Those who attended the joint meeting of the New Jersey and Southeastern Pennsylvania Sections of the American Association of Physics Teachers at Princeton University on 12-13 March 1999 were treated to a double feature of talks on communications from outer space. Jocelyn Bell Burnell, who tells the story of her discovery of pulsars in A Science Odyssey (reviewed in our Spring 1998 issue), related that story on 12 March. The following morning, David Wilkinson, who is also featured in A Science Odyssey, presented an updated perspective on "Search for Intelligent Extraterrestrial Life." SETI and Little Green Men at Princeton
by John L. Roeder
Bell, who set out to earn a doctorate at Cambridge University by building a radio telescope to search for quasars and scanned miles of chart recordings looking for them, was mystified to find strange pulses occurring a second and a third apart. Then, from another part of the sky, came equally strange pulses occurring a second and a quarter apart. These signals, and thousands of others like them, some as close together as one and a half milliseconds, are now attributed to rotating neutron stars (which Bell illustrated by a rotating flashlight), but when she first detected these signals at frequencies which seemed far too high for a rotating star, she labeled them "Little Green Men."
Thus far "Little Green Men" have remained relegated to fiction, and three years ago Congress forbade funding any further search for them, but private funding continues to support the search with the equipment originally funded by the government. Wilkinson has co-taught a freshman seminar at Princeton University with TIME science editor Michael Lemonick (whose father is also a member of the Princeton faculty) on "Searching for Life in the Galaxy," and he shared some of the insights gained from that seminar.
He began by citing many reasons to expect extraterrestrial life: 1) the formation of algae after Earth was only a billion years old indicates that simple forms of life are easy to make, a conclusion also supported by the ease of making amino acids in the laboratory. 2) finding organic matter in comets and meteorites means that its origin is not limited to Earth; in fact searches for life continue on the planet Mars and the Jovian satellites Europa and Ganymede. 3) The increasing rate of finding extrasolar planets increases the likelihood that one of those planets could support life.
But what is the likelihood of intelligent extraterrestrial life? Here Wilkinson acknowledged a problem. "Intelligent life, capable of developing science and technology, started to develp on Earth only a million years ago," he said. "If the age of the Earth were shrunk to one year, our science and technology developed in the last second of 31 December." Therefore, he concluded that "Intelligence may be a very rare result of evolution."
Because interstellar travel is too expensive and too time consuming, Wilkinson felt that our most probable contact with other civilizations will be made by receiving their signals. In addition to the program of scanning the sky for radio signals, new optical searches are starting, an idea of laser inventor Charles Townes. Wilkinson is hoping to set one up in conjunction with Paul Horowitz at Harvard, with both universities using their otherwise unemployed telescopes to survey the same regions of the sky at the same time and look for coincidences in nanosecond optical pulses.
If we do detect signals from an extraterrestrial intelligent life, Wilkinson expects that almost certainly it will have highly advanced science and technology. He showed this in terms of a graph of "Technical Level of Civilization" on Earth vs. time. The key to this graph is that we are now in a region of very steep slope. The 500 years in which we have developed our communications technology are but an instant of cosmic time. On the other hand, we cannot continue this rate of technological progress without establishing an equlibrium with our energy supply and natural resources. If we are unable to do this, our civilization will self-destruct. Above and beyond establishing an equilibrium with our energy supply and natural resources, we could develop the ability to colonize and utilize our solar system -- which we will have to do anyway in anticipation of the Sun becoming a red giant in five billion years. Similarly, an extraterrestrial civilization with which we communicate is likely to have passed its period of rapid technological progress toward an "equilibrium" or "colonization" stage.
When a star has reached the red giant stage, it is "past its prime," Bell stated in her talk -- in an aside that showed how the entire gamut of stellar evolution is contained in one very familiar part of the sky -- the constellation of Orion and his dogs. Orion's right shoulder, Betelgeuse, is such a red giant, while new stars are forming in Orion's belt. The "dog star," Sirius (whose appearance in the dawn sky foretold the flooding of the Nile) is an example of a middle-aged star like our Sun, but its companion has already reached the white dwarf stage for which our Sun is eventually destined.
When I asked Bell whether she found any of the quasars for which her radiotelescope search was targeted, she replied that she had and that they had formed the basis of her doctoral dissertation. The discovery of pulsars proved more sensational, however, though she said the press focused most of their scientific interest on her male advisor while focusing "human interest" on her.
Wilkinson observed that the freshman seminar on "Searching for Life in the Galaxy" seemed to leave his 13 nonscience majors liking science more than the 300-odd students who are required to take the standard introductory course every year in order to earn an engineering degree.
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