MIT Family Weekend Convocation: "Footprints in the Rock" and "The 2.70 Introduction to Design Contest" (1989)

HECHT: I'd like to welcome you and introduce myself, and then begin this morning's convocation. My name is Bill Hecht. I'm a member of the class of '61, and I'm the Senior Officer at MIT for Alumni Affairs. And in the last seven or eight months, I have become one of the dozens and dozens of people who have become involved in the parents program. So on behalf of all those dozens and dozens of people, welcome to MIT.

I want to thank you for doing two things. One is joining us today, but perhaps the most important thing you do is to share those exceptionally talented youngsters who are your children with us. The currency of an MIT education involves two rare sets of talents, extraordinary faculty-- you'll hear from several of them-- and your young people. The combination is rather remarkable, and we owe you some debt, even though you owe us a lot of debt too, for sharing those people with us.

We hope that yesterday and today, you've gotten some glimpse of the kind and quality and intensity of education that your young people have. MIT's education has been likened to getting a drink from the fire hose. I want to assure you they mean not the range but the intensity of the education. We've turned the taps down a little bit, so this is perhaps a high pressure garden hose that we're feeding you in the last 24 hours and then the next eight or 10. But nevertheless, I think you'll go away with a glimpse of what this enormous, exciting, and energized place is all about.

There are, as often is true with great successes, literally hundreds, if not a thousand, people who I should list the name of and thank. I won't do that. There's been one person on my staff, [? Marsha ?] [? Hartley, ?] who is a parent of an alumnus, and would have been the parent sitting in this audience had we started this program several years ago, who coordinated this effort. And I want to thank [? Marsha, ?] the students, the faculty, the staff. We simply could not have done this without an extraordinary outpouring of energy from the community.

This morning it's my great pleasure to introduce the first family at MIT. I often get the pleasure of introducing President Gray. It's rare that I get the extraordinary honor of introducing my good friend, his wife, Priscilla Gray. Priscilla Gray brings an enormous amount of grace and care and personal warmth to this place, and there aren't very many of us who don't feel as if it's a better place because Priscilla is here.

She's also distinguished in one way, and that is that MIT does not offer honorary degrees to anyone, but the Alumni Association has been able to make honorary members. And Priscilla is one of that rare body, an honorary alumni. Priscilla Gray, please.

[APPLAUSE]

PRISCILLA GRAY: Welcome to MIT. Having you here on this campus with us is a 10-year dream come true. I wish to salute all of those on the committee who have worked so hard on this first parents weekend at MIT. You are to be congratulated.

I have concluded in the past few years that being a grandmother is one of the very best roles that life offers. For me, being the partner of the President here at MIT has some of the same wonderful aspects of being a grandmother. Since we live on this campus in the midst of all the students, I am able to see firsthand the intelligence, the vitality, and the stamina the students bring with them. It's a joy to watch your sons and daughters mature, and the friendships I make with them are gifts. I am a fan of theirs.

Thank you for coming this weekend. I hope that you feel a part of this great extended family called MIT.

[APPLAUSE]

HECHT: It's now my great pleasure to introduce, regrettably in his last year as our president, President Paul E. Gray, '54. President Gray came to MIT from northern New Jersey a number of years ago. I won't say how many, but he did get his bachelor's degree in 1954, and if you're as bright mathematically as your children, you can figure out how many years ago. Earned his master's and doctorate here, and save a few years in the company of the United States Army, has taught and worked at MIT for all of his adult life.

For those of us who were here, that has been an enormous gift. Paul brings many talents to the place, but perhaps the best one is an ability to listen to one more voice all the time and care deeply about this place, your children, and its faculty. Paul?

[APPLAUSE]

PAUL GRAY: Thank you Bill. Good morning and welcome. It is an enormous pleasure to greet you on this glorious New England October morning. It's a particularly delightful morning given that we've had four days and four nights of unremitting downpour. And never does a crisp October morning look better than following that.

I would like to express my pleasure, indeed, our pleasure, this place's pleasure, all the folks who are around here, at the number of parents and family members who are here for this family weekend. This is the first time we've tried this in at least 30 years, and now, for a university that is much more concerned with shaping the future than it is with recording the past, its own included, 30 years might as well be infinity.

