and as you've seen in our documenta documentary, the youngest victims are considered the most vulnerable in the aftermath of this disaster many organizations have created programs to help provide for the thousands of children left to fend for themselves. to find out more about how you can help make a difference in the lives of these children, go to cnn.com/impact. i'm soledad o'brien. thanks for watching. >> larry: tonight, could aliens from other worlds conquer and colonize planet earth? astrophysicist stephen hawking says it's possible, and issues a warning for all of us. stop trying to contact other life forms now, just in case they're out there and they're hostile. >> they are likely to be more advanced than us. >> larry: hawking joins us, answering our questions, sounding the alarm. and believer dan aykroyd is here too. >> honestly, don't think they're a mass threat, but i do believe they're breaking the law.

>> larry: aliens from out of space, a real threat to the human life? next on "larry king live." >> larry: good evening. you can say that this show tonight is out of this world. john smithson is executive producer of "into the universe with stephen hawking." as is ben, both joining us from london. in their documentary astro physicist stephen hawking will join us later, warns that contact with extraterrestrial life may not go so well. watch 3 >> so if aliens ever visit us, i think the outcome would be much as when christopher columbus first landed in america. which didn't turn out very well for the native americans. >> larry: john, you're producing the show. do you accept the theory?

>> well, we -- we're working with one of the greatest living scientists, one of the best scientific brains in the world. and i'm not a scientist. my job on this series for discovery channel was to bring the views, the vision, the imagination of this great scientist to a mass audience. these are the words of professor hawking. i don't have the scientific credentials to secondguess professor hawking. i'm prepared to believe him because he is such a great scientist. and what we said about aliens in that program was very much what stephen hawking wanted to say. for years he had been lecturing about -- about lots of things, including the possibilities of alien life. what we were able to do for the first time using the wonders of computer graphics was to visualize with professor hawking hypothetically what they might

look like. that's what we're able to do here. larry >> larry: ben, how did this come about? how did you and stephen and john all get together and do this? >> well, discovery wanted to do a new and exciting show on cosmology. and so we sat around the table for a while and thought who best to do it. and there isn't a bigger name than stephen hawking. so it was a very simple, very, very short list of who we wanted to work with. and then we pitched it to him. and you may know that stephen takes quite a while to respond to questions. so we gave him our pitch, showed him the tape, and we had to wait a while. but thankfully the answer was yes, i'd love to do it. so that's how it got going. >> larry: john, are you surprised at the reaction it has gotten around the world? >> no, i'm not, because, you know, professor hawking is this distinguished academic, as we've said. but also, he wants to bring science to a new generation, to

people around the world. and he's prepared -- everything he says of course is immaculately scientifically sourced. but he wants to entertain people. and by entertaining them, he wants to interest them in science. you know, every -- this was done really incredibly closely -- we've been working with stephen hawking for three years on this. and he really did want to somehow popularize his views, the universe inside his mind. so i think he lept atta chance of doing a series that was both totally big-deal science, definitive science about what we know about the cosmos, but in an educating and in an informative and in an entertaining way so that the global audience on discovery channel could be sort of interested in this >> larry: ben, does the british government take this seriously? >> i'm not -- i'm not sure i'm

qualified to answer that, but i don't think so. >> larry: john -- well, ben, you first. the tendency has been to kind of dismiss this, until mr. hawking arrived, as kind of kooky, right? >> i think that -- you know, maybe it's been overstated slightly from what he actually says in the film. what he says in the film is that if intelligent aliens exist -- that a big if -- and if they were to meet us -- that's another big if -- then we might be wise to treat them with caution. it's not stephen saying as far as i know in any way, stephen is not saying aliens are coming, we've got to hide under the bed. he's not trying to frighten anyone. he is just saying if you follow the argument logically, then he thinks that we would be wise to be -- to exercise caution when dealing with aliens. >> larry: so what do we do with this, john, other than entertain and inform us? what's the next step? >> well, what we're trying to do with this -- you know, what is just so amazing about this

subject, it just blew my mind. i'm not a scientist. my job is to make tv programs. what blew my mind is the huge scale of the universe. i'll never look at the night sky the same way again. just during the three years we've been making this show, someone told me the other day 300 billion stars have been born. 300 billion stars have died. these are just awesome figures. and what we're doing next really is just -- literally what we're doing next on sunday night is the ultimate story on the discovery channel, the ultimate story of how it all began 14.7 billion years ago, and how it might all end. and it is really the ultimate story. >> larry: let me get a break and come right back. >> fascinating. >> larry: we'll get a break and come right back with john smithson and ben bowie. stephen hawking is coming up. but first, how would we respond if alien life landed on earth? stay with us. to stay on top of my game after 50,

