The Search for Alien Life

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The Search for Alien Life

• Can E.T. hear me know?

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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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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.

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The Drake Equation

• N Number of communicating civilizations in our
  galaxy right now.
• And what about the rest?

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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
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Fraction with Planets fp

• What fraction of stars have planets?
• Extrasolar planet research since 1995
• 539 confirmed planets
• 414 planetary suystems
• 55 multi-planet systems
• 1 star has six

fp 1/20
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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

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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).

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Fraction with intelligence fi

• What fraction of life bearing planets have life
  evolve to intelligence?
• Is intelligence inevitable?

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Fraction that communicate fc

• What fraction of intelligent civilizations become
  technological enough that we could communicate?
• Is technology inevitable?
• Desirable?

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Lifetime L

• How long does a civilization last?
• Do we have time to communicate with them?
• For us L 75 years!

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Whats the Answer?

• R 10 /year
• fp 1/20
• ne 1
• fl ?
• fi ?
• fc ?
• L ? year
• N _____ ? of technological civilizations in
  Milky Way, right now.

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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!

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How far to the neighbors?

• If there are 100 civilizations in 700 billion
  cubic parsecs, then
• 1 civilization in every 15 billion cubic parsecs
• Imagine every civilization surrounded by a bubble
  in which it is alone.
• V 15 billion cubic parsecs
• R 3 kpc
• Distance between civilizations
• 3 kpc 900 LY (optimistically)!

R
R
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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.

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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

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E.T. FM

• Most natural radio sources are broadband.
• Radio stations are narrowband.

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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.

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SETI_at_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.

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SETI_at_Home
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Is there anybody out there?

• We have made three attempts to communicate.
• The Arecibo broadcast to Hercules Cluster.

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Heres my card.

• 2. The Pioneer 10 and 11 plaques.

Pioneer 10 is now 12 billion km from Earth 80
AU ? 11.3 light hours!
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The Voyager Record Club

• 3. Voyagers 1 and 2 contain a plaque and a record.

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Voyagers 1 and 2

• Greetings 55 languages
• 115 images
• Music

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• Sumerian"May all be well."
• Arabic"Greetings to our friends in the stars. We
  wish that we will meet you someday."
• Urdu"Peace on you. We the inhabitants of this
  earth send our greetings to you."
• Italian"Many greetings and wishes."
• Ila (Zambia)"We wish all of you well."
• Akkadian"May all be very well."
• Romanian"Greetings to everybody."
• Hindi"Greetings from the inhabitants of this
  world."
• Nguni"We greet you, great ones. We wish you
  longevity."
• Nyanja"How are all you people of other planets?"
• Hittite"Hail."
• French"Good day everybody." recorded by Alexandra
  Littauer
• Vietnamese"Sincerely send you our friendly
  greetings."
• Sotho"We greet you, O great ones."
• Swedish"Greetings from a computer programmer in
  the little university town of Ithaca on the
  planet Earth."
• Hebrew"Peace."
• Burmese"Are you well."
• Sinhalese"Greetings."
• Wu"Best wishes to you all."

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• Kechua"Hello to everybody from this Earth, in
  Kechua language."
• Japanese"Hello? How are you?"
• Polish"Welcome, creatures from beyond the outer
  world."
• Luganda"Greetings to all peoples of the universe.
  God give you peace always."
• Cantonese"Hi. How are you? Wish you peace, health
  and happiness."
• Dutch"Heartfelt greetings to everyone."
• Punjabi"Welcome home. It is a pleasure to receive
  you."
• Nepali"Wishing you a peaceful future from the
  earthlings."
• Amoy (Min dialect)"Friends of space, how are you
  all? Have you eaten yet? Come visit us if you
  have time."
• Russian"Be healthy - I greet you."
• German"Heartfelt greetings to all."
• Turkish"Dear Turkish-speaking friends, may the
  honors of the morning be upon your heads."
• Mandarin Chinese"Hope everyone's well. We are
  thinking about you all. Please come here to visit
  when you have time."
• Marathi"Greetings. The people of the Earth send
  their good wishes."
• Thai"We in this world send you our good will."
• Bengali"Hello! Let there be peace everywhere."
• Welsh"Good health to you now and forever.
• Gujarati"Greetings from a human being of the
  Earth. Please contact.
• Kannada"Greetings. On behalf of Kannada-speaking
  people, 'good wishes'."

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• Bach, Brandenburg Concerto No. 2 in F. First
  Movement, Munich Bach Orchestra, Karl Richter,
  conductor. 440
• Java, court gamelan, "Kinds of Flowers," recorded
  by Robert Brown. 443
• Senegal, percussion, recorded by Charles Duvelle.
  208
• Zaire, Pygmy girls' initiation song, recorded by
  Colin Turnbull. 056
• Australia, Aborigine songs, "Morning Star" and
  "Devil Bird," recorded by Sandra LeBrun Holmes.
  126
• Mexico, "El Cascabel," performed by Lorenzo
  Barcelata and the Mariachi México. 314
• "Johnny B. Goode," written and performed by Chuck
  Berry. 238
• New Guinea, men's house song, recorded by Robert
  MacLennan. 120
• Japan, shakuhachi, "Tsuru No Sugomori" ("Crane's
  Nest,") performed by Goro Yamaguchi. 451
• Bach, "Gavotte en rondeaux" from the Partita No.
  3 in E major for Violin, performed by Arthur
  Grumiaux. 255
• Mozart, The Magic Flute, Queen of the Night aria,
  no. 14. Edda Moser, soprano. Bavarian State
  Opera, Munich, Wolfgang Sawallisch, conductor.
  255
• Georgian S.S.R., chorus, "Tchakrulo," collected
  by Radio Moscow. 218
• Peru, panpipes and drum, collected by Casa de la
  Cultura, Lima. 052
• "Melancholy Blues," performed by Louis Armstrong
  and his Hot Seven. 305
• Azerbaijan S.S.R., bagpipes, recorded by Radio
  Moscow. 230
• Stravinsky, Rite of Spring, Sacrificial Dance,
  Columbia Symphony Orchestra, Igor Stravinsky,
  conductor. 435
• Bach, The Well-Tempered Clavier, Book 2, Prelude
  and Fugue in C, No.1. Glenn Gould, piano. 448
• Beethoven, Fifth Symphony, First Movement, the
  Philharmonia Orchestra, Otto Klemperer,
  conductor. 720
• Bulgaria, "Izlel je Delyo Hagdutin," sung by
  Valya Balkanska. 459

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Homework 25

• Group Presentations on Friday.
• Review Session for Final on Monday.
• Final Saturday, 300pm in AHON 116