What was going on when I was born?

Energy Secretary James B. Edwards witnessed a nuclear bomb explosion for the first time this morning and said he found it ''exciting.'' The nuclear test today was the first in two years to be opened to viewing by reporters. In response to a question, Mr. Edwards denied that his visit here was timed to coincide for publicity reasons with the anniversary of the Aug. 6, 1945, bombing of Hiroshima and with the debate today in Congress on nuclear issues. Asked if more tests are planned, Secretary Edwards responded, ''That's a reasonable assumption,'' adding, ''Some of our weapons now are more than 20 years old.''

Two dozen Republicans, including six Congressmen, defied the President and pledged to defeat a $98.5 billion tax bill. Page D1. WASHINGTON, Aug. 5 - The Senate today approved spending cuts totaling $12.6 billion over the next three years, completing its major work in the long process of reconciling previous budget proposals. At the same time, however, the Senate instructed its negotiators working with House members on a separate tax bill to aim at extending unemployment benefits by 10 to 13 weeks. Senate aides put the cost of extending the current maximum of 39 weeks at $1.3 billion to $1.9 billion but suggested that the price could be met by lowering the threshold at which those who receive benefits pay taxes.

PIANISTS and violinists have their paths laid out for them, but singers are often torn between two worlds. Take, for example, Benita Valente and Florence Quivar, who will be appearing tonight and tomorrow night in liturgical music by Beethoven and Mozart at the Mostly Mozart Festival in Avery Fisher Hall. Both won their early recognition in the concert and recital world. Success in opera has come late for both. Over the years, Miss Valente's soprano has been admired by connoisseurs and critics alike - her lieder singing praised for its ''perfect legato control,'' her oratorio work for its ''pure tones and birdlike trills.'' Miss Quivar's career as a mezzo-soprano is marked by high musicianship and versatility, her range of styles stretching from Handel's ''Messiah'' and the Verdi Requiem to Stravinsky's ''Oedipus Rex.''

Conservative Republicans, who have been increasingly concerned about the direction of President Reagan's economic policies, revolted today over proposed tax increases. A group of two dozen conservatives, including six members of Congress and several former Reagan advisers, pledged their ''best efforts'' to defeat a tax bill that would raise $98.5 billion in revenues over the next three fiscal years. Mr. Reagan accepted the tax increases as part of a budget compromise earlier this year, and Wednesday the President expressed strong backing for the legislation, which is now being debated by a House-Senate conference committee. ''In the present weak economic climate,'' the conservatives said in a statement today, ''and during a time in which the Congress refuses to support the spending cuts required by the budget resolution, we friends and supporters of Ronald Reagan oppose the tax increase now before the House-Senate conference. We believe that to restore the health of the economy and put Americans back to work, America should follow a course against high taxes and Federal spending.''

''A Midsummer Night's Dream,'' The New York Shakespeare Festival's second dramatic offering of the summer at the Delacorte Theater in Central Park, is playing at 8 every night except Monday. James Lapine has directed the cast of 22, which includes William Hurt as Oberon. Tickets are distributed free, beginning at 6:15 P.M., to those who wait on line at the foot of the Great Lawn, at 80th Street in the park. Those who make financial contributions to the Shakespeare Festival are entitled to tickets without waiting. ''A Midsummer Night's Dream'' will run through Aug. 27. Performances are canceled if it rains. Information: 598-7100. NEWHALL PHOTOGRAPHS Beaumont Newhall's book ''The History of Photography'' is a classic in its field. And Professor Newhall, who worked as a librarian and curator at the Museum of Modern Art for 10 years, is a photographer as well as a historian. Fifty of his black-and-white pictures - landscapes, architectural studies and portraits of prominent photographer friends - are the subjects in ''Beaumont Newhall: Photography 1928-82,'' an exhibition that opens today at the International Center of Photography, on 94th Street at Fifth Avenue. The center opens daily at noon and closes today at 8 P.M. Tomorrow and Sunday the closing hour is 6 P.M. Admission is $2; students and the elderly, $1. Information: 860-1777.

