Nora Vale
Writes for the wisst team about science, nature, health and food.
- Why popcorn popsEvery popcorn kernel is a tiny pressure cooker. Heat turns a little water inside it to steam, until the hull gives way and the inside turns to foam.
- Why your ears pop on a planeThat full, muffled feeling on take-off and landing comes from a small tube between your ear and your throat. Here is what it does, and why landing is often worse.
- Tardigrades survived ten days in open spaceIn 2007, dried-out tardigrades rode on the outside of a spacecraft, exposed to vacuum and the Sun's raw ultraviolet light. Some of them came back to life.
- 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.
- Why cutting an onion makes you cryA whole onion doesn't sting. The tears come from a chemical reaction that starts the moment the knife breaks its cells, and ends in your eyes.
- Smallpox is the only human disease we have wiped outSmallpox killed hundreds of millions of people in the twentieth century alone. In 1980 the world was declared free of it. Here is how that was done.
- An octopus has three hearts and blue bloodTwo hearts pump blood through the gills, a third sends it round the body, and the blood carries oxygen on copper instead of iron. Here is how the pieces fit.
- 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.
- Chilli heat is a trick played on your heat sensorsCapsaicin, the compound that makes chillies hot, doesn't burn anything. It switches on the same nerve sensor that warns you about real heat.
- The doctor who drank bacteria to show what causes ulcersFor decades, stomach ulcers were blamed on stress and spicy food. Two doctors in Perth found a bacterium behind many of them, and one of them drank it to make the case.
- A tree is built mostly from airA large tree weighs tonnes, yet it doesn't leave a hole in the ground. Most of its mass came in through the leaves, as carbon dioxide.
- 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.