There was at about this time of the year five or six years ago on the campus a spirited and prolonged debate about the scheduling of commencement. This debate arose because the workings of the academic calendar, as presided over by the registrar, the workings of that calendar had set commencement that May, or June, had set commencement in a way in which it fell on a religious holiday. And so the question was should the commencement date be changed in order to remove that conflict.

Eventually, that debate made its way to the floor of the faculty meeting, because it is the faculty at MIT who control the academic calendar. And if we were going to change commencement, the faculty had to act to do so. There was a prolonged debate in the faculty meeting about the pros and cons of changing the date. And I was presiding at that meeting, and my impression was that the outcome was quite uncertain. I would not have wanted to predict whether we were going to leave it as it was or change it.

Until a senior, a young man in electrical engineering and computer science, stood up and made a brief comment which absolutely carried the day. He said simply that for four years, his parents knew MIT only as a black box into which they poured money, and would we please work it out so that they could come at commencement and find out that there was something else to the place. Well, that remark carried the day, and I hope that you all have in the few days here some opportunity to find out that MIT is not just a black box, that it is a vibrant, exciting, diverse, rich, enthusiastic community.

We hope also that you will share with us your impressions, critical and otherwise, about this undertaking. We expect to do this again, and we hope you will let us know what works and what doesn't work, as seen from your perspective. You will have in these few days many opportunities to learn something about our academic programs, about athletics, about coursework, about the social climate at MIT, and the program this morning is an important part of that.

Before we turn to that program, I want to take just a couple of minutes to say something about a set of subjects with which you are already intimately familiar, and I speak about your sons and daughters. They are, to my way of thinking and my experience, the liveliest, the brightest, most energetic, and inquisitive group of young people gathered together in one place in this nation-- indeed, I suspect, on this planet.

They are valedictorians and academic prize winners. They are football players and cellists. They are math whizzes and experienced actors. They are concerned about their fellow students and their fellow citizens around the globe. They are creative, they are intellectually tough, and they know how to play. In short, they bring to MIT all the richness that makes college the most rewarding time of their lives, and that makes this place a continuously exciting, continuously renewed environment for all the rest of us.

Now, that's not just my view. It's not even just the view of the faculty. We had during this week, this remarkable third week in October, the every 10-year re-accreditation visit for MIT. Every college and university that wishes to represent itself as having accredited programs must, every 10 years, invite to the campus a team of other educators who spend the better part of a week here. They have spent a great deal of time in preparation before they come, and then they will, in due course, within the next six weeks, render a written report.

But at the end of that week, they sit down, the whole team, all 10 of them, with the president, and express over a two-hour interval it took this time, the content of their report and the general conclusions. That team this year was headed by Frank Rhodes, the President of Cornell, and involved nine other individuals from colleges and universities across the country.

In that exit interview day before yesterday, they were clearly tremendously impressed with MIT students. They spoke about the candor, the creativity, the intelligence, the enthusiasm of the student body. One comment, which I think will appear in this form in the final report, struck me particularly, and I want to relate it to you this morning. They said, "we are impressed with the energetic engagement of MIT by its students. There are no listless young people here. Now, you know that all the time. We know that all the time. But it's nice to see that the visitors who were here for four days also were struck by that.

It is, I suggest, because we have students of this caliber, of the caliber you send us, that we can attract faculty of the caliber you will hear from this morning. Students and faculty are the two sides of the coin of excellence at MIT. They go together. They are inseparable. You won't long have a good students without a strong faculty and vice versa. Faculty come here, stay here because of the opportunity of working with young people of such capacity.

Our first presentation this morning has been prepared and will be conducted by Phillip and Phyllis Morrison on the subject "Footprints in the Rock," that is, how to tell something about the creature who made the impression, whether that imprint is one hour old or more than a million years old. Phillip Morrison is Institute Professor Emeritus. He is one of the premier physicists and science educators of our time. He's been on the MIT physics faculty since 1965.

Phil displays an extraordinary range of interests and talents, astrophysics, science education, the history and philosophy of science, the role of science and technology in society. He is known surely to many in this audience as the man in front of the camera in the PBS series The Ring of Truth, which he developed with his wife Phyllis.

Phyllis Morrison is a writer, a weaver, an educator, a frequent collaborator with Phil on their many projects. She was co-author, co-participant in The Ring of Truth and co-author in the book that went with that series. She is a passionate believer in the ability of science and technology to play a crucial role in maintaining the diversity of life on this earth.

