Is the straight line a human invention? © Getty Images

Is the straight line a human invention?

Asked by: Dileep Bagnall, Lancashire

You could argue that there’s no such thing as a straight line, because everything – if you zoom in close enough – has irregularities. Even a beam of
laser light is slightly curved, as light is bent by the Earth’s gravitational field.

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But if we relax our definition to ‘something that looks straight to the human eye’, then we can find plenty of straight lines in nature – rock strata, tree trunks, the edges of crystals, strands of spider silk.

The reason we like straight lines is because of a fundamental property of the Universe – the shortest distance between two points is a straight line. Nature also follows this principle. Spiders, for example, make their webs by stretching silk strands across the shortest path.

It’s true that curved lines are common in nature, but many of these are just an extension of this principle into three dimensions. The smallest surface area to enclose a volume is a sphere. So the bonds between water molecules pull raindrops into a sphere, and cells have rounded shapes to reduce the amount of cell membrane they
need.

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