How To Invent (Almost) Anything : 2.4.2. Size

2.4.2. Size

Things can be large and small and anywhere in between, although in any application there tend to be breakpoints and viable ranges along the scale from microscopic to massive.

When size increases, volume and surface area do not change at the same rate. Double dimensions and the volume goes up by a factor of eight. At a constant density, this equates to bigger meaning much heavier. It also means greater heat insulation and retention as heat is lost from the surface, and a deep core will only change its temperature slowly.

In the animal kingdom, it is probably not a coincidence that humans are about half way along the scale. Small animals find it easier to jump, fall, fly and hide, whilst larger animals can defeat predators and lose less heat (and so need to eat less for their size). In the middle, we get the best of both worlds.

In the fight against gravity, small wins. A small insect falls more slowly and can rise more easily. The only problem that it faces is going forward: small wings need to fight hard against air resistance. Birds have found the best balance with longer wings and hollow bones.

Flight is an example where mimicking nature is not necessarily the best answer. Years of flapping-wing machines proved fruitless. The Wright brothers successfully took to the air by using large and doubled-up wings to get lift and a powered propeller to get the extra forward speed needed to get sufficient lift for the additional weight. Birds learned long ago the balance point between size and flapping flight. It took man’s ingenuity to overcome the problem of size by turning it into an advantage: big wings mean lots of lift.

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2.4.2. Size

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