The Age of Exploration

The Age of Exploration

A lecture by Professor Carl Sagan
Cornell University, October 13th, 1994

Reading time: 20–30 minutes


WE HUMANS HAVE HAD CIVILISATION ONLY FOR ABOUT TEN THOUSAND YEARS. Our species is a few hundred thousand years old. Our genus, the genus Homo, is a few million years old and, therefore, for the vast bulk of our tenure on earth, we were something other than sedentary and the word has such an aura of self-congratulation: civilised. 

What were we? We were hunters and foragers. We wandered in small itinerant extended families.

Our knowledge of the hunter-gatherer lifestyle is due to a few courageous and far-seeing anthropologists who went and lived with the few remaining hunter-gatherer groups before they were finally and utterly destroyed by civilisation. 

The anthropologist from whom I learned the most about hunter-gatherers is Richard Lee of the University of Toronto. He studied a people, the !Kung San of the Kalahari Desert, in the Republic of Botswana. And I want to just give a little flavour about my understanding of our ancestors from Richard Lee’s study of the !Kung San:

The first thing, that I think is very important, is that they are highly technological. The technology is wood and stone and domestication of fire technology. But it's absolutely technology. And there are experts and other people who are not quite as good at the technology. But not only are they technological for fun, they are technological because their lives depend upon. Chipping and flaking stone tools – back before they had a little trickle of metal into their economy – is very difficult to do, and of course they did it superbly well. 

And the archaeological and anthropological record is clear that we were technologists all the way back to the beginning. So the idea that science and technology is something new, something unusual, something – we can even find books that say, not really very human – is completely backwards. 

Technology is, if anything, the most characteristically human activity. Although, as I'll mention later, it is not exclusively a human activity. 

One very interesting insight, I thought, is hunter gatherer tracking techniques. A small group with their bows and poisoned arrows, and digging tools, and a few other lightweight technological contrivances, is following the gang. They come near a stand of trees. They take one close look at the ground. Immediately they know how many animals went by, what their ages and sexes were, how long ago they passed.

„This one is lame in the back left foot.“

„At the pace they're going we should be able to overtake them in another two hours, if we hurry.“

Now, how do they know all this? In fact, what do they notice?  In order to follow the gang, on which their lives pretty well depends? 

One thing is a hoof-print. Different animals have different characteristic shapes of their hooves. Different sized animals leave different sized hoof prints. But the decay of the hoof crater, the falling of pebbles in, the collapse of the raised rims, debris blown into it, tells you age. 

In fact, it reminds me of nothing so much as determining ages of planetary surfaces by looking at how fresh the impact craters are. I think the reason that studying crater in physics seems so natural to us, is because we've been doing it for a million years. 

They also know, that hurt animals in the hot sun like to avoid the sun. If there is a shadow on the ground they will deviate from their path to just run through the shadow a little bit. Well, where the shadow is depends on where the sun is. And therefore when you see the deviation, you know, that there had to be a shadow at that spot when they passed. Well, where in the sky did the sun have to be in order to cast that shadow? Oh, it was 11 o'clock this morning. 

I don't claim that every contemporary – well, there are none, but back 10, 20 years ago – every contemporary !Kung San made a scientific calculation, did the trigonometry of the angle of the sun. That's not, what this is about. This was tradition that each generation taught the next. But someone had to have figured it out. And that someone had to be a scientist. And this is another reminder, that we've been scientists and technologists from the beginning. 

Tribal hunters and foragers in Botswana. The Age of Exploration by Professor Carl Sagan. Woolday

Tribal hunters and foragers in Botswana. Technology is, if anything, the most characteristically human activity.



Having said that, I want to turn to the important and rueful fact, that every human culture has considered itself at the center of the universe. What's this about? 

Well, I think, it's very straightforward. Back then, in hunter and forager times, many modes of modern nocturnal entertainment were unavailable. Some were available, but many were not. Television was not available. So over the dying embers of the campfire, people watched the stars. And they did it, I imagine, for many reasons. One, it’s just dazzling. We today, living under polluted skies and in cities with light pollution, have mainly forgotten how gorgeous the night sky can be. It is not only an aesthetic experience, but it elicits unbidden feelings of reverence and awe. 

