Summary: In 1961, American astronomer Frank Drake developed his famous equation for estimating the number of technologically advanced civilizations in the galaxy. However, more and more scientists are having their doubts about the optimistic numbers and a substantial number of researchers consider the equation as obsolete as a black and white television from the '60s.
Drake's factors irrelevant in our lonely galaxy
In 1961, American astronomer Frank Drake developed his famous
equation for estimating the number of technologically advanced
civilizations in the galaxy.
Known ever since as the Drake Equation, it is simply a list of
six factors that Drake said multiply together to yield an
estimate of the number of other planets harbouring life forms
technically equal to or more advanced than humans.
The six factors are: (1) the fraction of stars that have
planets, (2) the fraction of those planets that are habitable,
(3) the fraction of habitable plants upon which life actually
develops, (4) the fraction of life-bearing planets upon which
intelligent life evolves, (5) the fraction of the intelligent
life that engages in interstellar communications and (6) the
length of time the communication continues.
The Drake Equation has been featured in countless books and
articles on the possible existence of extraterrestrials.
Because all factors but the first are very poorly known,
different authors plug in different numbers for each factor,
resulting in a vast range of results.
In the 1960s, Drake and astronomer Carl Sagan concluded that one
in 1 million stars might harbour creatures capable of
communicating with each other. That means approximately 1
million civilizations in the Milky Way that could be using radio
telescopes or other means, in Sagan's words, to "reach across
immense interstellar distances to their neighbours."
The Drake Equation went on to become the conceptual foundation
for the search for extraterrestrial life, which continues today
in the form of radio telescope searches for signals from other
However, more and more scientists are having their doubts about
the optimistic numbers and a substantial number of researchers
consider the equation as obsolete as a black and white
television from the '60s.
Writing in the current issue of Mercury, published by the
Astronomical Society of the Pacific, editor Robert Naeye argues
that the factors in the Drake Equation are almost certainly much
less optimistic than Drake and Sagan ever imagined.
Moreover, Naeye says the original factors used by Drake exclude
the possibility that extraterrestrials might travel across the
galaxy in search of life on other worlds. Drake, 74, maintains
that spaceships will never routinely transport intelligent
creatures across the vast reaches of the galaxy.
"The fuel requirements of such ships do not make any sense in
terms of cost and efficiency," he said in a recent talk at
Naeye counters: "At least some technically advanced
civilizations are not going to sit around on their home planet
waiting to pick up radio signals from other civilizations. They
will figure out how to engage in interstellar travel."
For this reason alone, the Drake Equation should be retired as
The reality today is that more than 40 years of radio searching
for extraterrestrial signals have turned up nothing and there is
not a shred of evidence that aliens are travelling around the
galaxy in spaceships.
It all leads to the conclusion that, if we aren't alone, we are
Terence Dickinson is editor of Skynews magazine and author of
books for backyard astronomers.