh and he even said what some of those molecules might be and uh they are what we call organic molecules, plus he explicitly said ammonia plus phosphates by about 1870. This is a remarkably good idea even though it was something that he never actually published just in private correspondence, so Darwin got the idea that the origin of life was connected to the origin of certain organic chemicals.

Now, all current life on this planet is at least based on one category of molecules called nucleic acids and nucleic acids encode the construction of another category of molecules called proteins and certainly life on Earth is primarily a matter of acids. nucleic acids and proteins. If we could understand the origin of nucleic acids and proteins without pre-existing life, we would certainly understand it. be taking a substantial step towards understanding the origin of life, it is not the same if you have the basic components lying around, that does not mean you have a living being, but if you look closer you will see that nucleic acids are in some way Similarly, self-replicating molecular systems, under the right conditions, make identical copies of themselves.

If you could imagine a primitive organism that was nothing more than a molecule that could make copies of itself, then you could be there or pretty close if you had a molecule. that it could crudely make copies of itself, then there would be mutations, the replication would not be perfect, the cosmic rays would produce changes in the molecule and then the next generation that molecule would copy would change in that direction, well, that's all there is to it. you need if they have replication and mutation, natural selection is at work and as we know that nucleic acids self-replicate, it is a very important step towards understanding the origin of life if we can understand the origin of these particular molecules, so I want to emphasize It is not the same.

But it's an important step, so where did this come from four billion years ago? I say 4 billion years ago because we know the time of the origin of life quite well to a precision of 10 and the argument is this: the first fossils. We know they were about three and a half billion years ago, although the carbon isotope chemistry of sediments from 3.8 billion years ago may indicate the presence of life, even then it is difficult to find fossils back then because there are almost no pieces of continents dating back three and a half billion years. So far there is a paucity of geological records and it could be that there were fossils a little before that, the first fossils we have are of colonial microorganisms and that is quite advanced, they could not have been the first organisms, so it took a while. substantial period of time before the first organism ran in the opposite direction.

The Earth at the time of its formation was a very inhospitable environment because the Earth fell in pieces from the sky and in the process it melted and produced a vapor atmosphere and the pieces that caused the Earth to continue falling and in a sense , are still falling today. Each impact of a comet or asteroid, which I will discuss shortly, is in a sense the end of the distribution function. of the Earth's fall and in the early days before the solar system was cleared by a collision, things were falling from the sky all the time and big things falling from the sky that you can see could make the Earth an unpleasant place , especially if it would melt large areas of the Earth and even four billion years ago there were occasional massive impacts 4.1 or 4.2 billion years ago sterilizing impacts that would simply sterilize the entire ocean or vaporize the entire ocean and send it to the space. still occurs so you can see that the time of the origin of life is limited and maybe it is between 4.2 and 3.8 billion years ago, loosely we will call it 4 billion years ago and there are some people who think that if the origin of life happened quickly in terms of the geological time scale at least, maybe it's a probable event, maybe you just set the conditions right and, uh, life arises now, no one has ever made a experiment in which, I don't know, you mix the gases and the waters of the early Earth and maybe things that fall from the outside and shine with ultraviolet light and attack it with electrical discharges for a while and then, at the end of the experiment, someone crawls out of the reaction vessel, no one has managed to do that, we are very far from that. but, on the other hand, in making the building blocks of proteins, nucleic acids, as I will explain, we have been very successful.

You know, there's a strange feeling you get when lecturing here and that's that every time you wave your hands there's a bright light that goes off. It's a very remarkable correlation and when I leave here I'll have this sense of disappointment that some kind of superpower has been lost, you know, William Huggins was an affable 19th century astronomer who unintentionally scared the world. he was just minding his own business, which was spectroscopy, but one thing led to another, you never know what's going to happen if you're a scientist, you're a very arcane and abstruse job that can suddenly have all kinds of social relevance. and You better be prepared, so this is what happened.

