The Atlas Farnese
In 1575, this marble figure of Atlas holding a celestial globe was found in Rome. It is called the Atlas Farnese, as Farnese was the name of the collection it entered. It was created by sculptor Crates. The exact date of the sculpture is not known. However, scholars assume that it was made sometime after 150 A.D. because of the representation of the vernal equinox on the globe, which is similar to that in Ptolemy’s Almagest. To give you an idea of the size, the sphere has a diameter of about 251/2 inches.
THE STORY OF ERATOSTHENES AND THE EARTH’S CIRCUMFERENCE
‘The discovery that the Earth is a little world was made, as so many important human discoveries were, in the ancient Near East, in a time some humans call the third century BC, in the greatest metropolis of the age, the Egyptian city of Alexandria. Here there lived a man named Eratosthenes.
… He was an astronomer, historian, geographer, philosopher, poet, theater critic and mathematician…. He was also the director of the great library of Alexandria, where one day he read in a papyrus book that in the southern frontier outpost of Syene … at noon on June 21 vertical sticks cast no shadows. On the summer solstice, the longest day of the year, the shadows of temple columns grew shorter. At noon, they were gone. The sun was directly overhead.
It was an observation that someone else might easily have ignored. Sticks, shadows, reflections in wells, the position of the Sun—