Both Phyllis and Phillip Morrison are dedicated to demystifying science, a critical matter these days when so many issues affecting the quality of our lives-- indeed, the future of this planet-- depend on a broader public understanding of science and technology. It is my great pleasure to present Phillip and Phyllis Morrison.

[APPLAUSE]

PHILLIP MORRISON: The black box is a powerful metaphor out of science and technology. We all know them, even though nowadays sometimes they're brushed aluminum with lots of knobs and buttons. Of course, opening the black box is also a powerful image, and that, I think is the best [INAUDIBLE] I can say for what we mean by trying to do science. To get people [INAUDIBLE] by looking-- not fully. Most of the world remains a black box to science and technology today-- but looking into it, then to find our way inside that structure.

Now the wonderful part of it, turns out after 30 years of doing it, turns out to us to be that you do the same thing, whether it's the general public, such as whether you're watching a television set, or whether it's the properly praised students at MIT, the beginning is much the same. The style is much the same. Of course, the valve is turned on higher for those who will be professionals. But there is no difference in the quality of what you do. You can't do it without a vehicle for presentation.

We've chosen a title. It has a rather nice metaphorical ring. But we also mean it quite literally. We hope you'll think about it both ways. We're going to talk about footprints in the rock, what can be squeezed out of them, which is a simple introduction to the broadest methods of science and engineering.

PHYLLIS MORRISON: Now that title, "Footprints in the Rock," is a perfectly good all-purpose title for almost any talk you care to name. But today, we are going to talk about, literally, footprints in the rock. And I think that distinction, that concreteness, is a piece of what Phil and I try to do as we present the stuff of science, whether it be by entering your living rooms or teaching freshmen. Some of you have seen us in your living rooms, and we are working right now on a freshman physics course with hands-on experiments in it. Some of your kids will be in our classes.

That business, the results of science, are very easily available. That's all around us. But the behind the results is the stuff itself, the way science is done. And a year ago maybe, Phil became a Brown study as he read yet another book. This one had footprints in it. And he was caught by and thought about that. And we talked about it and tried some things out, and then thought about even more footprints, and that is what we'd like to bring to you this morning.

PHILLIP MORRISON: There are two points that we hope this is giving an example for. First, that science has to do with the concrete and the particular, which is usually not just what the lecturer writes at the bottom line. That's very thin. The bottom line is what people talk about. But it's not that. It's the enterprise that describes that is the important one in science. And so it's not only concrete, but it's concrete in a context. It has many things around it.

And second, it can't be done entirely passively. I read and write a lot. I'm a professional book reviewer. So I hold books very high. But they are only opening a gate. To walk on the path, you've got to do more than books. You've got to at least work. The book at least gives you a chance to turn the pages and go back and forth, which I have to say, the video screen does not do for us yet.

And this is the other side. You must be to some degree participant in the activity in order to make some progress in science. Do you think that this is the science? Those words the poet might have said. That is not the science. It's what they mean that counts. And that meaning is broader than any formulation. And that's what we're going to try to show in a very simple but quite romantic context of "Footprints in the Rock."

I would like first to take you to a different landscape, and the first slide may reveal this for us. It is not unfamiliar. I hope that some people in the audience will have been there. I never have. But I admired very much the distant desert aerial scene, and you can see the a ravine and a rather deep gorge going across the front of the scene. This is the famous Olduvai Gorge. Very important, because around it in the region that you see here, this region covered with volcanic ash and lava flows, a desert scene, is part of the ancestral home from which our species, after many years, descended. In this region, there's, we'll show you, the direct evidence of the life of those beings, those ancestors of ours, who are not of our species, who we would recognise as on the way, but not yet present in this scene.

Now, within the 20-mile stretch around this scene, there lie to your right on the horizon-- we don't see them here-- a couple of old volcanoes, those which are responsible for this flow. And to the left, downstream from the end of the gorge, the land slowly tilts and gives way, water courses, cutting through many layers of the ash down to a salt lake 15 or 20 miles away.

This is a very strange landscape. It looks a little Arizonan. I know the desert of Arizona and New Mexico pretty well. But it's probably stranger that we don't have such recently active volcanoes with their outpour.

