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.
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 civilizations.
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 Stanford University.
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 irrelevant.
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 almost alone.
Terence Dickinson is editor of Skynews magazine and author of books for backyard astronomers.