The Astronomy Book

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at the National Radio Astronomy
Observatory in Green Bank, West
Virginia, set out to look for them.
Drake founded Project Ozma,
named for the queen of author
L. Frank Baum’s imaginary Land
of Oz—a place “difficult to reach
and populated by exotic beings.”
After a briefly exciting and noisy
encounter with some top-secret
military radio-jamming equipment,
Drake and his team were met with
silence. More than 50 years later,
the silence has not yet been broken.

Order of the Dolphin
Drake drew together a diverse group
of scientists to lay the foundations
and protocols for the search for
extraterrestrial intelligence (SETI).
The group jokingly called itself the
Order of the Dolphin, in reference
to the work of neuroscientist John
Lilly, who pioneered the science of
speaking to dolphins. As one of the
few people dealing with interspecies

communication, Lilly was an

important part of the group, which

also included a young astronomer

Carl Sagan, who was an expert

on planetary atmospheres.

In preparation for the Order’s

first meeting in 1961, Drake came

up with a formula for the number

of alien civilizations in the galaxy:

N = R* × fp × ne × fl × fi × fc × L

The total (N) was reached by

multiplying the factors necessary

for intelligent extraterrestrials

to evolve and be discovered. It

depends on the rate at which stars

suitable for intelligent life form (R*);

the fraction of these stars that are

orbited by planets (fp); the number

of planets in any given planetary

system that can support life (ne);

the fraction of these planets upon

which life actually appears (fl); the

proportion of life-bearing planets

that go on to produce intelligent life

(fi); the proportion of civilizations

that develop technology that betrays

LIFE ON OTHER PLANETS

detectable signs of their existence

(fc); and, finally, the length of time

such civilizations survive (L).

With these terms in place,

bounding limits could theoretically

be placed on each one. In 1961,

however, not a single one was known

with any confidence. Delegates

at the meeting concluded that N

was approximately equal to L,

and a potential 1,000 to 100 million

civilizations might exist in the

galaxy. Although values for some of

the variables in the Drake equation

have been narrowed down over the

intervening years, modern estimates

of N still vary wildly. Some scientists

argue that the figure may be zero.

Message in a bottle

In 1966, Sagan cowrote Intelligent

Life in the Universe, perhaps the

first comprehensive discussion of

planetary science and exobiology.

The book was an expanded and

revised version of an earlier edition,

published in 1962 by the Soviet

astronomer and astrophysicist

Iosif Shklovsky. Although highly

speculative, the book ignited

discussion among scientists. It

inspired NASA’s Project Cyclops

report, an influential document

now referred to as the “SETI Bible.”

The search for extraterrestrial

life is one of those few

circumstances where both

a success and a failure would

be a success by all standards.

Carl Sagan

The Pioneer plaque

contains information

about the location

of Earth within

the Milky Way.

Hydrogen atom

Position of

sun in galaxy

Pulsar

locations

Sun

Earth

Pioneer craft Galactic

center