Now I hope you have this feeling of what's going on in this land. And of course, there are animals in this land, especially in the rainy season. At the end of summer and the monsoon, there will come the rains, and the land will be greener than it is here, and a lot of animal life will appear. They are hidden and move back and forth across the area seeking higher ground by dry time, and going down to the lowlands in the winter time.

The famous contentious family of Leakey's premier archaeologists and paleoanthropologists worked here, as you know, for 50 years. And about 50 years ago, 45 years ago, they were told by a Maasai friend who stopped in to watch the work looking for bones on the edge of the Olduvai Canyon where they very successfully found many relics, they said, well, you go downtown 15 miles from here to a place called Laetoli, which means the Place of the Red Lilies, and in that lily place, he said, there's a lot of bones on the ground. A lot.

And they took note of that, but they didn't go there for some years. They were pretty busy. When they went there, indeed, they found a lot of bones in Laetoli, very few of them hominids. Almost none. But in the course of that investigation, they found many remarkable things. And the second slide will show something of what they found.

Well, these are birds' eggs, fossil birds' eggs, half petrified, dug from the ash. They are the eggs of the guineafowl. You can still see this wild bird freely around the region. Birds haven't changed very much, and in the next slide--

PHYLLIS MORRISON: These are fossils?

PHILLIP MORRISON: These are fossil eggs. They're not new eggs. They are rock-like. And here, you may see the track of the guineafowl. This track is not a track in the dust. You will see those, too. This is a track in hard rock, the congealed ash which we call tuff, which dominates the landscape, just what you saw there. And the very same tracks can be found there. Guinea fowls are conservative organisms. They haven't changed very much since this became lithified.

PHYLLIS MORRISON: Now, what you'll have is layers and layers and layers of tuff, of the stuff that blew out of the volcano. And essentially, those are the pages of a book of time. And as you flip through those pages, which the river cut the gorge made possible because then you see them on the sides of the gorge. You go down, down, down in time.

PHILLIP MORRISON: It's exciting to find a place, and they found it, a page in this book, which is exposed here and there by chance. Often, it's covered by other material. Often it's covered by heavy lava flow. We'll never get to it. But here and there, the chance erosion and flow and bowing of the winds in the long past has revealed a certain layer. Actually, it's a few pages. It's maybe five inches thick. And in those five inches, you can count 10 different layers by their texture. And by little partition, the texture, as you cut through it, you can see, yes, it was not the same here. Little coarser and a little finer, little coarser, and then a little finer-- that sort of marking gives you the pages.

I should say, this book is quite thick. It is 500 or 1,000 feet thick. If you go all the way down to the salt lake, crossing layer after layer after layer after layer as you go down, you can build all those up. But only in one place, only in six inches of that entire thick book, there is marked a lot of footprints like this. And they found and exposed them. When the expeditions went there in the '80s, the description has now been made really as a time of the '80s now. It took many years to bring suitable experts there to spend a long time to study what was there.

Maybe 30 places or 40 places, a few acres each here and there across the place of lilies, a five-mile square some distance from Olduvai Gorge, they found the exposed, gray-brown hard surface that they call the footprint tuff. And when it wasn't quite exposed, it was close by, they would cut it away a little bit to see what might be found. They knew it was a significant layer, and that was of course the early discovery made in the '30s. It tool a long time to get around to studying it.

Here is someone at work on the footprint tuff. Next slide please. There you see her, one of the archaeologists. And if you look more closely, you'll see she's looking at a very big footprint, which turns out to be recognizable as the footprint of an elephant in hard rock.

Now I'm not here to describe the ology of that time. I'm not a biologist. I'm not a paleontologist. I'm a simple physicist, and I'm interested in the physical situation that we can learn from these things. But I'm especially anxious to talk about the context in which these particulars occur. It is not just the headline. It is what goes behind it. Here you see, the front shows you a very nice large print, which I think looks elephantine. And it's pretty impressive that these things are there.

But now what astonished me-- I had read the articles in the magazines and the newspapers, and I knew that the Leakeys had found wonderful footprints of ancient beings and our ancestors there, hominids. What I didn't realize was the depth and richness of this context. I was, I must say, frankly a little skeptical. How could you find and interpret correctly a trackway of 50 footprints in the whole history of geology? Why should that be meaningful? Why can we believe what they say? And it wasn't until I read the great, thick expedition report-- that was the book that Phyllis talked about-- that threw me into a feeling of genuine understanding for the first time, appreciation of what these people could do.

