A Special Thought for Christmas 1999

Link: Neil's Usual Home Page

"Voyager 1" view of Earth from 6.4 billion Km

In 1989 both Voyager probes had crossed the orbit of Pluto. At that time, Carl Sagan remembered how the famous "Earthrise above the Moon" picture taken during the Apollo 8 mission forced humans to step back and see the Earth as just a part of the universe. In the spirit of that realization, he convinced NASA/JPL mission managers to swing Voyager 1 cameras around to take the picture below.

We succeeded in taking that picture [from just past the orbit of Neptune], and if you look at it, you see a dot.

{ the blue circle was added by an artist }

Look again at that dot. That's here. That's home. That's us. On it everyone you love, everyone you know, everyone you ever heard of, every human being who ever was, lived out their lives. The aggregate of our joy and suffering, thousands of confident religions, ideologies, and economic doctrines, every hunter and forager, every hero and coward, every creator and destroyer of civilization, every king and peasant, every young couple in love, every mother and father, hopeful child, inventor and explorer, every teacher of morals, every corrupt politician, every "superstar," every "supreme leader," every saint and sinner in the history of our species lived there-on a mote of dust suspended in a sunbeam.

The Earth is a very small stage in a vast cosmic arena. Think of the endless cruelties visited by the inhabitants of one corner of this pixel on the scarcely distinguishable inhabitants of some other corner, how frequent their misunderstandings, how eager they are to kill one another, how fervent their hatreds. Think of the rivers of blood spilled by all those generals and emperors so that, in glory and triumph, they could become the momentary masters of a fraction of a dot.

Our posturings, our imagined self-importance, the delusion that we have some privileged position in the Universe, are 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 help will come from elsewhere to save us from ourselves.

The Earth is the only world known so far to harbor life. There is nowhere else, at least in the near future, to which our species could migrate. Visit, yes. Settle, not yet. Like it or not, for the moment the Earth is where we make our stand.

It has been said that astronomy is a humbling and character-building experience. There is perhaps no better demonstration of the folly of human conceits than this distant image of our tiny world. To me, it 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.

Carl Sagan
Wikipedia Article: Pale Blue Dot

Pale Blue Dot
Photo: Earth (inside the blue circle)
Distance: 6.4 billion Km (4 billion Miles)
Date: 1990-02-14

(Earth is a) Pale Blue Dot

From this distant vantage point, the Earth might not seem of particular interest. But for us, it's different. Consider again that dot. That's here, that's home, that's us. On it everyone you love, everyone you know, everyone you ever heard of, every human being who ever was, lived out their lives. The aggregate of our joy and suffering, thousands of confident religions, ideologies, and economic doctrines, every hunter and forager, every hero and coward, every creator and destroyer of civilization, every king and peasant, every young couple in love, every mother and father, hopeful child, inventor and explorer, every teacher of morals, every corrupt politician, every "superstar," every "supreme leader," every saint and sinner in the history of our species lived there – on a mote of dust suspended in a sunbeam. The Earth is a very small stage in a vast cosmic arena. Think of the rivers of blood spilled by all those generals and emperors so that, in glory and triumph, they could become the momentary masters of a fraction of a dot. Think of the endless cruelties visited by the inhabitants of one corner of this pixel on the scarcely distinguishable inhabitants of some other corner, how frequent their misunderstandings, how eager they are to kill one another, how fervent their hatreds. Our posturings, our imagined self-importance, the delusion that we have some privileged position in the Universe, are 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 help will come from elsewhere to save us from ourselves. The Earth is the only world known so far to harbor life. There is nowhere else, at least in the near future, to which our species could migrate. Visit, yes. Settle, not yet. Like it or not, for the moment the Earth is where we make our stand. It has been said that astronomy is a humbling and character-building experience. There is perhaps no better demonstration of the folly of human conceits than this distant image of our tiny world. To me, it 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. -- Carl Sagan

Alternate Blue-Dot Video: www.youtube.com


Carl Sagan Interview by Charlie Rose - January 5, 1995

Subject: Publishing of Book: Pale Blue Dot

CR:
Perhaps, I don't have the numbers here, perhaps "Civil War" had more viewers in attendance but "Cosmos" was a terrific series and got a lot of attention for Carl Sagan. He has a new book which is called "Pale Blue Dot". It is a vision of the human future in space and that is our subject this evening. I want to turn this picture, and to get some sense of what a pale blue dot means. This is taken from, Carl, welcome to the broadcast, this is taken from Voyager 2, is it?
CS:
Voyager 1 actually.
CR:
Voyager 1. But take a look at this and you see can see, here, what? What is the meaning of this?
CS:
Well, here is this spacecraft, that has flown by the Jupiter, Saturn, Uranus, Neptune systems...
CR:
Right
CS:
...and is on its way, astonishingly, to the stars. A triumph of human engineering. We turn the cameras back and take a photograph of the planet from where it came. And we can barely see it. Here is a fragile, delicate, pale blue dot and that's where we live, that's where every human has ever lived and you can see the vulnerability at a glance. And that gives a humbling and character building sense of where we are...
 

