Planetary Radio: Space Exploration, Astronomy and Science - Optical SETI Has an Eye for Extraterrestrial Messages

Episode Date: February 17, 2003

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This is Planetary Radio. Hi again everyone and welcome back. I'm Matt Kaplan. Remember flashlights with a button you could push and release to send messages to your buddies? Could an extraterrestrial civilization be using a giant laser to do the same thing? It's possible. Even we earthlings have the technology within our grasp. Dr. Paul Horowitz is watching for those flashes from afar, and he'll soon be doing so with the biggest telescope in the eastern U.S. He joins us on today's Planetary Radio. Bruce Betts will return with another trivia contest and more fascinating space facts in

What's Up. First, though, here's Emily in the sky with diamonds. Hi, I'm Emily Lakdawalla with questions and answers. A listener asked, I heard that it actually rains diamonds on Neptune. Is that true? How? We asked Laura Benedetti, who published the Diamonds on Neptune story in Science magazine,

to answer the question. Yes, it's probably true that diamonds rained on Neptune at least early in its history and possibly still today. The atmospheres of both Uranus and Neptune contain methane, a simple molecule containing carbon. The conditions deep inside these planets are extreme, with very high pressures due to the weight of overlying material and very high temperatures left over from the gravitational energy of planetary formation. In laboratory experiments simulating these extreme conditions, methane becomes unstable and breaks down, and pure carbon is formed as diamond. If the same reaction occurs in the atmospheres of Uranus and Neptune, the resulting diamonds would drop like rain or hail, or maybe like grains of sand sinking to the ocean floor.

What other weird environments exist in our solar system? Stay tuned to Planetary Radio to find out. If you visit Paul Horowitz's website, you'll find a recipe for hot fudge sauce, a scientific paper on the possibility of ice skating, and an audioophile with the correct but virtually unknown pronunciation of Huygens, as in Christian Huygens or however it's pronounced, the Dutch astronomer of long ago. You'll also learn that he's a physics professor. That's Paul Horowitz, not Christian. He's a physics professor at Harvard and that he co-wrote a classic tome titled The Art of Electronics.

Jump over to the Planetary Society's website, and you hear about Paul's leadership role in a new kind of search for extraterrestrial intelligence, optical SETI. He joins us now on Planetary Radio. Hi, Paul. Hi. So rather than listening, you're looking? That's correct. Well, we never were listening because

radio waves are also not sound, although people tend to think of radio as sound. But we are looking. We're looking for optical flashes of the sort that we would make on Earth with lasers. So you're looking really at the same stuff, electromagnetic, but just much,

much higher frequency. Yeah, that's again another wavelength that happens to go through the atmosphere satisfactorily. That's why humans have eyes. It would do a good job of communication or beaconing between civilizations in the galaxy. And I think you've written that with the technology we have today, we could be sending optical pulses out, what, a thousand light years? We can see the fringes of our galaxy as long as we stay out of the smoggy plain, and we can see other galaxies.

In fact, we can see out pretty far to the edge of the universe. So space is basically transparent to light, and as you say, the interesting fact, maybe the fundamental fact here, which has been realized by pioneers like Charlie Towns for a long time, is that with technology no more advanced than we have now or only maybe about 10 years in our future, we could make a flash of light, a laser feeding a telescope in the outgoing direction, a flash of light that would be brighter, seen from far away, would be brighter than our own star, that is the sun, by a factor of 5,000 or 10,000 or thereabouts. In other words, we can outshine our star with no problem. So let's turn to what's currently underway, and that is watching for these flashes of

light from out there. What is the history of optical setting? Well, you know, if we go back to the turn of the century, the turn of the last century, people were talking about looking for creatures on Mars and the possibility that they might look for bonfires on Earth and all that kind of stuff. People have been talking about this for quite a while. I think the first serious discussion of actually doing such a thing is probably the 1961 paper by Schwartz and Townes, which proposed the use of optical masers, as they called them then.

They did not like the term laser. Optical masers as a potentially interesting way to communicate across galactic, well, certainly planetary distances, that is our solar system, and potentially galactic distances. distances, that is our solar system, and potentially galactic distances. I think that there have been some searches by the Russians for pulses of light. Townes in 1983 wrote a paper really fleshing this out in detail, but I think things didn't get seriously going until the 90s when it became apparent from our own progress in laser technology on Earth that this wasn't a hokum, this was for real.

