A wheel rolling without slipping combines two motions: it moves forward with the car and spins around its axle. At the top, the two speeds add up, so that point travels at twice the vehicle's speed. At the bottom they cancel out, and the point touching the road is momentarily at rest. In photos, the upper spokes look blurrier.
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.