What was going on when I was born?

HOBOKEN NOT yet 21 and still in braces and sneakers, Edward Johnson has created a novel and, he says, much more reliable, way of interpreting electrocardiograms. Others his age - and younger - have found enzyme differences in the livers of victims of acquired immune deficiency syndrome (AIDS), built artificial lungs or kidneys or have worked on one of more than a dozen technical projects involving computers and chemistry, synthetic medicinal chemistry or biomedical studies. Eighteen young scientists took part this summer in a program at the Stevens Institute of Technology here. And they did so not for credit, but for the love of research. Most are still in their teens, and all were selected through a rigorous screening process.

EVERETT J. WARNER, a quiet man who lived 73 of his 94 years above his paint store on Main Street, was never known to attend church, but when he died last spring, he astonished the Village of Greenport by leaving most of a $2 million-plus estate to six churches and one synagogue in the village. ''He had never darkened our doors,'' said the Rev. Rocco Gallitelli, pastor of St. Agnes Catholic Church, where the late Mrs. Warner was a communicant. ''I saw him briefly when he was in the hospital, but it was more of a social visit,'' said the Rev. Joel Bibey of the First Baptist Church of Greenport. ''It was his way to say thank you to the village in which he lived all his life - he loved Greenport,'' said Oscar Goldin, his friend and president of Tifereth Israel Synagogue. There is only one string attached to the bequest. The money must be used locally. The will stipulates that it may not be transmitted to higher church authorities anywhere else.

In almost every museum in the Western world there is at this moment a new generation of curators. Not yet broken on the wheel, they can't wait to excel. They are out to form collections without parallel, to organize exhibitions that will draw visitors from all over, and to publish scholarly catalogues that will rival those of the National Gallery in London. Organized, motivated, competitive, driven and most often specialized, they came qualified, they came recommended, and they're all set to go. Yet being a curator is like conducting an orchestra. You can pass all the exams. You can be a doctor a dozen times over. But in the one case, as in the other, the only way to learn it is to do it. The great conductor of the past did not come to prominence by winning an international competition. He began as a coach in some ratty little town in the Austro-Hungarian provinces, and he did everything, all day and all night, till one day the top man got sick and someone told the coach to come running.

THE ROSENBERG FILE A Search for the Truth. By Ronald Radosh and Joyce Milton. 608 pp. New York: Holt, Rinehart & Winston. $22.50. WERE Julius and Ethel Rosenberg guilty of transmitting American atomic secrets to the Soviet Union in the 1940's, or were they scapegoats of the cold war whose execution was a grave miscarriage of justice? That both are true is the intriguing argument of Ronald Radosh and Joyce Milton in their definitive account of the controversial case, ''The Rosenberg File: A Search for the Truth.''

No pine tar was involved, but the Mets still got embroiled in an odd brush with the rules last night in Shea Stadium while they were defeating the Chicago Cubs, 5-1, for the 10th victory in their last 13 games. The victory was chiefly the work of Tom Seaver and Jesse Orosco, whose pitching helped the Mets survive their strange encounter with the umpires over ''coach's interference.'' The coach was Bobby Valentine, who was accused of trying to prompt a balk by the Cubs' pitcher. Instead of a balk Valentine prompted a ruling by the umpires that wiped out the runner at third base and removed the coach from the game for unsportsmanlike conduct.

The terms ''performance art'' and, more generally, ''performance'' crop up everywhere these days. Galleries, museums and concert-exhibition spaces like Franklin Furnace, the Kitchen and the Brooklyn Academy of Music present performance events, and will if anything augment their offerings this coming season. Summer series like Art on the Beach on the Battery Park landfill and Art in the Anchorage in Brooklyn are devoted to collaborations that involve performance, and this year their presentations extend through September. Books and journals have been devoted to the subject. A performance artist has even had a hit rock single, in Laurie Anderson's ''O Superman,'' and Miss Anderson provided what might be called the summa so far - in terms of the attention it attracted - of the entire performance-art movement, with her two-evening ''United States'' last season at the Brooklyn Academy of Music. All well and good, but what is ''performance art''? Where did it come from, how well established is it, where is it going and what, if anything, has it produced of durable significance?

