Thousands of dancers filled the vast ellipse of the Seoul Stadium beneath a cloudless blue sky. And so, on Saturday, began the 24th Olympic Games.

An audience of more than 70,000 cheered as a single runner carrying a smoking torch loped once around the track, stepped lightly up to the base of the tall white candelabrum and touched his brand to its base. Instantly the fire leapt from the wide round meniscus. Overhead, five Korean air force jets screamed in arrow formation across the length of the stadium, trailing streamers of colored smoke."Just walking through this will be the highlight for me," said American tennis ace Chris Evert, as the ceremony got under way. "I've never done anything like it."

Two years in preparation, three hours in execution, the Olympic opening ceremonies unfurled with stopwatch accuracy before a world-wide audience of perhaps 3 billion people. More than 13,000 performers, each of whom had rehearsed for an average of 160 hours, ran, whirled, sang, jumped, chop-kicked or just fell from the sky in a breathtaking flourish-after-flourish display whose message said "This is Korea. Welcome."

The theme of the extravaganza, often expressed in terms so mystical and symbolic that onlookers were provided with tiny FM radio receivers to explain it all, was "Beyond All Barriers."

As the official program put it:

"The stadium becomes the sacred site of genesis, the center of the entire world. Korea, long a symbol of ideological division, has been reborn as the stage for a magnificent reconciliation of all humanity."

The refrain might have sounded hackneyed anywhere else, but in the bitterly divided Korean peninsula it took on an urgent poignancy. Families have been sundered here for more than 43 years and even though the border is only 24.8 miles from the stadium, the Demilitarized Zone forms one of the world's most unbridgeable chasms.

The inaugural rites were a delightfully warm evocation of Korean history and culture. Behind it all lay immense labor. There were 65 different types of costumes, 36,000 small props and 302 large ones including the giant, booming Korean drums used to summon the dawn at the start of the ceremony. The opening and closing ceremonies will cost $9.4 million altogether.

Among the participants were 88 Korean children born on Sept. 30, 1981, the date Seoul was awarded the Olympics. Among the honorary invitees were a selection of common people, chosen for their service to the country: ". . . professors from isolated islands, postmen, railway employees, miners, firemen, prison officers, lighthouse keepers and truck drivers," according to an official announcement.

The ceremony began with the throb of massed drums and a Dragon Drum procession that shook the air.

Then 1,351 dancers wearing red and blue sashes ran onto the field for the "Passage at Dawn" segment of the program. On a large white banner were the Chinese characters "Tian Xia Tai Ping," or "Great Peace Under Heaven.

Suddenly a spray of fireworks burst over the Han River and thousands of balloons floated up from all around the stadium. In white, flowing gowns, two groups of 44 women, one Greek, one Korean, danced together to signify the meeting of East and West.

Another group of 1,525 dancers flung themselves to the ground to form the numbers "88," the word "Welcome," the five interlocking Olympic rings, and finally, in a flurry of technicolor scarves, the curving logo of the Seoul Olympics.

The 88-horn Olympic Fanfare rang out to welcome South Korean President Roh Tae Woo and his wife, Kim Ok Sook. Then the Olympic athletes made their entrance, the Greek delegation first, the Korean last. As each delegation was announced, its national flag was formed by banked colored cards that changed every few seconds.

Some swimmers from the U.S. delegation wore Mickey Mouse ears, souvenirs of their sendoff last week from Disneyland in California. An American basketball player flung a frisbee into the crowd.

Next came speeches by International Olympic Committee chairman Juan Samaranch and Korean President Roh.

Then, in a ripple of white silk, the flag of the games was borne into the stadium by eight Korean Olympic medalists and raised to the top of the flagpole. As it crested, 2,400 white pigeons were set free in a whirr of wings.

At 12:21 a torchbearer entered the stadium and the central moment of the ceremony was at hand.