Could there be life beyond Earth? Only recently has it become possible to scan the skies in a systematic attempt to find out. NOVA joins the search with guest host Lily Tomlin.
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00:00For centuries, people have wondered, could there be intelligent life beyond Earth?
00:10Finally, science has developed the means to find the answer.
00:14The methods include sophisticated computers, some unusual ideas of how a message might
00:19be sent, and an assist from science fiction.
00:23Their goal?
00:24To answer one of humanity's oldest questions.
00:27Is anybody out there?
00:28With host Lily Tomlin, tonight on NOVA.
00:39Major funding for NOVA is provided by this station and other public television stations
00:43nationwide.
00:46Additional funding was provided by the Johnson & Johnson family of companies, supplying health
00:51care products worldwide.
00:55And by Allied Signal, a technology leader in aerospace, electronics, automotive products,
01:01and engineered materials.
01:36Say, you ever wonder what goes on when the theaters close, when no one's watching?
01:46What I think, that's when the space visitors show up.
01:50I mean, they think we're a little weird, so they're shy, you know what I mean, in the
01:53day.
01:54That's why you don't see them, unless you know how to communicate.
01:59Hey, I mean, you gotta admit, it's likely there's all kinds of beings all over the solar
02:06system, don't you?
02:08The way I see it, we can't be the only things going, can we?
02:13And that must mean that they're all over the galaxy.
02:16For thousands of years, people have been looking at the skies, wondering what might be out
02:26there.
02:27Hey, it's moving!
02:30Hundreds of science fiction films have depicted what happens when there's a failure to communicate.
02:36Everybody understands when you wave the white flag, you want to be friends?
02:42During the 1950s, at the height of the Cold War on this world, many classic science fiction
02:47films suggested there was no reason to figure out how to communicate.
02:51The aliens were implacably hostile, and the sooner they were gone, the better.
02:56By the 1970s, contact, not conflict, became the theme of the most successful science fiction
03:04films.
03:05The characters in these films try to communicate in pure tones, a language that they think
03:14might be universal.
03:20Movies like Close Encounters of the Third Kind and E.T. the Extraterrestrial reflect
03:25and shape our changing concepts of the universe and the beings who may inhabit it.
03:30And in fact, it just might help determine if and when we humans make contact with real
03:35E.T.s.
03:36Hello, I'm Lily Tomlin.
03:39Recently, I was on Broadway playing Trudy, a bag lady who receives extraterrestrial messages
03:44through her umbrella hat.
03:46It's kind of primitive, but for Trudy, it works.
03:49I like to think of her as someone who lets her imagination overpower the reality that
03:53surrounds her.
03:55But this program is about the real thing, how we might contact alien civilizations not
04:00in our imagination, but in actual fact.
04:052 a.m., September 24th, 1985.
04:16In a physics lab at Harvard University, Earth's most sophisticated detector in the search
04:21for life in space is put to its first real test.
04:29In the tradition of hackers and inventors everywhere, Professor Paul Horowitz and his
04:33student Brian Matthews burn the midnight oil.
04:42It's been weeks of late nights to ensure something happens when the system is switched on for
04:46the first time five days later.
05:12This may seem like a shoestring effort, and it is, but previous efforts have been less
05:17specialized, using receivers not custom-made for the search.
05:21What sits here in the lab, stripped to its silicon guts, is only half the system.
05:27It now says start and start frequency.
05:29We've got a nice big signal.
05:31So I'm making a chirp, and you're looking for a chirp.
05:34This is the real thing.
05:36Soon it will be linked to a large radio antenna, and the search to detect a signal from an
05:41alien civilization will begin.
05:43Okay, it's only two channels wide.
05:47Scientists have known about radio since the start of the 20th century, but only in this
05:51decade have advances in computers provided tools powerful enough for SETI, the search
05:58for extraterrestrial intelligence.
05:59Okay, great.
06:00So we've really, we've run it all the way through the system.
06:04Synthesized chirp is detected as a synthesized chirp at this end, and it tells you exciting
06:08messages on the screen.
06:12Five days later, September 29th, astronomers gather at a radio telescope near Boston.
06:18For the ceremonial switching on of the detector, Horowitz had scrounged up a knife switch from
06:25a derelict laboratory, and inside was still making last-minute fixes.
06:31He calls the system META, short for Mega- or Million-Channel Extraterrestrial Assay.
06:38Here's what frightens me.
06:41Some of the scientists most interested in SETI came to the ceremony, including astrophysicist
06:48Philip Morrison, who first proposed, some 25 years ago, the basic methods META uses
06:54to listen for other civilizations.
06:57The member-supported Planetary Society funds the operation of META with the help of a donation
07:02from movie director Steven Spielberg, who created E.T. and Close Encounters.
07:07When I was your age, we had rabbit ears on our TV set.
07:10An even more powerful detector than META is now under design by NASA.
07:15These SETI experiments may fail to make contact with real E.T.s, but scientists want to go
07:20beyond our movie fantasies and communicate with another civilization.
07:24Well, I'm very happy to be involved in this project, because you all know I've benefited
07:31so much from science fiction.
07:33I just thought it was time to get involved in some science reality.
07:39I just hope that there is more floating around up there than just old reruns of the Jackie Gleason show.
07:46Among the scientists who have helped SETI grow from pure speculation toward legitimate
07:51science is Planetary Society president Carl Sagan.
07:59There is some chance that in the next few decades we will get a signal from some spectacularly
08:06distant, spectacularly exotic civilization, and everything on Earth will, as a consequence,
08:12change.
08:13That is possible.
08:15If other civilizations are out there, where are they?