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for as low as $8.92 a day, our best price guaranteed. i'm marie osmond, and i lost 50 pounds on nutrisystem. i lost over 100 pounds and lowered my blood sugar on nutrisystem d. based on the proven science of the glycemic index, nutrisystem works, and now it can work for you. that's me 22 pounds ago, and i'm never going back there again. roll back prices no matter who you are or what program is right for you. people say i look 10 years younger. i feel 10 years younger. smart money named nutrisystem the best value of popular weight-loss programs. now our best price just got better. call 888-988-thin and start losing weight today. with nutrisystem, there are no more excuses. the nutrisystem roll back sales event won't last long. call or click now. >> larry: do you believe in life in other places, other planets?

>> life appeared on earth fairly soon after the earth was formed, 4.5 billion years ago. that success at primitive life will appear spontaneously on any suitable planet. on the other hand, intelligent life seems very rare. it has yet to be detected on earth. >> larry: stephen hawking has a great sense of humor. in 1977, a radio signal was received called the wow signal. take a look. >> on august 16, 1977, a radio telescope in ohio picked up a signal that became famous. the signal was a steady source of radio waves, just the kind an alien race might send because it stands out from the radio static that fills the universe.

a computer recorded the signal as six letters and numbers. astronomer jerry ehman saw the data and wrote one word in the margin. >> larry: this is a remarkable, remarkable entertaining feature that will air on discovery sunday. john smithson and ben bowie are the executive producers of "into the universe with stephen hawking." this would be an opinion, ben. do you think we would be hostile or not hostile to another environment coming here? >> do i think -- i don't think you can really say. i think the only thing you can say is that you don't know. if you don't know, then caution seems to be the most sensible approach. i'm not one to call whether aliens will come here and stroke us and pet us or zap us with lasers. i think we just don't know, and therefore you can't really

say -- you can't say one way or the other. you can think maybe caution would be a good idea. >> larry: stephen theorizes the negative aspect, does he not, john? >> he rightly thinks we should be cautious, and i'm not going to secondguess professor hawking. but that is what is so intriguing, isn't it, about this whole subject? could there be life out there? if so, is that just some sort of green gloop or is it something that is a real menacing threat? that's what we don't know. many better scientific minds than mine are obsessed with looking. i think you've got guests later who will tell us a lot more about that. but it is just totally intriguing. it's been the subject of literature. it's been the subject of movies. and i think the one of most intriguing questions of all, which is why it's one of the questions stephen hawking himself wanted to deal with in this series.

because it really is one of the big questions we all face. are we alone in this planet of ours? and we're talking even if it is one in a billion, then there are billions of dollars. so we're playing a big numbers game here. >> larry: john, was this fun to do? is he easy to work with? >> it was -- it was fun, but it's probably the most complex and challenging program i've ever been involved with because you're dealing with the most ferociously complicated story, most ferociously complicated science imaginable, but we were trying to make it in a way that people like myself could understand. so it was -- it was brain-numbingly difficult, but also really good fun. and stephen hawking is just a remarkable man. i mean, he just has this presence. everyone feels it. we did something with him last night in london. and the whole room stops when he comes in. he has -- you know, it's weird. we almost talk of him as a rock star of science.

he has this extraordinary aura about him. and we just know that trapped in this body that he can't use is this quite brilliant brain. and there's something about that that is such a powerful and poignant image that i know it just -- it just seems to touch people. >> larry: thank you both very much, john smithson and ben bowie. the second part of this special will air sunday on discovery. we'll be back. we'll talk with stephen hawking and we'll meet an expert panel as well. stephen hawking in his own words, next. to the seekers of things which are one of a kind. the authentic, the rare, the hard to define. to those who'd climb mountains or sail across seas...

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it is important to use the product as directed. fixodent and forget it. if civilizations take billions of years to evolve, only to vanish virtually overnight, then sadly, we've next to no chance of hearing from them. they are simply too far away in space and time to reach. but there is one last possibility. that aliens who have avoided destroying themselves are already colonizing the universe.