All in all, they discovered in these 10 or 15 areas that they studied, 30,000 tracks in the footprint tuff, all in the rock, all in the same few layers. All made, therefore, within the time of a few falls of ash from a distant volcano. Not very distant. Across the horizon. Most of those tracks were recognizable today. They got a local hunter, a skillful tracker. He said, yes, yes. That's the track of a dik-dik, one of the little antelopes, or the track of a hare. The hare and the dik-dik are still the most important wild animals of this region, and they made up maybe half the tracks.

But the rest of the tens of thousands of tracks, he could, the tracker, identify many of them. And the experts who came from all the museums in the world all over the world who knew their animals could recognize, yes, they were this, that, and the other kind. Generally, the species were not the same, not exactly. This is a long time ago that those tracks were made. It doesn't lie at the top of the present land. It lies way down, as you go downhill towards the lake. And we know the dating, but I'm not going to talk about dating. We know it was a long time ago. That's all I want to say. Much longer than any witness can possibly bring to us. Only the mute witness is present. And these 30,000 prints are the subject of what we want to talk about.

That's what gives reality to the interpretation, it seems to me. It isn't just a chance, one or two things. It might be a fake. It might be a misunderstanding. But it's in the context. They're all over the place, and they cross each other, and they interweave, and they spell out the entire list, the ecology, if you like, of living forms of some distant time. Preserving, in a very strange way, a single page or two out of a book of millions and millions of yearly pages, just one page is exposed to us-- even the ephemeral passage of some little animal leaving hoof prints in the dust, which was there. It was not rock then. It was only dust.

Now, I guess the first print is worthwhile. This, of course, is a marvelous object. It's a contour map of the print which they call a hominid print. Contour maps are not the easiest things to read, but I wanted to show it just to emphasize the care with which these matters have been studied. These are millimeter contours. They photographed it stereoscopically. Specialists were brought in that can do that. He spent a whole summer photographing all footprints of human beings. Not the 30,000. Only 40 or 50. They spent a lot of time on them, and then they made these maps to send them all over the world and publication so that everywhere, people who knew about feet and about walking, about orthopedics and about gait and about prints could study in detail the material as well as they could represent it. So this is the footprint of an ancient ancestor, and I'll say a little later something to give you some feeling for how old that print actually is. But that's not my main task. And the next, I think.

This is a map again. It's the map of the trackway. I think you can see what it looks like. Here is a collection of footprints. Here is a big gap where a fault has come across that since it was made, one indication of the age. Of course in California, it might be two weeks. But it is something. Phyllis has pointed out the set of tracks, little and big, that go together right across the footprint tuff.

This is a wonderful discovery. Some very alert archaeologist noticed just one print, which he said looked to him rather humanoid. Nobody believed him. They all trooped around to look at it. That was right. And then they began to take away the two or three inches of tuff that remained above this rather hard layer. They could take it away at its parting layer and uncovered a whole trackway until they ran out. And this is the trackway, as you see, some 40 step prints or so that represent all we know of the situation.

PHYLLIS MORRISON: Now, What do we know of what has made these tracks?

PHILLIP MORRISON: Yes. We would like to know. We can't doubt from our experience with footprints since Friday was discovered by Robinson Crusoe, we can recognize that footprints are the sign of some quick impression on the rock, maybe 30 seconds or 60 seconds of walk. And that's all we have, a snapshot seized out of the past, a frame grabbed, if you will, out of the long movie of history. And in this frame, we're going to try to find out who made those tracks, how they were made, what else can we say about them. And we can say, of course, quite a good deal.

Next, I have to say this already was on our wall when the book came. So it wasn't something that we made. I'm not sure if the authors of this record are here, but I think maybe they are.

PHYLLIS MORRISON: Are the Adamses here? Would they be willing to walk across the stage so we can see your heights and your feet as you walk past?

PHILLIP MORRISON: Now, these are hominids, clearly, of our species. Very detailed prints, because it's much better to have ink and paper than it is to have tuff millions of years old to work on. See a lot more detail here. We have no doubt about this. But it's very nice because we can present the actual specimens. You don't often get to do that in paleontology, and this is really good stuff. And when they appear, I think you'll have no doubt which is which. I'll simply say we have [? Dar, ?] Mary, Jake and Ben Adams who kindly sent us this. But I have to say, this is really something like paleontology because they're not the way they are now in these prints. This is the newborn print of the youngest of the family.

