Even as new telescopes are built to search for signals from other planets, changes in the nature of human telecommunications are forcing researchers to reconsider their view of what to look for and how they scan the skies.
Scientists with SETI, the Search for Extraterrestrial Intelligence, have painstakingly combed the stars since 1960, looking for signals from other civilizations -- signals either sent intentionally or inadvertently as part of regular communications.
That search, captured in such movies such as "Contact" in 1997, largely has been for fairly strong radio signals -- the types of signals that use the frequencies such as those of telecommunication satellites or television.
The rationale was, explained Frank Drake, chairman of the board at the SETI Institute of Mountain View, Calif., other civilizations would operate communications systems that evolved in the same way as those on Earth. Therefore, the assumption has been, researchers should look for the same type of signals.
Recently, however, human communications have shifted to high data rates and lower power signals to handle demand and the crowding of the radio spectrum. Such signals are more difficult to detect.
If aliens used communications that evolved in a similar manner, then their signals also would be harder to detect.
The researchers had also assumed, Drake told an audience this week at the World Space Congress in Houston, that optical signals -- flashes of light -- would not be worth looking for because they would be would be lost in the wash of surrounding starlight. Now, developments at Lawrence Livermore Laboratory in Livermore, Calif., have challenged that assumption.
Scientists have developed pulse lasers intended for use in fusion power generation. A signal from a distant planet using such a laser would be far brighter than starlight and could be strong enough to be seen on Earth.
"The search for optical signals is plausible and desirable," Drake told United Press International. In 1960, Drake was the first researcher to begin scanning the skies for radio signals from other civilizations.
It will be a while, though, before these shifts in perspective can be incorporated into ongoing SETI projects. One such project, the Allen Telescope Array, is under development and should be operational by 2005.
The ATA will link 350 six-meter antennas at the University of California at Berkeley's Hat Creek radio observatory to search the sky for signals in the 0.5 megahertz (million cycles per second) to 11 MHz range. Funded by Paul Allen, a co-founder of Microsoft and Nathan Myhrvold, the firm's chief technology officer, the project is expected to cost $25 million.
Three antennas are in place to test concepts for the ATA. A final decision on the engineering approach and whether to proceed should take place early next year.
The key advantage to ATA is that it will be available every day of the year. Research is being done at the Arecibo Radio Telescope in Puerto Rico, but that telescope is only available for SETI research 20 days a year.
"ATA will make our SETI search 100 times faster," said Jill Tarter, director of the SETI Institute's center for research. She told UPI it was not just that ATA will be a dedicated telescope but it also can monitor 100 stars at a time, instead of one by one at Arecibo.
Also already under construction, at Harvard University's Oak Ridge Station, some 30 miles west of the main campus, is a 72-inch (1.8 meter) telescope that will search for optical signals, including nanosecond bursts.
Due to go online soon, the telescope cost only about $350,000, said Drake.
Two new projects, still very much on the drawing board, will be better aimed at detecting the weaker signals researchers now expect. Both would cost in the range of a $1 billion or more and are looking at sites in either the Southwestern part of the United States or the sparse expanses of western Australia.
The Omnidirectional SETI Search, as it is called, would link millions of small antennas to scan the sky for signals in the microwave range. The Square Kilometer Array, which would take longer to build and may cost more, would use multiple instruments to capture fainter radio signals with better resolution. Both projects will require funding and significant political cooperation, Drake said, and a drop in the price of data processing also is necessary for the OSS to become realistic.