>> larry: we're back. in a new discovery channel documentary, astrophysicist stephen hawking said that communicating with aliens could be a threat to earth. hawking says it's likely that alien life exists, and that a visit from extraterrestrials might be similar to columbus' arrival in the americas. in other words, didn't turn out too well for native americans. joining us are dr. michio kaku, futurist, physicist, beth selling author. his best new book "physics of the impossible: a scientific exploration into the world of phasers, force fields, teleportation and time travel." seth shostak, the senior adviser of the seti institute. david brin, astronomer and futurist, and our friend the well-known actor dan aykroyd who believes that alien life exists. we wanted to hear directly from the renowned british scientist, former guest on this program stephen hawking about his controversial claims. so i sent him some questions.

here are his answers. do you think there will ever be direct contact between the inhabitants of earth and alien life? >> it's nice to see you again, larry, after ten years. i think we may find primitive life, but it's unlikely there are intelligent aliens within 100 lightyears, or we would have detected their radio signals. >> larry: if contact does occur, will it -- do you think it will be initiateded by us or by them? >> they are likely to be more advanced than us. so they will contact us first. >> larry: you're warning that it may be too risky to try to contact space aliens has stirred a lot of debate. do you care to react to some of the criticism, those who say the search for extraterrestrial life is central to space exploration? >> i think we should look for primitive life.

if advanced life exists, they'll contact us. aliens haven't contacted us so far, except maybe in the state of arizona. >> larry: in your mind, what would an advanced alien look like? >> they are bound to have a mouth opening because they will have to take in nutrition. and they will probably have legs because they will need to move around. and they'll need eyes. but don't expect them to look like marilyn monroe. >> larry: should we ban messages into the universe for fear of attracting dangerous aliens? >> it is too late. if they are looking, they will already have detected us. >> larry: thanks for joining us. stephen hawking. >> goodbye, larry. i hope to see you this fall when my new book with leonard mlodinow, "the grand design" is

released. thank you. >> larry: what do you make of his thinking? >> i think, first of all, don't quit your day job, larry. don't sell the store. the aliens are not going to invade any time soon. i think what stephen is doing is giving us a wake-up call. in the next few months to next few years, we have two satellites out there that are going to detect ette-like twins in outer space. maybe with liquid oceans, maybe with life on them. when we look at the night sky in the next few years, we're going have to get used to the fact that somebody could be staring back at us. we're going to have an existential shock when the results of the satellite announce they have found earth-like planets in space. >> larry: seth shostak, you buy it? >> well, of course i buy that. but look, i think what stephen hawking is saying we're going to hear from them first. that's exactly what we try and do in the seti business. we have big antennas scanning the skies looking for

signals from civilizations that would be quite far away. there's to danger in that, of course. you tune in the radio, you don't have to worry about the deejay jumping into your home and giving you a hard time. that's a completely harmless sort of thing and interesting because it would tell you whether earth is really, really special, or whether there is enormous quantities of life out there. >> larry: but, david, one thing is has done with stephen hawking about it, it has opened many eyes, hasn't it? >> oh, yes. the problem is that everybody seems to have their own idea, of course, of what aliens ought to be like. we all say of course our broadcasts have already been detected by now. when seth himself has calculated and most of the astronomers have calculated that our tv broadcasts actually dissipate pretty soon after they leave our solar system. it's these narrow beams that are being sent out from taxpayer-paid observatories like

arecibo and ukraine that are causing the fuss. without consulting the taxpayers, without consulting the governments, without consulting fellow scientists at all in other disciplines. these people have taken upon themselves to act on their assumptions that aliens are universally altruistic. it's not so much the beamed messages that we object to, those that have been dissenting lately, but, rather, the arrogance of not talking to anybody else on this planet before assuming they have the right to do this. >> larry: and by the way, the images you're seeing are images and imaginations. all right, dan, how do you contrast with david brin who is saying that -- what do you really know? >> well, thank you for including a hollywood constituent here. i'm the new fund for hollywood new fund ufo network. i have to speak for the people today and for hollywood. we've made some pretty good

movies about this, "e.t.", "close encounters," "indiana jones, crystal skull" and "coneheads" and "the earth stood still," one and two. the significance of the hawking speech that i heard was that he specifically referenced a july 1952 sighting over the united states coast guard station in washington, d.c. no astrophysicist of his credibility and reputation has ever actually mentioned a ufo sighting. so to us in that community, we sit up right away. and what we say is seti, please continue. maybe focus in on where there might be planets. please continue, but please also accept the fact that they may have been coming and going here for many years without calling seti back. in fact, i believe they're in violation of title 18, section 1202, paragraph a of the united states code, that says whoever abducts someone for ransom or otherwise is liable to criminal prosecution. and if you know the story of barney and betty hill, stanton friedman's book, herb

