At −273.15 °C, atomic jiggling would drop to the bare minimum allowed by quantum physics. But the third law of thermodynamics forbids getting there: no finite series of cooling steps can reach it. Each step closer costs more effort than the last. Physicists get within far less than a billionth of a degree, yet the finish line always stays just out of reach.
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.