He was a pioneer. I'm going to take off my jacket. He was a pioneer in observing astronomical objects whose light passed through a telescope and then a spectrometer that scattered the light. into its constituent colors and then recognizing the signature, the pattern of absorption lines that gave him insight into the chemistry of the source, often from sunlight reflected by the solar system object or light emitted from a distant star, He managed to recognize some of the atoms in distant stars, he looked at planets without success and, as if by chance, he looked at comets and found a set of absorption lines and comets that were different from those of the stars and he could not understand them for a long time. what it was and then he and some French scientists, uh, the French scientists must have been especially good at this idea of ​​looking at the absorption spectrum of olive oil, which I imagine was more present in the French laboratories than in the English laboratory of William Huggins. and to his amazement the olive oil looked like comets now if it were true we would have an economic motivation for space flights that is missing today but what turned out was not that there was olive oil there but that if the olive oil was vaporized and dissociated it produces a c2 molecular fragment, two carbon atoms bonded together, which is also in the comments, so although they didn't use this word exactly, this was evidence of organic matter in comets.

Organic, of course, simply means a carbon-based molecule. It does not mean of biological origin, there are astronomers who refuse to use the word organic because they are worried that people will misinterpret what it means of biological origin and a colleague of mine calls it the word oh, you find all kinds of circumlocutions. that astronomers use, including that they contain carbonaceous carbon and then, after the experimental results on Halley's Comet, a new phrase was introduced particles chune c-h-o-n carbon hydrogen oxygen nitrogen it is a great effort to avoid saying the word organic, but I hope not offend anyone.

I'm going to just use the word organic, since chemists usually do well, so Huggins discovered some organic matter in comets, but he continued over the years and then in the 1880s he found evidence not of the molecular fragments cc but of the molecular fragment cn. nitrile radical, except it has another name, names count in this business, the other name is cyanide and um, but nobody paid much attention to it until just before 1910 because in the year 1910 it was predicted that the first landslide, please, the land would pass through the tail of Halley. comet, of course, I will need to turn off the lights with the slides on, thanks, there is a little intelligence test between here and turning off the light, this light, well, I failed the test, so this is the idea, the tail of the comet pointing in the opposite direction to the sun the earth thanks passing by the tail of the comet and then people suddenly thought: My God, there is cyanide in the tail of the comet.

Prussic acid is potassium bound to the cyanide radical, and a single grain of prussic acid on your tongue can kill you. the idea that there were huge amounts of cyanide in the tail of the comet the earth passing through it frightened many people there were sustained national panics in Japan and Russia one hundred thousand people in Constantinople ran to the rooftops in pajamas people dressed in stuffed rags of Chicago and newspapers under their doors the pope banned the hoarding of oxygen cylinders in rome a handful of people around the world committed suicide because they didn't want to die with poison gas and poor william huggins was responsible for all this and he had never Talked to a journalist in his life, plus there were a lot of scientists, he said, wait a minute, it's not even clear that the Earth is going to pass through the tail of the comet and, if it does, we can calculate what the density is. of the cyanide radical is and will be at most one part per billion of things 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 that it is less dangerous than breathing the harmful atmosphere of london, but that didn't help once the idea was in the public mind, people became tremendously worried, except the people who committed suicide, no one died in 1910 due to halley's comet, except the fact that william huggins died in 1910 , but not because of 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 basic components of proteins and nucleotide bases, the basic components of nucleic acids, it's a really strange fact that this molecule that can kill you, you happen to be an oxygen breather, it might actually have been central to the origin of your distant ancestors and I'll come back to that shortly, what I'd like to do now is Give a quick idea 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 passed by, except the two last before the era of the telescope and you can see that people had quite different views, including this, as you can imagine, a medieval interpretation which was that a comet looked like a sword, even here comets are psychological projective tests.

There are some other representational comments that I haven't included here. People see what we're a little interested in, but what did most people think? Or was it something, was it a signal sent by God to warn us of an impending disaster that has always been on the verge of scientific interest in comets or Aristotle's opinion that it was a kind of meteorological fire in the upper atmosphere an exhalation from the interior of the earth that remained burning in the air, then the question is whether this is something in the earth's atmosphere as almost everyone thought or is it something astronomical in the 16th century, the Danish astronomer Johannes Kepler's teacher realized that there was a way to answer that question.