shermer, the nebraska highway patrolman, he spoke to witnesses, callahan of the faa -- >> larry: dan, i've got get a break. you're making a strong point. one question i always ask, why did they land in wyoming? why not new york? chicago? >> i'll tell you that later. >> larry: maybe we'll get answers ahead. e to get everyone together for a night where everyone gets just what they want. combine two or three favorites, from new creations like crab-stuffed shrimp and pecan-crusted shrimp to classics like decadent shrimp scampi. it's everything you want in a night out. starting at just $11.99, during the festival of shrimp.

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>> larry: i love that. stephen hawking weighed in on what alien life might be like on other planets. here's what he had to say. >> the laws of physics appear to be the same everywhere. so, it follows that the laws of life should be universal, too. even if the detail is different. we can use life on earth as a kind of alien hunters handbook, a field guide to what life actually is and how it works, no matter where it occurs. >> larry: dr. kaku, you're a renowned physicist.

you accept that? >> well, yeah. life is going to be, i think, found throughout the universe. however, i don't think they're going to want to come and strip mine the earth. there are a lot of planets out there that are probably uninhabited without restive natives. if you're a camper, are you going to sit down where there are a lot of scorpions and tarantulas and rattlesnakes? no. you're going go where it is clean of pests. why would they bother with earth when there is lots of pristine planets with lots of resources out there? there is no point to mess with the natives. it's not going to be quite like columbus meeting a native and genocide. think more like the vietnam war, okay? an intelligent species may simply say, it's not worth it to get the natives angry. >> larry: "avatar." did you see "avatar"? >> i did. great movie. >> larry: you liked it. >> uh-huh. >> larry: as a physicist, you liked it? >> well, it opens up whole worlds. right? perhaps a europa-type moon circulating around jupiter could have oceans under the ice cover.

>> larry: seth, isn't it all kind of incomprehensible? isn't it, with the exception of dr. kaku, is isn't this larger than -- can't imagine it. i don't know what i'm going to have for lunch. >> well, i hope it's not unimaginable, because after all we're trying to imagine it, and we're not only doing that, we're trying do an experiment, right? we would like to know if it really is true out there. i agree with michio that they're not going to come here and strip mine the planet. you don't have to worry about that. in the movie they go to pandora, for $20 million a killy gram, but you can work out the cost of transport. and this would be like ordering a book for amazon and paying $6,000 for the shipping. we're not -- you wouldn't do that, and the aliens are not going to come here for that. could they come here for some other reason? possibly. but you know, david brin said that they might not pick up our television, but they might pick up our very strong radars. look, if they have the technology to come here and actually threaten us, they long ago could have the technology to pick up our signals. they'll know we're here. >> larry: david, succinctly put, what do you believe?

>> well, that's the whole point, larry. as an astronomer, as a science fiction author, i've been thinking about the alien, discussing the alien with everybody i could for the last 50 years. and what i believe is that everybody is too strong in their beliefs right now. seti, the search for extraterrestrials is called the only topic without a subject matter. and everybody gets passionate. they believe that they would have seen our signals by now. they believe that space flight is impossible, which is the standard seti position, or that if there are aliens out there, they'll automatically be altruistic, which is wishful thinking where we're heading. i would like more open conversation about this. i would like the seti people to get involved. >> larry: dan, isn't it true that we know a little bit, but there's so much we don't know? and the answer to the question is, why don't they land in l.a. and new york, dan? >> well, first of all, i'm glad this is grounded in real

science. i can't wait to see the discovery special. but they don't land here. they only land in isolated places. they have taken people, i believe. they do have technology. lord hill norton of the british defense staff said he -- >> larry: why not new york? >> -- believed 23 people are coming here. that 23 species are coming because they don't want anything to do with us. i don't think we'll ever have a formal relationship, a formal contact with any alien species out there, especially after 9/11. when we broke our toys in the sandbox, if they were observing that, goodbye human race. and honestly, i don't think they're a mass threat, but i do believe they're breaking the law. i'm serious. title 18, 1202. read the travis walton story. >> larry: so how do you arrest them? >> that's the thing. the fbi should be on that right away. i don't think they're a mass threat. if you want to save lives in this country, teach people to drive better, remove the cocaine appetite in the united states and stop people from texting while driving. that's the way to save lives. i look at this through the entertainment filter, larry. that's why i -- >> larry: i gather that. that's why you're going to do

