Mars had an oxygen-rich atmosphere around 4 billion years ago
13
An unprotected human can survive up to 1.5 minutes in space with no permanent bodily damage.
82
Sound doesn't travel in space.
255
A neutron star (what remains after a Super Nova) is so dense that a portion of it the size of a sugar cube would weigh as much as all of humanity, or more than all the cars in the United States.
5