Secondly, people made up stories about the stars. They invented Rorschach tests. 

“Up there. Follow the dots constellations. Looks like a bear to you?” 

“Arghh, yes, I guess it does.” 

And then force their children to memorise these absolutely arbitrary patterns. 

“I don't see the bears tailed, dad.” 

“Shut up."

And then myths were invented. Either, before or after. So these were visual reminders of stories. The-bear-ate-your-grandpa-something-like-that was put up in heaven as an example. Or there was the story first and then people put the Bears up there. 

But beyond that, there was something enormously practical. That is the stars and their rising and setting are a great clock and calendar in the sky. And in the absence of artificial time pieces that's extremely important. Because there are certain seasons of the year when the herds are running. There are certain seasons of the year when the trees are ripe with nuts or fruit. And if you know what those seasons are, and you know what the moment is, you can prepare. And you can also eat. 

Now, the most superficial examination of the sky shows: the stars are rising in the east, some of them pass directly overhead, and some of them pass on small circles close to the horizon.  But they all rise in the east, they all set in the West. And then, in the daytime, they do something else. They somehow go around the bottom of the earth, that none of us has ever seen. 

“It's flat as a board, of course.” 

And then the next morning, they come up again, in the east. 

Now, there is absolutely no doubt from this fact, that the stars, the planets, the sun and the moon, all go around us, and we're obviously not moving, that we are at the center of the universe. It's an observed fact. Anybody who denies that, there is something wrong with them. This is the geocentric conceit. 

Not only did every culture draw this conclusion, but I think it's clear that our ancestors took enormous personal satisfaction in it, because, think about it: We are at the center of the universe. The center of the universe is surely an important place. Not only that. What other animals, what plants make use of the apparent motion of the stars? Only us. Therefore the stars have been put there for our benefit – and the sun and the moon are practical objects. 

Maybe there was some confusion. Maybe you know the old story about the the Persian wise man and philosopher who was asked which is more useful: the sun or the moon? And he replied, of course, the moon. Because the sun shines in the daytime when it's light out anyway, whereas the moon only shines at night when we need a little light. But even when people got things, you know, a little wrong the centrality of our position was stunning. 


I imagine an extraterrestrial visitation – of the sort, that there is absolutely no evidence for – coming upon the earth, of course, running around the sun once every year. And then listening in on what people all over the planet are saying. And they're saying: We are at the center, we are important, we are special, everything goes around us. And then I imagine the extraterrestrials thinking of us as the planet of the idiots. 

But that's too harsh. Because there's a resonance here between the most obvious interpretation of absolutely straightforward observational facts, that every person can verify for him- or herself. A resonance between that and our emotional hopes and needs. The idea, that the universe is made for us, not because of any particular merit of ours, but just because we're here or just because we’re human. 

To me this seems to resonate with the same psychic wellsprings responsible for the view that our nation is special – and the center of the universe. Which, by the way, is the literal meaning of the Middle Kingdom, for centuries applied by the Chinese to China. 

By the way, you can see it in the maps. How often each nation has itself at the center of the map. When other nations look at it, it's extremely peculiar to see Peru at the center of the map. 

“What's it doing there? It's weird.” 

And the same psychic wellsprings that our gender, or our ethnic group, or our particular melanin content in the skin, or a particular language, or head dress, or clothing style, or convention of pulling out the handkerchief when we sneeze, or anything is important and central. All those alternative ways of being human are somehow less sensual, less important, less worthy, than we are. 

We have a weakness! 

And scientists are creatures of the culture in which they swim, in which they have grown up. And so we also are vulnerable to this siren song, which we can call chauvinism, or geocentrism, or anthropocentrism. 


You know the story about what happened next. Except for a little blip, associated with the name of Aristarchus of Samos,  we went on – every human culture, every great philosopher, every scientist, every religious leader – thinking, we were at the center of the universe. 

We put it in various guises in our scriptures. Declared the scriptures to be infallible. Thereby making it not just a secular, but a religious crime to even think about the issue, until in the late 15th century. An astronomer cleric from Poland, named Nicholas Copernicus, thought he had an alternative idea: namely that the sun was at the center and the earth, like the other planets, went around it. 

