The Stumbling Progress of 20th Century Science – How Crises and Great Minds Have Shaped Our Modern World

(Preface and afterword to Lars Jaeger’s new book about the revolutionary events in all sciences in the period from ca. 1880 to ca. 1950; https://link.springer.com/book/10.1007/978-3-031-09618-1)

By the end of the 19th century, almost all scientists were convinced that they had thoroughly understood the laws of nature, and thus everything about the very essence and depth of the world. Newton’s laws were regarded as an eternally valid world formula, and the recent findings in the fields of magnetism and electrodynamics seemed to round the picture off beautifully. With this attitude it happened that, when the young Max Planck asked one of his teachers in the 1870s whether he should study physics, he was given the answer that there was not much more to discover in the field. Fortunately, Planck did not listen to this advice.

Knowledge that had been so painstakingly gained and was believed to be certain proved in the end to be unexpectedly volatile. What earlier generations of researchers believed to be absolutely true is, in the vast majority of cases, no longer true for us today. Scientists have learned this lesson. Today they explicitly assume that knowledge can only ever be temporarily correct. What is valid today can turn out to be wrong at any time.

This turn away from eternal claims to truth began at the end of the 19th century and triggered a comprehensive crisis in the sciences. In the eighty years from 1870 to 1950, a period that is a blink of an eye in the history of humankind and covers not even an average human lifetime, there was what is probably the greatest revolution in thinking of all time. It was far more significant than the paradigm shifts of the Renaissance and the Enlightenment (even if one hears little about it in school history books). This crisis in the sciences was accompanied by two world wars, the downfall of traditional social orders, and a reorganization of the world.

Where suffering is great, salvation is not far away. From the end of the 19th century and in the first half of the 20th century, a number of scientific geniuses of breath-taking creativity where at work, ultimately leading the sciences out of this crisis. This book describes their contributions and follows science on its exciting and bizarre journey into the modern age. Along the way, we shall meet, among others, the mathematical and physical genius of James Clerk Maxwell, the intellectual giants Georg Cantor and Ludwig Boltzmann, engaged in serious psychological struggles, Charles Darwin, who was so moved by questions of faith as well as science, the reluctant revolutionary Max Planck, the Swiss revolutionary Albert Einstein, numerous ingenious and youthful physicists gathered around Niels Bohr, who overturned the world of physics for good at the age of not much more than 20, and last but not least the mathematical geniuses John von Neumann, Kurt Gödel, Alan Turing, and Emmy Noether, whose revolutionary thinking would not even stop at the basic principles of logic.

This book is divided into two parts. Chapters one to five describe a first phase that can be roughly associated with the period between 1870 and 1925, in which developments took place almost simultaneously in physics, mathematics, biology, and even psychology that led to the deepest crises in those disciplines. Chapters six to twelve discuss those same sciences in the subsequent years up to 1950, which brought about the transition to modernity. This period also marks the decisive turn from a science oriented towards theory and philosophy to its present more practical and application-oriented approach.

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To this day, the Church has not recovered from the turning point of the Enlightenment and the subsequent decline of its interpretive sovereignty. However, the fact that modern science was also led to the edge of the abyss by a deep crisis, but retook control within a few decades, is hardly known. Around 1900, scientists had reached their limits, because at that time, in order to progress further, they had to leave the realm of the immediately visible. Within a very short period of time, many of the certainties they had hitherto believed to be unquestionable collapsed. Only with the help of a fifth virtue were they able to enter completely new territory and thus overcome this crisis: intuitive genius.

This brought the necessary creativity into play without betraying sober rationality. The history of science over the past 150 years shows that, just as a great leap in knowledge is about to be taken, there are almost always intuitive, sometimes even irrational ideas put forward by individual scientists. It can thus be understood as a dialectical process between occasional outbursts of genius and constant, soberly rational diligence in thinking and observing. In this way, intuitive genius became a particularly strong driver for the decisive breakthroughs of the 20th century.

The path of science from dogma and superstition to rational thinking and empirical research has been and still is long and arduous. All the more valuable is the realization that the search for knowledge never ends. This was a (new) scientific characteristic recognized by the philosopher Karl Popper: Popper argued in the 1920s that logically no scientific theory can be confirmed once and for all from an experimental test, whereas a single experimental counterexample can logically disprove it. Popper’s presentation of the logical asymmetry between verifiability and falsifiability is at the heart of his theory of science, which is still known today. De facto, according to him, a theory can only be considered scientific if it is (potentially) falsifiable. This is also a revolutionary move within the sciences themselves, since until the late 19th century the opinion of physicists had been that theories, once confirmed and consistent, were valid forever.

Many scientific laypeople, on the other hand, wish for immutable truths. At a time when populists abuse this longing for their own purposes, when an irrational criticism of science is on its way to becoming socially acceptable, and when doubts about it are being presented ever more aggressively, we must consistently ensure that the voice of rationality remains clearly heard.