# The Search for Extraterrestrial Intelligence Can E.T. hear me know?

## Presentation on theme: "The Search for Extraterrestrial Intelligence Can E.T. hear me know?"— Presentation transcript:

The Search for Extraterrestrial Intelligence Can E.T. hear me know?

Goals How likely is intelligent life in the Universe?

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

Fraction with Planets: f p What fraction of stars have planets? Extrasolar planet research since 1995: –851 confirmed planets –126 multi-planet systems –1 star has six f p = 1/4

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 = 1/5

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

Fraction with intelligence: f i What fraction of life bearing planets have life evolve to intelligence? Is intelligence inevitable? f i = ?

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

Lifetime: L How long does a civilization last? Do we have time to communicate with them? For us: L = 80 years! L = ? years

Whats the Answer? R * = 10 */year f p = 1/4 n e = 1/5 f l = ? f i = ? f c = ? L = ? year N = _____ # of technological civilizations in Milky Way, right now.

But space is vast Milky Way is a giant cylinder (disk). –Radius = 15000 pc –Thickness = 1000 pc Volume = (Radius) 2 x Thickness V = 7 x 10 11 pc 3 = 700 billion cubic parsecs!

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

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

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.

SETI@Home

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

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!

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

Voyagers 1 and 2 Greetings 55 languages 115 images Music

SumerianSumerian"May all be well." ArabicArabic"Greetings to our friends in the stars. We wish that we will meet you someday." UrduUrdu"Peace on you. We the inhabitants of this earth send our greetings to you." ItalianItalian"Many greetings and wishes." Ila (Zambia)Ila (Zambia)"We wish all of you well." AkkadianAkkadian"May all be very well." RomanianRomanian"Greetings to everybody." HindiHindi"Greetings from the inhabitants of this world." NguniNguni"We greet you, great ones. We wish you longevity." NyanjaNyanja"How are all you people of other planets?" HittiteHittite"Hail." FrenchFrench"Good day everybody." recorded by Alexandra Littauer VietnameseVietnamese"Sincerely send you our friendly greetings." SothoSotho"We greet you, O great ones." SwedishSwedish"Greetings from a computer programmer in the little university town of Ithaca on the planet Earth." HebrewHebrew"Peace." BurmeseBurmese"Are you well." SinhaleseSinhalese"Greetings." WuWu"Best wishes to you all." UkrainianUkrainian"We are sending greetings from our world, wishing you happiness, goodness, good health and many years." AramaicAramaic"Peace." SpanishSpanish"Hello and greetings to all." GreekGreek"Greetings to you, whoever you are. We come in friendship to those who are friends." KoreanKorean"How are you?" PersianPersian"Hello to the residents of far skies." EnglishEnglish"Hello from the children of planet Earth." IndonesianIndonesian"Good night ladies and gentlemen. Goodbye and see you next time." LatinLatin"Greetings to you, whoever you are; we have good will towards you and bring peace across space." ArmenianArmenian"To all those who exist in the universe, greetings." SerbianSerbian"We wish you everything good from our planet." PortuguesePortuguese"Peace and happiness to all." recorded by Janet Sternberg