Phun physics facts #2

We're on a roll now. A couple more delicious factoids to tickle your mental tastebuds:
  • In 1980 Hans Dehmelt of the University of Washington isolated a barium ion (an ion is an atom with electrons missing, or extra electrons added, giving it an electrical charge). When illuminated by the right color of laser light, the ion was visible to the naked eye as a pin prick of brilliance floating in space.
  • Since 1972, the remains of fifteen natural nuclear reactors have been found. Around 1.7 billion years ago a stable nuclear reaction took place in underground deposits of uranium. Because the amount of uranium 235 in the ground drops as it decays, it is unlikely such natural reactors would be found now.
  • It’s sometimes thought that glass is a liquid, because medieval window glass seems to have run down the panes, making them thicker at the bottom – but this merely reflects the way glass was made. Panes were uneven, and it made sense to put the thicker edge at the bottom.