For centuries, humans have wondered if there might be intelligent life on other planets. With the goal of turning this wonder into a scientific pursuit, the SETI Institute was founded in 1984.
SETI (www.seti.org) stands for the Search for Extraterrestrial Intelligence, and its major effort has been to search the heavens with very large radio telescopes listening for radio signals that have a pattern expected of messages created by sentient beings.
These telescopes are capable of detecting very faint signals and were often plagued by the radio noise created here on Earth. The idea was that since we were sending powerful radio signals back and forth to one another across our planet, and since these signals leaked out and could be detected far out into space, aliens might detect them and attempt to contact us.
Some have thought that laser beams carrying messages might have a better chance of being detected. Powerful light beams and radio waves do come from space but, to date, all those detected can usually be accounted for by astronomical events occurring on distant stars and do not have a pattern suggestive of purposeful messages.
A significant improvement in this search could made if we were to place a radio telescope on the far side of the moon where it would be shielded from the cacophony of communication signals coming from Earth.
Now, however, the focus has shifted to a potentially more fruitful search for planets that have the potential of harboring life and are associated with suns not more than a few dozen light years from Earth. That is, planets with rocky surfaces, gaseous atmospheres, and circling at an appropriate distance from their sun. These searches have been made possible by means of the Hubble telescope and significant improvements in the resolution of ground-based telescopes, and a few candidate planets are presently under investigation.
Among the programs currently run by the SETI institute is a website devoted to publishing ideas people have had regarding what we might say in reply to aliens should we receive a message from such beings. Stephen Hawking, the famed theoretical physicist, has reasoned we should not reply as there might be danger for us in so doing.
Nevertheless, many have made concrete suggestions and one can get some interesting perspectives on our own species by reading those posted on SETI's website. Far more controversial have been suggestions regarding what to say to aliens prospectively, that is before we know for certain whether anyone is “out there.” As a result it seems unlikely that an internationally agreed upon message will be devised. However, it has been pointed out that soon so many will have the capability of sending signals into space it will be impossible to control what we earthlings say anyway.
Aside from all these concerns is the consideration that radio and laser signals travel at the finite speed of light. Thus, to be heard and responded to in any reasonable length of time, aliens must reside on a planet circling a nearby sun and be at a level of technological expertise similar to our own. What might be the likelihood of that?
Questions and suggestions from readers are welcomed and will be responded to in future editions of this column. Contact me at firstname.lastname@example.org.