Cosmic rays constantly create carbon-14 in the upper atmosphere. While alive, an organism absorbs it and keeps a steady proportion. At death the intake stops and the carbon-14 decays: half of it disappears in about 5,730 years. By measuring what remains, scientists can date bones, wood or fabric up to roughly 50,000 years old.
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.