[APPLAUSE]

Now like a proper physicist, Phyllis has marked the scale on this picture, 10 inches, and we will draw upon that from time to time. This is an exercise in measuring space and time, as you will soon see.

OK. Thank you. That's very good. And now then, we want to show another remarkable thing you can get out of measuring footprints. This was astonishing to me, but I should, of course, have anticipated it. Of course, we have made here a graph. This is an extremely simple graph, actually. We didn't make it. It was made by the paleontologists who reported on the Place of Red Lilies and Laetoli.

Here is the length of a footprint. Here is the stature of the hominid that made that footprint, in this case, all living human beings but two dots. And these dots represent 50 years of anthropological investigation. The dots usually represent the average in a well-defined population of people. Very strange populations. There is an average of 500 persons chosen at random in some city in North China in the '30s. There is the average of 100 Smith College students. And so it goes. People with shoes and without shoes, tall people and small people, all kinds of people are represented in this curve. Very interesting, but I can't go into all that detail.

However, I will show you that on this point, here is G3. Now G3 is the length of the footprints that we saw-- the trackway footprint, of which I gave you a map not long ago. That's the length of that one. And this is the length of the little one that went beside that. On the map, you saw big prints and small prints, the larger one and the smaller one, those two points. And they were not measured by anybody. They were measured from the tuff. But they fit the line really surprising well.

PHYLLIS MORRISON: No, they were put on the line because we only knew--

PHILLIP MORRISON: Yes, yes. We only knew the footprint size, so they were put on the line. Thank you. They established a point. But they used this line, which is the average line of all these things. Well, you might doubt that a little bit, so we produced some data of our own in a participatory way.

PHYLLIS MORRISON: But when you put them on the line, you then were able to read their height.

PHILLIP MORRISON: Yeah, that was coming. First, we'll talk about how good the line is.

PHYLLIS MORRISON: We added some data, and--

PHILLIP MORRISON: Can we put the last one on?

PHYLLIS MORRISON: Ah, yes. Let's move this a bit. We had a friend--

PHILLIP MORRISON: We had a very tall friend.

PHYLLIS MORRISON: --even up there. But of the four people who just walked across the stage, here's [? Dar, ?] here is Mary, here is Jake, and here is Ben. Ben is so far off the line that I suspect he is going to grow up to be a very tall person.

PHILLIP MORRISON: But that's only a vague forecast. We're not sure of that. But of course, now I must say something to disabuse you. I was quite puzzled by this because it fits so well, and yet we know you can't just buy shoes by writing to the shoe shop your height. And the reason for that is that we like to have our shoes fit within an eighth of an inch or a quarter of an inch, and that won't do. A shoe size is something like an eighth of an inch.

These are broader errors. We allow that. But those who know some statistics will know, this regression coefficient is 0.94. That's to say, 95% of the variation-- I'm sorry, I moved it.

PHYLLIS MORRISON: I'll fix it.

PHILLIP MORRISON: --is given by that nice, straight line. An extremely simple relationship between the height and the footprint length of people roughly independent of where and how and what they are. This friend of ours was 6 feet 7. This friend of ours is three 3 feet and 1/2. And yet, they lie-- these green dots, which we measured ourselves, we didn't trust all those 50 years of anthropologists. But by heavens, they were absolutely right. And a little error doesn't make a lot of difference.

So I think we can successfully read off this graph and say very likely, the being who made the bigger print in the tuff is this person, this hominid, about four feet, a little plus four feet. And here, four feet and a half, and here, a little bit under four feet, the accompanying print, these two tracks that went together.

Then here you will see the map of the tracks. Here's the larger one and the small one. Notice that they accompany each other very well. They're in step. The experts on footprints say there is very little doubt that that was done by the two creatures walking hand in hand. Otherwise a small person, who you'll see soon, cannot really keep pace with a large one. There has to be an kind enforced rhythm. And indeed, they showed breaks in the rhythm in the small step where the small gait has had to break the rhythm in order to catch up a little bit with the hand holder, who was moving ahead. So remarkable affair.