Jack Morris, Detroit's No. 1 pitcher, and a Detroit fan combined tonight to defuse Dave Winfield's devastation of the Tigers. Winfield, who in the first two games of the series hit three homers and drove in five runs, produced a run with a sacrifice fly, but Morris struck him out twice as the Tigers beat the Yankees, 6-3. Two-run homers by Lance Parrish and John Wockenfuss against Ron Guidry powered the victory that gave the first-place Tigers a one-game lead over Milwaukee in the American League East. For the second straight night, the Yankees could have moved into first place by winning, but they didn't win and now stand one and a half games behind the Tigers.

Ever since the bankrupt King's Department Store pulled out of the Putnam Square shopping mall in 1981, the mall, at the intersection of Routes 6 and 118 in Mahopac, N.Y., has seen a steady loss of both shoppers and tenants. But in October it will take on a new name and character as a retail center devoted to discount or off-price shopping.

THE former S. Klein store, boarded up since 1975, is a melancholy monument to a once-thriving commercial district. A huge sign on the clutch of gray midrise buildings on the corner of 14th Street and Union Square East still promises ''A Square Deal'' for bargain hunters from all parts of the city. In the 1950's, the departure of emporiums such as Hearn's and Orhbach's sped the decline of what had once been a vibrant retail district, a fashionable entertainment district and, earlier, an exclusive residential enclave. Today, Mays is the only large department store amid a crush of fast-food restaurants, small discount outlets and sidewalk entrepreneurs. But now the Klein site, pivotal in Union Square renewal efforts, has moved a step closer to redevelopment. Last month, William Zeckendorf Jr. acquired a two-year option to buy the property from Rapid American Corporation, the owner. Mr. Zeckendorf, whose father was one of the leading developers of the postwar period, has developed the Columbia, a condominium on Broadway at 96th Street, and other Manhattan properties.

Slippage in Housing Starts? Don't expect to see it in the July figures to be released Tuesday, but by October, some economists expect evidence of a downturn in housing starts. ''Every 1 percent change in interest rates results in a 100,000 to 150,000 change in housing starts,'' says Michael Evans, president of Evans Economics, a Washington forecasting firm. Since long-term interest rates have moved up 2 percent since early May, he predicts that housing starts will fall by 200,000 to 300,000 units in September and October, or to an annual rate of 1.5 million units from an expected 1.8 million for July. Timothy Howard, the Federal National Mortgage Association's chief economist, agrees: ''At recent interest rates, housing starts will not continue to rise.'' He expects monthly starts will average about 1.6 million by year-end, down from about 1.7 million in the first half.

Governor Cuomo signed legislation yesterday giving artists the right to sue when they believe that alterations made in their works have damaged their reputations. Under the legislation, New York has recognized what France, Italy and West Germany have long regarded as the ''moral right'' of artists to protect their works through the courts. The law was opposed by the major New York museums, including the Metropolitan Museum of Art and the Museum of Modern Art. It was supported by artists, some of whom complained that it did not go far enough.

Bill and Ginny Passafiume are part of a growing phenomenon in the American work force, one that does not show up in unemployment figures: a dramatic increase in part-time work. At his last full-time job, at the United States Steel Corporation's plant at Homestead, Pa., Mr. Passafiume, a 39- year-old welder, made $14 an hour, plus benefits that probably amounted to $10 more an hour. Today Mr. Passafiume has a part- time job, three or four days a week, three hours a day, cleaning up a Pittsburgh movie house. He makes the minimum wage, $3.35 an hour. He receives no benefits. He has not worked full time since he was laid off by U.S. Steel in 1981.