CERN's Large Hadron Collider is about 27 km around. Its superconducting magnets are chilled to 1.9 kelvin, or –271.3 °C, colder than the background of deep space at 2.7 kelvin. Keeping it that cold takes nearly 100 tonnes of liquid helium. One of the world's biggest refrigerators is hidden underground, beneath the French-Swiss border.
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.