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Comet Levy
Comet Levy

To the stars

Chat: Astronomer David Levy

Web posted on: Friday, May 15, 1998 5:30:39 PM EDT

(CNN) -- In his latest book, "Comets: Creators and Destroyers" David Levy shows how comets have wreaked their special havoc on Earth. Beginning with ground zero as comets take form, he tracks the paths their icy, rocky masses take around our universe and investigates the enormous potential that future comets have to directly affect the way we live on this planet and what we might find as we travel to others.

David Levy took part in an hour-long CNN "Author's Chat" on May 12, 1998. This is a transcript of the chat.

Helyn-host: Hello! Welcome to CNN chat. Tonight's guest is comet chaser and author David Levy. Please submit your questions to the host, and our guest may answer your question!

First question: What was it like the first time one of your discoveries was confirmed?

David Levy: Wow! Let's party!!!!!... Actually, the feeling was better than anything I had ever experienced in astronomy before. It was as though I had broken the bonds of Earth and was in space.

Question: How much danger is the Earth in for getting hit by an asteroid in the near future?

David Levy: About one in 1,000 during a human lifetime.

Question: What is your opinion of the current state of physics education in this country?

David Levy: Wow! That depends on the school. At the elementary level it is not bad. It needs some improvement at the high school level.

Question: How does one "chase" a comet?

David Levy: Through a telescope, I search the sky, one field of view at a time, for about an hour after dark, and again before dawn. Comets are brightest when near the Sun. Photographically, I search by taking pictures of the sky in large areas, and retake the picture an hour later to see if anything has moved.

Question: Can you expand on the chance of 1 in 1,000 of an asteroid hitting Earth? Is that a catastrophic strike, or does it include small strikes?

David Levy: That figures as follows: A 1 km-diameter (.5 mile) object should hit the Earth on an average on once every 100,000 years. So that's about a 1/1000 chance during a human life span of 100 years. However, we don't know. One could hit in the next 5 minutes!

Question: How did you get started in your profession?

David Levy: I have never taken a course in astronomy, and started as a youngster by reading all I could and by observing the sky on many, many nights, either with unaided eye or with a small telescope. In later years, I learned from the best, like Gene Shoemaker. I was particularly moved by comet hunter Leslie Peltier's writing: "I had watched a dozen comets ... slowly creep across the sky as each one signed its sweeping flourish in the guest book of the Sun."

Question: Mr. Levy: The Leonids are expected to be spectacular this year ... is this hype or can we expect a great show? And do you think the danger to satellites is real?

David Levy: Leonids ... Yes the danger to satellites is very real. The Hercules communication satellite (I think that was its name) was disabled by a meteoroid strike around 1992. The Leonids could be spectacular on Nov 17, 1998, over the western Pacific, and in 1999 over the Meditteranean. In fact, I'm working on setting up a Med. cruise to see the possible Leonids in 1999. There could be as many as 5,000 meteors an hour then.

Question: What would you suggest for someone at home wanting to observe the stars?

David Levy: I strongly suggest beginning with the Moon. Even with the smallest telescope, the Moon is a fabulous place to visit. There are mountains to climb and craters to fly over, and a small telescope will do that.

Question: How much is pollution on Earth forcing observatories into space?

David Levy: Good question! There are still many beauitiful dark sites from which to observe, and still lots of observations than can be done from semi-dark sites. However, a space telescope is capable of observing all the time, without any disruption from the currents of our atmosphere.

Question: How big was your scope that you used to find the comet?

David Levy: I use three scopes here: a 6-, 8-, and 16-inch diameter. For photography, Gene and Carolyn Shoemaker and I used an 18-inch diameter telescope. Good question.

Question: Mr. Levy, how old were you when you started observing the sky?

David Levy: My first observation session was in August 1960; I was 12. The first thing I saw was Jupiter. Little did I or anyone else know that Comet Shoemaker-Levy 9 was already in orbit around Jupiter, headed for its fateful crash 34 years in the future.

Question: Hello Mr. Levy. I find that the technological (aspect of) astronomy quite innovative. We have "morphing" mirrors to compensate for our atmosphere and more. At the rate our technology is developed, will we eventually find new life and civilizations?

David Levy: We might! One of NASA's big new projects is called Origins, to search for planets like Earth where life might exist. Also, although I don't think we've been visited yet, we might be some day. And through SETI searches, we might find a signal.

Question: Are you still working with Carolyn hunting for comets?

