When I take people out for a stargazing session on a dark night, they’re always surprised to find out how many human-made satellites are visible as they pass overhead. In fact, if you stay out for an hour or two, you can easily spot a dozen or more making their way across the sky! I understand the confusion, though. Satellites seem so far away—in space—that you’d think they’d be almost invisible and only rarely seen.
But this is misleading: most of them are a lot closer than you might think. Many are also big and shiny, which makes them brighter—and although it may be night where you are on the ground, a satellite above you can still bask in full sunlight and merrily reflect all those solar photons. All this makes most satellites fairly easy to spot.
There are presently more than 7,500 active satellites around Earth. They range from military “birds” with classified capabilities to far-seeing astronomical observatories to run-of-the-mill commercial spacecraft that provide weather forecasting, communications and other consumer services. And thousands more are inactive. Many of these defunct satellites are spent rocket boosters that still circle our planet long after they lofted their orbital payloads.