The Writer's Almanac with Garrison Keillor

Today is Star Wars Day. According to the online resource Wookieepedia, it is typically celebrated by sci-fi fans the world over with parties, movie marathons, Star Wars-themed toys, the occasional light-saber duel, and movie-quote exchanges on Twitter. You could also celebrate by reading one of the many Star Wars-related novels, playing a video game, or gazing at your collection of action figures in their original packaging. "It's nice that this particular date seems to observe and celebrate the power of the Force, and we're thrilled that Star Wars fans continue to find new ways to connect with a galaxy far, far away," said a Lucas Films spokesperson.

Despite the fervor of some of its fans, Star Wars Day is not a religious holiday yet, although the Church of Jediism is lobbying hard. The City of Los Angeles prefers to celebrate Star Wars Day on May 25, the anniversary of the film's release, but as for the rest of us ... May the Fourth be with you.

On this day in 1675, England's King Charles II commissioned the Royal Greenwich Observatory, the center of time and space on Earth. He also created the position of the Astronomer Royal at the same time, to "apply himself with the most exact care and diligence to the rectifying of the tables of the motions of the heavens, and the places of the fixed stars, so as to find out the so much desired longitude of places for the perfecting of the art of navigation." The building was designed by Sir Christopher Wren, and it was the first structure in Britain that was built specifically for a scientific purpose.

The prime meridian marks the boundary between the Eastern and Western hemispheres just as the equator marks the boundary between north and south, and it was established at the Observatory in 1851. The prime meridian was originally marked by a brass strip, then stainless steel, and now it's marked by a green laser. The laser actually marks the historical location of the prime meridian; old methods of calculating geographical coordinates involved using measurement of local sea level, and since sea level can vary worldwide, the coordinates weren't consistent. Once an Earth-centered — rather than local — system was used, the prime meridian shifted about 103 meters to the east.

Greenwich Mean Time was also calculated at the Observatory, when it was still active; before the establishment of GMT, each town kept its own time, and they varied widely. Since 1833, people have been able to set their clocks by the time ball, which still drops every day at precisely one o'clock p.m.

The Royal Observatory was gradually decommissioned over the first half of the 20th century, and it's now a museum, planetarium, and tourist attraction. Light pollution from London and electrical interference from the nearby railway system made it impossible to carry on as a working observatory, but it's still the official starting point for each new day, year, and millennium.

It's the birthday of the man who said, "Education is our only political safety. Outside of this ark, all is deluge." The father of American public education, Horace Mann, was born on this day in Franklin, Massachusetts, in 1796. He grew up without much money or schooling, and what he did learn, he learned on his own at his local library, which had been founded by Benjamin Franklin. He was accepted into Brown University and graduated in three years, valedictorian of his class.

He was elected to the state legislature in 1827, and 10 years later, when Massachusetts created the first board of education in the country, he was appointed secretary. Up to this point, he hadn't had any particular interest in education, but when he took the post he dedicated himself to it wholeheartedly. He personally inspected every school in the state, gave numerous lectures, and published annual reports advocating the benefits of a common school education for both the student and the state. He spearheaded the Common School Movement, which ensured all children could receive a basic education funded by taxes.

He was elected to the United States Congress in 1848 after the death of John Quincy Adams, and in his first speech, he spoke out against slavery. He wrote in a letter later that year: "I think the country is to experience serious times. Interference with slavery will excite civil commotion in the South. But it is best to interfere. Now is the time to see whether the Union is a rope of sand or a band of steel."

When he left politics, he moved to Ohio to accept a position as president of Antioch College. "I beseech you to treasure up in your hearts these my parting words," he told one graduating class: "Be ashamed to die until you have won some victory for humanity."

It's the birthday of British author Graham Swift (books by this author), born in London in 1949. He was named one of Britain's best young novelists by the prestigious literary journal Granta in 1983. There was nothing in his background to suggest this was in his future; he came from a lower-middle-class family that was in no way creative. But fear, he told the Guardian, may have been what set him on his path. "I had a fear of becoming anything, a fear of becoming a specialist. I might have become a doctor, but if you become a doctor, that's your specialty in life and you are defined by it. One of the attractions of being a writer is that you're never a specialist. Your field is entirely open; your field is the entire human condition."

He's published a book of nonfiction, two collections of short stories, and eight novels, including Waterland (1983), which was made into a film starring Jeremy Irons, and Last Orders (1996), for which he won the Booker Prize.