Current Issue #488

Bragging another science centenary

Bragging another science centenary

It’s something of a year of Science Centenary Celebrations for Adelaide.

It’s something of a year of Science Centenary Celebrations for Adelaide and, while we’ve already seen the interest around the 100 year celebration of Douglas Mawson’s Antarctic Expedition, I’d like to now turn the spotlight on another science son of Adelaide and the centenary of his achievement. In fact, it’s the tale of two scientists, father and son, who went on to change the world.

At the ripe young age of just 23, and on the recommendation of his friend J.J. Thomson, William Henry Bragg (July 2, 1862 – March 10, 1942) was appointed to the chair of Mathematics and Theoretical Physics at the University of Adelaide in 1885. On his first day in Adelaide he met the family of Charles Todd, the Senior Scientist of the colony, and three years later married his daughter Gwendoline. They had three children, the oldest son being William Lawrence Bragg (March 31, 1890 – July 1, 1971). I’m told that, within the family, the senior was referred to as William while the son was always Lawrence to avoid confusion.

Five-year-old Lawrence fell off his bike and broke his arm which William investigated using the newly-discovered X-rays. It is the first recorded use of X-rays for medical purposes in Australia.

Lawrence was a bright student at St Peter’s College in Adelaide where he was repeatedly moved ahead in the years and still topped the class in his studies. This continued through university where he received his BA with first class honours in Mathematics while he was only 18. Soon after graduating, the family sailed to England so that William could take up a Chair in Physics in Leeds and Lawrence could continue his studies in Cambridge.

It was in England that Lawrence, assisted by his father, began to take an interest in experiments with X-rays and crystals. They fired X-rays at simple crystals such as salt and measured the scattering patterns. Working backwards, they could for the first time describe the atomic structure of crystals – a feat likened to describing a chandelier by measuring and analysing the patterns it casts on the surrounding room. From these experiments they derived Bragg’s Law.

Bragg’s Law had its first public outing on November 11, 1912 when Lawrence Bragg presented a paper before the Cambridge Philosophical Society. Put simply, Bragg’s Law gives the angles of scattering of radiation as it bounces off the atomic structure of a crystal. While the Law is relatively simple, its impact at the time was immense and it continues to serve at the heart of material sciences.

It was confirmation of the atomic particle nature of matter – something that, at the time, was little more than an untested theory. And it’s still employed in the day-to-day lab work of material scientists around the world. Invoking Bragg’s Law was instrumental in Watson and Crick’s decoding of the structure of DNA in February 1953, work which they coincidentally conducted in the Cavendish Laboratory in Cambridge when Lawrence was the Director there.

Father and son were awarded the Nobel Prize in Physics in 1915, the only father and son recipients and, at the age of just 25, Lawrence remains the youngest ever Nobel Laureate. It must have been the ultimate bittersweet year for the family when receiving news that Lawrence’s younger brother Robert had been killed at Gallipoli.

There are continuing links between Adelaide and the Braggs. Both William and Lawrence were involved with the Royal Institution in Great Britain, William as Director of the Davy-Faraday Research Laboratory from 1923-1942 and Lawrence as Director from 1965-1966 – both having lectured there on several occasions. It’s a link to the Royal Institution of Australia that we commemorate at The Science Exchange with an exhibition of some of their memorabilia. And later this year, in December, The Bragg Symposium for Crystallography will attract scientists from around the world to Adelaide to celebrate 100 years of Bragg’s Law. It’s a celebration we should all be proud to take part in.

Dr Paul Willis is the Director of RiAus (Royal Institution of Australia)

Photograph by Lotte Meitner-Graf. Extracted from Biographical Memoirs of Fellows of The Royal Society

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