John Lloyd

Because so much of an octopus’s nervous system is in its extremities, each limb has a high degree of independence. A severed tentacle can continue to crawl around and, in some species, will live for several months. An octopus’s arm (or leg) quite genuinely has a mind of its own.

Male octopuses also have a specialised arm in which they keep their sperm. It’s called the hectocotylus and is used for mating. To transfer the sperm, the male puts his arm into a hole in the female’s head. During copulation the hectocotylus usually breaks off, but the male grows a new one the following year.

Hardness is simpler to determine: if one material can make a scratch mark on another, it’s harder. The German mineralogist Friedrich Mohs (1773–1839) devised the Mohs Hardness scale in 1812. It starts at the softest end with talc (MH1). Lead is fairly soft at MH1½; fingernails are graded MH2½ (as hard as gold); in the middle are glass and knife blades at MH5½. Ordinary sandpaper (which is made of corundum) is MH9, and right at the top end is diamond at MH10. Since ADNR can scratch diamond, it is literally off the scale.

nothing else in nature is found simultaneously as liquid, solid and gas. A sea full of icebergs under a cloudy sky may appear natural, but in chemical terms it is anything but. Most substances shrink as they cool, but when water falls below 4°C it starts to expand and become lighter. That’s why ice floats, and why wine bottles burst if left in the freezer.

So many things can be dissolved in water that it’s known as the ‘universal solvent’. If you dissolve metal in acid, it’s gone forever. If you dissolve plaster in water, when all the water has evaporated, the plaster is still there. This ability to dissolve stuff without eradicating it also paradoxically makes water the most destructive substance on the planet. Sooner or later, it eats away everything – from an iron drainpipe to the Grand Canyon.

Most of Earth’s water is inaccessible, locked deep inside the planet, carried down when tectonic plates overlap, or held inside the mineral structure of the rocks themselves.
If this hidden water were released it would refill the oceans thirty times over.

For water to freeze, it needs something for its molecules to latch on to. Ice crystals form around ‘nuclei’, such as small particles of dust. If there are none of these, you can get the temperature of water down to –42°C before it freezes.

Antarctic icefish and herring produce proteins in the pancreas that are absorbed into their blood. These prevent the formation of ice nuclei (much like antifreeze in a car radiator).

Halobacteria. They belong to the Archaea domain, the oldest life forms on the planet. Archaea are so ancient that, on the evolutionary timescale, human beings are closer to bacteria than bacteria are to Archaea.

Giant sequoias are also the fastest-growing trees in the world: for this they need not just air, but fire. The trees rely on the heat of forest fires to open their tough seed cones and to expose the bare soil. So the US Forest Service deliberately sets fire to the sequoia groves on a regular basis.