He knew that this was dangerous stuff and so he withheld the publication of his book, until he was on his deathbed. And even then, the way it worked out when the book was published, it had a preface by a well-meaning friend of his,  Andreas Ossiander, which essentially said: 

“Dear reader, when you look at this book, it may appear that the author is saying that the earth is not at the center of the universe. He doesn't really believe that. You see, this book is for mathematicians. If you're not a mathematician, close the book.”

Of course, I’m paraphrasing slightly. 


"Of course, there are differences between chimps and us. But, we can't say, that they don't have any technology."


“Mathematicians find, that if you wish to know where Jupiter will be two years from next Wednesday, you can get a good answer by assuming that the sun is at the center. This is a mere mathematical fiction and it does not challenge our holy faith and please have no emotional angst in reading this book.”

This peculiar split-brain compromise actually lasted for almost two centuries, in which people actually said: 

“Well it's all right, it’s only for mathematicians. The Bible says the earth is at the center, we all believe that.”

And then, as you know, Galileo made a forthright and brilliant defense of Copernicus, based in part on a set of observations from the newly invented astronomical telescope. The church got increasingly annoyed. Galileo remained obdurate. 

I once had the pleasure at the behest of Franco Puccini, director of the archery observatory, to actually trod in Galileo's footsteps and hold a close replica of his telescope. In any case, when Galileo became too insistent, the princes of the church showed him the instruments of torture in the dungeons. They weren't making any particular point just thought he'd like to see them. And shortly thereafter, Galileo made his famous confession, in which he abjured the abominable doctrine that the sun and not the earth was at the center. 

But the stage had been set, the debate went on. And when in the 18th century Bradley discovered the aberration of light and then in the 19th century the long-sought annual parallax was found. The opposition collapsed. And now, everybody is taught that the earth is not at the center of the universe.


Except, I think, there's a lot of evidence that we are all geo-centrists with a heliocentric of veneer that's been painted on us. Think, for example, about our language: sunrise – I was up before sunrise. Sunset – it was a gorgeous sunset. 

But the sun isn't rising or setting. The earth is turning. Think of how difficult it is for us, to simply parse a simple word or phrase which conforms to the Copernican perspective. 

“Billy, be sure to be home before the rotation of the earth makes the local horizon occult the sun…”  — Billy’s gone before you're halfway through.  

Why isn’t there any snappy phrase like sunrise or sunset in the Copernican context?  

Recent opinion polls show that 25% of adult Americans do not know that the earth goes around the sun and takes a year to do it [this is from 1994. The latest numbers from 2014 didn’t show any significant change to that number]. In China the figure is 70% [today still more than 50%]. If you bear in mind that the Copernican perspective got to get a lot of press in the United States. I mean there is NASA; there are television programs other than “In search of our obscure and erroneous mysteries” or whatever it's called. We do hear that the sun is at the center and still a quarter of us have missed it. And in China you can see where there isn't a NASA and where the television programs are much less sophisticated, a much larger percentage of people have missed it. 

If anything like China is typical it may be that today, five centuries after Copernicus, most people on this planet still think in their heart of hearts, that the earth is at the center. So, I think, congratulations on our insights in deducing there's something fantastic and great about human beings. 

There is then actual observation of the circumstances nobody ever thought to look before. And then the result is the daunting and disquieting discovery: 

No we're not at the center. No we're not important.

And to my mind, many of the key findings of science and much of the modern scientific perspective evolves from debates with that character. 


So let me just try to outline a few examples: Shortly after Copernicus there were people who said: 

Okay, okay, maybe we're not at the center of the universe. Maybe the sun is. But we're close to the sun. Look we're almost at the sun. So we're almost at the center of the universe. It's almost as good. 

Well, was the sun at the center of the universe – which we can loosely translate as: at the center of the Milky Way galaxy? 

The answer is: No. We are not at the center, where it looks important or at least well-lit. Instead we are in or at least near an obscure spiral arm 30,000 light-years from the center of the Milky Way galaxy, in the galactic boondocks. 

