## Newton saved the UK economy £10 million

by Jacob Aron

Where’s a scientific genius when you need one? A statistical analysis suggests that Isaac Newton saved the UK economy the equivalent of millions of pounds by implementing measures tostandardise the country’s gold coins.

Although Newton is famous for his theory of gravity, he also spent the last 30 years of his life running the Royal Mint, where the country’s coins are manufactured. Ari Belenkiy, a mathematician at the British Columbia Institute of Technology in Vancouver, Canada, has now compared coins produced before and after Newton’s stint at the mint to study the effect of measures he introduced to prevent rich goldsmiths from exploiting a currency loophole.

The quality of coins produced by the Royal Mint is assessed each year at the Trial of the Pyx, a ceremony begun in the 13th century. As coins are minted, a few from each batch are placed in a small chest, or pyx, and later weighed to determine how far they stray from the required standard.

This was essential because if coins weighed more than their face value, canny goldsmiths would buy them from the Mint, melt them down, then sell them back to the Mint at a profit, a process known as culling. “Neither counterfeiting nor clipping was involved,” says Belenkiy. “The culling was a vocation of the rich!”

Belenkiy modelled the weight of the coins as a normal distribution, or bell curve. He then used a combination of records from the trials, Newton’s notes and mathematical reasoning to calculate the standard deviation of the distribution, revealing the effects of Newton’s improvements. His analysis suggests Newton reduced the standard deviation from 1.3 grains – roughly 85 milligrams – to 0.75 grains, or 49 milligrams.

Unfortunately, no historical accounts detail exactly how he achieved this, but Belenkiy suggests Newton may have applied his recently derived “cooling law” to slow the coins’ cooling and reduce variability. However he did it, Belenkiy calculates Newton’s improvements saved £41,510 during his time as Master of the Mint, which is roughly £3 million today. Belenkiy suggests this is an underestimate, however, as the four Masters who followed Newton also applied his techniques, saving twice as much again, which means Newton may have saved the UK around £10 million in today’s money.

Journal reference: *Journal of the Royal Statistical Society*, DOI: 10.1111/j.1467-985X.2012.01037.x

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