Search for Extraterrestrial Intelligence

What might you do for your SETI Interlude 'project' due Friday?

A presentation (no more than 3 people). Please contact me about scheduling.

A short video about SETI. Contact me about about scheduling.

What message could we (Earth) send to contact another civilization. How would the message be sent?

A poster or other 'art' work project. Please sign up.

A paper about some area outside (theology, geopolitical, social, art, law etc.) of astronomy that would be greatly impacted by a SETI signal.

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Fermi Paradox Enrico Fermi was both a great theoretical and experimental physicist. In 1950 while discussing recent 'sightings' of flying sauces (like Roswell) and a New Yorker cartoon (by Alan Dunn) over lunch in the Los Alamos lab cafeteria, Fermi ask the question “Where is Everybody?”

'The disappearance of dustbins in New York allotted to mysterious interest by the aliens.'

Alan Dunn

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Fermi Paradox

Fermi was a master of the order of magnitude estimate calculation (or 'guesstimation'). These order of magnitude estimates are often called 'Fermi problems'. Fermi's 'Where is Everybody?' statement is based on some straightforward numbers.

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The Sun is a typical star, and there are 200-400 billions of stars in the galaxy that are billions of years old.With some reasonable probability, some of these stars will have Earth-like planets, and if the earth is typical, some might develop intelligent life.Some of these civilizations might develop interstellar travel, a step the Earth is investigating now.Even at the slow pace of currently envisioned interstellar travel (0.1 c), the Milky Way galaxy (105 light years in diameter) could be completely traversed in about a few million years.

Start of SETI

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In 1959 Giuseppe Cocconi and Philip Morrison published a paper “Searching for Interstellar Communication”. They speculated the 21 cm line in hydrogen (1.43 x 109 Hz) would

be a good place to look. Radio telescopes had become increasingly sensitive and communication with a civilization around another star might be possible. In 1960, Frank Drake used the radio telescope at Green Bank WV to look look for radio communications from two nearby stars. He did not find anything. In 1961, Frank Drake, Philip Morrison, Carl Sagan organized a meeting in Green Bank WV which became the SETI organization.

The Drake Equation

N = R* fp n

e f

l f

i f

c L

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The N is the number of technologically advanced civilizations in the our galaxy (the Milky Way) whose messages we might be able to detect.

Drake proposed the equation not so much as something to be solved but as a way of thinking about the probabilities of there being advanced civilizations we could detect.

Drake Equation Parameters

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R* = The rate of formation of stars suitable for the development of intelligent life.

fp = The fraction of those stars with planetary systems.

ne = The number of planets, per solar system, with an environment

suitable for life.

fl = The fraction of suitable planets on which life actually appears.

fi = The fraction of life bearing planets on which intelligent life emerges.

fc = The fraction of civilizations that develop a technology that releases

detectable signs of their existence into space.

L = The length of time such civilizations release detectable signals into space.

Drake Equation Parameters

R* and fp are numbers that can be found from

observations. The rate of formation of stars that have the right conditions for life, R*, is about 1 per year These are stars that are not too big … they burn out quickly before life can form or not too small … they don't provide a enough warmth. The number of stars that form planets can be also about 1 as we know from the Kepler satellite data.

All of the other terms are guesses at best. The number of planets that could support life, the fraction of planets where life actually evolves etc. are highly uncertain. Even with very optimistic numbers for the unknown parameters, N might be 10 in our galaxy.

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How do we Look for Extraterrestrial Intelligence?

Life is thought to require water. Water has properties that make it common and unique. If a civilization evolves based on water based life, what form of EM waves might they use to communicate. Since an atmosphere on such a planet would have water like our own, their transmissions would be in the 'water hole'.The 'water hole' is a band of the EM spectrum in the radio wave region where the background noise is low and the transmission through the atmosphere is good.

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How do we Look for Extraterrestrial Intelligence?

The water hole is a frequency range from at 1 GHz to 10 GHz. The main source of noise from CMB. This regionalso includes the 21 cm wavelength of hydrogen and the frequency associated with hydroxyl ion (OH).

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The High Resolution Microwave Survey (HRMS) was a NASA project in 1989 that was to scan ten million frequencies from 1 GHz to 10 GHz using radio telescopes, primarily Arecibo. They planned to scan 800 near by stars. The project was scheduled for 10 years but funding was canceled by Congress after 1 year

Nongovernmental organization have funded the search for SETI since HRMS. The SETI Institute began 'project Pheonix' in 1995 to scan 800 solar type stars. The SETI institute has also started a the Allen Telescope Array of many small telescopes. The hope to eventually scan 10,000 solar-type stars.

There has not been a confirmed SETI signal.

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How do we Look for Extraterrestrial Intelligence?

Question

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Could aliens every visit the Earth? "Klaatu barada nikto"

Would we want 'Aliens' to visit?

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Question

Question

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How would we communicate?