This was really a plausible and, in many ways, competitive or equally attractive technique to the use of radio waves for establishing communication. Why would an extraterrestrial civilization choose light wavelengths over radio? Well, you know, you choose. If you want to make a communication, you do what works well, what you can do and what works well, and what might be guessable or searchable for by the other side, absent a preexisting communication. In other words, you choose something that's both technologically feasible

and guessable by the intended recipients, because they, after all, have not yet had the communication from you. Radio waves are good because, at least in our culture, they were discovered fairly early on and they're demonstrably terrific for communication. But lasers are, in many ways, simpler devices than complicated radio transmitters. The reception of laser pulses is technologically actually a simpler process, something as simple as a photo avalanche detector or a photo multiplier or a hybrid avalanche detector, as they're called,

or a solid-state photo multiplier is a very simple device and is able to receive these kinds of pulses that we're talking about with rather less complexity than is required in the radio regime. We should say these devices, photo multipliers and so on, they're basically very light sensitive devices for turning a pulse of light, in this case, into a little electrical signal? Yeah, that's right. The photo multiplier is probably one of the earlier of the very sensitive photo devices. It goes back at least 50 years. It's extremely simple and it's able to detect single photons of light with reasonable efficiency, about 25%. And it has a very low background count rate, so it's not too easily fooled into hallucinating.

It knows when it's seen. So you take one of these devices, or perhaps now a solid state device like, what, a CCD sensor, and you put it at the end of a telescope and start pointing it at stars. Yeah, in the simplest form. In fact, a lot of this work was pioneered not by our group here but by some of the California folks and by Stuart Kingsley, but Dan Wertheimer's group at California. Early on, just try the experiment of pointing one of these things at a star,

and what do you see? Well, you see a dribble of light from the star, but you don't see a bright flash ever. You just see single photons. And you can split the beam and use two of these things to make sure that they're really not just seeing single events or their own dark count, as we call it, but a true flash of light. So the simplest apparatus that seems to work in this business is a telescope, a beam splitter, that is a 50-50 mirror, and two of these photo multipliers

electrically wired so that you only report when both of them apparently see a flash of light at the same time. We should mention that your colleague at Berkeley on this end of the country, a colleague in SETI, I should say Dan Wertheimer, will probably join us on the show in the next few weeks.

I think it's amazing, and a lot of people I mention it to find it rather amazing that we have progressed to the point that we actually have detectors that can see, in a sense, a single photon of light. Well, as I say, that's not even new. I say, you know, that's 50 years old. I think what's new is, and even this is not terribly new. These experiments could have been done 25 years ago. I think it's just simply the culture wasn't ready for it yet in the SETI community.

But I think the trick here is having the good telescope attached to the good detectors with good electronics behind it so that you recognize when this has happened when you're pointed at an interesting candidate star, and you do something about it. We probably will take a break here in the next few seconds, because it's a good time to do it, and then we'll come back and talk about the work that you're doing, which is with some support from the Planetary Society,

to expand the optical search for extraterrestrial intelligence, and that is using, as I understand it, what will be the biggest optical telescope east of, what, the Mississippi, is it? Well, we say east of Texas in the U.S. Our main sponsors are you guys and a curious little foundation called the Bozak-Kruger Foundation, Bozak-Kruger Charitable Foundation, they're called. And they've been sponsoring us for a decade. And their sponsorship is basically of our graduate students and of a certain amount of equipment in our laboratory.

The telescope we're now using for our targeted search is now the largest telescope east of Texas in the U.S., although, you know, we don't build big telescopes east of Texas for good reasons. And the one we're building now with Planetary Society support is 72 inches, that's 6 feet, a little larger than the 60-inch or 5-foot telescope we have now. And that, when completed, will be the largest telescope east of Texas. We'll have number one and number two right here about 100 feet apart from each other. Well, that's a good teaser.

That should keep people around through the break, which we're going to take right now. Our guest on Planetary Radio is Dr. Paul Horowitz of Harvard University, and we will continue this discussion of Optical SETI, the search for light intentionally sent by extraterrestrial intelligence. That will be when Planetary Radio continues in just a moment. This is Buzz Aldrin. When I walked on the moon,

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The Planetary Society, exploring new worlds. Matt Kaplan here on Planetary Radio, back with our special guest this week, Dr. Paul Horowitz, who is a physics professor at Harvard University, about to turn on, I guess, the optical search for extraterrestrial intelligence on what will be the largest optical telescope east of Texas, as he told us just before the break. of Texas, as he told us just before the break. Paul, let's talk a little bit more about this telescope with a six-foot mirror, a 72-inch mirror.