In the next life, if there were two observing stations on Earth very far apart and the comet was close to Earth in the atmosphere, then this guy would look at it and see it in front of one. background set of stars a constellation and this guy looks at it and sees it against a different background and therefore there is an excellent way to see if it is down if on the other hand it is very far away next slide please then two very separated stations will see it more or less against the same background and this method, known as parallax, which many of you probably know, not only works qualitatively but also quantitatively, by the relative displacement against the background stars, you can actually know how far away you were while brahi organized a cooperative international program to examine a comet and discovered, beyond a doubt, that the comet was beyond the moon, at translunar distances that everyone considered truly strange, especially since the prevailing religious doctrine was that nothing could change in the heavens , which was one of the main reasons people wanted comets to be in the atmosphere, but it's hard to say no to what a comet is in mathematics, it wasn't up to Tycho Brahe to figure it out and this was, uh,I'll get to that in a moment, uh a. an idea provided by uh edmund halley, but let me show you what the contemporary context of comets is on the next slide, 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 It is chauvinistic for astronomers to decide that the distance from the Earth to the Sun is an astronomical unit.

The entire universe is measured by our distance from the Sun, but it is a kind of presumption 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 that you can see lives more or less in the inner part of the solar system on the next slide this scale is one hundred astronomical units so that everything we saw in the last image is inside this small square and here are 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 can see, lives part of its time beyond the orbit of Pluto.

The next slide increases the scale to an astronomical thousand. units, everything we saw in the last one is in this little square and here is the orbit of a longer period comet, not unusual, called comet Mirkush, which mainly lives well beyond the planets and crosses a very interesting regime in which no spacecraft has ventured yet. in which the nuclei of comets quietly orbit around the sun and if we go to the next step of 10 slides at a scale of 10,000 astronomical units, then we find ourselves in what is called the urt cloud of comet nuclei, a spherical cloud Of perhaps a trillion comets the typical size of one, perhaps a kilometer in diameter, orbiting the sun from time to time, a passing star or a passing cloud of interstellar gas and dust shakes the earth, the cloud forms a wave and occasionally a comet will be redirected in the new orbit towards the inner solar system and there is a new comet in our skies, in addition, the short period comets were probably captured by the planets in the inner solar system from original orbits long period, so comets come from halfway to the nearest star in general they are visitors from the interstellar darkness they are not the same as things from the solar system the fact that they can carry organic matter becomes doubly interesting by the distance of its origin the next slide here is now for the inner solar system it is the orbit of Jupiter a small fraction of the set of orbits of comets look how many there are look how all the orbits cross each other and it is very clear that if the earth orbits something like this once a year and These guys come and go once every few years and the earth lives for four and a half billion years that can't be avoided.

Some of these guys crash into Earth. Collisions with comets are simply inevitable and if we go back earlier in the history of the solar system it is much more inevitable the next comet glide is made primarily of ice every time a comet approaches the sun, about a meter thick, the ice it evaporates and eventually, after enough perihelion passages, all the ice disappears and all that. What's left is the non-icy matter, mainly rocky and organic material, and some of that breaks up and what we have is the comet's orbit starts to fill up with these fine particles.

The entire orbit, each fine particle is a separate small comet or planet that rotates well around the sun, if the earth passes through that orbit, these fine particles will enter the earth's atmosphere within a certain size range, the small ones burn a blade in the upper atmosphere, mainly about 100 kilometers 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 see a lovely little flash that is a piece of a dead comet in its last moments before dissipating into atoms and I think that's a lot more moving, charming and realistic vision than the other vision, which is that it is something the size of the sun falling into the Earth's atmosphere, a Shooting Star.

Think about how that phrase is integrated into language and poetry, and what a mistaken view of nature. carries with it the same meaning that the word sunrise and sunset are pre-Copernican, they are words that come from a time when everyone imagined that the earth was stationary and the sun moved, instead of the other way around, the language has fossils in it. In addition to the geological record, the next slide shows that larger objects that enter Earth's atmosphere also burn up. This is called a fireball and several UFO reports are due to pieces of comets larger than the dust or pea-sized objects that form meteors very small particles float like a fine rain slow down so quickly that they do not burn up and particles very large massive objects rocks city-sized objects will pass through the Earth's atmosphere and reach the surface without burning up much there There will be an ablation crust on the outside that will burn up, but the body of the thing will reach the surface of the Earth.

