Do scientists think we are the only intelligent beings in the universe? With billions of stars and billions of galaxies, this is hard to believe.

Astronomers have been listening for decades with radio telescopes for extraterrestrial (ET) signals, as in the movie “Contact,” and more recently for optical signals from extraterrestrial lasers. (NASA was forbidden by Congress to do such research.) So far they have detected none that could be confirmed – the interesting ones have always turned out to be either natural phenomena or artificial signals of terrestrial origin (such as from satellites). Why is this? Are we really alone in the universe?

There are several possible explanations. The most obvious is that ET signals are being received, but we don’t recognize them. Suppose, for example, that we had been listening in 1930 for ET signals. If the ETs were using FM radio to contact us, we wouldn’t know it since there was no FM radio in 1930. There may be ET signals coming in using some modulation technique we don’t recognize, (We are incidentally listening on a wide range of frequencies, so that is probably not the problem.)

Another possibility is that communicative intelligent beings, those who can build radios or lasers, are rare or even non-existent in our galaxy. Imagine, for example, a water-covered planet inhabited by intelligent dolphin-like creatures. These “dolphins” could never contact us, since living in water would prevent them from making metal or glass, much less radios or lasers.

A third possible explanation is that we may actually be the first communicative species to arise in the galaxy. It has taken 4.5 billion years for communicative intelligence to arise on Earth. This is roughly one-third the age of the universe. Furthermore, the emergence of humanity and human intelligence has been the result of what seems to have been a series of unlikely events over geologic history. If the dinosaurs had not been eliminated by an asteroid or comet, large mammals might never have emerged. Even the development of complex multicellular life some 2 billion years ago may have been an unusual and perhaps unique event in the galaxy.

This week's question comes from Dr. Paul Lowman. Paul Lowman is a geophysicist, originally a geologist, in the Geodynamics Branch of the Laboratory for Terrestrial Physics. He joined GSFC in December, 1959, in the Theoretical Division led by Dr. Robert Jastrow. He initially worked on the origin of tektites, argued by Dr. John O'Keefe to come from the Moon. He helped plan the Apollo geophysical experiments, and trained Mercury, Gemini, Apollo, and Skylab astronauts in geologic terrain photography. His most recent work has been compilation of a global tectonic activity map, appearing in his 2002 book "Exploring Space, Exploring Earth." AND he fearlessly (or foolishingly, if you ask him) rides his bike to work along Greenbelt Road (a very high trafficked road) every day!! WOW!