David Levy: YES!! She was here last week and we observed for a few nights. And we'll be observing again in June. (Carolyn Shoemaker, her husband Gene, and I found the Shoemaker-Levy comets.)

Question: Are you a memeber of SETI? Has NASA dropped SETI?

David Levy: No, I'm not a member. And I do belive that Congress has cut funding for SETI so that the search continues on private funds, I may be wrong on whether there's government funding for SETI.

Question: Which of your many discoveries do you feel is the most important? Most impressive? Most curious?

David Levy: Most important: Comet Shoemaker-Levy 9. Impressive: The discovery that the star TV Corvi is in fact an explosive variable star. Curious: The discovery of asteroid 5261 EUREKA, which "chases Mars" around its orbit. Good question!

Question: Mr. Levy, do you believe there is intelligent life on other planets?

David Levy: Yes. However, I also believe that intelligent life is not too common. It is my hope we'll find some one day.

Question: Has David ever aspired to ride the Space Shuttle so he could get a better view...?

David Levy: Actually, no!! I wouldn't turn down an offer (!), but I feel I'm as close to space as I need to be when I'm observing from my back yard.

Question: How is a comet formed?

David Levy: A comet is a dirty snowball, typically about 5-8 miles in diameter. It is made of mostly organic molecules gathered over billions of years from all over the galaxy. Most comets were already formed when the Earth got going.

Question: What value do you feel astronomy and astronomers have to society as a whole ?

David Levy: Good question. Our society needs people to look up at the stars. Astronomers do teach us more about the Universe and the solar system we live in, but more importantly, they show that if we understand other worlds, we will understand our own better.

Question: Why does a comet tail always point away from the sun, and if the tail is ice, why doesn't it melt when it gets near the sun?

David Levy: Nice!... A comet tail points away from the Sun because the pressure of sunlight and other radiation drives the tiny atoms of gas, and the particules of dust, away from the Sun. ... The ice actually does melt when the comet gets near the Sun, but instead it goes directly into a gas. So in (the movie) "Deep Impact", when the fissures erupt on the comet after the Sun rises on it -- that shows the effect of warmth on the comet's ices.

Question: Is it feasible to alter the trajectory of a comet/asteroid and how could it be done?

David Levy: Just like how do porcupines make love? Very carefully. The idea would be to explode a powerful nuclear weapon off the bow of the comet. The shock wave from the explosion might push the comet into a very slightly different path.

David Levy: Funny story ... In 1994, the day the first fragment of Shoemaker-Levy 9 struck Jupiter, The Shoemakers and I walked into the Space Telescope Sci. Institute. We met Miles O'Brien from CNN. "This is very exciting!" We agreed. Then he said, "CNN is covering this whole thing live. Your comet had better perform, or you three are going to be so embarrassed!" We wanted to crawl under a rock!! Happily, the comet was listening and CNN -- and everybody else -- got a great story that night."

Helyn-host: hahahahahaha, sounds familiar!

David Levy: CNN did a superb job covering the Shoemaker-Levy 9 impacts.

Helyn-host: thank you!

David Levy: They were all over that story!

Question: Are comets a danger for Earth?

David Levy: They can be! If a comet were to collide with Earth, the results would be devastating ... In my book I describe what would happen: A miles-high tidal wave, followed by Earth's atmosphere heating to about the same as an oven set for broiling, followed by worldwide firestorm, followed by thick dust that would block out the Sun for months. One of the chapters of my book describes in lurid detail what I thought would happen if Shoemaker-Levy 9 had plowed into Earth instead of hitting Jupiter.

Ron: Please welcome our student group from Brazil, joining us tonight for CNN's Book Chat ...

David Levy: Welcome, students from Brazil! I am delighted you joined us tonight.

Question: Do you calculate for a comet to increase speed after the orbit around the sun? And is it possible to increase speed, after rounding sun?

David Levy: No -- the comet would be going fastest when it is closest to the Sun, then would slow down as it tries to leave the Sun's vicinity. However, a typical velocity of a comet near the Earth is about 140,000 miles per hour.

Question: Are you excited about the Stardust Mission as well as the International Space Station, and will you get the chance to help with either of these projects?

David Levy: Yes!... I am very excited about Stardust. Because this mission will actually capture a sample of dust from a comet and return it to Earth, we will learn amazing things. When comets stuck the Earth billions of years ago, they deposited the Earth's carbon and water supply. In a sense, they brought the building blocks for life with them. So Stardust's mission is to actually bring back a portion of our ancestors! In a real sense, we are the progeny of comets. And the Space Station, I hope, will peer at comets as well!