08:18Why aren't they here?
08:21After all, we humans are space travelers.
08:25Wouldn't any civilization advanced enough to send a message, come to Earth in person,
08:30like Spielberg's E.T.?
08:33In reality, space visitors would have to come a very long way, for we on Earth seem to have
08:39no close neighbors.
08:41The Viking spacecraft touched down on Mars and found no clear signs of life.
08:47Other spacecraft have found no evidence of advanced beings on any other planet in our
08:51solar system.
08:53The Voyager 2 spacecraft is the fastest vehicle ever built by humans, but it still took nine
08:59years to reach the planet Uranus, just over halfway to the edge of the solar system.
09:06To find another advanced civilization, we must look to the stars and any planets that
09:10surround them.
09:13But Voyager would take 100,000 years to reach even the closest stars.
09:19Barney Oliver, head of NASA's planned SETI project, thinks aliens would be daunted by
09:24these realities.
09:25I think they're smart enough not to travel.
09:27I think when you compare the costs of interstellar travel with interstellar communication, they
09:32like us would choose interstellar communication.
09:34It's far cheaper.
09:35It's cheaper by billions of times.
09:38So if we have to expect distant, not close encounters, what's the best method of communication?
09:44That depends on who you're trying to talk with and where they live.
09:49In the 19th century, some scientists still believed our solar system was teeming with
09:54life.
09:55They assumed that beings on other planets would be studying Earth carefully.
10:00In 1833, a German mathematician, Karl Gauss, suggested planting in Siberia a huge triangle
10:06of wheat bordered by dark green pine trees.
10:09Alas, for devotees of environmental art, Gauss's project was never funded.
10:15Nor was the idea of Johann von Littrau of Vienna, who suggested digging geometrical
10:19shapes in the Sahara.
10:22Von Littrau wanted to fill the trenches with kerosene and to set them ablaze to make a
10:26glowing beacon on the night sky of Earth.
10:30In fact, these bizarre schemes might well have worked if aliens had existed on the Moon,
10:36on Mars, or Venus.
10:39But methods of communication that work over interplanetary distances have no chance at
10:44all between the stars.
10:48Distances between the stars are so enormous that astronomers measure them by the velocity
10:52of light, the fastest speed in the universe.
10:56One light year is the distance light travels in a year, six trillion miles.
11:03Our galaxy, the Milky Way, is 100,000 light years across.
11:09The galaxy contains an enormous number of stars and a vast potential for other civilizations.
11:16Skeptics say that advanced civilizations would surely have made themselves visible, but as
11:21yet we have seen no evidence of life out there.
11:26So, what scientific reasons justify continuing the search?
11:31In 1960, Frank Drake made the first radio search for civilizations in space.
11:37Drake's experiment produced some exciting false alarms, but no real messages.
11:42For over 25 years, Drake has kept on looking.
11:45What does he think we might learn?
11:48Oh, the most important information by far would be just the simple fact that they exist
11:53in space.
11:54That will tell us that civilizations like ours can thrive for long periods of time,
12:00that they can overcome the threat of nuclear war, that they can preserve their environment,
12:05that they can maintain high technology and a high quality of life.
12:09And all of that, I think, is very important for us to know.
12:13Drake called his pioneering search Osma, after a princess in the fictional land of Oz.
12:18He said SETI also deals with faraway lands, difficult to get to and populated by exotic beings.
12:26But maybe SETI itself is just as fanciful as the land of Oz.
12:31Drake argues that what we already know, plus what we have good reason to believe, justifies the search.
12:38He came up with a way to organize our knowledge and our ignorance, to give some substance to our speculation.
12:44Scientists call this the Drake Equation, though you don't need an A in algebra to understand it.
12:50The Drake Equation presents seven conditions astronomers think necessary for the existence of a civilization which could send a message to us.
12:59If you make an estimate for each of the terms and multiply them all together,
13:04you end up with an informed guess about how many advanced civilizations are out there.
13:08The larger that number, the easier to establish contact.
13:16The first term in the equation is the number of stars in the Milky Way.
13:21Of all seven terms, this is the only one we know with a fair degree of accuracy.
13:26By observing other galaxies as well as our own, we estimate that the Milky Way contains about 400 billion stars.
13:35Second, how many planets might orbit these billions of stars?
13:40We don't have clear evidence of any planets outside the solar system,
13:44but with much improved technology to help in the detective work, the hunt for planets is on.
13:50In 1985, Rich Turiel of NASA's Jet Propulsion Laboratory was co-discoverer of a faint disk of material
13:57surrounding the young star Beta Pictoris, about 50 light-years from Earth.
14:02This may be humanity's first glimpse of another solar system.
14:06The disk of material may be about to form planets.
14:11Some scientists argue that like our sun, the majority of stars have planets.
14:19The third term in the Drake Equation asks, how many planets are there in the Milky Way?
14:25The Drake Equation asks, how many planets or their large moons would provide an environment suitable for life?
14:33In our own solar system, we have found no evidence of life on the airless, waterless moon.
14:40Nor on broiling Mercury.
14:43Nor stifling Venus.
14:46Nor in the swirling clouds of Jupiter.
14:49Nor beneath the majestic rings of Saturn.
14:53But some scientists believe that Mars was once more habitable.
14:57They point to its polar caps of ice, and to riverbeds that channeled liquid water a billion years ago.
15:04They look at Jupiter's large moon, Europa, and wonder about possible life beneath its frozen crust.
15:12They yearn for a future mission to pierce the clouds that shroud Saturn's moon, Titan,
15:17where conditions may resemble those on Earth at the time when life arose.
