What was going on when I was born?

Posters of pinup girls dot the walls, and a giant picture of a Playboy bunny is painted on the side of the Van de Graaf accelerator. This laboratory, which takes up only one floor of a nondescript Fujitsu Ltd. building, hardly seems like the kind of place that would unnerve American industry. But the Optoelectronics Joint Research Laboratory is indeed the center of one of those industrial efforts funded by Japan's Government for which the nation is known. The mission of the laboratory's 50 researchers, who pad about the place in slippers, is to spearhead Japan's thrust into the emerging field of optoelectronics - the combination of light, usually from lasers, and electronics. Optoelectronic technology is used now mainly to provide long-distance telephone communications through hair-thin glass optical fibers that can transmit information hundreds of times faster than conventional copper wires.

She had prepared all year for this race, knowing it would be her last, but with 50 meters left, she was coming up short on the 79-kilometer road race. Connie Carpenter was a few centimeters behind Rebecca Twigg, all the difference between gold and silver. With a furious thrust of her bicycle at the finish line, Miss Carpenter caught her younger rival to win the first American cycling medal since 1912, in the first Olympic cycling race for women. A long and hot afternoon later, Alexi Grewal of the United States, who was nearly disqualified from the Summer Games last week because of a doping discrepancy, surged past Steve Bauer of Canada for the second United States gold medal of the day, in the men's 190-kilometer road race. The two narrow finishes stirred up the tens of thousands of sun-baked fans enjoying one of the few free events in these high-priced Summer Games. People chanted ''U.S.A.'' as the United States proved it has come of age in one of the world's most popular sports.

Foreign Minister Andrei A. Gromyko was quoted today as saying he did not expect negotiations to be held in September on banning weapons in space. Former Senator George S. McGovern, who is here on a private visit, said Mr. Gromyko made the statement Friday during a three-hour conversation between the two men in Yalta. Mr. McGovern, a South Dakota Democrat, said that Mr. Gromyko also predicted that President Reagan would be re-elected and that if he was, the Soviet Foreign Minister did not expect ''productive'' American-Soviet relations for the next four years. 'Very Pessimistic' Of Mr. Gromyko's view of the prospects for space arms talks between the Russians and the Americans, Mr. McGovern said: ''He's very pessimistic about it. He doesn't expect the talks to go forward now.''

Brazil has decided to follow Mexico's example in seeking to postpone all principal payments coming due on its debts for the next several years, according to officials here. The request is expected to be made when Brazil resumes debt negotiations with foreign banks in New York this week. Foreign bankers and economists said that, if successful, the Mexican and Brazilian attempts to obtain multiyear reschedulings could mark a turning point in the two-year-old regional debt crisis by providing the two largest debtors with time to rebuild their troubled economies. At the London economic summit conference last month and in other forums, officials of the industrial nations have been urging that those debtor countries that make an effort to control inflation and reduce international payments deficits should receive favored treatment on their debts. Models for the Region By easing conditions for Brazil and Mexico, analysts say, both nations' austerity programs could become regional models.

Lambert Pohner has seen the snout. The small butterfly, named for what looks like a long, skinny nose protruding from its head, is rare in New York City, and urban butterfly watchers speak of it reverently as ''the legendary snout.'' Mr. Pohner says he has sighted eight snouts so far this summer, all in Central Park. ''This is the summer of the snout,'' said Mr. Pohner, who has seen more than 40 summers come and go in the park during the years he has monitored the wildlife there. In summers past, he said, he considered himself lucky if he saw a single snout.

An article in Metropolitan Report July 20 about plans for a new housing development on Roosevelt Island misidentified the president of the Roosevelt Island Residents Association. He is Kenneth R. Kimbrough.

Some of New York City's leading retailers of jewelry, furs and other luxury merchandise have systematically joined their customers in evading the sales tax, according to city and state officials. Investigators say they are pursuing civil and criminal penalties against the stores and their officers. Sales and shipping records have been subpoenaed and audited, employees and customers have been questioned and undercover agents, posing as potential customers, have secretly recorded conversations with salespeople. Officials said they had uncovered patterns of evasion at ''scores'' of stores as well as isolated cases in which overzealous employees had induced customers to make a purchase by suggesting ways to dodge the 8.25 percent combined city and state sales tax. No stores or individuals have been named by the authorities.

Machine tool orders plummeted 40 percent in June from the strong levels in May, the National Machine Tool Builders' Association said yesterday. Nevertheless, June's orders, which totaled $192.2 million, were still 32 percent higher than orders in June of last year. In its report, the machine tool association said that in the first six months of the year, orders for machine tools - power-driven machinery that cuts and forms metal - were 91 percent higher than in the first half of 1983. Orders totaled $1.37 billion in the first half of 1984.

Apparel makers, cash-rich after record earnings in 1983 but with stock prices still depressed, have become a target of investors looking for undervalued takeover candidates. Last week these three buyout offers were announced: - United Merchants and Manufacturers Inc. proposed an $81.25 million tender offer for control of Jonathan Logan Inc., a producer of women's apparel. - At Palm Beach Inc., a men's apparel maker in Cincinnati, a management group has arranged a $140 million leveraged buyout. - A group led by Kelso & Company intends a $470 million leveraged buyout of Blue Bell Inc., the nation's second-largest jeans maker after Levi Strauss & Company.

New York City's subway system, starting to undergo its most extensive overhaul since it was completed 50 years ago, is inflicting on its riders a catalogue of miseries that promises to get worse before it gets better. The beginnings of a well-publicized multibillion-dollar capital program two years ago raised expectations that conditions would quickly improve. But as a new leadership tries to pull the system from the depths, officials are finding that they cannot effectively spend so much money so fast. And they expect a level of service interruptions that will appall riders already accustomed to pacing crowded platforms and peering down empty tracks. For more than a decade, the subways have been a system in radical decline - with antiquated tracks, flawed rolling stock, water seepage in tunnels, a sharply rising crime rate, vandalism in the storage yards and on the lines, filthy and noisy stations and trains, misguided financial and management priorities, chronic purchasing deficiencies, entrenched but often unproductive labor practices, a defensive bureaucracy, political maneuvering and routes that have been undermined by changing demographics.

Mitch Gaylord and Peter Vidmar became the first Americans to score 10's in Olympic gymnastics history here tonight, and their performances helped boost the United States into the team lead after the men's compulsory exercises, ahead of the current world champion, China. The United States, which has never won a team medal in the Olympics, had a score of 295.30. Chinese had compiled 294.25 earlier in the day on the strength of their six 10's. The Japanese, who earned two 10's in the morning session, were third with 292.40 points.

Competition began today in the Summer Games of the XXIII Olympiad, and the United States quickly won four gold medals in swimming and two in cycling. In swimming, Steve Lundquist of Jonesboro, Ga., won the men's 100- meter breast-stroke with a world record of 1 minute 1.65 seconds. Tracy Caulkins of Nashville finished 15 meters ahead in the women's 400- meter individual medley in 4:39.24, an American record. Nancy Hogshead of Jacksonville, Fla., and 16-year-old Carrie Steinseifer of Saratoga, Calif., finished in the first dead heat in Olympic swimming history. They tied for first in the women's 100-meter freestyle in 55.92 seconds, and each received a gold medal.