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Depending on where you look, Daniel Bernoulli was born in the Dutch city of Groningen sometime between the 29th January and the 9th of February 1700. Early in his life Daniel, along with the rest of the family, were forced to move back to Basle in Switzerland where his father and uncle had originated and where they found a haven from persecution by the Spanish.

It was while he was here that Daniel dedicated his life to the study of liquids, which may sound a bit dull but if it wasn't for his diligent research, arguably driven by a desire to out do the rest of his family, then we may still be jealously watching the birds soar about the sky instead of joining them.

Daniel is credited with a simple but very important principle which is that a liquid flowing over an object from one point to another will travel faster when the distance between the points is further on one of the surfaces of the object than on the other. And it took a lifetime to discover this? Well that is of course just one half of the principle. The other half is that by travelling faster the pressure of the liquid lowers relative to the difference in distance. When this happens the low pressure will be forced away from the high pressure on the opposite surface, creating a movement that aeronautical engineers call lift. This is clearly an adaptation of the work that Robert Boyle had been doing in Ireland about 50 years earlier but proved to be the essential breakthrough for those scientists and engineers who were scratching their heads and trying to make heavy things, like servants with wings strapped to their backs, stay in the air instead of landing in a crumpled heap.

If you want to prove the principle to yourself, don't waste money throwing an expensive servant out of an upper storey window, simply tear off a strip of inexpensive paper and hold it between your fingers and blow over the top surface; as if by magic the strip of paper will rise because the air you have blown move the top is moving faster than the air beneath it and so has a lower pressure.

If Bernoulli had invested in a cruise to Australia he might well have met Aboriginal hunters who had successfully employed this principle to make boomerangs that had been used to kill lunch and neighbouring tribes for thousands of years.

Anyway, it is this principle that has been refined and used as propeller and a wing that keeps aircraft and helicopters in the air.

Learn more about this author, Ian Pauley.
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