I'll come back to that on the next slide as well. Now, pieces of comet are coming to us, as I have been saying. but mainly they burn up it's hard to get a piece of a comet we also fly planes at stratospheric altitudes they're sending me a message but we also fly planes at stratospheric altitudes with that kind of fly paper on their wings to catch dust particles comets it's very hard to grab a piece of a comet, so in addition to the comments that come to us, we can go to the comments in 1986. Halley's Comet made its next return to Earth after Huggins' appearance in 1910.

It orbits the Sun every 76 days . years, so 10 plus 76 is 86, like clockwork, it went backwards, but in 1986, for the first time, the human species had invented a means to go say hello to 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 who was carrying a set of instruments from 17 European nations plus the American instrument that came on board despite the defense department's best efforts to prevent it. A European spacecraft called Giato that had contributions from 13 European nations and Japan's first two interplanetary spacecraft were more basic spacecraft and flew at greater distances.

It was conspicuous by its absence. It was a spacecraft from the United States. It was rejected at the White House because it was too expensive. would have cost Even a single b1 bomber of which we then committed to buying 100 99 would have compromised national security, which is why there are no American spacecraft near Halley's Comet and this may be a chauvinistic comment because scientific opportunities have been lost, eh, on understanding Halley's Comet, Soviet spacecraft and especially European spacecraft. Giato came very close. Giato came within a few hundred kilometers of the comet's nucleus. Look, there's a solid object there and then there's a fuzzy cloud of gas and dust called the coma and then the gas and dust are blown back by the pressure of radiation in the solar wind to form the long, beautiful tails of comets and what we see from Earth is a bit of a coma and mainly the tail and the core hidden there.

No one has seen what these European and Soviet spacecraft did: fly through the coma almost crashing into the nucleus to see what a comet nucleus looks like and the next slide shows this dark, dark, peanut-shaped object that measures approximately 10 kilometers long. The nucleus of Halley's Comet is very dark. The amount of sunlight it reflects is something like three, four or five percent. It's very dark. It is as dark as black velvet. In fact, that is evidence of worked organic matter and what we are seeing here are jets of ice coming out of the comet heated by sunlight, vaporizing, carrying dust in it and which will then form the tail.

The next slide is maybe you can see a little better. I recognize the people in the back. Some of this may be. I apologize for that, but perhaps you can see the nucleus of Halley's Comet more clearly here. There were now instruments on board these 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. fact in fact about 25 percent of a variety of organic molecules the problem is for technical reasons that if anyone is interested I can summarize in the question period the reliability of the specific identification of particular organic molecules is weak but that their organic nature is Sure, okay, so if comets are loaded with organic matter, if comets hit the Earth today, there was a small one that hit Siberia in 1908, and if they hit the Earth much more frequently at the time of the origin of life, maybe Once organic matter played a role in delivery to Earth. the things from which life arose on the next slide so here is a conception of the artist this is the Japanese artist kazuwaki iwasaki uh a beautiful image of the earth about four billion years ago the moon is closer to the earth so It looks bigger in the sky, what is it?

What is represented here is that there are things that fall from the outside, exogenous material and things generated in this case by lightning inside, down here, endogenous, exogenous organic matter, the xo is the same root as uh, exit, which means outside and uh endogenous, the root endo is the same. as input then molecules from up there molecules from down here what is the relative contribution of these next two slides um this is a schematic representation of a mechanism of production of amino acids, the building blocks of proteins, as fully demonstrated in the laboratory of the earth were rich in hydrogen the universe is rich in hydrogen the giant planets are rich in hydrogen hydrogen escapes quickly from the earth it is possible that the earth's primitive atmosphere had much more hydrogen than today so there is water up there, this type and this type is methane, this is ammonia, if those molecules are hit by ultraviolet light or by charged particles, they break into pieces, the radicals recombine, you can see the pieces here and two, the main products are, guess what it is hydrogen cyanide, and there's an atom right there.

