"Four hundred years ago this month, Galileo Galilei presented his eight-powered telescope to the Venetian Senate. He was soon working with a 20-powered telescope, and later that year, he proved that the moon's surface was rough, contrary to the prevailing view. Galileo went on to become one of the most recognized names in scientific history. But why do we call him by his first name only? Because that's how he referred to himself. At the time of Galileo's birth in 1564, surnames were optional in Italy. In daily interactions, an Italian would use the name his parents gave him at birth—what we'd now call a first name—and, if further clarification were required, add on his father's name (like di Antonio, or "son of Antonio"), his birthplace (Romano, or "from Rome"), his occupation (Pannetierre, meaning "baker"), or a traditional family surname (if one existed, like Galilei)." - Shannon Jiménez