Transcript Document

The Search for
Extraterrestrial
Intelligence
E.T. phone home using 10-10-220
11B
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?
11B
11B
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.
11B
The Drake Equation
N  R *  fp  n e  fl  fi  fc  L
N = Number of communicating civilizations in our
galaxy right now.
And what about the rest?
11B
Star Formation Rate: R*
N  R *  fp  n e  fl  fi  fc  L
• 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
11B
Fraction with Planets: fp
N  R *  fp  n e  fl  fi  fc  L
•
•
What fraction of stars have planets?
Extrasolar planet research in the last 10 years:
– 76 stars are known to have at least one planet.
– 7 stars have more than one planet.
– 1 star has three planets
11B
Upsilon Andromedae
11B
11B
Fraction with Planets: fp
N  R *  fp  n e  fl  fi  fc  L
•
•
What fraction of stars have planets?
Extrasolar planet research in the last 10 years:
– 76 stars are known to have at least one planet.
– 7 stars have more than one planet.
– 1 star has three planets
fp = 1
Optimistic!
11B
Number of Earths: ne
N  R *  fp  n e  fl  fi  fc  L
• 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
ne = 1/10
11B
Fraction with life: fl
N  R *  fp  n e  fl  fi  fc  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).
fl = 1/3
11B
Fraction with intelligence: fi
N  R *  fp  n e  fl  fi  fc  L
• What fraction of life bearing planets have life
evolve to intelligence?
• Is intelligence inevitable?
fl = 1
Inevitable!
11B
Fraction that communicate: fc
N  R *  fp  n e  fl  fi  fc  L
• What fraction of intelligent civilizations become
technological enough that we could communicate?
• Is technology inevitable?
• Desirable?
fl = 1
Inevitable!
11B
Lifetime: L
N  R *  fp  n e  fl  fi  fc  L
• How long does a civilization last?
• Do we have time to communicate with them?
• For us: L = 70 years!
L = 1000 years
Optimistic?
11B
What’s the Answer?
N  R *  fp  n e  fl  fi  fc  L
•
•
•
•
•
•
•
•
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 there are 500 billion cubic parsecs in the Galaxy!
11B
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.
11B
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
11B
E.T. FM
• Most natural radio sources are broadband.
• Radio stations are narrowband.
11B
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.
11B
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.
11B
SETI@Home
11B
“Is there anybody out there?”
We have made three attempts to
communicate.
1. The Arecibo broadcast to
Hercules Cluster.
11B
Here’s my card.
2. The Pioneer 10 and 11 plaques.
Pioneer 10 is now 9.5 billion kilometers from Earth – 8.5 light hours!
11B
The Voyager Record Club
3. Voyagers 1 and 2 contain a plaque and a record.
11B
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
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
•
•
•
•
•
•
•
•
•
•
11B
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.
11B