15:23In a solar system with some 20 worlds, one hit and three near misses, an optimist like Drake might say,
15:30implies that many planets may be habitable by some forms of life.
15:35The fourth question is, on how many of these suitable worlds does the complex process of life actually begin?
15:43In a now famous experiment, Stanley Miller and his colleagues took a first step toward answering this question.
15:51They tried to create a dynamic model of the Earth as it was four billion years ago.
15:57The flask was meant to represent conditions on Earth before life appeared.
16:03They mixed in simple chemical compounds,
16:05and used sparks to simulate lightning, or the sun's energy, in the early atmosphere.
16:11The simple molecules broke apart and then formed more complex compounds.
16:19Four billion years ago, these compounds would have reigned into the seas of the primitive Earth,
16:25where they could have formed even more complex molecules, such as glycine, one of the amino acids,
16:30the basic building blocks of life on Earth.
16:35Scientists have also found amino acids in some of the meteorites that have fallen to Earth from space.
16:41These amino acids apparently formed in an environment even more hostile than that of the primitive Earth.
16:48From simple organic molecules to a living, reproducing organism like us, controlled by DNA, is a huge step.
16:55But the most basic building blocks of life appear to be common throughout the universe.
17:01The fifth term in the Drake Equation asks, how many worlds nurture not just life, but intelligence?
17:08We know that on Earth, simple forms of life have gradually evolved to become intelligent life,
17:14able to manipulate the world around them.
17:17The survival value of intelligence may be determined by the number of living organisms on Earth.
17:23The survival value of intelligence may be so high that intelligence arises wherever life emerges.
17:30But for now, we just don't know.
17:34The sixth term is the fraction of planets with intelligent life, on which emerges a technologically advanced civilization,
17:41which we can arbitrarily define as one that knows how to use radio.
17:46On Earth, we're batting one for one on all these terms.
17:49But on other worlds, the most advanced forms of intelligent life might be rather like whales or dolphins,
17:55and may never develop this sort of technology.
17:58Even if there's a lot of them out there, we can't hope to communicate with them across interstellar distances.
18:06Does advanced technology carry with it the seeds of self-destruction?
18:10The seventh question, the average lifetime of a technological civilization,
18:15cannot easily be answered until we succeed in setting.
18:19If many civilizations flower briefly and then disappear,
18:23only a few can be sending messages at any one time,
18:26and setting will be difficult, if not impossible.
18:33If you ask scientists for their best estimates for each of the terms in the Drake equation,
18:39you find a wide variety of opinions, even on the factors we think we know fairly well.
18:43Few hundred billion.
18:45All right, gentlemen, how many stars are there in the Milky Way galaxy?
18:50There are 200 billion stars in our galaxy.
18:53About 200 billion stars in the galaxy.
18:56Everybody agrees about 100 billion stars in the galaxy.
19:00I think probably about 400 billion or so.
19:03Few hundred billion.
19:05Now, how many planets are there per star?
19:08We believe that there are about 10 planets in each planetary system.
19:11It would be about 10 planets per star.
19:14I think about 8.
19:16One star in 10 might have planets.
19:18Several per star.
19:20So, how many planets per star are suitable for life?
19:24One or two planets.
19:26One.
19:27Perhaps one.
19:28At least one per system.
19:30Let's get more speculative.
19:32On how many of the worlds that are suitable for life, does life actually begin?
19:36To save time, just the most optimistic and pessimistic estimates, please.
19:39I would guess that it's pretty close to every suitable planet.
19:43It's basically a sheer guess.
19:45My guess might be, say, 1 in 10 to the 8th, just because 8's my lucky number.
19:51Not for any better reason than that.
19:5310 to the 8th?
19:55One planet in 100 million?
19:57Okay, so what's the chance of life becoming intelligent?
20:00It now looks more and more as though every system of living things,
20:04given a few billion years, will produce an intelligent species.
20:06And again, because 8's my lucky number, I'd choose 1 in 10 to the 8th as my guess on that factor.
20:12And on how many worlds would intelligent beings develop the technology to communicate between the stars?
20:18On every world where intelligence develops,
20:21it is likely that given enough time, technology also will develop,
20:25and with it, the ability to communicate across space.
20:28After intelligence forms, I think perhaps a 1% chance of radio communication.
20:34Now, gentlemen, here's the big question.
20:36What are your guesses, no more than guesses I know,
20:39for the shortest and longest average lifetime of a technologically advanced civilization?
20:44I think there's a threshold here.
20:46I think if a civilization crosses a technological threshold,
20:49then that time could be measured in millions of years.
20:52If the civilization doesn't attain that threshold,
20:55then I think it could be tragically short, perhaps as little as 50 or 100 years.
20:59I think it will be billions of years, basically, the full main sequence lifetime of the star.
21:03I can't imagine that an advanced civilization would somehow self-destruct or let itself be destroyed.
21:12So what's the bottom line?
21:15On the optimistic side, Frank Drake says that there could be
21:18at least 10,000 technologically advanced civilizations in the Milky Way alone.
21:23Remember that the larger the number of civilizations,
21:26the nearer to us our closest neighbor might be.
21:29On the other hand, Ben Zuckerman's pessimism would lead us to conclude
21:33that no other civilizations exist in the Milky Way,
21:36and possibly not even in millions of other galaxies around us.
21:40With this wide divergence of opinion, how useful is the Drake equation?
21:45I mean, nobody takes these numbers to be tremendously serious.
21:50Nothing depends on there being a million civilizations as opposed to a billion or a thousand.
21:56The only question is, are there many, or are there very few, or are there none?
22:00And as long as there is a plausible argument for many, we ought to keep looking.
