Neil deGrasse Tyson @neiltyson
Even more Mach-talk… The @NASA orbiting International @Space_Station travels 17,000 mph in the near-vacuum of space. While that’s 22x the speed of sound (at sea-level & room temperature), it’s not Mach-anything. The ISS is not traveling through a medium that has a sound-speed. — PolitiTweet.org