Carl Sagan Interview by Charlie Rose - May 27, 1996

Subject: Publishing of book: The Demon Haunted World

CR:
Carl Sagan is one of the preeminent astronomers of our time. He is known for bringing the heavens to our living rooms with his PBS series "Cosmos". His latest work is "The Demon Haunted World (Science as a Candle in the Dark)".  It explores the country's growing fascination with pseudo science, astrology, faith healers, the supernatural and the like. All superstitions, he says, threaten to undermine true science. I am pleased to have him here and I also take note of the fact that he is the "David Duncan professor of astronomy and space sciences" and "directory of the Laboratory for Planetary Sciences at Cornel University", "distinguished visiting scientist at the Jet Propulsion Laboratory, California Institute of Technology", and cofounder and president of the Planetary Society, the largest space interest group in the world, and a former Pulitzer Prize winner, welcome back.
CS:
Thank you, great to see you.
CR:
Ah, listen to this, I hate to read to you too much but this is almost like they have been reading your book; from the New York Times for Friday May 24: "Americans Flunk Science" a study finds, less than half of all American adults understand that the Earth orbits the Sun yearly, according to a basic science survey. Nevertheless there is enthusiasm for research except in some fields like genetic engineering, and nuclear power, that are viewed with suspicion. Only about 25% of American adults get passing grades in a National Science Foundation (NSF) survey of what people know about basic science and economics. I mean, this is singing your song, isn't it?
CS:
Well it is certainly what I have been talking about in the "Demon Haunted World". My feeling, Charlie, is that, uh, its not that pseudo science and superstition and the new age so-called beliefs, and, uh, fundamentalist zealotry are something new. They've been with us for as long as we've been human. But we live in an age based upon science and technology with formidable technological powers.
CR:
Science and technology are propelling us forward at accelerating rates.
CS:
That's right. And if we don't understand it, by "we" I mean "the general public", if its something that, "oh, I'm not good at that, I don't know anything about it" then who is making all the decisions about science and technology that, uh, are going to determine what kind of future our children live in? Just, uh, some members of congress? But there's no more than a handful of members of congress with a background in science at all. And the Republican Congress has just abolished its own Office of Technology Assessment. The organization that gave them bipartisan competent advice on science and technology. They say "we don't want to know". "Don't tell us about science and technology".
CR:
Surprising because Gingrich is genuinely interested, I think...
CS:
He is!
CR:
...in these things as kind of his as of, you known, his own intellectual curiosity. Does the president still have a science advisor?
CS:
Uh, he does. He does. John Gibbons. And, and, the vice president is scientifically literate.
CR:
He's well known as being a science maven. I mean you, you blast them all: Creationists, uh, Christian Scientists who you say would rather allow their children to suffer than give them insulin or antibiotics, astrologers come in for particular scorn on your part
CR:
Well I wouldn't say scorn just derision.

Quote: Who is more humble? The scientist who looks at the universe with an open mind and accepts whatever the universe has to teach us, or somebody who says everything in this book must be considered the literal truth and never mind the fallibility of all the human beings involved?

Excerpt from Pale Blue Dot : Chapter #1 : You Are Here

Pale Blue Dot
Photo:  Earth (inside the blue circle)
Distance:  6.4 billion Km (4 billion Miles)
Photo Date:  1990-02-14

The entire Earth is but a point, and the place of our own habitation but a minute corner of it.

As the astronomers unanimously teach, the circuit of the whole earth, which to us seems endless, compared with the greatness of the universe has the likeness of a mere tiny point.

The spacecraft was a long way from home, beyond the orbit of the outermost planet and high above the ecliptic plane which is an imaginary flat surface that we can think of as something like a racetrack in which the orbits of the planets are mainly confined. The ship was speeding away from the Sun at 40,000 miles per hour. But in early February of 1990, it was overtaken by an urgent message from Earth.

