International Bath Day
According to Greek legend, on today's date—one week before the start of summer—Archimedes, a Greek scientist and mathematician, was taking a bath when he noticed that the water level rose when he got in, and it occurred to him that the volume of an object could be measured by submerging it in water. Upon realizing this, he jumped out of the tub and exclaimed "Eureka, Eureka!" while running naked through the streets of Syracuse, a city on the island of Sicily.
What was it about finding the volume of an object that made Archimedes get so excited as to run through the streets naked? He knew that once he could determine a crown's volume he could determine its density, and that would allow him to determine if it was made entirely of gold or partly with metals of a lesser value. His discovery became a law of physics known as Archimedes' principle. International Bath Day celebrates Archimedes and his discovery. It also is a day to encourage children to experiment with bath water just as Archimedes did, using toys and cups, so they can learn about volume and basic concepts related to physics like full, empty, floating, sinking, weight, and cause and effect.
How to Observe International Bath Day
If you have children, give them cups of various sizes and bath toys that float and sink, and let them experiment in bath water in a way similar to how Archimedes did. While they are learning some basic physics, you could read a book about Archimedes or physics. There's no stopping you from taking a bath like Archimedes did as well, but you might want to forgo the part about running down the streets naked.