Military satellite Poppy VII-B and space telescope Infrared Astronomical Satellite passed within a predicted 47 metres of one another on Wednesday night. The incident occurred at an altitude of 900 kilometres, in orbit over western Pennsylvania. (NASASpaceFlight.com)

Talking point: Entire satellites rarely collide, and Wednesday’s incident would not have endangered the people of Earth if they had hit each other. But the accrual of aging, broken-down objects in orbit—the two involved in this near-miss have been inactive for nearly four decades—has created more risk for crashes; meanwhile, several firms plan to launch new constellations of thousands of satellites, albeit in lower orbits than many of those sent up in previous decades. Montreal’s NorthStar is among the companies hoping to build a business out of space scavenging; it is building a system to track defunct satellites and other space debris, a venture for which it’s received significant government backing.