At number 9 in The Guardian’s list of the 10 best physicists is Ernest Rutherford. Rutherford is on this list for two great achievements, discovering the atomic nucleus and understanding the process of radioactive decay.
Rutherford’s brief biography
Rutherford was born in 1871 in Brightwater, a town near the northern coast of the South Island of New Zealand. He did his undergraduate degree at Canterbury College in Christchurch, New Zealand. Then, in 1895, Rutherford obtained a scholarship to go to do postgraduate studies at the Cavendish Laboratories at Cambridge University, England. After three years at the Cavendish laboratories, In 1898 Rutherford left Cambridge to go to McGill University in Canada.
It was at McGill that he did his work on radioactive decay which won him the Nobel Prize for Chemistry in 1908. He was the sole recipient of the Chemistry prize in 1908, and was cited by the Swedish academy “”for his investigations into the disintegration of the elements, and the chemistry of radioactive substances”. Ironically, although considered to be a physicist, Rutherford never won a Nobel Prize in physics.
In 1907 Rutherford left McGill to take up a position as a Professor at Manchester University in England. It was whilst here that he discovered the atomic nucleus. In 1919 he left his position at Manchester University to take over as Director of the Cavendish Laboratories in Cambridge, a position that was held by J.J. Thomson, who had brought Rutherford from New Zealand back in 1895.
In 1899, the year after he arrived at McGill, Rutherford was able to separate radioactive decay into two distinct types, which he called decay. The following year a third type or radioactive emission was observed, and in 1903 Rutherford was able to show that this third type was a fundamentally new type of radiation which he called rays.
In 1902, Rutherford published with his colleague Frederick Soddy a paper entitled “Theory of Atomic Disintigreation”. Rutherford and Soddy were able ot show in this 1902 paper that radioactivity involved the spontaneous disintegration of atoms into other types of atoms. For this work, Rutherford was awarded the 1908 Nobel Prize in Chemistry (not Physics!). Soddy would win the Nobel prize for Chemistry in 1921.
Discovering the atomic nucleus
Rutherford left McGill in 1907 to take up a Professorship at Manchester University, England. In 1909 Geiger and Marsden, under Rutherford’s direction, did an experiment which led to the discovery of the atomic nucleus. I will talk more about this experiment and how it showed atoms have nuclei in a future blog, but to briefly summarise the experiment what they found was alpha-particles bouncing back from a thin gold foil.
This could not be explained by the plum pudding model of the atom that J.J. Thomson had proposed after Thomson had discovered the electron in 1897. Rutherford published in 1911 a paper explaining that the results of the Geiger-Marsden experiment fitted perfectly with a model of the atom that has the negatively charged and very low mass electrons orbiting a dense positively charged nucleus.
If one were to represent an atom by the size of a football stadium, the electrons would be buzzing around where the stadium stands are. The nucleus would be way down in the centre, and on this scale would be about the size of a grain or rice. Thus an atom, and hence everything, is nearly entirely empty space!
It was for these two paradigm-shifting discoveries about the properties of atoms that Rutherford gains his place in this “best 10 physicists” list. How do you rate his achievements? And, if Rutherford is in the list, shouldn’t Thomson, the discoverer of the electron, also be in the list?
You can read more about Ernest Rutherford and the other physicists in this “10 best” list in our book 10 Physicists Who Transformed Our Understanding of the Universe. Click here for more details and to read some reviews.