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at this scale, each point of light is an entire galaxy. which not only puts our little world in perspective, but also makes it difficult to believe we really are alone. so to my mathematical brain, the numbers alone make thinking about aliens perfectly rational. >> larry: one thing true, this subject will never go away. the discovery channel documentary discusses several theories about how life originated on earth, and how it could also have originated on other planets. watch. >> it is extremely unlikely that life could spontaneously create itself. but i don't think that's a problem with this theory.

it's like winning a lottery. although the odds are astronomical, most weeks someone hits the jackpot. but there is another intriguing idea called panspermia, which says life could have generated somewhere else and been spread from planet to planet by asteroids. >> larry: dr. kaku, in your opinion, how did it all start? >> probably on the earth. probably in the oceans where there's liquid water. we physicists always say follow the water. liquid water is the amniotic fluid of life where dna got off the ground. >> larry: isn't water redundant? >> ice is actually quite common out of space. comets are made out of water. liquid water is the most precious substance. we have a lot of it on earth. >> larry: why here and why then? because there was water? >> and we think that water is the mixing bowl for dna getting

off the ground. >> larry: is there water on other planets? >> well, liquid water does not exist outside the earth other than maybe a satellite of jupiter. so we think that it's a very precious commodity, and that's what we look for in outer space, the presence of water, especially liquid water. and also you asked the question why don't we see them, why don't thy they make contact with us? maybe they're so advanced that we're not even on their radar screen. we're so arrogant to believe that they're going to want to land on the white house lawn. i mean, if you see an ant hill in the forest, you go down to the ants and say, i bring you trinkets, i bring you beads, i give you, if energy, take me to your ant leader? is that what you do when you see an ant hill? i don't think so. >> larry: seth, that concept sounds very interesting. do you, seth, do you factually believe they're there? >> well, in my heart of hearts, larry, obviously i think we're there, otherwise i wouldn't be doing this kind of research.

look, the seti institute is building a new an ten in northern california, the allen telescope array. this thing will be able to greatly accelerate the search. the fact that we haven't picked up a signal so far, and that's been mentioned several times here, it doesn't mean a thing because we've barely scratched the surface. it's the next 20, 30 years that counts. i think we may find a signal, otherwise i wouldn't do this job. it's not that lucrative. i did want to say something to dan aykroyd who thinks they're here. how many times does he go down to the l.a. airport and sit in the plane and the captain comes on and says, we're going to delay our departure a little bit because there are unidentified flying objects in the area and the faa wants us to stay on the ground? >> remember chicago, sir. >> it doesn't affect us at all. >> remember chicago? >> i remember chicago. >> what was that? was that a weather anomaly? something punched through the cloud. >> yes, it was a weather anomaly. >> i don't believe it was a weather anomaly. >> weather anomaly. >> all right. but i support seti. go to it. i just don't think they're

calling like they took barney and betty. >> larry: david, has nasa discovered anything? >> well, the -- we could go on for hours about paranoid theories like ufos. i personally find the ufo aliens unlikely because the number of cameras is doubling every single year, and the grays that they're talking about are such tedious boring versions of aliens. i support seth in that i have supported seti all my life. but i think it's been shown recently that seti needs to change track. seti has failed to see the garish, huge garish beacons that frank drake expected out there. seti should keep looking. they may be farther away. but it turns out that what we should be looking for is more of those wow signals. and you do that not with a single telescope, but with 10,000 amateur telescopes in backyards all over the world. and this system could make sure that all parts of the sky were

being watched all the time. and then we might see that wow signal come back, because calculations show that's how the aliens would far more likely try to communicate. >> larry: science fiction films have had some good alien story lines. which are true to life? our experts will weigh in, coming up. y buying? a shiny coat of paint? a list of features? what about the strength of the steel? the integrity of its design... or how it responds... in extreme situations? the deeper you look, the more you see the real differences. and the more you understand what it means to own a mercedes-benz. the c-class. see your authorized mercedes-benz dealer for exceptional offers through mercedes-benz financial. ♪ time to face the pollen that used to make me sneeze... my eyes water. but now zyrtec®, the fastest 24-hour allergy relief, comes in a new liquid gel. new zyrtec® liquid gels work fast, so i can love the air®.

