In 2009, astronaut Mike Massamino made headlines when he became the first person to ever tweet from space, and, a few months later, astronaut Timothy J. Creamer made additional headlines when he became the first person to ever live tweet from space. At least that’s what I’ve read. Truth be told, I don’t actually remember hearing about those milestones when they happened, and, if I did hear about them, I must have forgotten about them pretty quickly. With characteristic foresight, I understood that Twitter was just another flash in the pan with little real utility. Now, five years later, Twitter is not only more popular than ever, but has also revolutionized our relationship with the people who work in low Earth orbit. Every day, thousands of people around the world (including yours truly) anxiously await the latest batch of tweets from astronauts aboard the International Space Station. For those interested in learning more, NASA hosts a public Twitter account (located at this link) that compiles all the latest tweets from space. More useful still, geographer Dave MacLean has produced this convenient website, which maps all the photographs that astronauts have tweeted from space over the past few months. I was especially impressed with this incredible shot of downtown Philadelphia, which is home to (among other things) the Founding Fathers, the Duke Brothers, and the Philadelphia Area Center for the History of Science.