WORLD'S FAIR, N.Y., April 22,--The largest and most elaborate fair in history opened here today, but it did not get rave reviews.

A cold drizzle held the crowds to less than one-half the advance forecast of 000, and combined with civil rights demonstrations to rob even the most fabulous exhibits of some of their magic.

Like the great Crystal Palace Exhibition of 1851, the New York World's Fair unveiled the wonderful wizardry of a materialistic age, as Bell Telephone Company, IBM, General Electric, and an exhibit appropriately called "The Festival of Gas" tried to out-automate one another. The ever-present picket lines were themselves a prime exhibit, however, raising social questions that found expression elsewhere in the Fair.

President Johnson turned to these questions in his speech at the opening ceremonies in Singer Bowl. Noting that the 60's had already far outstripped all predictions of technological progress made at the 1939 World's Fair, he implied that man could no longer be amazed at, or ry in, the pace of his own inventiveness.

Instead, the President indicated, the hope of the future must lie in social and moral advances. "I prophesy peace is not only possible in our generation: I predict it is coming even earlier," he said. And he voiced his wish that the next World's Fair would see "an America in which no man must be poor, In which no man is handicapped by the color of his skin or the nature of his beliefs."

To give meaning to its official title "Peace through Understanding" the Fair solicited exhibits from 80 foreign countries in 37 different pavilions. The United Arab Republic and the "American-Israel" exhibits stood a respectable block apart. In the center of the international area, flags of the United Nations flew in twin rows.

Tour of the Future

Two American behemoths, General Motors and Ford, took the visitor on a tour of the future, presaging the day when man will more completely control his environment. Typically, G.M. was predicting at mid-day that its Futurama Exhibit would attract the most visitors of any at the Fair.

Not all the exhibits were ready, however, and not all of those open were complete. In some cases this was a disguised blessing. The Hall of Education, which will undertake to display the automated classroom of the year 2000, remained mercifully closed, at least for the time being.