Search for ExtraTerrestrial Intelligence
M. P. Birla Insitute of Fundamental Research.
Life elsewhere in the Universe
If we accept that life arose out of certain physical and chemical
laws then it can be supposed that life can occur elsewhere in
the universe too.
What are the possibilities of life elsewhere in the universe?
What is the probability of an intelligent civilization, similar or
superior to us?
Can we establish contact with them?
These are questions in the mind of a person who is involved with
Search for ExtraTerrestrial Intelligence.
Sample Space, Probability and our Knowledge
Age and Experience
Age of the Universe
136000000000 (13.6 billion years)
Age of the Earth
45000000000 ( 4.5 billion years)
Age of Chimpanzee
23000000 (23 million years)
Age of First human
1000000 (1 million years)
Time when early man started
moving out of Africa
60000 (60 thousand years)
Age of Modern Scientific
300 ( Roughly around 1700 BC)
Total number of stars that is estimated in
10 billion trillion
No of stars in the milky way
200 billion stars
What can we say from those?
We can derive a mathematical probability of existence
of life and intelligent life elsewhere in the universe.
The age of our scientific model and technological
advances that is searching for intelligent life elsewhere
in the vast universe.
Before we gained observational capabilities it was a
common belief that life existed on Moon and other
planets. That should be hardly 200 years ago.
Star Systems and Planets
If all stars developed in the same way like our
sun, then its very likely that other stars will
have a system, a set of non selfluminous
bodies revolving around it.
There has been evidences and observations
surrounding extra solar planets, and of stars
capable of having their own solar system.
VEGA Observed by Infrared Astronomy
American Space scientist, Stephan.H.Dole made a particular study of
this problem in his book "Habitable Planets for Man" (1956) and
derived certain conclusions that are speculative but nevertheless
Stars of appropriate size (neither too large or too small) and of
spectral classes F2 to K1 are suitable for nurturing planets are
comfortably habitable by human beings.
Dole estimated that there are 17 billion such stars in our own galaxy,
which are habitable.
Given the probability of a star of suitable size with an appropriate
period of rotation and appropriately regular orbit, Dole concluded that
it is probable that there may be 640 million habitable planets in our
galaxy alone, each of them containing some form of life or the other.
If those habitable planets are spread through out, then there is one
habitable planet in per 80, 000 cubic lightyears. So, the nearest
possible habitable planet, will be (cubic_root(80,000)) roughly 27
light years away from us.
Dole listed 14 stars within 22 light years that might possess habitable
planets. He concluded that habitable planets are most likely to be
found in the stars closest to us, Alpha Centuari, Alpha Centauri A,
Alpha Centauri B.
Of course, life may exists but we may not be sure of intelligent life.
And we have no intelligent way of guessing the possibility of
intelligent life on another planet and Dole was careful as not make
Earth has existed for more than 3 billion years with abundant life in
sea and only a million years since a creature more intelligent than ape
And this means that earth has possessed intelligent life for 1/3500 of
the time the it has possessed life of any kind.
We can say that of all life bearing planets, 1/3500 may possess
intelligent life considering the scenario of earth. Then out of 640
million habitable planets in our own galaxy, there may 180,000
Dole's Conclusions and Other Views
No of Habitable planets in our galaxy. (Which we can
go and colonize once we achieve that capability)
17000000000 (17 billion)
Number of Habitable planets in our galaxy already
containing some form of life
640000000 ( 640 million)
Number of Intelligent Civilizations possible in our
This view of Universe, rich in intelligence life forms, which Dole, Sagan and Asimov favored, is not held
unanimously by astronomers.
Since Venus and Mars have been studied extensively and found to be hostile to life, there is a pessimistic
view that conditions in which life may harbor in billions of years
is very narrow and earth is extremely fortunate for life to exist.
Fermi's Paradox and Drakes Equation
The size and age of the universe incline us to believe that many
technologically advanced civilizations must exist.
However, this belief seems logically inconsistent with our lack of
observational evidence to support it.
