In the foyer of Oxford's Clarendon Laboratory, a small electric bell has been chiming since around 1840. A clapper swings between two bells powered by dry piles whose exact composition is still unknown, because nobody wants to open them and end the experiment. It has rung an estimated ten billion times, very faintly, behind double glass.
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.