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The Search for Extraterrestrial Intelligence E.T. phone home using 10-10-220
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?
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.
The Drake Equation N = Number of communicating civilizations in our galaxy right now. And what about the rest?
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 R* = 10 */year
fp = 1 Optimistic! Fraction with Planets: fp • 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
ne = 1/10 Number of Earths: ne • 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
fl = 1/3 Fraction with life: fl • 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).
fl = 1 Inevitable! Fraction with intelligence: fi • What fraction of life bearing planets have life evolve to intelligence? • Is intelligence inevitable?
fl = 1 Inevitable! Fraction that communicate: fc • What fraction of intelligent civilizations become technological enough that we could communicate? • Is technology inevitable? • Desirable?
L = 1000 years Optimistic? Lifetime: L • How long does a civilization last? • Do we have time to communicate with them? • For us: L = 70 years!
What’s the Answer? • R* = 10 */year • fp = 1 • ne = 1/10 • fl = 1/3 • fi = 1 • fc = 1 • L = 1000 year • N = 330! 330 technological civilizations in the Milky Way, right now.
But space is vast • Milky Way is a giant cylinder (disk). • Radius = 15000 pc • Thickness = 1000 pc • Volume = p(Radius)2 x Thickness • V = 7 x 1011 pc3= 700 billion cubic parsecs!
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
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.
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
E.T. FM • Most natural radio sources are broadband. • Radio stations are narrowband.
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.
SETI@Home • 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.
“Is there anybody out there?” We have made three attempts to communicate. • The Arecibo broadcast to Hercules Cluster.
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!
The Voyager Record Club 3. Voyagers 1 and 2 contain a plaque and a record.
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
A Pale Blue Dot 43 AU Credit – Voyager 1990