22:06I think even if there's a plausible argument for a few, we ought to keep looking.
22:10I'd even go further than that.
22:12If there's a plausible argument that there isn't anybody out there,
22:15bearing in mind that we can be wrong, we ought to keep looking.
22:18Because the question is of the most supreme importance.
22:22It calibrates our place in the universe.
22:25It tells us who we are.
22:26And so it is worthwhile trying to find other civilizations, I would say, no matter what.
22:33Since these pessimistic and optimistic estimates are simply the results of multiple speculations,
22:39experimenters such as Paul Horowitz aren't willing to stop there.
22:44People have argued for a long time about the odds.
22:47What are the probabilities that there's life elsewhere in the universe?
22:50What are the probabilities that life is sending signals to us?
22:52What are the probabilities that life is sending signals to us?
22:55So it's pretty easy to come up with arguments that make it semi-probable or highly improbable.
23:02And lacking any data, they're nothing but arguments.
23:05And you can argue yourself blue in the face.
23:07But if you want to answer this question, you're going to have to do the experiment.
23:11Modern equipment is essential, but SETI involves more than electronics and computer wizardry.
23:16Making contact means you have to consider the technology, psychology, and biology of whoever might be on the other end.
23:24First, where and when to look.
23:26A gracious hello, Ernestine's message service.
23:29You stay in touch because we care so much.
23:32Messages for Graham.
23:34Mr. Green? Oh, good, good, good.
23:36Your rich uncle, Mr. Persewarden, did phone.
23:38He said that he would call back once more before he goes on his cruise to tell you how he's coming to town.
23:43He said you must stand by as you will not be able to reach him once he's gone.
23:48I did my part.
23:52EMT? Oh, Miss Pinkney, yes, of course.
23:56A conference call at five with Mr. Wright and Mr. Bryant.
24:00Do you happen to have their numbers?
24:03Do I have their numbers?
24:05If I did, would I be here?
24:09EMT?
24:10EMT?
24:12Oh, Mr. Persewarden.
24:14Oh, yes, sir, I am ringing your nephew.
24:17Two ringy dingys.
24:19Three ringy dingys.
24:21I'm sorry, there's no answer.
24:24I did tell him to stand by, sir.
24:27Very well, I will tell him, and what a pleasure talking with you.
24:30EMT?
24:32Yes, Mr. Jones, the 6 p.m. meeting is now at 7 for 6.
24:37That's what I said.
24:39There's nothing really hard to understand about that, Mr. Jones, if you just concentrate.
24:44EMT?
24:46Yes, Mr. Green, your uncle, Mr. Persewarden, did call.
24:49I don't mean to pry, but just where were you?
24:52Oh, really?
24:54Well, when I say stand by, I mean by the telephone.
24:57Well, I don't know.
24:59Let me see, what did he say?
25:01He's coming to town next month, and if you don't meet him, you're out of the will.
25:04No, no, he didn't say how he's coming, Mr. Green.
25:09No, I don't know if he'll call back.
25:12There is no need to yell at me, Mr. Green, just because you're a little confused.
25:16Yes, I suppose it is a little intelligence test for you.
25:20Just figure out where to meet him and stay there.
25:23Why don't you try the big clock at the station?
25:26Or maybe the airport?
25:28I think we can forget the bus depot.
25:31Yes, I'm sure that he meant this town, don't you, Mr. Green?
25:35Mr. Green, if you're going to shout, I'm going to give your plug a yank.
25:39I know he has millions.
25:42Very well, sir, I understand. No calls until you figure it out.
25:48In SETI, we're in even worse shape than Mr. Green.
25:52We don't know if there is a rich uncle, let alone when or where he wants to meet.
25:56Can we even figure out how a message might be sent to us?
26:02Consider a great canyon here on Earth as a metaphor for the chasm of space and time between the stars.
26:09Suppose you're on a camping trip and think that someone else might be out there, somewhere in the same hills.
26:15You want to get in touch, but how?
26:18Suppose, on the other side of the canyon, that someone also wants to communicate.
26:23Just by looking, there's no sign at all of anybody out there.
26:28But one thing's certain about communication on Earth or in space.
26:32Some methods work better than others.
26:36Suppose you realize that a Star Trek is impractical.
26:41In your frustration, you come up with an alternate strategy.
26:45Sending a message by unmanned probe might seem preferable.
26:50We humans have put slightly more sophisticated messages aboard the Pioneer and Voyager spacecraft.
26:57Still, there's the question of how much energy you can deliver.
27:01And space is awfully big in comparison to an interstellar probe.
27:06Maybe sending particles of matter, even small ones, isn't the best idea.
27:11Suppose you try sending messages by waves.
27:14You'll notice that the waves are much smaller than the particles.
27:18The waves are much smaller than the particles.
27:21The particles are much smaller than the particles.
27:24The particles are much smaller than the particles.
27:27Suppose you try sending messages by waves.
27:31Sound waves, for instance.
27:34If you did, you might discover that different frequencies have different characteristics.
27:39As every schoolchild knows, at a distance, a low-frequency shout attracts your attention less than a high-frequency whistle.
27:49But the most piercing whistle won't be heard even a few miles away.
27:56Well, life must go on.
27:59You need warmth and light.
28:01A camper, like a civilization, may do things for his own purposes that could be visible across the cosmic canyon.
28:08You might not even realize that you've stumbled on a means of communication.
28:16Across the canyon, the flames might be seen, but thought to be a brush fire.
28:21A natural event, not a beacon.
28:24There's no sign of intelligence just in a fire, but it might give you an idea.