When do you expect to have first light? I wish it were just about ready to turn on. We've had first light in the sense that we can see stars through this telescope, and we've put a little video camera on it. But the electronics to do the all-sky survey, which is the purpose of this new telescope, and we've put a little video camera on it. But the electronics to do the all-sky survey, which is the purpose of this new telescope, is still progressing along at the kind of speed that avant-garde projects often do, which is that we're waiting for some special silicon chips that we had to design, especially for the search. My best guess at this point is that we'll probably have

first light this calendar year, but not any time real soon. Now, you mentioned a new term, the all-sky search. Talk about that. Sure. The optical SETI that we've been doing since 1998, that is, looking for bright flashes from good stellar candidate stars, stars like our sun. Well, first of all, that was inspired by a wonderful talk that Charlie Towns gave at a set of workshops sponsored by the SETI Institute. It certainly brought to my attention something that I'd really not realized, which is how good optical signaling could be. At the same time, it became

clear that it's much harder to do the whole sky because you have to keep out the light from all the rest of the sky, and you have to look at stars pretty much one at a time, which is how optical telescopes tend to work. But this seems an interesting challenge. Could you do better than one star at a time and somehow cover more than the one millionth of the sky that we're able to cover with our ongoing search now, which, by the way, has looked at about 10,000 stellar candidates. But the field of view is so tiny

that we basically don't see anything in between those stars. We realized that it is possible using some new detectors that have been engineered only recently. They're basically 64 independent detectors in one package. With 16 of these devices, you can basically look at 1,000 places in the sky. At the same time, it's 1,000 points of light, I guess. And we figured out that with this kind of detector, we could do the whole sky. That's what we're trying to do with this new telescope, while at the same time we continue to chunk along on our target list of about 15,000 stars with our targeted search. So, again, this is really an outgrowth of those same 72 workshops. And what we've done is gotten ourselves a 72-inch telescope.

It's made actually down in Arkansas by a fellow by the name of Ray Damaris, and the detector behind it will have 1,000 of these little micro-detectors in it, and will cover a stripe of the sky, because these detectors are arrayed in a stripe of about two degrees in declination, that is, in the north-south direction of the sky, and it will be carried around in the east-west direction by the Earth's rotation. So we'll simply let the stars drift through our array of detectors, and in something like 150 clear nights, we will have covered the entire sky.

That is a million times more area than our current search with this new detector. I love that, a thousand points of light. Somebody really ought to tell the senior President Bush about that. Well, maybe he's responsible for this search, too. I wonder what you might expect to see, or do you have any expectation of what kinds of artificial flashes you might see if we are lucky enough for this new instrument to catch something like that.

Well, of course, the reason I was mentioning earlier what we could do with lasers on Earth was not because anybody seriously wants to build a billion-dollar laser setup to send flashes, but because we like to game it on both sides of the system. That is, what could one build with plausible technology that would do a good job of communicating? And if you can come up with a good idea there, then at least you have something that you know to look for. Basically, playing that game,

we decided that a bright flash is a very good kind of signal because it can be made so much brighter than your own star in the direction of its beam. If the extraterrestrial civilization is being cooperative and comes up with a similar idea, then what we would expect to see would be intense flashes, much brighter than the star for some brief period of time, perhaps in a pattern, periodic or periodic with some pulses missing, perhaps sending some sort of binary signal.

You could send a number, for instance. Alien Morse code. Yeah, or maybe it's simple. Maybe you don't start with Morse code because they don't know which Morse code we're using. Maybe you start by sending the bits of pi or prime numbers or something like that. People have talked a lot about what an initial message might look like. But even a simple periodic stream, a pulse for a billionth of a second every second, you get ten of those in a row and you know that this is not astrophysical phenomenon.

They don't do that kind of thing. Or if it isn't a previously unanticipated astrophysical phenomenon, it's one heck of a good discovery in its own right. It's a terrific consolation prize for us SETI searchers. In its own right, it's a terrific consolation prize for us SETI searchers. Of course, this whole area of SETI, what form would an intelligent message take, is one that people love to speculate about. I believe it was one of Carl Sagan's favorite topics. I love to ask SETI people this next question.

