What was going on when I was born?

Syria expelled Yasir Arafat today, one day after the guerrilla leader accused President Hafez al-Assad of orchestrating the anti-Arafat rebellion among Palestine Liberation Organization troops in Lebanon. A statement by the official Syrian press agency said, ''Because of Arafat's continued slanders against Syria and its sacrifices, and its positions of principle, he was informed today of Syria's desire for him not to continue coming to its territory.'' The statement was issued several hours after Mr. Arafat was escorted to the Damascus airport by Syrian security officials in six cars and put aboard a regularly scheduled Air Tunisia flight for Tunis. Given 3 Hours to Leave Syrian officials said the expulsion order was written by the Syrian Army Chief of Staff, Maj. Gen. Hikmat Shehabi, who had it delivered to Mr. Arafat's Damascus office at 11 A.M. According to the officials, the letter gave Mr. Arafat three hours to get out of the country, ''otherwise we will make sure you leave ourselves.''

Finally, a chance to get even. Ridiculed and rarely praised, New Jersey put itself on display here this week. In a bit of unabashed hyperbole, Governor Kean bragged that the state had the ''best tomatoes in the world.'' State officials spent $60,000 re-creating the Atlantic City Boardwalk. And squads of eager agricultural students tended hundreds of potted fruits and vegetables - all in the name of the Garden State. And who could blame them. The Smithsonian Institution had invited New Jersey to be the featured state in this year's Festival of American Folklife. It was a chance to give an expected crowd of one million to two million people a positive image of a much-maligned state. And excesses aside, the $410,000 exhibit seemed to do just that - and more.

The following article is based on reporting by Raymond Bonner and George Volsky and was written by Mr. Bonner. On the redwood deck between the swimming pool and Biscayne Bay, Alberto Duque Rodriguez last month played host to the Mayor of Miami, one of Vice President Bush's sons, and some of Miami's most prominent bankers and lawyers. In deference to the Arab bankers who were the guests of honor, the 33-year-old host invited no women to the lavish dinner. The May 3 party was the most recent sign that Mr. Duque, who came to Miami only six years ago, had made it into the highest reaches of the city's financial and political circles. But only a few days after the dinner, Mr. Duque's high living came to an abrupt halt. His financial empire collapsed, leaving debts of more than $100 million, widespread allegations of fraud, and the Federal Bureau of Investigation sifting through the financial rubble.

Dioxin has rapidly become the most feared of all toxic chemicals in this country, but now there is an emerging argument over whether the fear has outstripped the hazard. President Reagan became the latest to join the fray when he suggested Thursday that news reports about dioxin ''have frightened a good number of people unnecessarily.'' He was reacting to a resolution approved Wednesday by the American Medical Association that condemned the news media for conducting a ''witch hunt,'' generating ''unjustified public fright'' and ''hysteria.'' Two scientific publications have also editorialized recently that dioxin is less worrisome than popularly thought. Science, the journal of the American Association for the Advancement of Science, said dioxin is highly toxic when swallowed but when bound to soil, as is the case in most sites where it is found, ''it does not pose much of a hazard.'' Chemical & Engineering News, a publication of the American Chemical Society, said it was ''fair to say that dioxin is far less toxic to humans than the public has been led to believe.''

The Supreme Court ruled unanimously today that the Reagan Administration had improperly revoked a Federal requirement that new cars be equipped with airbags or automatic seat belts. The decision was a major and unexpected blow to the Administration's deregulation program. Withdrawal of the airbag rule in October 1981 was a cornerstone of that policy. Today's ruling that the action was ''arbitrary and capricious'' was therefore important both in substance and as a symbol. The rule, which was under study for 10 years before the Carter Administration issued it in 1977, was to have gone into effect this September. The Court suspended that deadline indefinitely today to give the Administration time to reopen the administrative record in the case. The ruling ordered the Department of Transportation either to carry out the requirement or to provide a precise justification of its refusal to do so.

