Science
Short articles about science, one idea in each.
- A lightning bolt is about five times hotter than the Sun's surfaceFor a few millionths of a second, the air in a lightning channel gets far hotter than the visible surface of the Sun. That heat is also where thunder comes from.
- Helium is leaking off the planet, a little every secondHelium is the second most common element in the universe, yet on Earth it is scarce. The reason is that our planet can't hold on to it.
- The Moon is drifting away from Earth, about 3.8 cm a yearMirrors left on the Moon let scientists time laser pulses to the millimetre. They show the Moon slowly moving outward, and Earth's days slowly getting longer.
- Bananas are slightly radioactive, and so are youA banana gives off a little radiation from the potassium in it. Here is what that dose amounts to, and why eating more of them doesn't add up the way you'd think.
- Why lakes freeze from the top downMost liquids get denser all the way down to freezing. Water stops at about 4 °C, and that small quirk keeps lakes liquid underneath through the winter.
- Old windows aren't thicker at the bottom because glass flowsA favourite classroom fact says glass is a very slow liquid that sags over the centuries. The real reason old panes are uneven is how they were made.