28:31Suppose you build a fire, but modulate, to use the SETI term, or manipulate the puffs of smoke.
28:37Now you're talking.
28:39You're sending a clearly artificial signal that travels at the speed of light and is visible for miles.
28:45But if the laws of Murphy, as well as those of Einstein and Newton, hold true throughout the cosmos,
28:50then even your best idea may fail to establish contact.
28:54One civilization may be asleep when the other is sending.
28:58But suppose you were given a method of communication, common to both sides of the canyon.
29:04Suppose it was fast, cheap, and efficient.
29:14Call it radio.
29:17It might seem that your troubles were over once you've learned to turn on and tune in.
29:25But in fact, your work is just beginning.
29:35Hello.
29:38Channel one, it's too obvious. Channel two.
29:42Hello.
29:44Even with just two channels on a primitive walkie-talkie, it takes time to figure out how and when to speak or listen.
29:52Hello.
29:55Hello.
29:57Successful communication requires mutual agreement on how to communicate.
30:03In SETI, an unspoken agreement must somehow occur without a meeting.
30:07Hello.
30:09For all these difficulties, most SETI scientists think radio is the way to go.
30:15You can see why if you look at how well signals of different frequencies can be recognized across vast distances.
30:21Hello.
30:27Hello.
30:28Light and radio are both parts of the electromagnetic spectrum.
30:32Light differs from other kinds of electromagnetic radiation in its frequency, the number of vibrations per second of each wave of light.
30:41Light itself comes in many different frequencies, which we call colors.
30:46Red has the lowest frequency, blue a higher one.
30:50All the colors of light span only a tiny part of the electromagnetic spectrum.
30:55At infrared frequencies, below those of visible light on the spectrum, the black but still warm campfire glows brightly.
31:04So does the sun in the sky, in the trees, the bushes, and people on the surface of the Earth.
31:10At still lower frequencies, we observe the scene in radio waves.
31:15The sun is only a weak source of radio, but the Milky Way galaxy in the sky on the left is a strong one.
31:22Artificial sources of radio, like our camper's walkie-talkie, stand out brightly because the Earth has almost no natural radio sources.
31:34The same principles apply in the heavens.
31:37In visible light, the sun outshines the Earth by more than a billion to one.
31:43That's one reason we haven't been able to detect planets around other stars with even the largest optical telescopes.
31:49It's like trying to see a firefly perched on the rim of a searchlight.
31:57In infrared, even the dark side of Earth glows.
32:01The Milky Way forms a bright band across the sky.
32:05But it's radio that gives Earth its unique signature as the home of intelligent life.
32:11At certain times and frequencies, the Earth outshines all other sources within the solar system by nearly a million to one.
32:20These radio waves also make Earth stand out to distant civilizations.
32:31The program you are watching is an embryonic interstellar message.
32:34Thirty-three minutes after this broadcast began, our opening sequence has traveled 370 million miles and has nearly reached the orbit of Jupiter.
32:46Some of the radio waves that carry TV broadcasts leak into space and form a spherical shell around our planet and its sun, expanding at the speed of light.
32:57Three hours from now, this program will overtake Voyager, two billion miles from Earth.
33:04Voyager has been traveling for nine years.
33:09If in our imagination we could travel much faster than light, we could overtake our radio and TV broadcasts.
33:18Four and a half light years from Earth, we might find news of the wedding of Prince Charles and Lady Diana, passing the sun's closest neighbors Alpha Centauri A and B.
33:28Any planets around the star Altair, 17 light years from Earth, are now receiving our news from the late 1960s.
33:48If they had sensitive enough detectors, they could watch as we became a space-faring civilization.
33:57Any beings on planets around Fomalhaut, 23 light years from Earth, might see evidence of humanity's nobler aspirations.
34:13Planets near Arcturus or Pollux, each about 36 light years from Earth, might pluck from the cosmic background shows from the early years of television before Jackie Gleason was in reruns.
34:28Aliens might not share our sense of humor, and in reality they might find it hard to decipher individual programs, but there's still much to be learned.
34:39As the Earth turns, TV, military radar, and microwave signals appear and disappear over the horizon, flashing like a cosmic lighthouse.
34:49As a guide to what we might someday learn about another civilization by eavesdropping on its unintended signals, astronomer Woody Sullivan has studied what our radio transmissions reveal about Earth.
35:02And we found that you could get the Earth's spin rate, you could get the size of the Earth, you could put together the map of where the television stations are located on the Earth quite easily,
35:15you could get the size of the Earth's orbit and the length of time it takes for the Earth to go around the Sun, you could get the temperature of the Earth from basic physical principles,
35:24and think about the difficulty of trying to purposely send a bit of information such as the temperature of the Earth, whereas here it falls out in a pretty natural manner.
35:35What about a message deliberately beamed toward us? There may be a clue to its contents and how we might decipher it in the single message we on Earth have intentionally sent into space.
35:46The Arecibo radio telescope in Puerto Rico is the largest single collector of radio waves on Earth, but it can also transmit.
35:55In 1974, 14 years after asthma, Frank Drake used the Arecibo dish to beam a signal toward a distant cluster of stars.
36:04The signal was a stream of on-off pulses, shown here as zeros and ones, 1,679 pulses repeated several times.
36:13An alien civilization might consider the signal meaningless unless it realized that 1,679 is the product of two primes, 23 and 73, numbers that are divisible only by themselves and one.
36:29The language of mathematics may be universal, so they might hit on the mathematical device of arranging the ones and zeros into a pattern of 23 columns and 73 rows.
36:41If they darkened the ones, they'd begin to see a picture. They would see a crude representation of the beings that sent the message.