I have to say a little bit about how these prints were made. It's really quite interesting. You recognize that these creatures are co-specific we believe. Species are hard to define in the path. There are very few data, only a few skeletons, a few bones, a few skulls. They make much of it, but they make more, I think, than is recognizable. This kind of material is better than the placing of the few remains they have into group by species. But the famous hominid Lucy is about the same age and about the same size and nature, fully bipedal, as these two-footed walkers across the ash.

Now how come that this footprint can be preserved in the whole footprint tuff? How does it work? Does that make any sense? It does make remarkable sense. I don't want to describe it in detail. I'll simply say that the volcano that made this tuff is lying there in ruins 20 miles away. We can look at its crater. We can sample its chemistry. It has a very unusual chemistry. It puts out an ash which is a mixture of volcanic ash, pumice, and washing soda-- sodium carbonate. This material, called carbonatite, and when it changes, we call it [? trona, ?] is mined extensively in Wyoming and Saskatchewan in million-ton quantities each year to supply the glass and soap industry of the North American continent. That was, too, an ash fall from a volcano of a strange kind.

Now, that kind of ash, as you recognize from just mentioning washing soda, when water falls on it, chemistry occurs. The rain came. The ash dissolved in part. And when it dried, it had cemented the particles together with the [? trona ?] that is made, as it is called. And that mineral is much harder than the ash solidified on either side above and below. And it's that that took the footprints and held the footprints so wonderfully.

So we know the rains had to come rather soon. We know from measuring the thickness how much ash had to fall. We know that the whole season does not occupy very much, that this track is made in a time small compared to a season, because you can see the rain come and the dry season alternating through the ash, just as it alternates today. So they can say with good probability this was made in the early fall, when the rains came on top of a strange fall of ash from the volcano, which of course, did not occur every season, but occurred very frequently.

And indeed we may suspect from the orthopedist who had said, these beings are walking through there very cautiously, that they were walking in a darkened light of day, darkened by the heavy ash fall. And they were undoubtedly afraid-- we can impute that to them-- of the circumstances.

PHYLLIS MORRISON: Some places in this layer, there is even preserved for us the splats of the rain drops.

PHILLIP MORRISON: There is also across this track-- not shown here, but a little off this trackway down here-- the crossing of a horse, which is a very nice thing to see, because unmistakable horse's hoofs-- I don't want describe it in detail-- but that horse is making footprints and stride distances that are quite small compared to any horse or pony you can find today. And in fact, there are two. You can imagine there's a good bet that at least one was rather adult. Most horses are adults. Only a few are young at any time. That horse can be shown to be walking in a gait that is like that of the Icelandic pony in difficult circumstances. The smallest of all our modern ponies, and this horse is even smaller than that.

Well, you know that when small horses existed, it was not very up to date. There are not horse's left any longer in the Serengeti Plains. But if they were they would not be 3 and 1/2 feet high as these horses are, some indication of the age. And the remarkable thing is the gait of this horse is the same gait the Iceland pony uses called single foot-- horse people will recognize that-- which you use when the footing is unstable and slippery. A horse picks his way across moving the two feet delicately in the rhythms of the floor to carry out the gait called single foot. And these beings are also worried about the slippery slope on which they are moving.

So that's the story, and it gives us an enormous sense of presence. I think it is fair to say that two hominids walked across this in the darkened and poor visibility of an ash fall on a slippery, early, recently wetted soapy kind of ash, afraid of slipping and falling and not able to see very well. And their heights were, as we've indicated, learned from the footprint. So all that comes out of reading footprint size. Should I show the last? No. We're going to save it.

This very remarkable story of what has to be a minute, which can certainly only be a minute of alarm and concern, and the fact that the older one and the smaller one walk exactly at the same gait, not running back and forth means they were certainly made at the same time, and probably made-- you can't see the hand motion, but it's very easy to understand that these completely two-footed creatures, who never put their knuckles on the ground like the chimpanzees, but are erect as we are, though they come from a time when horses were small, when lions and tigers both lived in Olduvai, saber tooth tigers at that, then we know this is not the present day. I don't want to talk about the dating, but it's actually about 3 and 1/2 or four million years ago that these tracks were made.

And out of that moment we pick this kind of thing. Not just from the headline, not just from finding these tracks, which of course are wonderful, and have acquired a great deal of study, but from the whole context of 30,000 footprints around this five-mile square piece of the Place of Red Lilies. It's really a superb and romantic story, and I don't want to talk about it exclusively.

