A bubble's colours come from no pigment at all: light reflects off both surfaces of its wall, and the two reflections reinforce or cancel each other depending on the thickness. When the film thins to a few tens of nanometres, they cancel for every colour. Dark patches appear at the top, a sign that the bubble is nearing its end.
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.