If you were an intergalactic traveler coming into the Milky Way. What would you think of someone, who said: 

“Excuse me, captain, that's the center of the Milky Way.”

“It's true.”

“But count out spiral arms with me. So there is one. There's another one – really big and beautiful. There's another one. Then over there, you see,  that somewhat obscure spiral arm? Well, don't look exactly in it but just a little out of it. See over there? I know, it's hard to see. Take a closer look. Right there. No, no, not that one. That one! See? Yeah. Yeah. The guys who live on that one say, they're at the center of the universe. And that the entire universe is made for their benefit.” 

What would you think of those guys? And then suppose, you had the information there's not one soul on that planet who thinks otherwise. Every one of them thinks they're at the center of the universe. 

Then there was a moment, when it was thought, well, at least the Milky Way. We are in the only galaxy. But no, that's not the case. Not only are there other galaxies, there may be as many as a hundred billion of them. 

Then there was a moment when the Hubble flow was discovered, when it was found that the galaxies are all running away from us. The more distant galaxies running away the fastest, as if we had committed some dreadful cosmic social blunder. When there were people who breathed the sigh of relief – this was in the 20s of this century – look we're at the center. Our galaxy at least. We are not at the center of our galaxy, okay, but our galaxy is at the center of the entire universe. 

This is based upon a serious misapprehension. There is no center to the universe, at least in ordinary three-dimensional space. And astronomers in any one of these galaxies would see all galaxies, would see all the others, running away from them – in the same way that we do. 


Then there was for a long time, all through my growing up and undergraduate and graduate school career, the statement: there are no other planets. There was always a nearby star that was suspected to have planets – and it never did. Barnard's star was for a long time a leading hope. 

And if there are no other planets. If life has to arise on planets,  then there's no other life and there’s no other intelligence. And so in that sense, we're at the center of the universe. Well, one of the things about the age we live in, the last 15 years, is, that this chauvinism is in the process of teetering and collapsing. Because we find that more than half of the nearby young sun-like stars have circumstellar disks of gas and dust extremely like what has been deduced for the birthing grounds of the planets in our solar system. 

The key datum being that the orbital planes of the planets are very largely coplanar – and this was, by the way, something that Isaac Newton, no less, thought, he could deduce the hand of God from.

That is God took each planet and threw it in the initial condition – all in the same plane. But Campton Laplace independently knew better. They used nothing more than Newtonian physics. Newton had just missed it, that the conservation of angular momentum meant that an irregular spinning contracting cloud would collapse into a disk and the planetary formation would occur in the disk and therefore you had to have – collisions aside – coplanarity of the orbits of the planets. 

Not only are there amazingly numerous circumstellar disks, but we now have the first bona fide extrasolar planetary system going around a star that must be at the bottom of the list of potential candidates, that anyone would have imagined: a pulsar named B1257+12. This particular pulsar is something like an atomic nucleus, the size of the Cornell campus, spinning at 10,000 revolutions per minute. It's a supernova remnant. There was a colossal catastrophe that blew off most of the mass of that star, and going around it are at least three planets to roughly earth-like mass, one roughly lunar mass, a little closer than Mercury, Venus and the Earth. And whether these planets survived the supernova explosion, or formed recently out of the supernova debris, whichever it is, the processes which lead the planets look to be a very broad in general application.

The technology is now improving so that in the next 10, 20, 30 years, in other words, in the lifetime of most of the students in this audience we ought to have completed comprehensive surveys of the nearest few hundred stars – maybe much more than that – to see what planetary systems they have. So this chauvinism, I think, we can also chalk off. 


Watch the Cornell University's video of Carl Sagan's lecture (96 minutes)



There's been the view, that, if there is nothing special about us in space, maybe there's something special about us in time. We’ve been put here by the creator to take care of things. Stewardship is the very engaging word that is often used. Who knows, what would happen to the environment without us? So we have an obligation to make sure everything goes as god would have wished it. 

