The Celsius and Fahrenheit scales have neither the same zero nor the same degree size: one Celsius degree equals 1.8 Fahrenheit degrees. Yet they cross at a single point, minus 40. At that temperature, there is no need to name the unit: −40 °C and −40 °F mean exactly the same cold. It is regularly reached in winter in polar and subarctic regions.
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.