36:51A map of our solar system with Earth singled out, a diagram of the Arecibo dish, and the all-important DNA molecule.
37:02The Arecibo message was beamed toward a star cluster in the constellation Hercules, 25,000 light-years away.
37:1150,000 years from 1974 and about the year 51,974, humanity could receive a reply.
37:21At a symposium held to celebrate the switching on of META, Carl Sagan and others discussed whether we should be sending messages or listening.
37:29They argued that waiting for a reply takes a little too long.
37:34Because if you send, you know darn well you're going to have to wait around for travel time, at least 10 or 20 years.
37:39Experiments that take 10 or 20 years are intrinsically less interesting than ones that might return an answer tomorrow.
37:45And that's a very optimistic number, 10 or 20 years.
37:47For 10 or 20 years, even the most optimistic estimates of the distances to the nearest civilization generally come out to be hundreds of light-years away,
37:55which would mean that if you were saying hello to a lot of guys, it would be, you know, 25, 11 or something that the message would get back and be a little disappointing for you personally to take that long.
38:08What might a message arriving here on Earth say? What would we like to know?
38:12Like perhaps a cure to some of our own human ills, like cancer or pollution or the loss, gradual loss of our resources and stuff like that.
38:22I think with all the scare that science fiction puts into the public's minds of these monsters and creatures that want to take over our planet,
38:32I think that a friendly, I think that a friendly message would make everything worthwhile.
38:37And I hope that they can teach us a little bit about how to handle all the technology that we're dealing with now
38:45and teach us about how we can prevent the environment from being ruined.
38:50Most SETI scientists have a rather different perspective.
38:53What I would like to know is an answer to a very simple question.
38:56Are we alone as conscious beings in this entire buzzing 400 billion star galaxy, one of 10 to the 10th other galaxies?
39:06It seems pretty implausible.
39:09Bill Morrison thinks that the signal itself would intrigue scientists, but that the public would have different interests.
39:16It'll be a sensation when it's confirmed. In fact, it'll be quite a sensation before it's confirmed.
39:20And then it'll turn out to be false. And then finally it'll be confirmed, and that'll be a sensation.
39:25It'll occupy the front pages of all the newspapers for a week.
39:28And it'll occupy the inside pages for another month.
39:30And then it'll occupy a weekly piece every once in a while for six months, and that'll be the end of it.
39:36But then scholarship and interested people will go up everywhere, fascinated to hear the latest.
39:43And they'll demand other receivers being built. All countries will pretty soon have them.
39:47They'll all be pulling their stuff. A whole branch of knowledge will go in.
39:50The existence of signal will be all we know for a while.
39:53And then, of course, where it's coming from.
39:54And then a thousand speculative authors will arise to say what they look like and who they are and so on, all of which will be false.
40:01And then gradually the truth will come out.
40:04But you know that the television cameras will come the very next day and say, now, what do they look like?
40:09And do they speak English? And a number of other questions.
40:13So, if radio is the medium of choice, and listening is our best strategy, does this make contact easy?
40:21Is it enough to turn on our radio detectors and wait?
40:24Well, not exactly.
40:29Oh, gracious, hello, ET and T.
40:32Ernestine Tomlin atop the transmitter.
40:35Let's see what's on the radio, daddy-o.
40:38Oh, yikes, yikes, yikes, there's that crazy radio beacon again.
40:45Oh, aggressive bunch of jokers in that galaxy.
40:48Too bad no one listens to that frequency, you fools.
40:51They broadcast one minute every thousand years.
40:54Just how long do they live?
40:56Try 1420 megahertz and keep doing it.
41:03Oh, those nude nicks.
41:05They think they're so great with their zeta waves.
41:08What a shame no one else has discovered them yet.
41:10If they'd just think archaic, they'd get an audience.
41:14Jackie Gleason.
41:16Oh, there's that catchy tune.
41:19Da, da, da, da, da, da, da.
41:22Da, da, da, da, da, da, da.
41:25Oh, I do love that fat guy and that Norton.
41:30Must be a real fun planet down there.
41:33Too bad it's so far away.
41:36What a great job.
41:38These life forms are so fascinating.
41:40But, of course, none so much as I.
41:43Ernestine is grappling in her usual efficient manner
41:47with the many problems that remain for steady scientists
41:50who have chosen radio.
41:52What kinds of signals to expect?
41:54Blips, pulses, or sustained waves?
41:57When to listen and where?
41:59And, above all, how many frequencies to monitor?
42:03An ordinary FM radio dial shows frequencies in megahertz,
42:07or MHZ, meaning one million vibrations per second.
42:10For the radio waves carrying the broadcast.
42:13To avoid interference,
42:15we on Earth license radio stations to a channel,
42:18a small range of frequencies,
42:20like those around 89.7 megahertz.
42:24But the cosmic radio dial is very different.
42:27In cosmic reality,
42:29the region between 90 and 92 megahertz
42:32can contain not 10, but 20 million different channels,
42:36each of them capable of transmitting
42:38a message from another civilization.
42:41With a conventional radio receiver,
42:43the finely tuned signal would be lost
42:45in the sea of background noise.
42:48Not only must the cosmic radio dial be sliced much finer,
42:52it's also much longer.
42:54On the cosmic dial,
42:56the region from 88 up to 108 megahertz
42:58contains about 200 million potential channels.
43:01And FM is just a tiny part of the spectrum.
43:04Below FM are frequencies shown.
43:06Below FM are frequencies used for some TV broadcasts.
43:10Higher than FM is UHF TV, then microwaves.
43:15The radio spectrum technically extends
43:18all the way down to zero frequency.