The only trouble with this idea is – well, there is several, but for me the principle trouble with this idea is – that 99.998 percent of the lifetime of the universe, from its beginning to now, was over before any human appeared on the scene. So, if we are the caretakers, where have we been for most of the time we were supposed to be doing our job? We have been terribly lax. I could see that the chief gardener might be very annoyed with us, which in turn might explain a great deal.

We could not have been put here as caretakers because we have not been taking care. A, because we weren't here. And, B, because when we have been here, we haven't been doing very well either. 

Then there was the view, that, if there is nothing special about our position in space or our position in time, there's something special about our motion. We have a privileged frame of reference. This was the classical absolute motion physics, that every great physicist bought into until 1905. 

Albert Einstein, a keen critic of privilege in the social sphere, immediately mistrusted the contention that the planet we happen to live on was affixed to an imaginary frame of reference, which had special merit with regard to the laws of nature. He instead asked: What kind of physics would it be, if you deduced the same laws of physics, no matter what planet you lived on, what star you lived on? 

And that is one approach to special relativity which is repeatedly confirmed and is the way the universe is put together. Another chauvinism biting the dust.


This is a set of, what Ann Druyan [Carl Sagan’s widow] has called the great demotions. And there are people who find it very upsetting.  Who still long to be at the center. 

One area where you can see the emotions – not hidden, but written out in clear – is in special creation. The notion that we are the particular objects of the devotion of the creator of the universe; that we are different from the other animals and plants; not just in degree, but in kind. 

You know the list: No one else has altruism, compassion. No other animal loves their young. Nobody else can foresee the future consequences of present actions. Nobody else has art or music. Nobody else can use tools. Nobody else can make tools. 

And this list, it goes on and on. It is essentially agreed to by Plato, Aristotle, St. Augustine, St. Thomas Aquinas, Hobbes, Locke. All the great figures in philosophy, – with a single exception of David Hume. Hats off to him. Bought into by all scientists, including highly skeptical ones up until the year 1859. Bought into, of course, by all the religious leaders of at least the Western religions, especially the judeo-christian-islamic religion. 

In 1859 Charles Darwin made the first and heroic effort at pricking this balloon, showing that one species could, in fact, evolve by absolutely natural processes without anything ordained from another species. And then, when he got up the courage, – it took a great deal of it –more than a decade later, he published his second book on the subject, suggesting: not only does it apply to lots of species, but us, too. 

We and the chimps have a common ancestor. They are our cousins. This contention really makes a lot of people upset: 

“Have you been to a zoo lately? Have you looked at what a chimpanzee does? Maybe you're related to chimps, buddy, but I'm not.” 

Well, we can learn about chimp behaviour in zoos, about as well, as we can learn about human behaviour in jails. And for exactly the same reasons: they don't bring out the best in us. 

But when people like Jane Goodall devote themselves to observing chimpanzees in their natural habitats – the chimps get used to them; the chimps have no trouble recognising,  after a while, that the humans are somewhat inept chimps – then we find very different behaviour. 

This Chimpanzee is fishing termites with a reed. It turns out that we share 99.6 percent of our active genes with chimpanzees. We share the same ancestor – they are our cousins. 



I can't resist telling the story of Géza Teleki, an anthropologist and animal behaviourist, who wished to learn chimpanzee technology. Particularly the termite fishing industry, in which they are adept. And so he apprenticed himself for nine months to a chimp named Leakey, who was expert. 

The chimpanzee termite fishing industry goes as follows: You find a reed, not any kind of reed, the right kind of reed. You strip it of supernumerary branches, feel that it’s right and then go to the enormous termite mound. Now, each night, the termites cover over the entrances to their nests. The chimp takes one look, scratches away two, three places, where the entryways have been walled up; takes the the reed or grass stem in one deft motion; puts it down into the termite mound; gives a few twists; carefully pulls it out; the thing is covered with termites. The Chimps goes yam, yam, yam and here is a good source of protein. 

If a human were dropped down in this same place and had a need for protein, this source is unavailable to humans. Teleki, spending full time on this problem for months, could, A, not break off the right kind of reed – in fact he had to use the leftovers, that chimps had picked out – and could not, after nine months, find the openings to the apertures, that the chimp takes one look at it and opens up. And B, he could not put it down deftly. He would do that and the thing would come out accordioned. Could not wiggle it enticingly to get the termites on and could not withdraw without scraping off almost all the termites. At the end of nine months he’d come up with one termite birch.

