In 1928, Paul Dirac wrote an equation describing the electron. It allowed a strange solution: an identical particle with a positive charge. In 1932, Carl Anderson photographed the track of this "anti-electron" in cosmic rays: the positron. Today antimatter is used in hospitals, in the scans known as positron emission tomography, or PET.
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.