Cosmic rays create muons about 15 kilometers up. They live only around 2.2 microseconds: even at light speed, they should cover only about 660 meters. Yet many reach the ground. Racing at nearly the speed of light, they experience time passing more slowly, exactly as relativity predicts. Einstein is, quite literally, what keeps them alive.
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.