Chimps know how to do stuff. And how do young chimps know to do what Géza Teleki did not learn how to do? They were apprenticed for years. By the way, in Teleki’s wonderful paper, in the acknowledgments, he thanks his patient tutor and apologises for his failures. Because they are not the fault of the being, he was apprenticed to. It's just humans aren't very good at this stuff. 

There is in fact a bonobo, a kind of chimp, who lives in Atlanta, who not only knows how to use stone tools, but knows how to make stone tools. This source of human pride is again misplaced. 

Of course, there are differences between chimps and us. We have electric light bulbs and police cars, CD players, nuclear weapons, all sorts of things that chimps don't have. But, we can't say, that they don't have any technology. And when it became possible in the late 19th century to do DNA-based sequencing, you could get a quantitative measure of the relationship between humans and chimps. It turns out that the two species share 99.6 percent of their active genes. So one way to look at that is: 0.4 percent is a much larger number than we had guessed. Another way to look at that is: You want to know about us? Take a look at chimps, there's a lot there to learn. 

In any case, the idea of special creation is really an idea for another time. If nothing else, but the molecular biological evidence were available, it would be very clear, that there is nothing in us that is qualitatively different from our nearest chimpanzee relatives.


That takes us to the present stands where these great chauvinism battles are taking place. One is the search for extraterrestrial intelligence. We have not found life, much less intelligence, anywhere else, yet. We send spacecrafts to other planets to look for life. We construct large radio telescopes and listen if anyone is sending us a message. Lately both of these activities have led to occasional tantalising data, but none of it of a sufficient quality to say that we've detected life or intelligence elsewhere. 

In our ignorance, the geocentrists find hope. They confuse absence of evidence with evidence of absence: 

“You haven't found life elsewhere? Well, there isn't any. We are the only living creatures in the universe. On this planet. You haven't found intelligence elsewhere? There isn't any elsewhere. It's only here! We are at the center of the intellectual cosmos.”

And while I could give you what I consider to be a strong plausibility argument, why this conceit is also erroneous, it's only fair to say that nobody knows the answer to this issue. We have not found life or intelligence elsewhere. We are in the course of looking. Maybe we will find it tomorrow? Maybe it will take centuries? Maybe we will never find it? 

All we have to do is keep an open mind. There is no other approach. You don't have to make up your mind in the absence of evidence.


And then, finally, there is a new and to my mind bizarre field for this debate. Something called the anthropic principle. Which would be much better called the anthropocentrism – which comes in strong, weak and various shades of middling flavours:

The weak anthropic principle says, if the laws of nature and the fundamental constants of nature were significantly different, then the paths which led to us, would have been different and we wouldn't be here. That is unexceptionable certainly true. No problem. 

But then there is a strong anthropic principle, which to my mind, is dangerously close to the following argument: 

“We would not be here if the laws of nature and the values of the physical constants were other than they are. Therefore the laws of nature and the physical constants are as they are in order for the universe to produce us.”

God had us in mind at the time the universe was made. And here we are.  Back at the center of the universe again. 

There are many things which can be said about this, including the point, that Philip Morrison, among others, has made: who has traced through, what other laws of nature and physical constants will lead to the functional equivalence of life and intelligence? 

It's impossible to do. You can also argue against it, that it is not very vulnerable to experimental investigation, but I would just like to point out that there's something telling about calling it the anthropic principle. Because, the same laws of nature and the same physical constants are required to make a rock as to make a person. So why is it not called the lithic principle?

There's a strong and weak lithic principle. And in the strong lithic principle the laws of nature and the physical constants are as they are, so rocks could come into being. Not nearly as satisfying, right? But if rocks could philosophise, I bet you would hear nothing of the anthropic principle and at the cutting edge of rock philosophy would be the lithic principle. 

Billions and Billions of stars. The center of our galaxy, the Milkey Way, with its luminous starfields, that build a continuum of light. 



