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Grape; satsuma; and stilts

November 6, 2013

An experiment. Get a grape, and a satsuma [mandarins will do fine- an occasional row chez Beardsworth is whether what we buy are mandarins or satsumas, or even tangerines: no one really knows the difference, but we can still argue], and put them just over a metre apart. Then find a brightly coloured man on stilts (a baby giraffe will do- you can probably buy a stuffed giraffe at Harrods- or maybe even a real one) and ask him to stand around four hundred meters away.

Then, look at them. If you put your eye by the satsuma and stare past the grape, in the distance you will see the man on stilts, and he will appear to be ever so slightly large than the grape. (If he doesn't, he has cheated when counting out his strides to get to 400m).

Get hold of the satsuma and grape, and walk in a big circle, four hundred metres radius, around the man on stilts. It doesn't matter if your circle is not accurate, ever so slightly squashed will do. As you walk your four hundred meter circle, spin round, much faster, spinning the satsuma and grape around as you do: do one full swivel for every single degree you walk round the big circle.

Oh, and slightly tilt yourself as you swivel. On some swivels, you will be able to see the man on stilts more than others: and he seems to be moving, though you know he is still.

And, roughly, you then have an idea of the moon's, Earth's, and Sun's positions and scale.

Of course the moon is not a grape, it is made of cheese: so use a cheese ball for greater accuracy. And look after the mandarin, and remember it is rude (and dangerous) to stare directly at the man on stilts.

The moon has diameter 3,475km, say 1 unit, or 1 cm, the size of a grape. The Earth's diameter is 12,756km, or 3.67 units, and the Sun around 400 units. The moon is 381,600km from the Earth, 110 units, and the Sun 43,160 units, or 392 times greater than the Earth-moon distance.

It is 'kind of neat' that the Sun is 400 times larger, but 392 times further away, than the moon: they thus appear to be roughly the same size, the Sun being slightly larger than the moon.


From → General, Maths, Science

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