Congress got an apocalyptic picture yesterday of a world falling into chaos as tens of millions of workers are displaced by fast-changing technology. Jean-Jacques Servan-Schreiber, the French author and politician, and the high-powered team of scholars and scientists he has assembled at France's controversial new World Center for Computer Science offered the pessimistic predictions.

Servan-Schreiber said that more than 30 million people are unemployed in the industrialized nations, and "all experts agree that, by the end of the '80s, at least an additional 25 million jobs will be lost . . . an army of 50 million jobless will appear on the horizon and signal a situation of discouragement and possibly despair."

Members of two subcommittees of the House Committee on Science and Technology listened attentively to Servan-Schreiber's projections because the task he has undertaken with the support of the Socialist government of French President Francois Mitterrand is nothing less than staving off that chaotic future and, at the same time, alleviating the economic problems of the developing nations.

The gospel according to Servan-Schreiber is that computerized access to electronic telecommunications and information systems will enable displaced workers to learn new skills, give Third World people access to technology and enable the world to keep up with an economic system that is changing "exponentially."

His goal of making that science accessible through international cooperation is shared by the World Center scientists who joined him at the witness table.

They were Nicholas Negroponte, an MIT professor on a two-year leave to serve as the World Center's executive director; Seymour Papert, a South Africa-born expert on computer programs for children and former assistant director of MIT's artificial intelligence laboratory; Edward Ayensu, a Ghanaian botanist who was director of the Smithsonian Institution's Office of Biological Conservation; Raj Reddy, a native of India and former head of the Robotics Institute at Carnegie-Mellon University; and Samuel Pisar, a lawyer and author who was made a U.S. citizen by act of Congress.

The presence on the staff of the French government-sponsored World Center of those scientists, who formerly worked in the United States, has stirred charges in the scientific community that the French are buying American scientific talent in a "reverse brain drain," and that the center, in the words of Rep. Albert Gore Jr. (D-Tenn.), who presided at the hearing, is "a stalking horse for the French electronics industry."

All said there was no truth to the charges.

"This is not intended to be a French institution," Pisar said. "It is worldwide in scope, a catalyst that might do something about pulling the industrialized world out of bankruptcy and the Third World out of misery."

In the face of potential worldwide economic disruption, "There is no time for nationalism, isolationism or protectionism," Servan-Schreiber said.

Gore suggested that developing countries aided by the center naturally might want to equip themselves with the hardware to which they are accustomed, but Servan-Schreiber replied, "They are accustomed to no hardware," which, in his view, is their problem.

In a test project to be set up to bring computerized learning to Senegal, the computers to be used will be manufactured not by a French company, but by Apple, an American company, he said.