Dan Kahneman and Amos Tversky’s behavioural economics theory modeling how we make decisions. It illustrates, among other things, some of the non-rational decisions we make as we are guided by emotion and heuristics in decisions. The sketch points out a few of the key points:

Loss aversion - the different shape of the curves as we make gains or losses (either side of the centre) represents how a loss of £100 annoys us much more than a gain of £100 gives us pleasure.

Diminishing sensitivity - the levelling off of the curves represents that we’ll enjoy winning £100, if we only have £100, much more than we’d enjoy winning £100 if we had £900.

Adaptation level - We don’t evaluate from some absolute level - we evaluate whether something is good or bad from a neutral reference point that we adapt to. So, by the end of a movie the movie theatre doesn’t feel dark, yet walking out feels blinding. Your reaction to the £100 example above was probably affected by whether you think £100 is a lot of money or a little, which is all to do with your adaptation level.

Prospect theory

In the Northern hemisphere you can use this handy technique to find the North star, or pole star, that is always almost due North. Follow the last two stars of the Big Dipper, known as the plough in the UK, to a prominent star. Handy for a navigation sanity check at night.

The North star is the star that stays fixed in those neat star trails photos with all the stars rotating in a circle as the earth turns.

In the Southern hemisphere you can use the Southern Cross and the Pointers to find South, but it's not quite as simple as in the North.

Find the North star

Where the Northern Hemisphere simply allows you to find the North Star, around which all the stars will rotate, finding your way in the Southern Hemisphere is a little more involved. Unlike in the North, there’s no obvious star due south in the Southern Hemisphere. Instead, you have to use two handy indicators: the Southern Cross — easily spotted, fortunately — and two stars known as The Pointers. Find where these intersect, as in the sketch, and you’ve found due south.

Or, if you prefer, you can follow the direction the Southern Cross is pointing for a distance equal to 4.5x the length of the Southern Cross to arrive at the spot.

Incidentally, I wondered about reliable methods of finding south in the Northern Hemisphere and north in the Southern Hemisphere. And I think the answer is to find north or south and turn around.

Use the Southern Cross to find South