One could stop, but we wanted to go on further because physicists like to have time as well as space. All this has been about space. But we're going to do something now about time, too. Because what is still more remarkable is that you can read time from footprints as well. Phyllis.

PHYLLIS MORRISON: Not the vast amounts of geologic time, although for this next piece of our story, one needs to go back a great deal longer in that book. But not to the celebrated gorge of Olduvai, but to the cut, the Connecticut River has made in New England and Massachusetts and Connecticut, particularly. In the 1830s in that valley, in many places, but for instance in the town of Turners Falls, when the new sidewalk slabs came from the quarry, they contained footprints too. And these footprints were first thought of rather as the footprints of giant birds. Not a bad first guess. There is a wonderful little state park right on the banks of the Connecticut where you can go and see such footprints in place on a slab of rock above the river, and I recommend it to you. So I have seen them myself. These particular ones appear in a publication of a man, Edward Hitchcock, who taught at Amherst College. And down in the basement of the geology museum there, there is a vast array of footprints of dinosaurs, most of them wonderfully collected in the middle of the last century when the discussions raged about what this was.

And before too long, they came to understand that they were not quite birds. It was a big argument then. Perhaps today, we see a closer connection between the giant reptiles and the birds than those people did. But that was there. Soon, from England and then from the marvelous deposits in the American West, the bones of the great beasts came too. And they have certainly been favorites of many of ours in all that time since.

PHILLIP MORRISON: So here we have a way-- we are jumping in geologic time far, far back, far, far back. As you know, the cave dwellers of our ancestors did not fear dinosaurs. They didn't know a thing about them. They may have found an ancient bone or two, but this is far, far back, much older than the hominids. And now the next print will show the kind of-- we have all over the world, the searchers have now found about 1,000 localities where there are dinosaur footprints, amounting to hundreds of thousands of prints. So this is becoming a study much richer even. Of course, over a long period of time, so many, many examples, and many, many forms of animal, and over a huge period, it's not easy to summarize in any way.

One of the most exciting, though, is this reproduction made here, a drawing of a place in northern Australia near Brisbane, Queensland, Australia. And there you see footprints, and I think you will see quite clearly this dramatic event. There are footprints of a very large creature. That's a two-foot pad, that footprint, that footprint. Those two-foot pads almost full size. Just about full size. You imagine how big that is. So the rest of that animal, all we see is his footprint. He's a pretty good sized animal-- or she, for all that matter.

And these little fellows are also bipedal dinosaurs. They are turkey-like. More or less, those are the prints of turkeys, big turkeys or very big hens and roosters running along. And it's quite characteristic of these hundreds of prints all going this way and these three big prints going that way, and we'll see what we can reproduce from that a little bit later. But that's an interesting part of the puzzle. People try to interpret these scenes. Again, a flash out of the film of all history.

Let's look a little bit at what we can say about time from a footprint. It turns out that when any creature walks or runs, there is an enforced relationship between the length of the stride and the speed of motion. This comes out of the physics of motion. We don't fully understand the control mechanisms that allow almost all creatures to run efficiently at a number of speeds. When they run, they can't change their posture and space and so on easily. If they try to do that, they will have a hard time performing. We are built to have a rather well-defined engineering of domain of behavior, which makes us walk and run.

As you run, as you know, you don't keep both feet on the ground. In fact, running can be said to be, that motion in humans when both feet are not simultaneously on the ground, you take off by pressing one foot hard against the ground, beating gravity. In order to make the speed high enough, you must push hard. When you push hard, you overcome the effect of the weight, and it breaks contact with the surface. And this is a necessary condition of running.

And it therefore turns out that all sorts of animals have a quite straightforward relationship between the stride length, which is here defined simply as the distance from the left foot coming down to the left foot coming down again, to the left for coming down again, for all these bipedal creatures-- I guess even some four-footed ones. In that case, you go through the whole stride. You have left to left, left-front to left-front, and so on.

These various curves, they're each rather good curves. Notice the cluster of dots of each kind. But I observe to you, this is dogs. Here we have the length of stride. Here we have the speed of motion. So the faster you go, the bigger the stride. No doubt about that, as we'll show in a moment. And you make that plot, I get this graph for dogs. And these circles are humans, adult men in this case. The squares are dogs, and the triangles are camels. And they all have curves which look like rather plausible straight lines like our height curve, but they're not at all the same curve.