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we're back. comedian stephen colbert had some fun with hawking's views on alien life encounters. watch. >> this hubbell humper is back with a new tv series "into the universe with stephen hawking." and here, here is what he had to say about the prospect of mankind encountering aliens. >> the outcome would be much as when christopher columbus landed in america, which didn't turn out very well for native americans. >> why do the aliens get to be columbus in this scenario? i think we humans have a proven track record of raping and pillaging. it's right there on mankind's resume.

special skills, 50 words per minute, powerpoint, smallpox. >> larry: you could have a lot of fun with this. do you accept the humor of it? >> i do. and we think hollywood likes david versus goliath stories, right? however, it could be goliath versus the mosquito in real life. they could be that advanced, we could be mosquitos. however, even goliath is not going to go where there is a swamp of mosquitos. so even though our technology may be primitive compared to goliath, it's not going to be a one-to-one combat like in science fiction. they may avoid us. >> larry: as a noted physicist, what puzzles you the most? >> what puzzles me the most, why aren't they here? if they're so expensive and so galactic in their scope, and billions of years more advanced. and i think the answer to me is pretty clear. we're not on their radar screen. we're simply too insignificant to them. >> larry: seth, is there any science fiction movie that came close to capturing what you think might be?

>> well, at the risk of sounding self-promoting here, obviously the movie "contact" which kind of portrayed the work of the seti institute. so, obviously, i like that one because the science was pretty accurate. carl sagan wrote the story. never mind you when jodie foster goes out into space to meet her dad on another solar system, well, that's maybe not so accurate. but, yeah, that film was at least pretty good when it came to the science. >> larry: david, do you have a favorite science fiction film? >> oh, there are so many. i -- i worry that we're concentrating so hard on things that can be filmed. i mean, i've had movies, and sure, they're entertaining, but it's in the science fiction novels where you actually get serious thinking about what aliens might be like. and then the next nole says, yes, but. and then the next says yes but. we need to bring this conversation out into the real world where people can maybe

watch you chair three or four hours of scientists really getting at it. because the historians have a lot to say. the biologists have a lot to say. and they have not been consulted in any of this so far. >> larry: i would volunteer immediately to do that. dan, didn't you make a film about your stepmother being an alien? >> well, yes. but i also made "coneheads." you will be spared when my species overtakes your miserable planet. and we had fun with that. one note to david brin, if photographic evidence in there, then bruce maccabee in the service warfare development agency has been wasting his life. i think you should talk to bruce david and he'll show you how he has broken down some of these photos, proved the ones that are hoaxes and ones that seem to be genuine photos of aircraft that are far more ergonomically than we. >> larry: why don't these stories make the front page of the new york times? >> but they do all the time. it's in the -- there was a

recent article in "the new york times," in one of the subsections about abductees visiting at the medical institute of new york and discussing how -- their experiences. all i have to say, it's very entertaining to me. and let's keep it grounded in science, but please accept maybe that the reality is that maybe they are here, coming to treat us like the ants that the doctor talks about. and that really, altima i will in the end, they will not want anything to do with us because we're basically pretty bad. >> larry: i got it. all right. hold it. does the united states have some kind of official policy with regard to aliens? that's next. [ male announcer ] parents magazine and edmunds.com called it "one of the best family cars of 2009." the insurance institute for highway safety calls it a 2010 top safety pick. with automatic crash response from onstar that can call for help, even when you can't. we call it peace of mind.

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>> larry: by the way, dr. kaku's newest book is "physics of the impossible: a scientific exploration of the world of farzs, force fields, teleoration and time travel." is there a government policy about this? >> well, we used to have the blue book. the government used to monitor these things, but then it shut it down and lost interest. and then, you know, the uk and other countries have looked as these things, but pretty much they're not taken seriously. however, i personally believe that 95% of these sightings can be dismissed, but 5% of them really give you the willies. 5% of them cannot be explained easily using the known laws of physics. that doesn't mean they're not natural, just difficult to explain. >> larry: seth, do you believe in the area 51 or the new mexico

