What was going on when I was born?

The MX missile, the foundation of President Reagan's program to strengthen American strategic nuclear forces, popped out of a towering white canister and arced more than 4,000 miles over the Pacific today on what officials called a successful first flight. ''We feel like we had a magnificent first launch,'' Brig. Gen. Aloysius B. Casey, the program director, said after it was confirmed that half a dozen simulated warheads had landed on target, within 50 miles of Kwajalein Island in the Pacific, 30 minutes after liftoff. ''Everything worked exactly as we expected it to work,'' he said, although he added that it would be several weeks before all of the data from the test are evaluated. Moments after the missile was propelled out of its white cylindrical launcher by clouds of billowing white steam, its firststage rocket ignited with a flash of brilliant yellow flame. Then the missile, which is intended to carry as many as 10 thermonuclear warheads, rose swiftly into a blue evening sky and vanished at the fringes of space.

The crew of the space shuttle Challenger reviewed plans today for a flight on which they are to deploy two commercial satellites and, for the first time, release and retrieve a satellite using the shuttle's 50-foot mechanical arm. The complicated retrieval maneuver is to be done by Dr. Sally K. Ride, the first American woman to fly in space. Barring last-minute malfunctions or bad weather, the astronauts were set to begin their orbital journey at 7:33 A.M. Saturday. Landing in Florida Planned The planned six-day mission, the nation's seventh shuttle flight, is also to include the operation of more than a score of scientific experiments.

More than a million Poles gathered at a soccer stadium to hear Pope John Paul II celebrate mass this evening, and when he was done the crowd saluted him with a forest of upraised arms, hands in the V-for-victory sign, and a thundering chant of the name of the founder of the outlawed Solidarity union, Lech Walesa. The huge gathering was filled with red and white banners of Solidarity, the very display of which is an illegal act here. It was another indication that the Pope's trip to his homeland turned into a political event the moment he landed. The streets of central Warsaw were almost totally deserted by early evening as the capital turned its attention to the Pope's mass.

Pope John Paul II urged Gen. Wojciech Jaruzelski today to allow Poland the ''renewal'' worked out in August 1980. The Polish leader responded by defending the imposition of martial law, which ended the country's brief experiment. After an exchange of formal speeches and 2 hours and 20 minutes of private talks between the Pope and General Jaruzelski, the Government agreed to let Lech Walesa, the founder of the Solidarity union, meet with John Paul during his weeklong visit. Solidarity, the first independent union in the Soviet bloc, was founded in August 1980. The movement flourished under the process known here as ''renewal'' until the Polish Government imposed martial law on Dec. 13, 1981.

An agreement on a bill that would permit two tenants who are not related to share rental housing was announced yesterday by members of both houses of the New York State Legislature, the State Attorney General and the New York Civil Liberties Union. The measure was introduced in the Assembly yesterday and will be proposed in the State Senate early next week. It specifies that tenants named on leases may share their dwellings not only with their families but also with one additional person and that person's dependent children. The bill, the Occupancy Protection Act, also says that at least one of the tenants covered by the original lease must remain in the apartment; otherwise, the added roommate must renegotiate the lease.

You can spot an old Odessan by the sharp tongue. At the Privoz farmers' market, as vast and teeming as any Eastern bazaar, their jabs rise above the din of haggling and hawking: ''How much for your influenza?'' ''Ah, you should be tied to a tree for those prices.'' You hear them lashing a freeloader on a crowded tram: ''May you arrive where you're going the way you bought your ticket.'' In a dank entryway, an old handwritten sign advises, ''The elevator doesn't descend to the upper floors.'' Another, by the crowded beach, declares, ''No bathing of dogs or other horses.''

Gen. Augusto Pinochet, under pressure after a week of political protest and strikes, said in a nationally televised speech tonight that he would not step down ahead of schedule but would make a number of concessions to the protesters. President Pinochet said he would make it easier for exiles to return, end book censorship, and publish debates of what had been the secret meeting of the Government's legislative commission over proposed laws. In his only tough note, he said he would ''severely castigate'' the people responsible for the violence and a national protest on Tuesday. He said the Interior Ministry would outline the specific measures Saturday. At another point in the speech, he blamed Communists for the violence, raising the specter that they would be targets. Three people died in the protest.

One of the two Indian reactors at Tarapur, a city north of Bombay, has been shut down because of the lack of needed parts such as monitors and coolant pumps, according to a State Department nuclear expert and Congressional staff members. ''It's an old plant and it's short of a number of spare parts needed to keep it going safely,'' said the State Department official. The Government of Prime Minister Indira Gandhi has reportedly made an urgent request for the necessary equipment. But because India has refused to abide by the comprehensive safeguards required under the Nuclear Nonproliferation Treaty, it is believed likely that the United States Nuclear Regulatory Commission would not grant the required export license.

She was 46 but she easily looked 10 years older. Her face was drawn, and the nervousness that had caused her to lose 16 pounds began to show as she told of how she had run up what for her were enormous debts to loan sharks. It started 13 years ago, with a $200 loan to help out her younger sister and to buy an inexpensive necklace for herself. But there were always more needs, most of which could not be met on the $1,000 a month she and her husband together earned at a small factory in northern Tokyo. Most of all, there were loan-shark interest rates of more than 100 percent.

Heavily armed rebels have destroyed a village in Zimbabwe's Matabeleland Province, leaving 156 people homeless or injured, The Herald newspaper reported today.

Thieves stole a car containing a secret itinerary for a trip to Northern Ireland by Queen Elizabeth the Queen Mother, throwing the planned visit into doubt, the police said today.

Erich Honecker, the East German leader, warned today that deployment of new United States missiles in Western Europe would be nuclear suicide, A.D.N., the East German press agency, said today. Speaking to the Council of State, he said the two Germanys had a duty to make sure no war broke out on German territory. ''Let no one forget: these devilish creations will be installed for a nuclear war, for nuclear suicide,'' he said.