IF you think that our major museums are just too much for any one human being to cope with on a warm weekend in high summer, the best way is to break the problem down. If there is more to see than you can bear to look at, you take one kind of picture and follow it through, the way Theseus followed the thread through the labryrinth. Among the sorts of painting that you could choose, still life would seem to me to be a good idea. The paintings are mostly quite small. But as against their fewness and their smallness, we can set the fact that as often as not they are of very high quality indeed. Many of them are by Paul Cezanne, for instance. And if the Metropolitan Museum, the Guggenheim Museum and the Museum of Modern Art have any one thing in common, it is that Cezanne stands out in all of them as one of the greatest painters who ever lived. He has a threefold pre-eminence - as a painter of the human figure, as a painter of landscape and as a painter of still life. Moving from one to another of these three museums, we find it hard to believe that he can maintain the same improbably high level of activity. But he does - everywhere, in all his chosen domains and all the time.

The National Conservative Political Action Committee said today that it had placed its campaign against Senator Daniel Patrick Moynihan ''in limbo'' and was unlikely to revive it. The committee selected the Democratic Senator from New York almost two years ago as a candidate it would Senator Moynihan's Republican opponents comment on decision made by conservative committee. Page B2. try to defeat. Mr. Moynihan is seeking re-election to a second term this fall.

Stock prices continued to retreat yesterday as investors registered deep concern over the direction of interest rates. In the credit market, rates moved slightly higher. The Dow Jones industrial average fell 7.61 points, to 795.85, bringing its three-day decline to 26.26 points. With the market slide gaining momentum, there was increased caution and apprehension among managers of the vast sums of pension and profit-sharing funds. ''One big worry of money managers revolves around the economic recovery,'' said Robert Grossman of Cantor, Fitzgerald & Company, an investment banking firm. ''In 16 years in this business, I've never seen so many people holding onto cash.''

''The thing they're talking about is the weapon that can preserve their ability for free political discussion.'' - Energy Secretary James B. Edwards, about critics of nuclear weapons. (A1:1.)

A group of conservatives rebelled against President Reagan's economic policy, vowing to fight a tax bill that would raise $99 billion in revenues by 1985. Most of the group, led by Representative Jack F. Kemp and including six members of Congress and several former Reagan advisers, are advocates of the supply-side theory that big tax cuts are necessary to spur economic growth. (Page D1.) House-Senate conferees, meanwhile, endorsed higher unemployment taxes, to generate more revenue for jobless benefits. The panel also passed a series of measures intended to lower Medicare costs. (D2.) The Senate approved spending cuts totaling $12.6 billion over the next three years. The reductions include cuts in the outlay for food stamps, a 4 percent cap on cost-of-living adjustments in Federal retirees' benefits, and a freeze in dairy price supports. (A1.)

The Soviet Union has barred American diplomats in Moscow from using a beach on the Moskva River outside the Soviet capital in retaliation for the decision by the City of Glen Cove, L.I., to bar Russian diplomats from its golf courses, tennis courts and beaches, a spokesman for the United States Embassy in Moscow said last night. In Washington, a spokesman for the State Department, Joseph W. Reap, acknowledged that the Soviet action was in retaliation for the vote by the Glen Cove City Council and expressed the department's regret over the Soviet action. ''We regret this decision on the part of Soviet authorities,'' Mr. Reap said. ''Neither side can benefit from an escalation of mutual restrictions on each other's diplomats.''

Because of inaccurate information from J. P. Morgan & Company, a table in Business Day on July 26 gave incorrect second-quarter data about Morgan. It earned 71 cents on each $100 of average total assets and $15.44 on each $100 of average stockholders' equity. Its average equity equaled 4.59 percent of its total average assets.