In a circular gallery, sound produced close to the wall skims along the curved surface in a series of reflections, without spreading towards the centre. A whisper can then be heard clearly on the far side of the dome, tens of metres away. Physicist Lord Rayleigh explained these "whispering galleries" in the late 19th century.
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.