Ernest Marsden(1889 — 1970)
Ernest Marsden
Royaume-Uni
6 min read
English–New Zealand physicist and collaborator of Ernest Rutherford. In 1909, together with Hans Geiger, he carried out the famous experiment scattering alpha particles off a gold foil, which revealed the existence of the atomic nucleus.
Frequently asked questions
Key Facts
- Born in 1889 in Manchester (England), died in 1970 in Wellington (New Zealand)
- Carried out the Geiger–Marsden experiment (alpha particle scattering) in 1909 under Rutherford's direction
- This experiment enabled Rutherford to formulate his model of the atom with a central nucleus in 1911
- Appointed professor of physics in Wellington (New Zealand) in 1915
- Played a major role in organizing scientific research in New Zealand
Works & Achievements
The observation of the unexpected bounce-back of alpha particles off a sheet of gold foil. This is the foundational experiment that revealed the existence of the atomic nucleus.
A paper co-authored with Geiger reporting the measurements of the particles' rebound. It provided the data that pushed Rutherford to rethink the atom.
The application of physics to locating enemy artillery by the sound of its fire. Marsden put his scientific skills at the service of the army.
Marsden built up New Zealand's scientific institutions and shaped their programmes. His name is today attached to a major national research fund.
The direction of wartime scientific work, notably the development of radar in New Zealand. He applied science to the defence of the country.
Anecdotes
In 1909, Ernest Marsden was only in his early twenties and still a student when Rutherford gave him a seemingly trivial task: to check whether alpha particles could bounce backward when striking a thin sheet of gold. To his great surprise, about one particle in 8,000 came back, a result no one expected.
Rutherford later summed up his amazement with a phrase that became famous: it was "almost as incredible as if you fired a 15-inch shell at a piece of tissue paper and it came back and hit you." This impossible rebound revealed that the atom contained a tiny, hard, concentrated nucleus.
The accepted model of the atom at the time, Thomson's so-called "plum pudding" model, imagined the positive charge spread throughout the whole atom. The experiment by Marsden and Geiger shattered it: it forced scientists to invent the atomic nucleus, the foundation of all modern nuclear physics.
After his career as a researcher, Marsden emigrated to New Zealand, the home country of his mentor Rutherford. There he became a professor and then a great organizer of New Zealand science, and was knighted, becoming Sir Ernest Marsden.
During the First World War, Marsden served as an officer and worked on "sound ranging," a technique for locating enemy guns by the noise of their fire — proof that his rigor as a physicist also served on the battlefield.
Primary Sources
It seems surprising that some of the alpha particles, as the experiment shows, can be turned back through a single collision with an atom.
The scattering of charged particles through large angles is explained by assuming that the atom contains a central charge concentrated within a very small volume.
It was the most incredible event that has ever happened to me in my life. It was almost as incredible as if you fired a 15-inch shell at a piece of tissue paper and it came back and hit you.
Key Places
Industrial village in northern England where Ernest Marsden was born in 1889. This is where the journey began for a son of textile country who became a physicist.
Physics laboratory led by Rutherford where Marsden, as a student, carried out the gold foil experiment with Geiger in 1909. Birthplace of the discovery of the atomic nucleus.
Institution where Marsden was appointed professor of physics in 1915. There he continued teaching and research after leaving England.
New Zealand capital where Marsden organized the country's national scientific research and where he died in 1970. A large part of his career as a science administrator unfolded here.
