Physicist Ludwig Boltzmann's grave bears the formula S = k log W. It links entropy to the number of ways a system's atoms can be arranged without changing how it looks overall. It explains why disorder grows: there are simply vastly more messy arrangements than tidy ones. A broken cup never reassembles itself, purely as a matter of statistics.
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.