When the Nazis invaded Denmark, chemist George de Hevesy had to hide the gold Nobel medals of Max von Laue and James Franck, entrusted to Niels Bohr's institute. He dissolved them in aqua regia, a mixture of acids. The flask sat on a shelf, ignored by the occupiers. After the war, the gold was recovered and the medals recast.
Cooled below −183 °C, oxygen turns into a pale blue liquid. Pour it between the poles of a strong magnet and, instead of flowing away, it hangs suspended between them. The reason lies in its unpaired electrons, which respond to the magnetic field. Liquid nitrogen, by contrast, is colourless and pours straight through.
In 2012, Felix Baumgartner jumped from a capsule hanging beneath a balloon, about 39 kilometres up. In that extremely thin air almost nothing slowed him down, and he reached around 1,358 km/h in free fall, or Mach 1.25. He became the first person to exceed the speed of sound with nothing but his own body.