If you found a signal, something that you at least strongly suspect has an intelligent origin, what would be the next step? It's a good question. You know, this is pretty astounding stuff, and you want to make sure that you have found what you think you've found. And so I think it's essential at first to make sure that what you're seeing is real, it's not an artifact of your apparatus, and that it can be seen by some other observatory,

that it's not an artifact of your location, or that you're not being spoofed, let us say. Extraordinary claims require extraordinary evidence, as Carl Sagan used to say. I think the very first step would be to ask another observatory to confirm our discovery. And by the way, I should mention that one thing we're doing right now and have been doing now for about a year is we are simultaneously observing with an identical setup installed at Princeton University

so that in our targeted search each night as we go through our 30 or 40 candidate stars for the night, the telescope in Princeton, operated by a team of volunteers, is looking at those same stars at the same time. We're synchronized through Internet communication. Therefore, in some sense, we already have a confirmation or a disconfirmation if we think we've seen something extraordinary. If we see a pulse and they see a pulse and it comes at the exact same microsecond, allowing for the geometry of the two observatories, and let's say we see a periodic train, and so do they,

we've seen something. But if we were operating in a standalone mode or with a new telescope where we don't have a twin, the first thing we'd do would be get confirming observations by us and by another observatory, and preferably at the same time. I think at that point, you scratch your head and you say, is there any plausible astrophysical explanation that we should be considering?

This is something that the discoverers of pulsars ask themselves. Yes. At first thinking that those might be little green men. They called it LGM for one. You ask yourself those questions. But I think at some point, particularly after you've asked other observatories to confirm this thing, the word's going to get out because after just a few days you have a dozen or a hundred people who are aware of a pretty incredible astrophysical phenomenon, and not

just those astronomers, but their wives and their kids and their dogs will know about it, and pretty soon the journalists are upon you. And I think you basically have to make a sober and factual explanation of what it is that you have seen and what it is that you haven't seen and what this may be, but basically caveating your announcement with all the sorts of things that we have learned over the years in science, which is not to assume more than you really know at any point. Even if that signal doesn't come, and I'm one who hopes that it does,

you're having a lot of fun with this, aren't you? Oh, I think SETI is terrific exploration. It's something that we have to do on Earth. It's inexpensive. It's harmless, I hope. And we're really the first or second generation on Earth that has the capability to make contact or to receive contact across these distances. And there's every reason to believe that other stars harbor life. There are 400 billion stars in our galaxy alone,

and there's at least 100 billion galaxies out there. It's unreasonable to expect that what happened here through completely natural processes on a rather ordinary planet, probably orbiting a rather ordinary star, and that we know for sure, did not happen many other places in the galaxy and in the universe. And, of course, discovery of another one of these would end our cultural isolation in a deep sense.

It would be a bridge across billions of years of independent evolution and independent origin of life. It would be the greatest discovery in the history of humankind. Paul, when it happens, we hope you'll be able to squeeze us in between CNN and Fox. Of course. Our guest on this segment of Planetary Radio has been Paul Horowitz, professor of physics at Harvard University and leader of a search for signals from extraterrestrial intelligence

that would come in the form of light, optical SETI as we call it. Thanks very much for joining us, Paul. Thank you very much. Hi, I'm Emily Lakdawalla, back with Q&A. Diamond rainfall on Uranus and Neptune is just one example of an environment in our solar system that could never exist on Earth. There are plenty of other strange places in the solar system. Our sister planet Venus' carbon dioxide atmosphere is so thick that it behaves more like the ocean than the sky.

If you were able to stand the crushing pressure on the surface of Venus, you wouldn't be able to see far through the dense air, and you'd feel the constant gentle push of fluid currents. The largest moon in the solar system, Titan, is a world unto itself with a thick atmosphere that probably hides oceans of liquid methane or ethane. If you could stand on Jupiter's moon, Io, you'd witness constant fire fountains of volcanic eruptions.

The lava, ejected directly into the cold vacuum of space, would quickly quench into rounded glass droplets and rain back onto the surface. And because Io is tidally locked with Jupiter, the enormous planet would always appear to sit in the same place in the sky, a giant striped ball 40 times wider than the moon appears in our sky. Got a question about the universe? Send it to us at planetaryradio at planetary.org, and you may hear it answered by a leading space scientist or expert.

Be sure to provide your name and how to pronounce it, and tell us where you're from. And now, here's Matt with more Planetary Radio. Time for What's Up with Bruce Betts, the Planetary Society Director of Projects. Bruce, welcome back. Thank you very much. How shall we start this week? We'll start as we traditionally do with what's up in the sky, and we still have lots of good planets to look at. Saturn and Jupiter in the evening.