story of hidden bodies? do you believe that? >> no -- well, no, larry, i don't believe that aliens came 500 or 1,000 light years to enjoy some tex-mex cuisine in the northeast and then made a navigation error and crashed into the desert. but there's a whole office of planetary protection within nasa, and it's not to defend us against the aliens as you would in the movies, but simply to understand if we bring rocks back from marches or send rockets to marches, that we don't contaminate either planet, so we don't mistake martian life for earth life or vice versa. >> dan, why doesn't the government treat it seriously. dan first. >> there's all kinds of footage

from the '50s from air force generals and majors going on tv saying, we know you saw something, we're not sure what it was. joint army and navy air force publication number 146 specifically instructs pilots and navy aviators, if you see one of these things, don't talk about it. assist breach of national security. the air force has been very interested. the memo says we have to look into these things, they're aerodynamically advanced. the airports have lost interest, but they have been interested and i think are today still. >> larry: david, is that true? >> i want to speak up for humanity in two ways. first off, michio is completely right that the earth was prime real estate for 2 billion years before we came around. we see no signs, even in the geology of the rocks, if they had tossed a coke bottle or emptied their latrine in our oceans, we would have seen the traces. so the paradox, the great silence stretches on a big time and it is the big question of why we're alone. but i want to speak up for

people in america. these retired, crotchety old engineers would have been speaking up a lot more if they had been in area 51, if there had been a roswell. do you know any engineers? >> larry: let me get a break. time for another "larry king live" moment from my 25 years here at cnn. i spoke to bill cosby in 1997 at his childhood home in philadelphia about the toughest thing any parent can endure -- the loss of a child. >> larry: we're at 919 parish place, apartment "a," philadelphia. the grow-up home of bill cosby. >> ennis was very, very small and i brought him by here, because i wanted him to see where i grew up. ennis said he wanted to go home.

he told camille that i took him some place and tried to prove to him that life was rough, but he didn't believe it. >> larry: i've known bill cosby for a long time, interviewed him many times. the hardest setting for anyone is death to begin with. >> we were all there and ennis was coming home. and we put the coffin in the place and everybody went to look at him. i didn't go. i don't want to see my son like -- i have memories. >> larry: how a guy could go on after a child has died is incomprehensible to me. i would never go on. one great thing you must have seen, as you saw all over the world, is the love people have for you. >> and the family. >> larry: and the caring. >> you never really know what people judge you by if you hit the mark and you made them very, very happy. and i mean to continue to do that. >> larry: you're an ace.

>> watch your mouth. ace of what? >> larry: hearts. >> thank you. >> larry: you can see this and other clips at cnn.com/lar cnn.com/larryking. and we want your help in ranking the top five. make your picks and we'll reveal what you decide the week of may 31st. you may win a trip to meet me, see the show, we'll have dinner. be back after this.

>> larry: we've about run out of

time. dan aykroyd, sum it up. your opinion is, succinctly, what? >> that they're here, science should look how they're here and look where they come from where they're coming from. they have abducted people, but i say, go, seti, go, because maybe the nice ones will call. >> larry: what do you believe, dr. kaku? what do you know, know. >> i believe, a, they're out there, but b, they're malevolent. the next time you hear "abducted," please, swipe a paperweight, swipe a pen. we have some alien dna, alien technology. that will settle the question right there. >> larry: seth, what do you believe? believe believe? >> well, i believe that we ought to keep looking. the big question is, is earth a miracle or is life just a cosmic infection. i think the latter's probably true, but let's go look and prove it one way or another. >> larry: david, what do you believe? i'll close with dan in a minute.

david, what do you believe? >> i believe that 15 years ago, we knew of no planets outside our solar system. now we know of 500. we are learning so much, so fast. it's not the time to be certain and it's not time to be yelling yo-hoo into the universe when we're the children in the jungle. let's keep learning and stop being so certain. >> larry: in this lifetime, dan, will we ever learn the truth? >> yes, i think a revelation is coming on a mass scale very soon. i don't know what form it's going to take, but there's a lot of witnesses out there. get on the website, let's keep it grounded in science, but there's so much photographic evidence. >> larry: thanks, guys. thank. >> thank you, larry! and this is the planet that create ed "satisfaction," the great keith richards song. that's a miracle.

>> larry: as you know, oprah winfrey is heading up the no-phone zone initiative, and as of today, i'm taking the no-phone zone pledge. i'm challenging others to do so as well. this includes no texting and talking on the phone while driving. here is the pledge that i have signed. hope this will make a difference, hope it will save lives.