I can't see formaldehyde very well and these two materials, cyanides and aldehydes, along with ammonia in the air and water in the oceans, are easily formed by high-performance amino acids, so it's quite remarkable: shots Very common things, very simple molecules, you apply any energy that breaks them into pieces and then they recombine and form some of the molecules of life. It need not be this way and we learn something from the fact that the laws of physics and chemistry allow this immediate synthesis of the building. blocks of life on the next slide, well, you can calculate how much ultraviolet light was in the early environment of the Earth, measure in the laboratory the production efficiency of organic molecules and then integrate and get the total amount that must have fallen, of course , the molecules fall. pieces in addition to being synthesized and thus it is calculated what the steady state abundance of organic matter could have been in this case from ultraviolet light and an endogenous source next slide the endogenous production of organic matter is occurring today it is not on earth because we have an oxygen atmosphere, but on Titan, Saturn's large moon, where the Voyager spacecraft found simple organic molecules in the gas phase, including hcn, and this impenetrable pink cloud layer is made of complex organic solids and those solids, if You drop them in water, they produce a lot of amino acids and the like.

The basic components of nucleic acids are also produced in the experiments, so it is possible that an enormous amount of products of prebiological organic chemistry are frozen on Titan, the substance that four billion years ago led to the origin of the Earth on Earth. Life may not have gotten very far on Titan because normally there should be very little liquid water there, the surface temperature is 95 degrees above absolute zero, but on the other hand, through cometary impacts and perhaps through through some tectonic activity, there may be episodic ice melting and maybe there's some liquid water chemistry there, we don't know, we hope to land there sometime early next century, return to earth, next slide It was almost endogenous, now exogenous, this is an image, of course, of the moon, you can see the aurora.

Illinois right there and as you well know, the highlands of the Moon are full of craters, but the saturation is full of craters, so the craters fall on top of the craters and the whole surface is full of craters and there are no processes of erosion on the Moon or almost none, so we're looking. Since very ancient times, the moon is an impact counter and since the moon is close to the earth, it isvery unlikely that the moon has received all these impacts and the earth has not, today we have very few craters, but that is because we have running water that Eh erodes the craters, so from the record of lunar craters it is possible that you can calculate how much stuff fell on Earth four billion years ago on the 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 rovers brought back samples of the moon from different places they got a sample they measured its age by radioactive dating and compared it to the crater count and there is a correlation, so four billion years ago you know Generally speaking, you can see on the error bars how many craters fell per unit time per unit area on the Earth or the Moon and if that was mostly, half or 10 comets you can calculate how much organic matter was produced on the next slide .

Well, I don't want to spend a lot of time on this, just to point out that from both exogenous and endogenous sources you can calculate how much organic matter per year fell on the Earth at each epoch from different sources on the next slide in the same way, so it is possible Take an inventory and see how many things there were. Can I have the lights? Please, no, no, the light is there, yes, of course, thank you, so what does it look like? is that there is certainly plenty of room for uncertainty here, but even within the range of uncertainty it seems that there was an enormous amount of organic matter on the early Earth, so much that in the most optimistic case, if you mixed it in oceans of in extent and depth In contemporary times, you would have an organic matter solution with approximately the size of Campbell's beef broth.

That is a good medium for the origin of life. A few hundred million years of those amino acids, nucleotide bases, um, you could make a lot of progress. For the origin of life, there is a lot of other work being done on the origin of life, including material on self-replicating RNA, a kind of nucleic acid molecule that has the magical property of being able to catalyze it to act like enzymes that The rest are all proteins and there are experiments in which amino acids join together to form things like proteins. There are experiments where nucleotides are joined together to form 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 hardly We can say that we are there, at the origin of life, but at least it seems very likely that through some mixture of up there and down here, enormous amounts of exogenous and endogenous organic matter. of the right kind were on Earth at the right time and therefore in this sense we are the beneficiaries of comets, but this is not the only way in which comets have influenced our evolutionary history and I would like to end with another way we are indebted to the comments below I will say comets but it is possible that what I mean is a large asteroid, suppose you were an extraterrestrial visitor, an extraterrestrial study biologist, descend to Earth for a short period of time, look around, examine the biology, but quickly make a brief report and then go to some other planet.

There are so many planets in the Milky Way that you can spend a lot of time on any one of them and leave it to graduate students to fill in the details later. Suppose you were dropped to Earth not today, but a hundred million years ago. Let's say you would find an Earth incredibly rich in life, but it wouldn't be the life we ​​know today or at least not at first glance. Next slide please, it would be an Earth with guys like this, animals bigger than trees this is the land of the dinosaurs they were on land in the water in the air they had filled every ecological niche they had been there for about a hundred million years before this time compare that to our species who have only been here for a few hundred thousand years they lived a thousand years a thousand times longer than us until now this was their planet on the next slide and some of them were fearsome hunters notice all the uh sharp little teeth right there, where were we 100 million years ago?

