Even to the scientists doing these experiments, it wasn’t obvious whether they were unimportant curiosities or a path to something deeper. Today, with the benefit of more than a century of hindsight, they look like epochal experiments, early hints of a new fundamental force of nature.

But even though it can be hard to assess the significance of scientific work, it’s necessary to make such assessments. We need these assessments to award science prizes, and to decide which scientists should be hired or receive grants. In each case, the standard approach is to ask independent scientists for their opinion of the work in question. This approach isn’t perfect, but it’s the best system we have.

With that in mind, we ran a survey asking scientists to compare Nobel Prize–winning discoveries in their fields. We then used those rankings to determine how scientists think the quality of Nobel Prize–winning discoveries has changed over the decades.

As a sample survey question, we might ask a physicist which was a more important contribution to scientific understanding: the discovery of the neutron (the particle that makes up roughly half the ordinary matter in the universe) or the discovery of the cosmic-microwave-background radiation (the afterglow of the Big Bang). Think of the survey as a round-robin tournament, competitively matching discoveries against each other, with expert scientists judging which is better.

For the physics prize, we surveyed 93 physicists from the world’s top academic physics departments (according to the Shanghai Rankings of World Universities), and they judged 1,370 pairs of discoveries. The bars in the figure below show the scores for each decade. A decade’s score is the likelihood that a discovery from that decade was judged as more important than discoveries from other decades. Note that work is attributed to the year in which the discovery was made, not when the subsequent prize was awarded.

The first decade has a poor showing. In that decade, the Nobel Committee was still figuring out exactly what the prize was for. There was, for instance, a prize for a better way of illuminating lighthouses and buoys at sea. That’s good news if you’re on a ship, but it scored poorly with modern physicists. But by the 1910s, the prizes were mostly awarded for things that accord with the modern conception of physics.

A golden age of physics followed, from the 1910s through the 1930s. This was the time of the invention of quantum mechanics, one of the greatest scientific discoveries of all time, a discovery that radically changed our understanding of reality. It also saw several other revolutions: the invention of X-ray crystallography, which let us probe the atomic world; the discovery of the neutron and of antimatter; and the discovery of many fundamental facts about radioactivity and the nuclear forces. It was one of the great periods in the history of science.