This short video explains how sites such as Youtube, Facebook, Google, and Twitter can recognize your password without actually having the password in their database. Yes, I know. That makes no sense, does it? Yet in three minutes, Tom Scott explains how this is possible and more importantly, why you should avoid any website that claims that it can email you your password back. We can thank Math for keeping our passwords safer from hackers.

By the way, Tom Scott has a Youtube channel of “Things You Might Not Know.” The videos demonstrate various ideas, principles and miscellanea such as “How Green Screen Worked Before Computers.” They are interesting and funny…although I might not show students “Ten Illegal Things to Do in London.” Lots of fun!