There are more than 2250 satellites orbiting the Earth right now. But that abstract number didn't prepare me for the shock of watching a Soviet-era rocket body whipping over my house in real-time.
Then I watched an elderly Russian intelligence satellite glide over Seattle. A NOAA weather satellite slid by Newfoundland and the ISS passed over Sumatra, while China's Tiangong manned station moved over the Mississippi River Delta. I was using Line of Sight, an extraordinary map created by Patricio Gonzalez, an artist and engineer at the open-source mapping startup Mapzen.
Satellites in orbit are moving at roughly 27,300km/h, meaning they pass over your city in a matter of minutes, but that's still enough time to spot them, if you know where to look — which has always been a challenge... until now. Using metadata about the thousands of orbiting satellites is available through sources like SatNOGS, Gonzalez's map monitors satellites as they criss-cross the globe, allowing you to track specific spacecraft or learn when and where you should look to see those passing over your house.
When I first opened up the map, I navigated to Lake Michigan, and watched as a satellite passed over Chicago, where I live.
A quick search of the name revealed the SL-16 is actually a rocket body built by the Soviet space program in the 1980s — essentially, space junk. There are actually 17 of them in orbit. It was part of a failed plan "to take over manned spaceship launches from Soyuz, but these plans were abandoned after the fall of the Soviet Union."
If it had been nighttime, I would have known where to look for the rocket body, which is about as bright as stars in the big dipper, according to Space Weather.
The data Gonzalez used to create this map is readily available, and it's not as though satellite-watching is a new idea. But for beginners, Line of Sight is a magical and visceral illustration of the spacecraft that make the modern world possible — turning them from an abstract idea into a blinking light, passing above your backyard. Go check it out here.