In 1871, Dmitri Mendeleev left gaps in his periodic table and predicted the properties of the missing elements. In 1875, Paul-Émile Lecoq de Boisbaudran discovered gallium but measured its density at 4.7. Mendeleev, who expected 5.9, urged him to measure again. With a purer sample, the chemist got… about 5.9.
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.