Either the initial assumption is incorrect and technologically
advanced intelligent life is much rarer than we believe, our
current observations are incomplete and we simply have not
detected them yet, or our search methodologies are flawed and
we are not searching for the correct indicators.
Drakes Equation: N = R * f(p) * n(e) * f(l) * f(i) * f(c) * L
Looking out for Observational
Can evidence of Life be obtained is the central
question of SETI?
A technologically advanced civilization might
have developed Radio Capablity.
So, lets get down to hunt the Radio Signals
1960, Cornell University astronomer, Frank
26 meter diameter radio telescope to examine
the stars Tau Ceti and Epsilon.
A 400 kilohertz band was scanned around the
marker frequency, using a single channel
receiver with a bandwidth of 100 hertz
First SETI Conference took place in the year 1961
and Soviets took great interest and scanned using
"Intelligent Life in the Universe" was published by
Carl Sagan and Russian astronomer, Iosif Shklovskii
in the year 1966.
Project Big Ear
Radio telescope located at Ohio for SETI from
1963 to 1998.
360 feet (110 m) wide, 500 feet (150 m) long,
and 70 feet (21 m) Krausstyle high radio
The radio telescope was disassembled in 1998
when developers purchased the site from the
university, and used the land to expand a
nearby golf course.
1971, NASA funded SETI study, involved Drake,
Bernard Oliver and others.
Suggested a 10 billion USD worth earth based
radio telescope that would detect inadvertent
radio signals from planets about 1000 light
It never got built, but the report formed the
basis of much SETI work to follow.
1974, Arecibo observatory made attempts to
send a message to outside world.
It sent towards the globular star cluster M13
which is 25,000 light years away from earth.
Project SERENDIP – UCB
Sentinel, META and BETA – US Planetary
Microwave Observational Program (MOP) –
(1992) NASA. Government Ridiculed and
Project Phoenix – SETI Institute (1995)
SETI League, Project Argus (Dish Antennas)
Search program, studying roughly 1,000 nearby
From 1995 through March 2004, Phoenix
conducted observing campaigns at the 64
meter Parkes radio telescope in Australia, the
140foot (43 m) Telescope of the National
Radio Astronomy Observatory in West Virginia,
USA, and the Arecibo Observatory in Puerto
Allen Telescope Array
SETI Institute, UCB to develop specialized radio
telescope array for SETI studies, something like
The full array is planned to consist of 350 or
more Gregorian radio dishes, each 6.1 meters
(20 ft) in diameter
First portion of the array became operational in
October 2007 with 42 antennas.
Why make the attempt when there are little chance
of succeeding? Is there a possibility that we can
understand the message?
The mere attempt will advance the state of radio
astronomy to the great advantage of humanity in
understanding the universe.
Volunteer run distributed computing project out
It analyzes the Radio Telescope data from the
SERENDIP IV instrument and uses the participants
computer for computation.
Distributed Computing Concept as well as SETI.
SETI @ Home
The Computation power achieved by this distributed
computing project makes it equivalent to a the
worlds second largest supercomputer.
SETI Involves searching only Narrow Bandwidth
The process of searching SETI is somewhat like
tuning the radio to receive the signal. If there is any
pattern found, more concentration and tuning is
done in that frequency.
Why has not ET discovered us?
May be it is is not Advanced enough?
May be it discovered but decided to wait for us
to develop further before it attempts to make
Both are weak arguments!
Self Appraisal for Earth
Stronger and frightening argument claims that
Intelligence is a selflimiting property. Perhaps, as
soon as a species develops a sufficiently high
technology, it destroys itself.
In that case, if we receive one message one
message the one fact it may reveal to us is that
somewhere a civilization has reached a high level of
technology and has not destroyed itself.
Irrespective of these arguments, a
communication with an ET will put to test many
of the fundamental theories of science.
It will help us understand the system better and
it is a scientific approach in our understanding
of the universe as we try to establish the first