43:21With this enormous range,
43:23how can we possibly figure out
43:25what frequency an alien civilization might choose?
43:27Is there any way to limit the search?
43:30There is a preferred region in the electromagnetic spectrum,
43:33we believe, that minimizes the energy required
43:34to make contact.
43:37And that is in the microwave region.
43:39And the reason for that is that the noise
43:41that would interfere with our transmissions,
43:43or theirs, is lowest there.
43:46If we map the interference,
43:48we find that the low frequencies,
43:50shown at left, are useless,
43:52because of the radio noise at interstellar space.
43:55To the right, our atmosphere absorbs the higher frequencies.
43:58In the middle lies the preferred region,
44:01from about 1,000 to 10,000 megahertz.
44:04Even so, there are about
44:06100 billion potential channels here.
44:09Are there any other clues to help narrow the search?
44:12One basic fact about the universe
44:15is that hydrogen is the most abundant atom.
44:18In their constant dance of energy capture and release,
44:21hydrogen atoms naturally emit radio waves
44:24at one particular frequency.
44:26They broadcast at 1420 megahertz.
44:30But the universe itself might tell us
44:32where to look in frequency,
44:34was first proposed by Philip Morrison.
44:37At the symposium on Metta,
44:39he reasoned that intelligent beings everywhere
44:41could reach unspoken agreement.
44:43This is an anti-cryptological game.
44:46A game where the rational transmitter says,
44:49I want to make it as easy as possible
44:51for those distant primitive folk
44:53to get onto this channel
44:55and begin to see how it goes.
44:57And therefore, I will not conceal it.
44:59I will make it anti-concealed.
45:00I will make it self-transparent,
45:02as self-justifying,
45:04as visible as possible.
45:06Betting on a magic frequency,
45:08such as 1420 megahertz,
45:10helps to simplify the task
45:12of sifting the cosmic haystack.
45:14An alien civilization might broadcast
45:16a powerful signal at just this magic frequency,
45:19hoping it could be detected
45:21above the heavy background noise
45:23from all the hydrogen atoms.
45:25Drake's OSMA search
45:27used 1420 megahertz
45:28to scan two stars for 400 hours.
45:31His receiver could cover only one channel,
45:34as if you had a radio
45:36that could only be tuned to a single station.
45:38A search called OSMA-II,
45:40made by Ben Zuckerman,
45:42looked at 674 stars
45:44also around this magic frequency.
45:47And Horowitz in Metta
45:49is still essentially playing
45:51the magic frequency game.
45:53Unlike the OSMA searches,
45:55which looked at individual stars,
45:56Metta is a sky survey.
45:59Metta's antenna sweeps out a beam
46:01across the entire sky,
46:03about the size of the full moon.
46:05In eight months,
46:07Metta surveys the entire sky
46:09visible from the observatory.
46:11When one survey is complete,
46:13Metta can begin another
46:15at a different magic frequency.
46:17But astronomers have come up
46:19with more than a dozen magic frequencies.
46:22And because the Earth
46:24and any source of radio
46:26are connected,
46:28any signal will drift in frequency
46:30over time.
46:33So SETI detectors must be able
46:35to scan many channels
46:37or groups of frequencies.
46:43Drake's OSMA detector
46:45had only one channel,
46:471 ten thousandth of a megahertz wide.
46:50Horowitz's system scans
46:528.4 million channels.
46:54It can do in a second
46:56like an OSMA five years.
46:59This complete array here
47:01therefore functions as
47:03an 8.4 million channel receiver.
47:05And by the way,
47:07not like a police scanner
47:09where you do one channel
47:11after another sequentially.
47:13This receiver box here
47:15is like 8.4 million radios
47:17all sitting on the table
47:19all tuned to successive stations.
47:21It analyzes them all simultaneously.
47:23Despite this tremendous progress,
47:24it's still on the spectrum.
47:26But it is perhaps
47:28the ultimate magic frequency machine.
47:30From this array,
47:32which will be the first thing to know
47:34if the signals come in,
47:36the information passes
47:38to this controlling computer here.
47:40This computer
47:42really rides herd over the whole system.
47:44It downloads the instructions
47:46to all of these different processors,
47:48keeps track of the motion of the Earth
47:50with respect to the signals
47:52that we're looking for
47:54and does the same thing
47:56as it may have done here.
47:58It will do several things.
48:00It archives interesting,
48:02unusual large peaks
48:04that may be extraterrestrial intelligence.
48:06And if the signal is really interesting,
48:08it turns on the tape recorder.
48:10Actually, a friend of mine
48:12came and looked at this the other night
48:14and he said,
48:16Horowitz, the reporter is going to say
48:18show us what it would be like
48:20if a signal actually came in.
48:22And so I said,
48:24have it say,
48:26notify operator immediately,
48:28possible signal of extraterrestrial origin.
48:30So that's what we're going to have it say.
48:32No such signal
48:34of extraterrestrial origin
48:36has been detected
48:38in the year META has been operating.
48:40We have hardly begun to search
48:42the great cosmic haystack.
48:44We've hardly searched
48:46all the various frequencies,
48:48the forms of signal,
48:50the places in the sky
48:52from which signals might come.
48:54Searching extraterrestrial life
48:56is not at all discouraging.
48:58We shouldn't have found it yet.
49:00We have hardly begun.
49:02In the heart of California's Mojave Desert,
49:04NASA researchers
49:06are testing prototype equipment
49:08specially designed
49:10for a far more comprehensive search.
49:12The site is
49:14the Goldstone Tracking Station,
49:16the main downlink
49:18for NASA's interplanetary spacecraft,
49:20such as Voyager and Pioneer.
