What was going on when I was born?

Governor Carey signed a bill today that would make it illegal for a physician to prescribe amphetamines for the sole purpose of helping a patient lose weight. The bill prohibits the use of such drugs for the ''exclusive treatment'' of ''obsesity, weight loss or weight control.'' A doctor who so prescribed an amphetamine would not be subject to prosecution, but Mr. Carey said the legislation would permit the state's Health Department to bring disciplinary procedings against physicians ''who persist in prescribing amphetamines for weight control.''

Egypt and Israel formally signed an agreement today establishing a 2,500-member international peacekeeping force in the Sinai to police their peace treaty. Nearly half of the force will be composed of United States combat troops and civilian observers. Secretary of State Alexander M. Haig Jr. signed the document as an observer in ceremonies at the State Department with the Ambassadors from Egypt and Israel. He said formation of the peacekeeping force, originally called for in the 1979 peace treaty between Egypt and Israel, was a ''clear manifestation of the United States' continuing support for a peace process in the Middle East.''

A demonstration against food shortages turned into a confrontation between the Polish authorities and the Solidarity union yesterday when the police halted a column of about 100 buses and trucks bedecked with flags and placards. The tense showdown between the state and the independent union was the first of its kind involving large numbers of people in Warsaw. Last night, thousands of Poles milled about the major crossroad of Marszalkowska Street and Jerozolimskie Avenue, most of them sympathetic to the demonstrating bus and municipal truck drivers. Scores of policemen and several police trucks were also at the intersection, but by early today all but two vans and a dozen officers had been withdrawn. The number of vehicles in the protest, however, rose overnight when 40 streetcars were parked end to end down Marszalkowska Street.

STING By JOHN NOBLE WILFORD RIDING the tides of summer once again are great shoals of jellyfish, which flourish in the warm coastal shallows through the brief season of their maturity. From July through September, along most American coasts, these translucent blobs of gelatinous matter with trailing tentacles are a menace in the eyes of fearful swimmers but intriguing animals to those few biologists who trouble to explore the nature of their stinging toxins. Scientists know that the jellyfish's reputation is worse in nearly all cases than its sting. The moon jellyfish, Aurelia aurita, so prevalent in New York waters these days is particularly harmless. A brush with these milky saucer-shaped creatures, usually less than a foot wide, will at most produce a tingling itch or a skin rash lasting no more than a few hours.

WASHINGTON SMALL high-technology companies, free of the bureaucratic fetters and institutional inertia of larger enterprises, are the wellspring of pioneering innovations in this country. But such firms, intrinsically fragile and risky, have found it increasingly difficult to make their way in these times of expensive research and high interest rates. Now a sleeper of a bill has suddenly arisen in Congress -a bill that would require all major science and research agencies of the Federal Government to devote 1 percent of their research and development money to help small businesses, as defined under the Federal Small Business Act, with promising ideas through the initial risky phase of demonstrating that a scientific innovation has commercial applications that would attract private venture capital. Having already gained 82 co-sponsors in the Senate, the bill, the Small Business Innovation Research Act, seems assured of passage in that body. And given the political clout of small business - akin to motherhood in Congress - a companion bill introduced last week in the House also has a good chance.

International A Warsaw protest over food shortages turned into a confrontation between the Polish authorities and the Solidarity labor union. The police halted a column of buses and trucks bearing flags and placards in the center of the capital and the independent union's spokesman warned that if force was used to break up the demonstration, an immediate strike would be called. (Page A1, Columns 1-2.) An accord on a Sinai peace force was signed by Egypt and Israel. The agreement establishes a 2,500-member international force in the peninsula to police the Egyptian-Israeli peace treaty. The United States will provide nearly half of the force. (A1:1.)

Interest rates rose sharply yesterday as securities dealers aggressively cut prices to levels they hope will attract buyers at note and bond sales this week. And three- and six-month Treasury bills rose to 15.67 percent and 15.576 percent, respectively, at yesterday's auction, up from 15.07 percent and 14.79 percent a week ago. Based on the auction results, banks and savings institutions may pay a top rate of 15.82 percent on new six-month money market certificates starting today, up from 15.04 percent last week. Despite record high yields in all maturities longer than a year, market participants said investor demand was weak for the $4.25 billion of 3 1/4-year Treasury notes to be sold today. Buying interest was even weaker, they said, for the $2.25 billion of 10-year notes to be sold Wednesday and $2 billion of 29 3/4-year bonds to be sold Thursday.

