Iranian mathematician Maryam Mirzakhani, the first woman to win the prestigious Fields Medal, would have been 41 today. Sadly, she died of breast cancer last year.

Today is designated by UNESCO as #WorldPressFreedomDay, which celebrates the principles of a free and open press. The world's first law supporting the freedom of the press and freedom of information was passed by Sweden in 1766. However, English poet John Milton had made the case for such a law more than a century earlier. "Truth and understanding," he wrote, "are not such wares as to be monopoliz'd and traded in by tickets and statutes, and standards."

On this day in 1979 Margaret Thatcher of the Conservative Party was elected prime minister of the United Kingdom. She was the first woman to hold the position.

In the desert of southern Peru, a group of ancient line drawings remain etched into the land. Many of these giant artworks depict animals, among them a monkey, a killer whale, and a spider.

#DidYouKnow that the abbreviation "Mrs." was originally short for "mistress"? In the 18th century the word "mistress" referred to a woman of economic or social capital, and it had nothing to do with marital status. Only later did the abbreviation come to signify a married woman.

The most famous English translation of the Bible, the King James Version, was first published this day in 1611. The work is named after King James I of England, who organized and approved the project. However, contrary to popular belief, he had no hand in the actual writing of it. The translation was done by a committee of 47 scholars and clergymen over the course of seven years.

On this day in 1803 the United States purchased the Louisiana Territory from France at a rate of less than 3 cents per acre. The purchase immediately doubled the size of the U.S.

Learn more: https://www.britannica.com/event/Louisiana-Purchase

Catherine the Great was born on this day in 1729. She engineered the abdication of her husband, Peter III, to become empress of Russia and one of the most powerful women in history.

Dogs don't see in black and white, but they are color blind. They see in combinations of blue and yellow.

Earth is the only planet in our solar system that does not derive its name from Greco-Roman mythology. (It comes from the Old English word "ertha," meaning "ground" or "land.") Do you know the mythological figures that the other planets are named after?

Citizen Kane, acclaimed by some critics as the greatest movie ever made, premiered on this day in 1941. Its director and star, Orson Welles, was only 25 years old at the time.

Since the late 19th century, the first of May has been celebrated as an international labor holiday.

The Act of Union, which united the kingdoms of England and Scotland under the name Great Britain, went into effect on this day in 1707.