Obediently, it turned its cameras back toward the now-distant planets. Slewing its scan platform from one spot in the sky to another, it snapped 60 pictures and stored them in digital form on its tape recorder. Then, slowly, in March, April, and May, it radioed the data back to Earth. Each image was composed of 640,000 individual picture elements ("pixels"), like the dots in a newspaper wire-photo or a pointillist painting. The spacecraft was 3.7 billion miles away from Earth, so far away that it took etch pixel 5.5 hours, traveling at the speed of light, to reach us. The pictures might have been returned earlier, but the big radio telescopes in California, Spain, and Australia that receive these whispers from the edge of the Solar System had responsibilities to other ships that ply the sea of space among them, Magellan, bound for Venus, and Galileo on its tortuous passage to Jupiter.

Voyager 1 was so high above the ecliptic plane because, in 1981, it had made a close pass by Titan, the giant moon of Saturn. Its sister ship, Voyager 2, was dispatched on a different trajectory, within the ecliptic plane, and so she was able to perform her celebrated explorations of Uranus and Neptune. The two Voyager robots have explored four planets and nearly sixty moons. They are triumphs of human engineering an. one of the glories of the American space program. They will be in the history books when much else about our time forgotten.

The Voyagers were guaranteed to work only until the Saturn encounter. I thought it might be a good idea, just after Saturn, to have them take one last glance homeward. From Saturn, I knew the Earth would appear too small for Voyager to make out any detail. Our planet would be just a point of light, a lonely pixel, hardly distinguishable from the many other points of light Voyager could see, nearby planets and far-off suns. But precisely because of the obscurity of our world thus revealed, such a picture might be worth having.

Mariners had painstakingly mapped the coastlines of the continents. Geographers had translated these findings into charts and globes. Photographs of tiny patches of the Earth had been obtained first by balloons and aircraft, then by rockets in brief ballistic flight, and at last by orbiting spacecraft giving a perspective like the one you achieve by positioning your eyeball about an inch above a large globe. While almost everyone is taught that the Earth is a sphere with all of us somehow glued to it by gravity, the reality of our circumstance did not really begin to sink in until the famous frame-filling Apollo photograph of the whole Earth, the one taken by the Apollo 17 astronauts on the last journey of humans to the Moon.

It has become a kind of icon of our age. There's Antarctica at what Americans and Europeans so readily regard as the bottom, and then all of Africa stretching up above it: You can see Ethiopia, Tanzania, and Kenya, where the earliest humans lived. At top right are Saudi Arabia and what Europeans call the Near East. Just barely peeking out at the top is the Mediterranean Sea, around which so much of our global civilization emerged. You can make out the blue of the ocean, the yellow-red of the Sahara and the Arabian Desert, the brown-green of forest and grassland.

And yet there is no sign of humans in this picture, not our reworking of the Earth's surface, not our machines, not ourselves: We are too small and our statecraft is too feeble to be seen by a spacecraft between the Earth and the Moon. From this vantage point, our obsession with nationalism is nowhere in evidence. The Apollo pictures of the whole Earth conveyed to multitudes something well known to astronomers: On the scale of worlds (to say nothing of stars or galaxies) humans are inconsequential, a thin film of life on an obscure and solitary lump of rock and metal.

It seemed to me that another picture of the Earth, this one taken from a hundred thousand times farther away, might help in the continuing process of revealing to ourselves our true circumstance and condition. It had been well understood by the scientists and philosophers of classical antiquity that the Earth was a mere point in a vast encompassing Cosmos, but no one had ever seen it as such. Here was our first chance (and perhaps also our last for decades to come).

Many in NASA's Voyager Project were supportive. But from the outer Solar System the Earth lies very near the Sun, like a moth enthralled around a flame. Did we want to aim the camera so close to the Sun as to risk burning out the spacecraft's vidicon system? Wouldn't it be better to delay until all the scientific images from Uranus and Neptune, if the spacecraft lasted that long, were taken?

