SETI: The Search for

Extraterrestrial Intelligence

Terry Bridges

Queen’s University

What is SETI?

SETI asks: are we alone in the universe?

SETI scientists are using optical and radio

telescopes to search for signals from alien

civilizations

The Beginning of SETI

1959

How do we search?

Radio waves can travel large distances … but there’s a

lot of radio “real estate” to cover!

One Magic Frequency Hydrogen is the most common element in the universe.

H atoms emit radiation in the radio spectrum at a

wavelength of 21cm and frequency of 1420 MHz

(compare CBC radio at 107.5 MHz)

The “Waterhole”

Water (H20) is also special. OH emits radiation at 1721

MHz. So “waterhole” between 1420-1721 MHz is a

good place to search

SETI Searches: Past and Present

Radio

Project Ozma, 1960: Frank

Drake looks at Tau Ceti &

Eridani

SETI Institute opens in

1985

META, BETA: 1986-1999, 60-70% of sky, using Harvard 26

metre telescope

-- searched 80 million frequencies!

-- dish now dead as is BETA (1999)

-- a good survey to detect rare but powerful transmitters

Project Phoenix: 1993-2004, funded by SETI Institute targeted search of 1000 nearby stars like the Sun used several telescopes including Arecibo and Parkes

Project Serendip: 1997-present piggy-backed onto other telescopes, 150 million freq some of the data goes to SETI@home

Project Phoenix: 1993-2004, funded by SETI Institute targeted search of 1000 nearby stars like the Sun used several telescopes including Arecibo and Parkes

Project Serendip: 1997-present piggy-backed onto other telescopes, 150 million freq some of the data goes to SETI@home

The “Wow” Signal

The Future of SETI:

The Allen Telescope Array Privately funded by Paul Allen and Nathan Mryhrvold

350 x 6m telescopes linked together

Search 100,000 to 1,000,000 stars, at 100 million frequencies

42 dishes now, 350 eventually (if funded!)

The Allen Telescope Array

The Allen Telescope Array

The Allen Telescope Array

Optical SETI look for optical laser pulses: very focused, can travel across

1000s of light-years, easily detected

Several programs around the world (Berkeley, Harvard, Lick,

Mt. Wilson, Australia

Harvard All-

Sky Optical

SETI Project

1.8m

telescope

Sending Signals!

In 1974, Frank

Drake sent a

message to the

globular cluster

M13

The Drake

Message

Can you figure

it out?

Should We Send Messages?

Pro: detecting another civilization would be very exciting

we could learn a lot from an advanced civilization

Con: will they be friendly or nasty?

What if we detect a signal?-- it would be checked carefully by the discovering scientists

-- it would have to be verified by other observatories

-- if real, all astronomers and governments would be notified.

-- how would the public react? Would there be panic?

Probably an internet meltdown …

-- could we figure out what the message says?

-- should we respond to the message?

-- if so, what do we say?

-- what would the long-term implications be?

Fermi-Hart Paradox: “Where are They?”

We have searched for 50 years with no detection: statistically,

probably less than 10,000 broadcasting civilizations

If there are advanced civilizations, would expect one of them to

have colonized the galaxy: so “they” should be here now! Fermi

asked: where are they?

Presumably means there's not many of them ...

Useful Resources

The SETI Institute: www.seti.org

The Planetary Society: www.planetary.org

“Confessions of an Alien Hunter” by Seth Shostak

“If the Universe is Teeming with Aliens …” by Stephen Webb

“Life Everywhere” by David Darling

SETI@home: http://setiathome.berkeley.edu/