Why do mirrors flip horizontally (but not vertically)?

Why do mirrors flip horizontally (but not vertically)? Why do mirrors appear to flip images horizontally but not vertically?Featuring Meg Chetwood @megatronvolleyThanks to Kyle Kitzmillerand Veritasium http://ift.tt/1CMZUw1: "Rhythm Changes," "Locally Sourced" Tags: from Pocket http://ift.tt/1zCBS9r February 19, 2015 at 07:30PM via IFTTT