18 The Search for Extraterrestrial Intelligence E.T. phone home using

18 Goals How likely is intelligent life in the Universe? How can we find out if there is? How could we communicate with it? Should we?

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18 Life in the Universe What are the odds of intelligent life elsewhere in the Universe? How many communicating civilizations are there in the Milky Way? How do you guess? How do you guess the number of jellybeans in a jar? Break the problem down into things you can guess.

18 The Drake Equation N = Number of communicating civilizations in our galaxy right now. And what about the rest?

18 R * = 10 */year Star Formation Rate: R * There are 100 billion stars in the Milky Way. The Milky Way is 10 billion years old. R * = 100 billion stars/10 billion years

18 Fraction with Planets: f p What fraction of stars have planets? Extrasolar planet research in the last 7 years: –87 stars are known to have at least one planet. –9 stars have more than one planet. –2 stars have three planets f p = 1 Optimistic!

18 Number of Earths: n e How many habitable planets are there in each of these planetary systems? Habitable zone: water should be a liquid Depends on star. –No O or B –No M –No binaries n e = 1/10

18 f l = 1/3 Fraction with life: f l On what fraction of habitable planets does life evolve? Look at our Solar System. 3 planets in habitable zone, life has evolved on 1 (or maybe 2).

18 Fraction with intelligence: f i What fraction of life bearing planets have life evolve to intelligence? Is intelligence inevitable? f l = 1 Inevitable!

18 Fraction that communicate: f c What fraction of intelligent civilizations become technological enough that we could communicate? Is technology inevitable? Desirable? f l = 1 Inevitable!

18 Lifetime: L How long does a civilization last? Do we have time to communicate with them? For us: L = 75 years! L = 1000 years Optimistic?

18 What’s the Answer? R * = 10 */year f p = 1 n e = 1/10 f l = 1/3 f i = 1 f c = 1 L = 1000 year N = 330!  330 technological civilizations in the Milky Way, right now.

18 But space is vast Milky Way is a giant cylinder (disk). –Radius = pc –Thickness = 1000 pc Volume =  (Radius) 2 x Thickness V = 7 x pc 3 = 700 billion cubic parsecs!

18 How far to the neighbors? If there are 330 civilizations in 700 billion cubic parsecs, then: –1 civilization in every 2 billion cubic parsecs Imagine every civilization surrounded by a bubble in which it is alone. V = 2 billion cubic parsecs R = 1 kpc Distance between civilizations: 1 kpc = 3300 LY (optimistically)! R R

18 How Can We Know? How can we tell if there are extraterrestrial civilizations? Go visit. Is this practical? Look for visitors? Is there evidence? Look, or listen, for signals from E.T.

18 SETI Search for Extraterrestrial Intelligence Several organized searches over the last 30 years. Use a radio telescope to try to detect signs of E.T. Why? The Earth floods space with radio waves. –TV –Radio –Cellular phones –etc

18 E.T. FM Most natural radio sources are broadband. Radio stations are narrowband.

18 Tuning the Dial Nearly all searches have been looking for extremely narrow radio signals. –But there are millions and billions of frequencies to listen to. –And millions and billions of stars Concentrate on nearby sun-like stars. –No luck. Point in the sky randomly. –No luck yet. But you can help.

18 Receiver piggybacks on Arecibo telescope. Constantly searches as telescope observes. Millions of channels. Thousands of hours. Lots of data. Needs lots of computer power. Your power.

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18 “Is there anybody out there?” We have made three attempts to communicate. 1.The Arecibo broadcast to Hercules Cluster.

18 Here’s my card. 2. The Pioneer 10 and 11 plaques. Pioneer 10 is now 12 billion km from Earth – 80 AU  11.3 light hours!

18 The Voyager Record Club 3. Voyagers 1 and 2 contain a plaque and a record.

18 Bach, Brandenburg Concerto No. 2 in F. First Movement, Munich Bach Orchestra, Karl Richter, conductor. 4:40 Java, court gamelan, "Kinds of Flowers," recorded by Robert Brown. 4:43 Senegal, percussion, recorded by Charles Duvelle. 2:08 Zaire, Pygmy girls' initiation song, recorded by Colin Turnbull. 0:56 Australia, Aborigine songs, "Morning Star" and "Devil Bird," recorded by Sandra LeBrun Holmes. 1:26 Mexico, "El Cascabel," performed by Lorenzo Barcelata and the Mariachi México. 3:14 "Johnny B. Goode," written and performed by Chuck Berry. 2:38 New Guinea, men's house song, recorded by Robert MacLennan. 1:20 Japan, shakuhachi, "Tsuru No Sugomori" ("Crane's Nest,") performed by Goro Yamaguchi. 4:51 Bach, "Gavotte en rondeaux" from the Partita No. 3 in E major for Violin, performed by Arthur Grumiaux. 2:55 Mozart, The Magic Flute, Queen of the Night aria, no. 14. Edda Moser, soprano. Bavarian State Opera, Munich, Wolfgang Sawallisch, conductor. 2:55 Georgian S.S.R., chorus, "Tchakrulo," collected by Radio Moscow. 2:18 Peru, panpipes and drum, collected by Casa de la Cultura, Lima. 0:52 "Melancholy Blues," performed by Louis Armstrong and his Hot Seven. 3:05 Azerbaijan S.S.R., bagpipes, recorded by Radio Moscow. 2:30 Stravinsky, Rite of Spring, Sacrificial Dance, Columbia Symphony Orchestra, Igor Stravinsky, conductor. 4:35 Bach, The Well-Tempered Clavier, Book 2, Prelude and Fugue in C, No.1. Glenn Gould, piano. 4:48 Beethoven, Fifth Symphony, First Movement, the Philharmonia Orchestra, Otto Klemperer, conductor. 7:20 Bulgaria, "Izlel je Delyo Hagdutin," sung by Valya Balkanska. 4:59 Navajo Indians, Night Chant, recorded by Willard Rhodes. 0:57 Holborne, Paueans, Galliards, Almains and Other Short Aeirs, "The Fairie Round," performed by David Munrow and the Early Music Consort of London. 1:17 Solomon Islands, panpipes, collected by the Solomon Islands Broadcasting Service. 1:12 Peru, wedding song, recorded by John Cohen. 0:38 China, ch'in, "Flowing Streams," performed by Kuan P'ing-hu. 7:37 India, raga, "Jaat Kahan Ho," sung by Surshri Kesar Bai Kerkar. 3:30 "Dark Was the Night," written and performed by Blind Willie Johnson. 3:15 Beethoven, String Quartet No. 13 in B flat, Opus 130, Cavatina, performed by Budapest String Quartet. 6:37

18 And if they answer? Should we be listening for E.T.? Should we be trying to contact E.T.? What if we do? What can we say? What can we learn? What do we have to fear? How will we be changed? Contact.

18 A Pale Blue Dot Credit – Voyager AU

18 Homework #17 Due Thursday: Read B24.5, S2 Do: –S2 Problem 5, 11 –B24 problem 9 –Math folks substitute 15 for 11