Wrinkly fingers are a decision, not an accident
Everybody assumes the skin has soaked up WATER and swollen. It has not. The wrinkling is done deliberately by the nervous system: after a few minutes in the TUB, nerves tell the blood vessels under the fingertips to narrow, and the skin above them puckers into ridges.
Doctors have used this as a test, because a finger whose nerve supply has been cut will sit in a bath all afternoon and stay perfectly smooth. As for the point of it, researchers gave people wet marbles to move and found the wrinkled hands were faster — the ridges appear to work like tyre tread, channelling water out from under the fingertip so it can grip.
Soap is older than the pyramids, and bubbles keep the time
A Babylonian clay tablet from around 2800 BC carries a recipe: fat, water and ash, boiled together. Thousands of years later that is still what SOAP is, and the chemistry has never changed.
Each speck of soap is a molecule with two ends that want opposite things. One end clings to grease and refuses to mix with water; the other end loves water and will not touch grease. Dropped into a bath they surround every scrap of oil and dirt, grease-end inwards, water-end outwards, and the whole bundle then floats away when you RINSE. Water on its own simply runs past the grease, which is the entire reason a WASH without soap does so little.
The swirling rainbow on a soap BUBBLE is not a dye. Light bounces off both the outer and the inner surface of that impossibly thin skin, and the two reflections interfere with one another — some colours cancelling out, others reinforcing — so the colour you see depends purely on how thick the film is at that spot.
The FOAM on the surface of the bath is doing this too, in miniature. It also means you can predict a burst: as the water drains downwards the top of a bubble thins until it is thinner than a wavelength of light, the colours drain away and it turns black. A bubble that has gone black has about a second left.
Twenty-eight thousand bath toys went to sea
In January 1992 a container ship crossing the Pacific lost part of its cargo in a storm, and around 28,800 plastic bath toys — a yellow DUCK among each set of four — went into the water at once.
Oceanographers were delighted: an enormous batch of identical floating objects released from one known spot on one known day is the sort of experiment nobody is allowed to run on purpose. The ducks turned up in Alaska, then Hawaii, then years later in the North Atlantic, and each landing helped map the currents. Some were still washing up fifteen years on.
A warm bath works by making you cold
The sleepiness after a bath is not the WARM water relaxing anybody. Sitting in hot water sends blood to the surface of the skin, and when you get out that blood sheds its heat fast, so core temperature drops below where it started. A falling core temperature is one of the signals the body uses to begin sleep, so the bath belongs an hour or so before bed rather than immediately at it.
The rest of the routine is in the grid: SHAMPOO, a SPONGE and a FLANNEL, a BRUSH for the TEETH, a good SOAK and a SPLASH, then the PLUG out, a TOWEL to get DRY, and a small CLEAN person who has run off.