In the early 20th century, the radiation in the air was thought to come from the ground and to fade with altitude. In 1912, Victor Hess carried detectors aloft in a balloon to about 5,300 meters. Surprise: the radiation grew stronger with height and did not weaken at night or during an eclipse. It came from space. Hess won the 1936 Nobel Prize.
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.