Federal air traffic controllers began an illegal nationwide strike today, grounding about half of the normal 14,200 daily airline flights. President Reagan warned the striking controllers that, if they did not return to work by 11 A.M. Wednesday they would lose their jobs under terms of the law. Tonight, a Federal judge here found the union in contempt of court for disobeying a back-to-work order. He Text of Reagan statement, page 10. ordered the controllers to comply tomorrow or face fines of up to $1 million a day. United States District Judge Harold Greene also found the union president, Robert E. Poli, in contempt and ordered him fined $1,000 a day if the union did not end the strike by 8 P.M. tomorrow. Mr. Poli said afterward that the strike would continue.

OF DISMISSAL By ROBERT D. McFADDEN Tens of thousands of air travelers scrambled for other transportation or encountered crowded planes and long delays at airports yesterday in New York and across the country. As the air traffic controllers' strike disrupted the nation's airways, vacationers and business travelers altered their plans, tour operators prepared to care for stranded travelers and the United States Postal Service and air freight companies forecast delivery delays. Airline service companies warned employees of possible layoffs, and business surged on bus and rail lines and at car rental agencies. The owners of major league baseball teams, just emerging from a long strike, postponed a meeting in Chicago today and, along with officials of the National Football and North American Soccer Leagues, expressed concern over potentially disruptive travel problems. The Air Transport Association, which represents numerous airlines, said that as many as 100,000 business trips were canceled yesterday, a third of those normally scheduled on a weekday. ''It's causing great inconvenience to business travelers,'' said Daniel Z. Henkin, a vice president of the association.

Salomon Brothers will be taken over by Phibro under a surprise $483 million merger plan. The acquisition, set for Oct. 1, will be the year's third big merger in the securities industry. (Page A1.) Salomon, the nation's largest private investment banking firm, is one of the last of the partnership empires. (D4.) Phibro is a large commodity trading company known among analysts as ''aggressive, secretive and independent-minded.'' In fact, some used to call it the ''Salomon Brothers of the commodities trading business.'' (D4.) Mobil increased the cash portion of its takeover bid for Conoco to $115 a share for slightly more than half the company's stock, bringing the total value of its offer to $8.6 billion from $8.2 billion. (D1.)

The New Tax Law First article of a series on how it affects investment and planning. By KAREN W. ARENSON The new tax-cut bill, which President Reagan is expected to sign tomorrow, will not only lower personal income taxes across the board, but will also have a material effect on investing strategies and individual financial planning, according to tax and investment experts. Among the provisions that could have the greatest impact, they said, were the incentives for savings and retirement accounts, along with measures that reduce the top rate on investment income to 50 percent from 70 percent and phase out the inheritance tax for all estates of less than $600,000 as well as estates of any size given to spouses. For the more well-to-do individual, the new law could affect the choice of investments and tax shelters and how estates are arranged. New Answers Required For the average American, it will mean opportunities to avoid taxes on a certain amount of interest income and to set aside tax-free dollars for retirement. Even such commonplace decisions as whose name the house or the insurance policy should be under will require new answers because of the tax legislation.

The Senate approved today, by 67 to 8, the 1981 tax-relief bill and sent it to the House of Representatives, which is expected to pass it tomorrow. President Reagan is scheduled to sign it on Wednesday. The Senate, with roughly a fourth of its members already gone for a five-week summer recess, acted on a bill reported Saturday by a House-Senate conference that reconciled differences between the bills approved by the two chambers last Wednesday. Senate action came after a two-hour debate in which personal criticism was directed at Senator Edward M. Kennedy, Democrat of Massachusetts, for having insisted that the Senate defer final action from Saturday evening until today, so that he could offer a motion to send the bill back to conference for reduction of the relief it contains from the ''windfall profits'' tax on crude oil production. The motion lost by 55 to 20.