In 1948, Hendrik Casimir predicted that two neutral metal plates placed very close together in a vacuum should attract each other. The reason: the quantum vacuum is never truly empty, and its fluctuations push less hard between the plates than outside them. This tiny effect was measured precisely in 1997, and engineers of micro-machines now have to account for it.
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.