Question: How is it that many of the recent comets have been discovered by Japanese with binoculars, and they escaped detection by better equipped scientists?

David Levy: Whoa!!! The binoculars that Hyakutake used to find his comet in 1996 are like 5-inch diameter monsters!! Actually the American record is not too bad, with people like Howard Brewington, Don Machholz, Mr. Stonehouse, and me out there looking.

Question: Then the same thing that brought life here could end it?

David Levy: Yes. A comet is truly a double-edged sword. Also, think of what we'd be like if the comet that struck 65 million years ago hadn't hit. Maybe the dinosaurs would stuill be here, and maybe we'd still be as large as mice? Who knows?

Question: How do you top the discovery of Shoemaker-Levy and the spectacular impacts with Jupiter?

David Levy: You don't, I guess. I plan to keep on looking, and hopefully find another comet, I still love searching, and of course writing.

Question: Mr. Levy, how has the internet changed astronomy?

David Levy: Internet has made it possible for communication of discoveries to happen faster than it ever has before. For me, I also appreciate the possibility of doing research over the net.

Question: When will your book be launched in Brazil?

David Levy: That is a good question. I do not know. I know that Simon & Schuster has an international department, and of course your school can always order one from the United States. In 1990 or so there was a chance for me to have a Brazilian edition of one of my other books, but that never came about.

Question: Does Levy really accept the Alvarez Comet Theory of Extinction?

David Levy: Yes I do. I think that the evidence is overwhelming, especially from so long ago. There is that impact layer all over the world, and there is a gigantic crater off the Yucatan, and there is the fossil record of almost everything -- 75 percent of all species, big and small, being wiped out at that time. The Earth did get hit by a comet or an asteroid almost ten MILES across, traveling at perhape 40 miles per second, back then.

Question: I find it amazing that the world is cooperating to put up an international space station.

David Levy: Yes, and I think that ultimately, the station will be good for the world in ways that we cannot even imagine now. I certainly hope so!

Question: What inspires you to search the cosmos?

David Levy: It is a very spiritual thing with me. When I was younger I even kept my comet searching a secret, sort of. It was that personal with me. Now it obviously is not, but it is still a very special activity. It's not so much the discoveries, but the search itself that is important to me.

Question: How many comets come in to the Suns attraction each year?

David Levy: It varies, but typically about 10 to 30 each year.

Question: Does Levy collect meteorites??

David Levy: Yes, I have a few! The best one is a piece of the Gibeon meteorite from Africa. This was cut into my wedding ring!!!!

Question: Are you affiliated with an observatory, or do you conduct scans by yourself? If so, how do you compete?!

David Levy: Good question. No I am not now affiliated with any observatory, except my own backyard one. I was before, but now I am fully independent!

Question: The depression in Iowa is thought to be a crater from a comet or asteriod ... I belive the size is about 200 miles in diameter. Can you eleborate on that??

David Levy: There is a small crater in Iowa, near Manson. It was formed some 9 million years before the dinosaur extinction one, about 74 million years ago. However I am not aware of any 200-mile diameter one, but maybe there is!

Question: What do you do for fun when you are not hunting celestial bodies.

David Levy: Hmmmm...... Lately I've had very little free time since I work so hard on my books and articles. However, Wendee, my wife, and I enjoy walking, swimming, and all the neat things that are our life together. We love taking walks in the desert.

Last question: Isn't it true that the fossil record indicates that the 65MY extinction was a gradual one, and that there were several mass extinctions subsequently?

David Levy: Good question. There were not very many big creatures samples, like dinosaurs, so it is difficult to say categoriucally that the dinosaurs died all from the impact. Maybe they were on their way out earlier, perhaps from too many Paula Jones articles. However, the smaller creaters, which are more thickly sampled, vanished immediately at the "boundary layer" between the Cretaceous and Tertiary periods when the impact happened. So I think it was a remarkably sudden extinction!

Helyn-host: Thank you for joining author and comet chaser David Levy in our chat tonight! We appreciate Mr. Levy"s participation! Great chat!

David Levy: Thank you! I think that this has been one of the best chats I've been involved in. Thank you all!

You can write to the author at: David Levy Touchstone Books Publicity Department 1230 Avenue of the Americas New York, NY 10020


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