And so we waited (and a good thing too) from 1981 at Saturn, to 1986 at Uranus, to 1989 when both spacecraft had passed the orbits of Neptune and Pluto. At last the time came but there were a few instrumental calibrations that needed to be done first, and we waited a little longer. Although the spacecraft were in the right spots, the instruments were still working beautifully, and there were no other pictures to take, a few project personnel opposed it. It wasn't science, they said. Then we discovered that the technicians who devise and transmit the radio commands to Voyager were, in a cash-strapped NASA, to be laid off immediately or transferred to other jobs. If the picture were to be taken, it had to be done right then. At the last minute actually, in the midst of the Voyager 2 encounter with Neptune, the then NASA Administrator, Rear Admiral Richard Truly, stepped in and made sure that these images were obtained. The space scientists Candy Hansen of NASA's Jet Propulsion Laboratory (JPL) and Carolyn Porco of University of Arizona designed the command sequence and calculated the camera exposure times.

So here they are, a mosaic of squares laid down on top of the planets and a background smattering of more distant stars. We were able to photograph not only the Earth, but also five other of the Sun's nine known planets. Mercury, the innermost, was lost in the glare of the Sun, and Mars and Pluto were too small, too dimly lit, and/or too far away. Uranus and Neptune are so dim that to record their presence required long exposures; accordingly, their images were smeared because of spacecraft motion. This is how the planets would look to an alien spaceship approaching the Solar System after a long interstellar voyage.

From this distance the planets seem only points of light, smeared or unsmeared, even through the high-resolution telescope aboard Voyager. They are like the planets seen with the naked eye from the surface of the Earth, luminous dots, brighter than most of the stars. Over a period of months the Earth, like the other planets, would seem to move among the stars. You cannot tell merely by looking at one of these dots what it's like, what's on it, what its past has been, and whether, n this particular epoch, anyone lives there.

Because of the reflection of sunlight off the spacecraft, the Earth seems to be sitting in a beam of light, as if there were some special significance to this small world. But it's just an accident of geometry and optics. The Sun emits its radiation equitably in all directions. Had the picture been taken a little earlier or a little later, there would have been no sunbeam highlighting the Earth.

And why that cerulean color? The blue comes partly from the sea, partly from the sky. While water in a glass is transparent, it absorbs slightly more red light than blue. If you have tens of meters of the stuff or more, the red light is absorbed out and what gets reflected back to space is mainly blue. In the same way, a short line of sight through air seems perfectly transparent. Nevertheless, something Leonardo da Vinci excelled at portraying, the more distant the object, the bluer it seems. Why? Because the air scatters blue light around much better than it does red. So the bluish cast of this dot comes from its thick but transparent atmosphere and its deep oceans of liquid water. And the white? The Earth on an average day is about half covered with white water clouds.

We can explain the wan blueness of this little world because we know it well. Whether an alien scientist newly arrived at the outskirts of our solar system could reliably deduce oceans and clouds and a thickish atmosphere is less certain. Neptune, for instance, is blue, but chiefly for different reasons. From this distant vantage point, the Earth might not seem of any particular interest.

But for us, it's different. Look again at that dot. That's here. That's home. That's us. On it everyone you love, everyone you know, everyone you ever heard of, every human being who ever was, lived out their lives. The aggregate of our joy and suffering, thousands of confident religions, ideologies, and economic doctrines, every hunter and forager, every hero and coward, every creator and destroyer of civilization, ever king and peasant, every young couple in love, every mother and father, hopeful child, inventor and explorer, every teacher of morals, every corrupt politician, every "superstar," every "supreme leader," every saint and sinner in the history of our species lived there, on a mote of dust suspended in a sunbeam.

The Earth is a very small stage in a vast cosmic arena. Think of the rivers of blood spilled by all those generals and emperors so that, in glory and triumph, they could become momentary masters of a fraction of a dot. Think of the endless visited by the inhabitants of one corner of this pixel the scarcely distinguishable inhabitants of some other corner, how frequent their misunderstandings, how eager they are to kill one another, how fervent their hatreds.

Our posturings, our imagined self-importance, the delusion that we have some privileged position in the Universe, are 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 help will come from elsewhere to save us from ourselves.

The Earth is the only world known so far to harbor life. There is nowhere else, at least in the near future, to which our species could migrate. Visit, yes. Settle, not yet. Like it or not, for the moment the Earth is where we make our stand.

It has been said that astronomy is a humbling and character-building experience. There is perhaps no better demonstration of the folly of human conceits than this distant image of our tiny world. To me, it 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.

"Because of the reflection of sunlight off the spacecraft, the Earth seems to be sitting in a beam of light, as if there were some special significance to this small world. But it's just an accident of geometry and optics. The Sun emits its radiation equitably in all directions. Had the picture been taken a little earlier or a little later there would have been no sunbeam highlighting the Earth."

Carl Sagan

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