When Ernest Rutherford won the Nobel Prize for chemistry in 1908, he was not as ecstatic as you would expect someone to be after having won such a prestigious prize. In one letter, he wrote: “I must confess it was very unexpected and I am very startled at my metamorphosis into a chemist.”  Rutherford saw himself as a physicist, and indeed he is typically described as such in contemporary physics education. Rutherford’s potential disappointment at having not received the Prize for physics could be exemplified by him having once said that “all science is either physics or stamp-collecting”. This particular quote could be interpreted in two distinct ways: either Rutherford was remarking on the trivial nature of scientific fields such as chemistry and life sciences by referring to them as ‘stamp-collecting’; or he was suggesting that these sciences can actually be encapsulated within physics. While it may initially appear to be a one-dimensional opinion, the quote truly does make us contemplate what physics means as a science and how it distinguishes itself from other sciences.
So, what is physics? According to the novelty mug that a non-physicist friend of mine decided to gift me last year, it is “a branch of science mainly concerned with using incredibly long and complicated mathematical formulas to describe how a ball rolls”. This is of course wrong – physics actually uses incredibly long and complicated mathematical formulas to describe how multiple balls roll. In all seriousness however, the dictionary definitions of physics often describe it as the study of the nature of matter and energy. On the other hand, science is typically defined as the study of the nature and behaviour of the physical universe through systematic methodology (i.e. observations, experimentation, and measurement). If we adopt this definition of science as the criterion, then physics is irrefutably a science. Systematic methodology is what has enabled the development of physics throughout time. This is perhaps best demonstrated by the evolution of our understanding of light. We went from Newton’s idea of light being made up of ‘corpuscules’, to thinking that light propagates through a ‘luminiferous aether’, to now widely acknowledging wave-particle duality. Additionally, matter and energy arguably compose the greater part of the physical universe that science seeks to study. This has the implication that it may not be the case that physics is a science, but rather science is physics, as remarked by Rutherford.
However, if we do take physics to encompass all science, is there no validity in having fields like chemistry and biology be classed as sciences in their own right? Take chemistry as a specific example; the dictionary definition states that it is the study of the substances of which matter is composed. With physics being the study of matter, it could be suggested that chemistry is derived from it. If we then consider biology, the definition of which is the study of living organisms that are obviously composed of substances, we could suggest that biology is derived from chemistry (and thus physics). Physics would appear to be the most fundamental of the sciences; but just like how it is tedious to look at first principles to solve every single problem, it would surely also be tedious to have a purely physical view of sciences. Furthermore, while other sciences are essentially the same as physics in the sense that they use a systematic methodology to approach their subject matter, their methodology does still differ greatly – and this has yielded more progress than if everything was approached with a physicist’s lens.
Though not directly referred to in the quote, I cannot help but wonder what role mathematics would play in Rutherford’s science ‘hierarchy’. It is a truth universally acknowledged that every physicist (at least at Imperial) has come across one mathematician that has called physics ‘applied maths’. Admittedly, there is some truth to this – without mathematics, physics would be reduced to qualitative observations that cannot be evidenced in a particularly logical manner. However, I do not believe that physics can be considered a ‘specialisation’ of mathematics, as this would imply that the very foundations of physics are derived from it. We can recall that as a science, physics relies on systematic methodology – mathematics only frames part of this methodology alongside observation and experimentation. It can instead be thought of as the language through which physics is spoken; it is a means of communication rather than the subject from which physics is derived. Therefore, if Rutherford were a mathematician rather than a physicist, it would appear quite unlikely that he would call physics ‘stamp-collecting’… unless he really did just want to insult subjects that were not his own.
It is undeniable that physics is a very far-reaching and significant subject, though I would argue that this does not reduce every other scientific field to be as trivial as ‘stamp-collecting’. Just as a mathematician cannot consider physics to be at all trivial, no physicist can neglect the impact that sciences such as chemistry and biology have in our general pursuit of knowledge. Therefore, if Rutherford did mean to insult sciences that are not physics by saying “all science is either physics or stamp-collecting”, he would be very wrong indeed. On the other hand, if Rutherford was actually suggesting that all sciences are encompassed by physics, he may not be entirely wrong. It would appear that physics plays a fundamental role in subjects like chemistry and biology, and this has arguably become more apparent through the fact that the sciences have become increasingly interdisciplinary over the past few decades. Nevertheless, the classification of sciences is not a particular disadvantage when so much progress has been made in so many fields because of specialisation. Rutherford may have been a physicist; but being called a chemist is certainly not the insult he may have perceived it to be.
 Rutherford in a correspondence to a former student at McGill University, 1908. (Dardo, Mauro. Nobel Laureates and Twentieth-Century Physics. Cambridge, England: Cambridge University Press, 2004, page 69).