The high-tech search for intelligent signals from space

Although E.T. has gone home, we could stay in touch through a new search for extraterrestrial intelligence (SETI). It's now under way at Harvard University's 84-foot radio telescope in Harvard , Mass.

Here, a project inaugurated March 7 by Prof. Paul Horowitz combines the latest in radio detectors with exclusive use of the telescope. Covering some two-thirds of the sky, it's the most extensive search for alien life yet undertaken.

The popularity of ''E.T.,'' the movie, underscored public interest in SETI, the search. Skeptics within the scientific community and the US Congress have criticized SETI as futile. Modest funds for such searching ($2 million a year) were dropped from the National Aeronautics and Space Administration (NASA) budget a couple of years ago. But the quest continues.

NASA again has SETI funding - $1.5 million for fiscal 1983. A group of 68 scientists, including seven Nobel laureates, last fall called for an international SETI program. And the International Astronomical Union now has a SETI commission.

The Harvard project reflects this interest. It's funded by the Planetary Society, founded by Cornell University astronomer Carl Sagan. Society members have already donated some $55,000.

Horowitz explains that he has two major advantages over earlier SETI investigators. First, he has exclusive use of a radio telescope. Also, he has a radio scanner which makes searching much more efficient. It monitors about 131, 000 separate radio channels simultaneously. Horowitz says he can do as much searching in one minute as pioneer SETI investigators could have done in 100,000 years using the technology available to them in 1960.

Alan Peterson of Stanford University and Ivan Linscott of the NASA-Ames Research Center are developing receivers that, in about 5 years, should be able to monitor 10 million to 100 million channels at once. Meanwhile, Horowitz's equipment - called Suitcase SETI because of its portability - is unique.

Whether or when the search might turn up a signal can't be foretold. Horowitz , like other SETI scientists, emphasizes that he may study a million stars before detecting a signal - if anyone is signaling. Yet, he says, ''it is useful to observe that, in all of nature's variety, we never see an example of a phenomenon that has happened only once! . . . It would be astounding (to say the least) if we turned out to be the sole example of intelligent life.''

Are you listening, E.T.? Arctic submarine 'stealth'm

Submarines sneaking about the Arctic Ocean may have a natural ally - rough sea ice. Ocean engineer Ira Dyer of the Massachusetts Institute of Technology says that the underside roughness of Arctic ice scatters sound and cuts sonar (sound ''radar'') effectiveness.

Commenting on this in the annual MIT Robert Bruce Wallace (ocean engineering) Lecture, he explained that sonar with a range of 300 miles in the open ocean would have an effective range of only about 30 miles under the ice.

Range could be increased by using lower frequency sound. But it would take bulky equipment, perhaps located on the sea bed, to use the lower frequencies.

Dyer explained that knowledge of ice roughness and its effect on sound is too limited for engineers to design equipment to cope with it. Noting that US submarine activity is picking up in the Arctic, he urged research to gain the needed knowledge. Test-tube video gamesm

In their quest to spread their sometimes esoteric knowledge, chemists have turned to video games.

Stanley Smith of the University of Illinois and his former student Ruth Chabay have developed games called Chemrain and Chemmaze for the American Chemical Society (ACS). According to the society, the games hold attention, are fun to play, and impart a feel for some kinds of chemical reactions.

Chemrain challenges a player to find how 15 different organic compounds might , or might not, react with a variety of reagents. Randomly selected, three of the reagents rain down the screen at a time, falling onto the organic compounds at the bottom. Players move the compounds to pick up the specific reagents with which they react - ten points for guessing right, five point loss for goofing.

In Chemmaze, there are obstacles that hold chemical elements or compounds. A player moves a flask through the obstacle maze. There are four stations at which flasks can be refilled. There also is a computer-controlled mobile beaker that can refill or destroy a flask. The object is to bring the flask into contact with an obstacle holding something with which the flask contents can react. The game demands good hand-eye coordination and knowledge of elementary chemical reactions.

The ACS magazine Chemical and Engineering News observes that ''chemists who start playing have proved extremely difficult to pry loose from the equipment.'' Anyone for Pac-Man? Now it's plastic sand!m

Ecologists concerned with the spread of deserts might try some plastic sand. Mixed with ordinary sand, it becomes a moisture absorbing soil which helps plants grow.

Actually the new ''sand'' is a polymer (complex molecule) called polyacrylamide. Its British inventor, Allan Cooke, has given it the simpler tradename Agrosoke because it can absorb 40 times its weight in water.

Tests at Egypt's Agricultural Research Experimental Station in Ismailia show that a mixture of 3 kilograms of Agrosoke to a cubic meter of desert soil cuts the water needs for sunflowers by 65 percent. A report in New Scientist adds that plants grown with the help of plastic sand were larger and leafier than those grown on untreated plots.