ahobson@uark.edu

The search for extraterrestrial intelligence, or "SETI," is serious stuff and good science. It is not at all like the kooky alien visitation stories that one comes across at grocery check-out counters. Furthermore, the SETI story contains an important message for Earth.

The story begins with the scientific search for planets around other stars (our sun is, of course, a star). Such planets are too small and dim to be seen directly in telescopes, but their effects can be seen in the wobbling of their parent star caused by an orbiting planet. So far, this method has detected 77 planets orbiting other stars. And there is indirect evidence, evidence that I won't take time to describe here, that most stars have planetary systems similar to our solar system.

Based on this kind of information, a reasonable estimate is that there are some one billion Earth-like planets--small rocky planets orbiting a star similar to our sun--in our Milky Way galaxy. And there are tens of billions of other galaxies out there, beyond the Milky Way.

Life probably emerged on many of these planets. Life on Earth appears to have emerged early and quite readily some 4 billion years ago. Life on other planets seems likely to have emerged in the same manner that life on Earth arose, from chemical reactions driven by external energy sources such as heat and lightning. Scientists have re-created the chemical conditions of early Earth in the laboratory, and found that the building blocks of life form readily.

Based on such knowledge, most scientists agree that life is highly likely to have arisen on millions of planets around other stars in our galaxy.

But most of this life would be single-celled bacterial forms, as it was on Earth for our planet's first 3.5 billion years. In how many cases did this life evolve into multi-celled, and eventually intelligent, life forms? Here, the evidence becomes murky. Scientists have no concrete evidence about the evolution of intelligence or about the even more difficult question of the development of technology by intelligent creatures.

About 40% of our Milky Way galaxy has now been searched for intelligent radio signals from other planets, searching in the places and in the radio-frequency bands that seem most plausible for communication. Nothing has turned up yet. Do check out the wonderful popular film "Contact" about such searches.

Enrico Fermi, inventor of the world's first nuclear reactor and discoverer of a lot of fundamental physics, added a thoughtful footnote to the SETI story. He enjoyed making speculative estimates of all sorts of things. One day at lunch with colleagues during the 1950s, he asked, out of the blue, "don't you ever wonder where they all are?"

Fermi went on to explain that he was thinking about extraterrestrial visitors to Earth. He knew, as essentially all scientists who have ever thought seriously about it know, that Earth has never been visited by extraterrestrials, despite those lurid stories at checkout counters. But he felt that intelligence was very likely to arise on other worlds, and that these other intelligent beings would eventually develop technology.

Fermi reasoned that such technological civilizations would have cropped up frequently during the long 10-billion-year history of our Milky Way galaxy, that some of them should have become "space-faring civilizations" that colonized large parts of our galaxy, and that therefore somebody should have visited us by now. Thus, Fermi's question: "Where is everybody?"

Among his friends at lunch that day, Fermi offered what he regarded as three plausible explanations for the absence of extraterrestrial visitations: First, he suggested that travel among the stars might be impossible because of some limitation such as high-energy particles that can penetrate any spaceship and destroy it. Second, he suggested that mature extraterrestrial civilizations might tire of such adventures as space travel and decide to stick to their own planet.

But Fermi seems to have considered his final suggestion to be the most plausible: Perhaps extraterrestrial civilizations, once they can develop things like spaceships and nuclear weapons, always destroy themselves. Perhaps there is an inherent inconsistency between the billions of years of evolution required to produce intelligent beings, and the requirements for living sustainably with technology.

This carries an obvious message for Earth. An example will clarify this message: During some 500 million years of animal evolution, our genes have become well programmed to make babies. Without a strong urge to procreate, no species will survive for long. Within the past few centuries, we have developed powerful technologies that greatly prolong life, technologies such as agriculture and medicine. The problem is that such technologies make it counterproductive follow our instinct to procreate abundantly. It now makes sense to limit ourselves to around 2 children.

But humans, for the most part, have continued to follow their instincts rather than their brains in this matter. Thus Earth is overpopulated today and will become far more overpopulated by the end of this century. Human overpopulation is a significant contributor to Earth's present environmental distress, and to the poverty and extremism that promotes wars.

The price of technology is that you have to start using your brains instead of your instincts. Examples like overpopulation show that we're not really doing that yet. If we do not apply our brains to the appropriate use of technology, we will perish just as, in Fermi's opinion, those other technological civilizations perished

LINK TO ART HOBSON'S HOMEPAGE.