Heroes of Science: Max Planck

If you had to choose two scientists of the 20th century whose work most affected its course and discoveries, the first would no doubt be Albert Einstein, but the second could be Max Planck. Einstein’s theory of relativity revolutionised how humans perceived and understood space and time, while theoretical physicist Planck’s development of quantum theory, with his  probing work into atomic and subatomic processes, radically transformed how physics was understood and directly led to many other discoveries and inventions that still have a widespread impact today. Easily Max Planck’s most important discovery was his realisation that the energy of electromagnetic waves is contained within indivisible ‘quanta’ packets that have to be radiated or absorbed as a whole. This is commonly referred to as Planck’s black-body radiation law and, as can be seen in detail within ‘The big idea’ explanation below, it is both simple and incredibly enlightening. However, when Planck delivered his research for the first time in 1900, it was anything but, with its suggestions seemingly conflicting directly with all of classical physics. Indeed, even Planck himself did not fully believe his
law was correct, only reluctantly deducing it through a cold sense of logic. His remarkable discovery was not recognised either by the existing scientific establishment, with recognition only coming after Einstein himself adopted the idea of quanta and later introduced the follow-on theory of wave- particle duality in 1909. Following this, Planck was suddenly seen as the genius he had always been and became one of the most prominent scientists of the early-20th century, attending among numerous others, the celebrated Solvay Conference in Brussels in 1911. Indeed, famously it was due to Planck’s input at the conference that Henri Poincaré – the most famous mathematical physicist of the 19th century – could provide mathematical proof that Planck’s radiation law required the existence of quanta and, as a knock-on effect, converted many of Europe’s top scientists to this new quantum theory. And so quantum theory was born, and over the following decades it was built upon and expanded by some of the most well-known scientists of all time. From Einstein to Niels Bohr, Erwin Schrödinger to Paul Dirac, Planck – as the father of quantum theory – had given them an entirely new way to look at and understand the processes of the physical world – one which they would go on to explore in much more detail through the nuclear age.