I have only two slides. This first image, an absolutely typical astronomical photograph of what is called a star field. Take a long look. What you are looking at is some, I'm not sure, tens of million stars. Something like that. One in front of another, so that they seem so closely packed, that from a greater distance or with a smaller aperture telescope you could not even tell they're individual stars. This is what the Milky Way is. It’s stars in line of sight so closely packed that it looks like a continuum of light. 

Many of these stars are more or less like the sun. As I was saying before, it now looks as if planets are a frequent if not invariable accompaniment of star formation and, again, I ask you to consider the contention, that the only life and intelligence in the universe is – let’s say – that dot. No, not that one, that one right there. See? That's it. 

Nowhere else maybe hard to extrapolate from one example, and one example is all we have. But this is so resonant with the other human conceits I tried to outline in the great demotions, that I am suspicious of it for that reason alone. 

I want to conclude with one of the many psychic rewards that planetary exploration has brought to me. As Ed Stone [Edward C. Stone - former Director of the NASA Jet Propulsion Lab] outlined in his talk this morning, there was a moment when the two Voyager spacecrafts had completed their close-up reconnaissance of the Jupiter, Saturn, Uranus and Neptune systems. No other planets that we were going to run, they were with, further out in the solar system. It was now possible to turn the cameras close to the sun. And if the worst happened and we burnt out the optics?  So what! There was nothing else we were going to photograph. 

Because I had wanted from the time of the Saturn encounter, to take a picture of the Earth from that remote vantage point. And at the same time I wanted us to get to Uranus and Neptune and see what was there. The spacecraft phenomenally outperformed its design specifications and the bulk of our knowledge of the outer solar system has come because JPL [Jet Propulsion Lab] did such a brilliant job with these extraordinary spacecraft – coming in on time, under cost and of vastly exceeding the findest hopes of their designers.

Anyway, as Ed well knows, it was by no means easy, even though, the downside was almost nil, to turn the cameras back. It required an actual intervention by the NASA Administrator to get it done. But it was done. 

It was clear that because the Voyager One picture was taken from beyond the orbit of Neptune, that the earth would appear only as a single picture element. A single pixel. You would not even see continents. You could not tell any detail. I still thought it would be useful to do it.  In the same sense, that the great frame-filling Apollo 17 picture of the whole earth has become a kind of icon of our age. Because it said something very powerful to us, including the fact that from that perspective national boundaries were not in evidence.

Pale Blue Dot. The last photo of the Nasa Voyager mission. Made on January 14, 1990 from more than six billion kilometers away. Composed of 43 individual images.




SO THERE IT IS. I mean take a look, it's a pale blue dot. That's us! That's home. That's where we are.

On it, everybody you love; everybody you know; everybody you've ever heard of, lived out their days there. The aggregate of all our joy and suffering. Thousands of confident ideologies, religions, economic doctrines. Every hunter and forager, every hero and coward, every creator and destroyer of civilisation, every King and peasant, every young couple in love, every hopeful child, every mother and father, every inventor and explorer, every revered teacher of morals, every corrupt politician, every uncorrupt politician,  every superstar, every supreme leader, every saint and sinner in the history of our species lived there. 

The earth is a very small stage in a great cosmic arena. Think of the rivers of blood, spilled by all those generals and emperors, presidents and prime ministers, and party leaders, so that in glory and triumph they could become the momentary masters of the corner of a dot. Think of the endless cruelties visited by the inhabitants of one part of the dot on the scarcely distinguishable inhabitants of another part of the dot. How frequent their misunderstandings, how eager they are to kill one another, how fervent their hatreds. 

Our posturing, our imagined self-importance, the delusion that we have some privileged position in the universe, seems to me challenged by this point of pale light. 

Our planet is a lonely speck in the great enveloping cosmic dark. In our obscurity in all this vastness there is no hint that there's anyone who will come and save us from ourselves. That will happen only if we do it. 

It's been said, that astronomy is a humbling experience, and I would add: character building. To me, this, is one of many demonstrations through astronomy of the folly of human conceits to me. 

This picture underscores our responsibility to deal more kindly with one another and to preserve and cherish the pale blue dot. The only home we've ever known.

Thank you.