It's good, we were not humans, we had not evolved, but we were at most a possibility, our direct ancestors were small mice the size of a mouse, shy, shrunken, nocturnal, insectivorous mammals, insectivorous means that we ate insects, nocturnal means that We went out at night, why do we only go out at night, that's why now part of your job as a biologist on Earth 100 million years ago is to predict the future course of evolution on this planet. Who would you bet your money on those mouse-sized guys who eat bugs and come out at night? These guys that had been around for a hundred million years, I'm not talking about this exact species because dinosaurs were also evolving.

I think there's no question that you would bet on dinosaurs, and yet 65 million years ago something happened in a very short period of time. geologically speaking, they exterminated all the dinosaurs, every last one of them was killed all over the Earth, in all the environmental niches, and not just the dinosaurs, but most of the species of life on Earth, most of plant species, most animal species, most species of oceanic and terrestrial organisms a terrible and colossal catastrophe happened to the earth, what was next? slide American physicist Luis Alvarez had the brilliant idea of ​​examining the atomic chemistry of the layer of rocks corresponding to the time when the dinosaurs were exterminated, so here is a section of a famous part of the Earth's sedimentary calm from Gubeo, Italy.

Here this white stuff is chalk generated by the microscopic calcareous foraminifera that lived in the Cretaceous seas at the time the dinosaurs flourished. it took carbon dioxide from the air and made shells of calcium carbonate and then they died and the calcium carbonate fell to the bottom of the ocean and there were large amounts of them and over millions of years a large amount of chalk accumulated most of the chalk that you use on your blackboards comes from these little guys that are contemporaries of the dinosaurs that the white cliffs of Dover in England are made of are made from the remains of these microbes these submicroscopic guys okay, here we are and here it stops, this is the dinosaur time, these are not dinosaur fossils up here and as you can see there is a transition layer, look at that right there, and it is made of clay and it corresponds to the time when all those organisms, including the dinosaurs, were exterminated , so naturally we would be interested.

Seeing if there was anything strange in that layer, what Álvarez found is that there was an abnormally high abundance of certain atoms of which the main one is iridium, which is not a very well-known word or at least it was not until this discovery, elements Chemicals whose names are unknown are probably rare because if they were abundant there would be names for them that everyone heard. The reason there is not much iridium on the Earth's surface is that it likes, has an affinity for iron and when most of the iron on Earth was segregated to form the Earth's core, the iridium was transported with him, while in objects such as comets and asteroids that were not large enough to melt and form the nucleus, the iridium remains distributed, so meteorites that come from asteroids have much more. iridium than the surface of the earth, so Alvarez's argument was that the reason there is a lot of iridium 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 had to be to distribute that amount of iridium throughout the earth and this is all over the earth not just in gouge italy dozens of places you dig into the sedimentary column there and find an excess of iridium that the shocking object had Álvarez calculated about 10 kilometers in diameter, that is the size of Halley's Comet and, therefore, the Berkeley group proposed that 65 million years ago a comet or asteroid collided with the Earth and that caused it to many men died.

Next slide, so here's an artistic view of this. comet hitting the Earth if the comet is 10 kilometers in size and the Earth's oceans are only three kilometers thick then the impactor doesn't care about the oceans it's the same situation as if there was no ocean it's like one of the big impacts. The Moon's craters hit the Earth and create a huge impact crater. The impactor fragments the material excavated from the crater fragment and these fine particles are launched into the upper atmosphere and, in effect, out of the Earth. Part of it leaves the Earth completely forming an orbit that the Earth gradually sweeps away and reaccretes from it, in fact, it is now thought that it did not fall into the ocean but on land near the Yucatan Peninsula in Mexico.

