Template:Are You Sure/February 13

• ... that mathematician David Hilbert was among the first to distinguish between mathematics and metamathematics?

• ... that mathematician John Hadley laid claim to the invention of the octant, two years after Thomas Godfrey claimed the same, and that Hadley also developed ways to make precision aspheric and parabolic objective mirrors for reflecting telescopes?

• ... that Pale Blue Dot is a photograph of planet Earth taken on February 14, 1990, by the Voyager 1 space probe from a record distance of about 6 billion kilometers (3.7 billion miles, 40.5 AU), as part of the Family Portrait series of images of the Solar System, and that Voyager 1, which had completed its primary mission and was leaving the Solar System, was commanded by NASA to turn its camera around and take one last photograph of Earth across a great expanse of space, at the request of astronomer and author Carl Sagan?