A lot of what people learn, they learn in school. Some really useful stuff, however, I didn't learn in school.
-
How to ride a bike.
-
To make an "s" sound, touch the tip of the tongue to the lower teeth without touching the top teeth. Touching the top teeth produces a lisp, while not touching the teeth at all and pointed the tip of the tongue toward the pallet produces a whistling "s" (which Billy Bob Thornton used in at least one of his movies; Sean Connery apparently does as well).
-
When tying shoelaces, make sure to follow right-over-left, left-over-right (or vice-versa). Going the same way both times means the loops naturally want to sit up and down the shoe, not across it. This page (different Ian!) explains it quite well.
Also cool is this way of tying shoelaces – I normally use it when tying my own shoes, although with the thicker and more slippery than normal glow in the dark laces on my boots (at time of writing) it needs a little more setting to make sure the knot is set tight. For a secure shoelace knot I use this one.
-
With any number, if the sum of the digits is a multiple of 3, the original number is also a multiple of 3.
This also works for 9. If the sum of a number's digits is a multiple of 9, so is the original number.
These are recursive, so if the digit sum is too big to easily tell if it's a multiple of 3 (or 9), just do it again. I have a page explaining other useful factorising tricks.
-
To find the south celestial pole (SCP), take a perpendicular line through the middle of the Pointers and a line through the top and bottom stars in the Southern Cross. Where they intersect is roughly where the SCP is.
Once this approximate location is found, I normally use a slightly more accurate method by taking a line from half way between the Pointers and the Southern Cross across to Achernar, the bright star opposite the SCP from them. The midpoint is quite close to the SCP.
-
Using a watch with hands to find north in the southern hemisphere, point 12 at the Sun. Half way between the hour hand and 12 is north. Don't forget to allow for daylight saving time, when 1 points to the Sun.
-
Ocean tides do not sweep past New Zealand twice a day following the Moon – what I was told in school is just plain wrong. Tides are powered by the Moon, but where they end up flowing depends on resonances largely determined by the position and shape of land masses.
Tides actually circle around New Zealand, going in an anticlockwise direction; the country is an amphidromic point. New Zealand and Madagascar are the only amphidromic points which are islands; amphidromic points are normally out in the middle of the ocean and have no tide (because the water is free to flow across the centre of it, cancelling out any height difference).
-
Resistor colour codes. So good.
0 = black.
1 = brown.
2 = red.
3 = orange.
4 = yellow.
5 = green.
6 = blue.
7 = violet/purple.
8 = grey.
9 = white.
-
When an adult says to a child "Just ignore him (her) and (s)he'll stop" the adult is quite possibly either lying or a complete idiot.
-
How to do parallel stops on skis. Oh yeah.
-
When you Look into the wind, the Low is on your Left. This works in the southern hemisphere because wind circles around low pressure areas clockwise. (For example, southern hemisphere tropical cyclones, which we just call cyclones, circle clockwise. Northern hemisphere tropical cyclones, normally called typhoons or hurricanes depending on their location, circle anticlockwise.) Knowing this means you know roughly what shape the isobars have on a weather map for the area around you, and therefore you know when a storm has passed – the wind direction completely changes as the low passes.
-
Don't cut finger nails too short. Ow.
