The air is full of nitrogen, but plants cannot use it directly. In the early 20th century, Fritz Haber and Carl Bosch developed a process to turn it into ammonia, the basis of fertilisers. According to a study in Nature Geoscience, nearly half the world's population now relies on this reaction for its food.
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.