The next slide shows the result. Dark skies across the Earth. Lower temperatures, which cause both. much but not all vegetation dies herbivores do not have plants to eat and are probably not well adapted to the cold die carnivores do not have herbivores to eat die you can see a helpless triceratops extremely unhappy, you can tell by the facial expression that says nothing of the remains of other dinosaurs scattered across the landscape he has a lot to worry about um on the other hand I don't know if many of you can see it but there is an extremely happy animal in this photo right there you see that little guy four legs and a tail and his head She's upright and there's a little smile on her face right there that guy is our great-great-great-great-great-great-great-grandfather and a great many more great-great-grandfather the death of the dinosaurs eliminated the main predators the main enemies Suddenly, the world of mammals was theirs, the competition had been eliminated and then there had to be a fantastic efflorescence of mammals filling many ecological niches and this so-called adaptive radiation of mammals that we are beneficiaries 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 for a moment, I mean, after all the comets are squirting, you know, These big jets of vaporized ice come off and just like, you know, an inflated balloon, you let it go and then the balloon goes all this weird way, it's essentially the same thing as a rocket engine, so if there was a slightly different distribution of the ice packs, it would have been a different stream. and a slightly different non-Newtonian motion of the comet and could have easily missed the Earth could have easily missed the Earth, suppose the comet had not hit the Earth 65 million years ago, suppose that happened, then the dinosaurs continue evolving, so what would it be? like today, then maybe in that case there would be a room in a school dedicated to science and mathematics and there would be a lecturer here on the platform and we would all be about nine feet tall with lots of slimy, sharp green scales. teeth and we would all think that we are extremely handsome and the lecturer would be imagining that if a comet had hit the Earth 65 million years ago, many of our ancestors were cold-blooded and we would have had a lot of problems and maybe there would have been all of us, the dinosaurs, we would have gone extinct and then the lecturer would say and then the lecturer would say that maybe in those circumstances the mammals that we've taken over took over the little mouse-sized guys that are hiding from us, you know, the vermin in the wood. it would have been their planet and then, as some people did, there would be a little laughter in the audience at such an absurd idea that mammals could have taken over and then the lecture would continue with something else which I will now do.

The next slide is a symbolic representation of a type of dinosaur that actually existed back then with a much larger brain for its body size than most extremely weak-minded dinosaurs and uh, that's the type of who, Uh, if the dinosaurs had not been exterminated, the intelligent dinosaurs that today fill this room and on stage might have evolved, but the only thing that can be said about the dinosaurs, of course, they were exterminated, is that their extinction was not their guilt, the human connection with comets. therefore it is very profound we are, as I said several times, the beneficiaries of comets we owe our lives to comets of course we will continue to study them we are alive in the sense that the matter from which we come and evolve was in part a comment origin and that humans perhaps would not have evolved if they had notOut of the impact comment we will continue to study them Halley's Comet will return in 2065 by then on the next slide please we will have substantially improved the capabilities of our spacecraft and perhaps we will have astronauts who will land on Halley's Comet and take samples.

You see, she is taking an 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 surely be around in 2065, so check it out. Find out how much more we learn about comets than the last slide I showed just because I forgot there isn't a last slide. I was about to say aesthetic reasons. Can I have lights? Please, one last thought I would like to leave you with is this if you take a look, just think about this talk, which is an attempt to describe a single topic.

Look at how it involved astronomy, geology, physics, chemistry, even some atmospheric sciences that have to do with dust climate change. In a topic like this you discover that it is tremendously interdisciplinary, the limits between subjects like chemistry and physics and so on are made by people, they are not part of nature, the limits are men and women made, what nature knows is a continuum, everything that connects you learn subjects by disciplines for the convenience of teachers and sometimes yourself, but nature is not like that, nature mixes all sciences, so it is very good, whatever science you are into go to study, learn many different areas. science, i think it's wonderful that an institution like this exists in the state of illinois or anywhere else.

I think it's fantastic that they made the commitment to leave their homes at a very young age to come to a place where they can learn at a high level in science and mathematics and much more. I hope that more includes a deep awareness of the social responsibility of scientists and I wish them the best of luck. Thank you, so no time for questions, thank you, thank you, thank you, Dr. Sagan, your comments. It has been fascinating and humbling, I must add on a personal note, you have dispelled a myth. I always thought it was chicken soup, not beef broth.

In fact, we will remember James R. Thompson's first inaugural lecture right now. I would like to present you with a commemorative card. Image that also contains his quote and we hope you will proudly display it on the wall of his office or anywhere as a memento of his time at the Illinois Academy of Science and Mathematics. Thank you.