Look for Saturn almost overhead in the very early evening above Orion. And Jupiter is very, very bright in the east as the sun sets and then overhead by midnight. In the morning, we've got Venus still exceedingly bright in the east that you'll see any time before sunrise. And if you look harder, you can try to see Mars to the upper right and maybe a smidge of Mercury, but it's tough again to the lower left. Now, is Mars going to get steadily better from now until, what is it, roughly June when it's supposed to be spectacular? Yes. It's actually a little later in the summer It will be spectacular And it should be getting better and better

You can hold off on Mars for a few months Stay tuned to Planetary Radio and What's Up And we'll tell you when it's spectacular We'll say go outside now Darn it! Okay, what's next? We have some This Week in Space history A lot of big milestones

In February 20th, 1962 John Glenn became the first American to orbit the Earth. And February 19, 1986, Soviet Union launched their Mir space station. And February 23, 1987, different twist. Supernova 1987A exploded. This was the first naked- eye supernova since 1604. And an enormous amount of science resulted from that supernova. Great deal. That is correct.

Do we go on now to space? Well, I'll let you say it because we might put some echo behind it. Oh, please, oh, please. Go ahead, go ahead. Random Space Fact! He's getting really good on the microphone too, folks. Go ahead. Random Space fact.

This week we're going to tie it a little to last week's trivia contest. Traveling at the speed of light, it takes over 12 hours for radio signals to reach the farthest spacecraft from Earth. Round-trip communication takes over a full 24-hour day. So we're talking 12 light hours hours roughly, a little bit more, as opposed to, what is it, four, four and a half light years for light to get here from Alpha Centauri? Right. And if you want to, comparing in the other direction, about eight light minutes for sunlight to get to Earth. So that spacecraft's getting out there. And which spacecraft is that?

Well, that would be the answer to last week's trivia contest. What is the most distant object from Earth that was built by humans? The answer, Voyager 1. Now, we had a lot of entries. And, folks, I am sorry to say that all of those of you who simply said Voyager, not specific enough. We were looking for Voyager 1 or Voyager 2. Now, those of you who said Pioneer 10, yeah, but displaced chronologically. If you had said that, oh, five, six years ago, you would still be right.

But in fact, Bruce, Voyager 1 has... Voyager 1. By the way, those of you who just said some spacecraft, that also is not specific enough. Right. We're sorry. But do try again next week. And here's our winner, Daniel Nascimento. I hope I'm pronouncing that right.

Daniel Nascimento of Cambridge, Ontario, our first Canadian winner. So congratulations, Daniel. You'll be getting that T-shirt from the Planetary Society. Congratulations. So we move on to our new trivia question. New trivia question. What planet has the highest average density? So what planet in our solar system has the highest average density? Now, when you mentioned this to me just before we started recording, I thought average density. That's a key part of this. And I actually guessed right.

I'm really proud to say that, but it was partly out of my own ignorance of some of the planets. So this one ought to be one that people ought to be able to look up pretty well and find on their own. And once they do that, Bruce, how do they enter the contest? Go to planetary.org, follow the links to Planetary Radio, and it will tell you how to enter the contest. Planetary Radio, and it will tell you how to enter the contest. One other thing to throw on this week, which is also on planetary.org, as a response to the Columbia disaster, the Planetary Society does have a declaration of support for space exploration up that both expresses our deepest sympathy to the families, friends, and loved ones of the seven astronauts

and also support for space exploration in its future. And you can go to our website and add to the already almost 10,000 names of people who have done that, and we will eventually present that to NASA. We want people to remember, I think, that this is not just for members of the Society. Anyone can go there, right? Right, exactly. This is for anyone and is just trying to show support in a troubled time for the space program. Bruce, thanks very much. We'll do it again next week, right?

We certainly will. It'll be fun and festive. I guarantee it. All right, Bruce, we'll see you then, and happy post-Valentine's Day. And happy, yeah, and post-Groundhog's Day to you too as well, Matt. Take care, everyone. Buckle up. Drive safely. Thank you. Good night.

Bruce Betts is the Director of Projects for the Planetary Society and he will join us again for next week's edition of What's Up here on Planetary Radio. That's it for this week. Thanks to all of you for listening and especially to everyone who has written to us. We try to answer every message.

You can tell us what you think of our little show by sending email to planetaryradio at planetary.org. That's planetaryradio, all one word, at planetary.org. And remember that you can find all of our past shows and a lot of other great information on the Planetary Society website, planetary.org. Have a great week.