49:22We're looking for a signal now
49:24from a spacecraft
49:26which is now outside the solar system.
49:28It's beyond the orbit of Neptune
49:30at a distance of about
49:32three and a half billion miles.
49:34Its carrier is a one watt signal
49:38and that is about the
49:41one twentieth of the energy
49:43of a candle burning.
49:45So we're picking up
49:47a really small signal indeed.
49:49Though it's difficult,
49:51finding the signal from Pioneer
49:52is much easier than detecting
49:54the beacon of an alien civilization.
49:56Let me note this down
49:58and have him turn his signal on again.
50:00Let's make sure we can get it.
50:02The signal is weak
50:04and drifting in frequency,
50:06but it's very close.
50:08I have to go to three three three
50:10one four seven.
50:12This test is only a tentative tryout
50:14for the real thing,
50:16challenging the computer's ability
50:18to recognize an artificial signal
50:20in a sea of radio noise.
50:22Two two nine one eight seven four.
50:24That's wrong.
50:26It's got to be wrong.
50:28The NASA effort has united
50:30Barney Oliver and other long time
50:32SETI proponents with a younger
50:34generation of computer builders
50:36and programmers.
50:38Let's see what happens here.
50:40Slated to last about ten years
50:42and to cost around one hundred
50:44million dollars,
50:46SETI is one of the least risky
50:48and lowest cost items
50:50in NASA's portfolio.
50:52Yes, I think that's it.
50:54This bright line you see
50:56going slanting down the screen
50:59is the signal from the
51:01Pioneer 10 spacecraft.
51:03The NASA team plans to avoid
51:05reliance on magic frequencies
51:07and to search the entire favorable
51:09region of the radio spectrum.
51:11By distinguishing different types
51:13of signals over a wide range
51:15of frequencies,
51:17they say they will cover millions
51:19and maybe billions of times
51:20of radio waves.
51:22NASA will use existing radio
51:24telescopes and equip them with
51:26new sophisticated signal
51:28processors.
51:30SETI Deputy Project Manager
51:32Mike Klein describes NASA's
51:34two search strategies.
51:36And they're complementary.
51:38One of them is called the sky
51:40survey and another is called
51:42the target search.
51:44And the objective of the sky
51:46survey is to search the entire
51:48sky, making no guesses as to
51:50how much of the system will
51:52link to time.
51:54We have to do it quickly,
51:56which means we sacrifice
51:58sensitivity to signals.
52:00We only detect maybe the
52:02strongest of the signals that
52:04might be there.
52:06NASA's sky survey will cover
52:08a frequency range 20,000 times
52:10wider than Paul Horowitz's
52:12meta.
52:14To cover the sky quickly,
52:16it will drive the radio
52:18antennas far more rapidly than
52:20the sun.
52:22So we say, let's concentrate
52:24on detecting with more
52:26sensitivity, be able to detect
52:28weaker signals, and to do that
52:30we look in a few directions for
52:32longer periods of time, and
52:34that's called the targeted
52:36search.
52:38And we pre-select a set of
52:40stars that we know a priori are
52:42more or less similar to our own
52:44sun in age and size, and look
52:46in those directions with more
52:48sensitivity and the ability to
52:50detect weak signals at 800
52:52nearby stars for about 1,000
52:54seconds each.
52:56NASA researchers hope to use
52:58the world's great radio antennas
53:00in their search.
53:02They say antennas in the
53:04Southern Hemisphere are also
53:06needed, such as the one at
53:08Goldstone's sister station in
53:10Australia.
53:12Most of the stars in the Milky
53:14Way are best observable only
53:16from the Southern Hemisphere,
53:18but so far only a few sporadic
53:20stars are different from the
53:22fantasy seen in the movies.
53:24Most scientists believe alien
53:26visits are unlikely, and a
53:28dialogue would take too long.
53:30So a one-way message via radio
53:32is the best we can hope for.
53:34But you know, it isn't a
53:36complete tragedy if we just
53:38receive a message and don't
53:40have time to talk back.
53:42I've received lots of one-way
53:44messages of great significance
53:46from Socrates and Shakespeare,
53:48Charles Dickens and Emily
53:50Mast.
53:52But in SETI, it's our future
53:54that might be speaking to us.
53:56I think this enterprise can
53:58best be understood as a kind
54:00of exercise in the archaeology
54:02of the future.
54:04We're well aware of the
54:06archaeology of the past.
54:08We find a site, a tumulus or
54:10a ruin, and we take a spade
54:12and we dig into the ground.
54:14And if you're lucky, you
54:16discover Ur of the Chaldees,
54:18or something marvelous.
54:20We can't do anything in
54:22reverse time, but in fact,
54:24in a way, we can.
54:26We know that it's possible
54:28that somebody who wants to
54:30do it will bring us in.
54:32Of course, it is their past,
54:34but our future, which we're
54:36investigating, to some degree.
54:38Even though they're made of
54:40different chemistry, even
54:42though they've never seen
54:44our star, even though they
54:46have nothing biological in
54:48common with us, they have,
54:50which is unmatched among
54:52in all the 10 billion species
54:54or more that have come to
54:56the face of the earth.
54:58So that's the story, and
55:00maybe the spade will turn up,
55:02luckily, a good site one day.
55:04We hope it will.
55:06It's just a question of
55:08being patient.
55:10When you've got the spade
55:12and you know the future is
55:14there, it seems very wrong
55:16not to dig.
55:20Wow.
55:50Wow.
56:20Wow.
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57:47NASA Jet Propulsion Laboratory, California Institute of Technology