The space shuttle Challenger returned to earth today after a triumphant six-day mission spoiled only by light rain and low clouds in Florida that forced a landing here in the Mojave Desert rather than at Cape Canaveral. ''Look, there he is, he's coming in -he's landing!'' Richie Riemer, the 4-year-old son of a test pilot, said joyously as he squinted into the sun shortly before 7 A.M., Pacific daylight time. A white speck, its skin reflecting the morning sun, descended swiftly high on the eastern horizon and grew larger. Then the Challenger leveled off, touched down smoothly and glided to a stop on a dusty dry lake bed. Congratulations From Reagan The five crew members - Capt. Robert L. Crippen, Capt. Frederick C. Hauck, Dr. Norman E. Thagard, Col. John M. Fabian and Dr. Sally K. Ride, the first American woman in space, walked out of the Challenger a few minutes later and waved. Almost three hours later they accepted congrulations in a telephone call from President Reagan.

An agreement on broad changes in the laws that affect 950,000 rent-stabilized apartments in New York City was announced today by key state legislators. The agreement would extend the laws for two years. Under the bill, which would also affect 50,000 apartments in Nassau, Westchester and Rockland Counties, tenants would no longer be able to sign three-year leases. They could choose either a one-or two-year first lease or a renewal.

The Reagan Administration reported today that the financial outlook for the Social Security trust fund had ''dramatically improved'' in the last 12 months but that the Medicare trust fund was in a precarious position, facing insolvency around 1990. To avoid depletion of Medicare's hospital insurance trust fund, the Administration said, ''either outlays will have to be reduced by 30 percent or income increased by 43 percent.'' The trust fund pays for hospital care for 26 million elderly and three million disabled people. Its receipts come mainly from the payroll taxes paid by 116 million workers. The Social Security oldage trust fund pays monthly cash benefits to 36 million people who are retired or disabled workers, their dependents or survivors.

Three Ethiopian men were walking the other day past the complex of buildings that houses some of this country's revolutionary institutions and whose security precautions include a metal fence severing what used to be the main approach to a cathedral. As the men came abreast the place of worship, they stopped, removed their caps and bowed in brief reverence, gazing past the armed revolutionary guards and the hammer and sickle emblems of the new order toward an older emblem - the ornate cross of the Ethiopian Orthodox Union Church. ''That sort of thing happens all the time,'' said a longtime resident of Addis Ababa, who, like most people here, offered to talk only in return for anonymity and thus protection from a stern regime. ''Religion was here a long time before Marxism.'' That much is apparent on Sunday mornings, when many of the 1.5 million people who inhabit this capital of high-rise buildings interwoven with shanties forgo food and drink to present themselves before the priests who officiate at ritual-laden services throughout the city. A missionary worker said church attendance in the last couple of years had blossomed, a kind of relief and quest for renewal after the darkest days of the revolution.

The Roman Catholic Church spoke out today in defense of political dissent against President Augusto Pinochet's regime and called for talks between the Government and its opposition. A statement by the Executive Committee of the National Council of Bishops made no direct mention of a truckers' strike, in its second day. Calls by leaders of other unions for a nationwide strike to support the truckers' demands for negotiations with the Government over democracy, economic relief and freeing of jailed union leaders also continued to go unheeded. Most Chileans appeared cautious after the many strikes and protests of the last 11 days. (The truckers said that the Government had indicated it was prepared to bail out the financially troubled union, United Press International reported. The union said it would study the offer over the weekend while continuing the strike.)

Seven days of United Nations-sponsored talks on withdrawal of Soviet troops from Afghanistan ended this afternoon with no sign of major progress on any of the significant issues. The talks, like an earlier round in April, were conducted by a United Nations negotiator who met separately and alternately with delegations from Pakistan and the Soviet-backed regime in Afghanistan. At a news conference, the negotiator, Under Secretary General Diego Cordovez, insisted that ''further progress'' had been made and that the peace initiative was still very much alive. But he acknowledged that ''obstacles'' remained and that the negotiating process was a long and difficult one in which sudden breakthroughs should not be expected.

Economics Minister Otto Lambsdorff flew to Moscow today for talks with Soviet trade officials to prepare for Chancellor Helmut Kohl's visit, which is to start July 4.