The Writer's Almanac with Garrison Keillor

Today marks the kickoff of the Hemingway Days festival in the Florida Keys. Ernest Hemingway (books by this author) first visited the Keys on his way home from Paris. He fell in love with the little island of Key West, and he spent much of the 1930s there, first renting a place and then buying a house with the help of his in-laws. He wrote such classics as "The Snows of Kilimanjaro" and To Have and Have Not in his Whitehead Street studio, and he spent many hours deep-sea fishing from his boat, Pilar. The Hemingway Days festival includes such "Hemingwayesque" activities as marlin fishing and a "running of the bulls" featuring fake bovines. There's a Papa Hemingway look-alike contest at Sloppy Joe's Bar, one of his favorite hangouts. There are literary readings, and a short-story contest that is organized by Hemingway's granddaughter Lorian. Hemingway's Key West home, now a museum, is also open for tours, and visitors may catch a glimpse of one of the descendants of the author's beloved cats. The festival wraps up on July 20, the day before the author's 115th birthday.

Twitter was launched on this date in 2006, only it was called "Twttr," with no vowels. The social media platform is famous for its 140-character "microblogs." On its launch date, the company reported 224 "tweets" for the whole day. On its fifth birthday, users logged that many tweets in less than one-tenth of a second. In an early review of the platform, the Techcrunch website reported, "People are using it to send messages like 'Cleaning my apartment' and 'Hungry.' You can also add friends via text message, nudge friends, etc. It [is] really a social network around text messaging." The reviewer later expressed concerns about the lack of privacy on the platform, writing, "I imagine most users are not going to want to have all of their Twttr messages published on a public website." People do announce their dinner menus with annoying frequency, but they also use Twitter to communicate quickly about emergencies like earthquakes, and they have used it to organize protests — even revolutions — in places like Egypt, Tunisia, Iran, and Moldova. For that reason, The Hill called Twitter a "strategic weapon ... which [has] the apparent ability to realign the social order in real time, with little or no advanced warning."

Today is the birthday of microbiologist Thomas Francis Jr., born in Gas City, Indiana (1900). T.F., as he was known to his friends, grew up in western Pennsylvania and studied medicine at Yale. He graduated in 1925. His early research projects involved bacterial pneumonia, but he was particularly interested in the study of viruses. He was the first American to isolate the human influenza virus.

He joined the University of Michigan in its newly formed School of Public Health in 1941. It was here that he developed the first flu vaccine, which used the dead influenza virus to provoke an immune response in the human body. Francis had discovered in 1940 that there was more than one kind of flu virus. That's why epidemiologists release a different flu vaccine every year, based on their predictions of which strains will be dominant. It's estimated that Francis's flu vaccine has directly saved more than a million lives.

While he was teaching at the University of Michigan, Francis established a virology lab to study viruses. One of his first students in the lab was Jonas Salk. Francis taught his student how to develop vaccines, and Salk eventually went on to develop a vaccine against polio. Francis designed the massive nationwide field trial that proved the effectiveness and safety of Salk's vaccine.

Francis also founded the University of Michigan's Department of Epidemiology, to study how diseases are spread through populations and develop ways of controlling outbreaks. Francis said: "Epidemiology must constantly seek imaginative and ingenious teachers and scholars to create a new genre of medical ecologists who, with both the fine sensitivity of the scientific artist and the broad perception of the community sculptor, can interpret the interplay of forces which result in disease."

It's the birthday of Thomas Bulfinch (books by this author), born in Newton, Massachusetts (1796). He wrote several books, but he is best remembered for his three-volume study of mythology and legends. The first volume, The Age of Fable (1855), was a retelling of classic Greek and Roman myths; the second, The Age of Chivalry (1858), covers the legends of King Arthur, Robin Hood, and other British folk tales; and the third, Legends of Charlemagne (1863), recounts stories from France, Germany, and Africa. The three books were later combined into one volume, titled Bulfinch's Mythology, first published in 1881 and never out of print since. The book entertained Victorian adults and children, and made mythology accessible and available to the common American reader for the first time.

It's the birthday of Iris Murdoch (books by this author), born in Dublin (1919). She studied at Oxford and was deeply influenced by a two-year stint teaching war refugees for the United Nations. She wrote all of her novels in longhand, twice, then delivered the manuscripts to her publisher in a plastic bag. And she never allowed her books to be edited. Among her novels are The Sea, the Sea (1978), which won the Booker Prize, and The Good Apprentice (1985).

In the 1990s, she wrote her final novel — a psychological thriller called Jackson's Dilemma (1995) — during her early stages of Alzheimer's disease. Murdoch's husband of 44 years, John Bayley, wrote a memoir about the progression of her illness called Elegy for Iris (1999), which was later made into a film starring Judi Dench.

Murdoch said: "Writing is like getting married. One should never commit oneself until one is amazed at one's luck."

On this date in 1838, Ralph Waldo Emerson delivered a commencement address to the Harvard Divinity School (books by this author). Emerson had graduated from Harvard Divinity in 1826. Before he graduated, he had given a lecture called "The American Scholar" to the Harvard Phi Beta Kappa society, in which he spoke of his philosophy of transcendentalism. The speech was published that same year. It made Emerson famous, and it brought the ideas of transcendentalism to young men like Henry David Thoreau.

Emerson had been a Unitarian minister, but he had resigned and was becoming very critical of the current practice of Christianity, which he made clear in this commencement address. He said: "The true Christianity — a faith like Christ's in the infinitude of man — is lost." Many in the audience were incensed by Emerson's speech, particularly the older faculty and ministers. It was 30 years before Emerson was invited back to speak at Harvard.