MIT Technology Review Explains: Let our writers untangle the complex, messy world of technology to help you understand what's coming next. You can read more from the series here. In mid-October, a mysterious object cracked the windshield of a packed Boeing 737 cruising at 36,000 feet above Utah, forcing the pilots into an emergency landing....

This is today's edition ofThe Download,our weekday newsletter that provides a daily dose of what's going on in the world of technology. What is the chance your plane will be hit by space debris? The risk of flights being hit by space junk is still small, but it's growing. About three pieces of old space...