100 years on, marking Rutherford’s breakthroughs
Heritage 10th October 2017
Did you know that Manchester is the birthplace of modern nuclear physics? It was created right here by Ernest Rutherford and his colleagues, and this year marks a century since Rutherford initiated the first artificial nuclear reaction.
And that wasn’t the end of the team’s breakthroughs. Between 1914 and 1919, Rutherford led many experiments in his lab (his desk is pictured above). These efforts resulted in the discovery of the proton and many other crucial breakthroughs.
Splitting the atom
Rutherford is often credited with splitting the atom during this period, but many physicists would argue this isn’t the most accurate way to describe the outcome of his research.
Sean Freeman, Professor of Nuclear Physics at the University, explains: ‘“Splitting the atom” is not a particularly good description of this work. Rutherford actually bombarded nitrogen with alpha particles from a radioactive source and thus became the first person to initiate a nuclear reaction.”
It was this experiment that led to the discovery of the proton. Previously, it was his mentor JJ Thomson’s ‘plum pudding’ model of the atom that was generally accepted by the scientific community. This theory held that atoms were made up of negatively charged electrons existing within a positively charged space.
With the discovery of the nucleus in 1911, Rutherford’s work undid this theory. He tasked Hans Geiger and Ernest Marsden with pointing a beam made up of alpha particles at a sheet of metal foil. If the alpha particles were neutral – which the plumb pudding model suggested they should be – the particles should pass through the foil. Instead, Rutherford realised that some of the particles bounced off in all manner of directions.
This led Rutherford to theorise that the atom must contain a highly concentrated positive charge at its centre. As we all know, this was the nucleus that lies in the middle of atoms and consists of protons and neutrons.
“The first nuclear reaction initiated by a human and the discovery of the proton are big steps.”
Over the next few years, Rutherford and his team conducted numerous experiments. These tests involved bombarding nitrogen gas with alpha particles, resulting in the absorption of some of these alpha particles by the nitrogen nuclei.
This loaded the nitrogen nuclei with additional energy, which caused it to emit a hydrogen nucleus and an oxygen atom. This hydrogen was a subatomic particle, which we know more commonly as a proton.
Says Prof Freeman: “Rutherford showed that the ‘nucleus of hydrogen’ existed in the nucleus of other atoms and thus appeared as a basic building block. The first nuclear reaction initiated by a human and the discovery of the proton are big steps in themselves, but from these reactions you can also infer the sizes of nuclei. It also led to the development of nuclear accelerators – so that you could induce all sorts of different nuclear reactions.”
Pass the bubbly
The anniversary of the Rutherford discovery is not the only big day being marked here at the Faculty of Science and Engineering this month. Monday (October 9th) was the 60th anniversary of the Lovell Telescope at Jodrell Bank.
The parabolic reflector radio telescope was the largest of its kind in the world when construction finished in 1957. It was also the only radio telescope capable of tracking the world’s first artificial satellite, Sputnik.
Today, the 3,200 tonne telescope is still busy gathering data from the depths of space. You can learn more about the landmark here.
And to learn more about the work of Rutherford, the University is opening the doors to his private research room for the first time next month. Book your place at this special exhibition here.
Words – Hayley Cox
Images – The University of Manchester & Billy and Lynn