21 years ago, NASA successfully launched the Spitzer Space Telescope. Until Spitzer, and later with the James Webb Space Telescope, infrared observatories had to be sent into space with a fixed supply of liquid helium that would allow them to cool the telescope from the heat emanating off Earth. On this day in 1944, Paris was liberated from the Nazis after a six-day city-wide insurrection by the French resistance, culminating in the arrival of U.S. and Free French troops.