Pope John Paul II used space-age technology in an unprecedented way yesterday to preach to the world a simple, 2,000-year-old message of peace and hope through God.

"Even in spite of unprecedented advances," he said from Rome by way of 23 television satellites and 100 cameras, "the man of today feels deeply shaken by the contradictions in the world, contradictions which sometimes make him doubt the very value of life . . . . And yet a voice is heard which . . . comforts and strengthens: the voice of God."

The hourlong "Prayer for World Peace," which reached an estimated 1 billion people in churches and in their homes, resonated with themes that John Paul has been championing recently, including a return to church tradition and prayers of earlier generations. It also represented a highly visible attempt by the Catholic Church to evangelize through television.

The Rosary, one of the church's oldest prayers, was the program's central feature, and was recited in unison by congregations in 17 countries, including the U.S. feed from Washington's National Shrine of the Immaculate Conception.

As more than 4,000 people at the shrine chanted the prayer's repetitive strains, their rosary beads clicking in unison, a master control booth in London was switching from Rome, where the pope was, to Washington, to Fatima, Portugal, to Manila and back to Rome. On several occasions, 16 locations around the globe were displayed on one screen.

The frenetic activity of the control booth contrasted sharply with the peace in the shrines.

"Hot-switch that sucker over," yelled Tony Verna, producer, from Limehouse Studios in London. "Get offa young kids laughing, change the shot in Austria . . . Frankfurt, ding it in."

Technical problems had dogged the operation for more than a week, often as a result of economic or political problems. On Thursday, Italian television technicians had gone on strike. That same day, France had denied Verna's company, Global Media Ltd., use of a French satellite to broadcast to Senegal, because of its broadcast of the French Open tennis tournament.

Even in the hour before airtime, at noon EST, there was an occasional moment of panic. "Apparently the communists in the Philippines have sabotaged the land lines," a spokesman for Verna reported.

The problems inside the truck at Washington's shrine were smaller but just as annoying. "We've lost audio in the church," one rather agitated technician said about 11:30 a.m.

Inside the shrine, which seats 2,500 comfortably, many more than that were squeezing into the pews to watch themselves and the other countries on two large screens at either side of the church. Some were older women on pilgrimages, others were young immigrants, still others young families from the Maryland and Virginia suburbs. Together, they looked like one giant artist's palette of Washington.

Those interviewed talked about current political crises, including the volatile Persian Gulf, and their dreams that somehow prayer could bring peace.

"I'm concerned, I worry," said Betsy Woytko, who was there from Springfield with her husband Bob and their three children, ages 7, 8 and 10. "I don't know how to convey my worries to my children."

"I'm here to pray with the pope for world peace, especially in my country," said Ana Porpillo, a 20-year-old Salvadoran who said several friends in her native country have been killed there recently.

Earlier in the day, John Paul II appealed to President Reagan to end the arms race and urged that moral and spiritual values be "truly integrated into daily life." He struck a similar chord in the broadcast, occasionally breaking into the half-smile that makes him photogenic.

Time and again, the pontiff has "called the world back to 19th century {values} when he seems to be looking into the 21st century," the well-known Catholic author Eugene Kennedy said in a telephone interview. Kennedy further noted that John Paul II "knows how to step onto a stage to maximize his message."

The stage that Verna proposed to the Vatican earlier this year was not very different from Verna's earlier productions, including the Live Aid rock concert in 1984. But despite commercial aspects, including considerable hawking by various public relations agencies, the show was like manna from heaven for the Vatican.

Top aides to the pontiff had been searching for a way to establish a presence on television, much like they have on the well-established Vatican Radio, a $20 million-a-year operation broadcast in about 20 languages. But a TV operation of their own was off to a shaky start.

In this country, there was similar support from the Catholic hierarchy for more sophisticated use of the media. A network started by Catholic bishops, the Catholic Telecommunications Network of America, has reached only half of the 180 U.S. dioceses projected when it started about 10 years ago.

Verna and his coproducer, Saturday Review publisher Paul Dietrich, told Catholic officials here and in Rome that if the Prayer for World Peace went well, they would find sponsors for a weekly, half-hour television program, along the line of CBS' "60 Minutes," to be shown in this country.

After the show yesterday, they were exuberant, and applause filled their studio. "There was someting that happened to the people here," said Michael McLees, technical coordinator. "Whether the crew was Catholic or Protestant or Jewish . . . we were indeed doing something for humanity."

At Washington's shrine, thousands of somewhat star-struck devoted applauded as well, long after London had signed off.Special correspondent Barbara Rosen contributed to this report.