Fifty years ago this Friday an earthquake struck -- not the kind of quake that destroys cities, roads and kills people, but rather a "cultural" tremor that would inspire millions around the globe and change the world forever.

On August 23, 1963, the EMI record company in Britain released a single by a new group, the Beatles, called "She Loves You." Recorded almost two months earlier, on July 1, "She Loves You" not only raced to the top of the British music charts, but it launched "Beatlemania," a social phenomenon that the United Kingdom had never witnessed before and which would spread across the world.

Lasting a mere two minutes and 18 seconds, "She Loves You" has flourished for five decades and become a cultural touchstone, a defining moment in pop music history and the very heart and soul of everything involving the Beatles. The "yeah yeah yeah" refrain itself has ascended to icon status in the pop/music culture lexicon and embodies the giddy, buoyant nature of those pre-color TV, pre-hippie days.

"She Loves You" would be released in the U.S. on Sept. 16, 1963, to little fanfare, but by the following the spring (after the Beatles had reached a number one in the States with the release of another massive hit, "I Want To Hold Your Hand"), the song would rank as one of an unprecedented five Beatles singles simultaneously occupying the U.S. charts. Of course, the Beatles’ spectacular appearance on "The Ed Sullivan Show" in early February 1964 would generate gigantic sales in the U.S. for all previously released Beatles material.

"She Loves You" was the biggest-selling single of 1963 in Britain, one of the top-selling ‘45s of the 1960s and, a half-century later, one of the most popular singles in recording history.

But "She Loves You" was highly unusual in many respects. For one thing, it was truly composed by John Lennon and Paul McCartney jointly and with equal participation. Most so-called “Lennon-McCartney” compositions were actually written by one or the other, even during the early years of their “partnership.”

For another, in direct contrast to most other love songs of the era that featured one or both protagonists pouring out their feelings or sorrow, "She Loves You" represented the perspective of a third-party outsider, presumably a male who is counseling another fellow to go back to his estranged girlfriend. (This same lyrical approach would be used again five years later with another historic single, “Hey Jude.”)

The song also ends on a jarringly odd major sixth (jazz-type) chord that likely had never been heard in a pop-rock song before. (Reportedly, this was added as a suggestion by lead guitarist George Harrison, although it was initially criticized by the Beatles’ producer, George Martin, as "corny.")

But the most enduring hallmark of the song is, of course, the “yeah yeah yeah” coda.

McCartney has said that the song was written on buses and hotel rooms in late June 1963, just a week prior to its recording while the Beatles were touring with Roy Orbison and another Liverpool group, Gerry and the Pacemakers, in the north of England. This was not unusual, since their hectic touring schedule afforded them little time to formally compose and arrange songs in the comfort of a studio.

Lennon, who frequently spoke disparagingly of the Beatles’ earlier songs, and was often less than generous in heaping praise on McCartney, nonetheless credited Paul with much of the inspiration behind "She Loves You."

“It was Paul's idea,” Lennon said in a 1980 interview, just prior to his death. “Instead of singing 'I love you' again, we’d have a third party.”

But Lennon claimed he had no idea where the “yeah yeah yeah” insert came from, though he admitted that Elvis Presley used some similar phrases in his 1957 “All Shook Up” single.

“It was the first time in my life that I had heard 'uh huh', 'oh yeah', and 'yeah yeah' all sung in the same song," Lennon added.

Interestingly, the "yeah yeah yeah" phrase caused some alarm among Britain’s educators and upper class snobs who were already annoyed by the increasing presence of American-type slang in daily conversations.

Before the song was released, even McCartney’s father, Jim, expressed his distaste for the "yeah yeah yeah" refrain.

That negative attitude was replicated by some overseas critics, who equated the very term "yeah yeah" with vulgar, commercial and disposable Western culture.

But, of course, the British public loved it and ate it up -- even before its release some half-million advance orders had been placed for it, guaranteeing it would be a hit.

The late British music critic Ian MacDonald, who wrote an exhaustive study of Beatles music in his book “Revolution in the Head,” referred to "She Loves You" as “one of the most explosive pop records ever made.” The song also marked a turning point in the Lennon-McCartney songwriting style.

“Already maturing, the partnership’s writing formula can be heard here as the dual expression of Lennon’s downbeat cynicism and McCartney’s get-up-and-go optimism,” McDonald wrote.

“Much of the pair’s musical originality derived from their self-taught willingness to let their fingers discover chord-sequences by exploring the architecture of their guitars rather than following orthodox progressions.”

He added: “The Beatles’ best work is as much the expression of a state of mind as a construction in sound, and in ‘She Loves You’ Lennon and McCartney can be heard fusing their different outlooks in musical form. The result is an authentic distillation of the atmosphere of that time.”