Gravitational waves and the slowness of scientific revolutions

LIGO's detection of gravitational waves occurs almost exactly a century after Einstein formulated his general theory of relativity. relativity and a paper that mathematically describe the possibility of gravitational waves. Or at least that is the story as it was presented to the public (including by yours). And in a way, it is even true.

But the reality of how relativity has progressed to the point where people have accepted that gravitational waves exist and could be detected is considerably more complicated than the simple story described above. In this week's Astronomy of Nature a group of science historians is exposing all the details of how we went from the dawn of relativity to the construction of LIGO . And, in the process, historians show that ideas about scientific revolutions leading to sudden and radical change can sometimes miss the point.

Has your paradigm changed?

The popular conception of scientific revolutions (as far as exists) was shaped by Thomas Kuhn. Kuhn described a process in which data gradually pushes an existing theory to the crisis, allowing almost everyone to see that it does not work. After a period of crisis, a revolution takes place and a new theory emerges. The ability of the theory to solve all the problems that precipitated the crisis quickly attracted attention, and a new period of Kuhn's theory, "paradigm-based" science, begins.

At one level, this fits well with the history of relativity. Einstein's proposals created a new paradigm of curved space-time, and they solved a number of problems with Newtonian gravity and quickly garnered experimental support and acceptance. And less than a year has passed before Einstein publishes an article using the new paradigm to produce gravitational waves. The paper was wrong, but he published a more correct version a few years later. The revolution that paved the way for discovery a century later was complete

But historians (Alexander Blum, Roberto Lalli and Jürgen Renn) would like to rain on this particular paradigmatic parade. And they do this by focusing on the consequences of Einstein's formulation of general relativity

(It is worth noting that the conclusion also does not support a Kuhn-like model of revolution. that problems had appeared, and that there was no clear crisis period even after Einstein had invented a special relativity: general relativity solved only the problem that Einstein he himself had created by introducing special relativity.) [19659004] Making the Wave

For starters, gravitational waves did not emerge clearly from Einstein's work on them. Einstein does not seem to have seriously contemplated their existence until Karl Schwarzschild (Ray's fame) invites him there. His first article on them contained a mathematical error, and his corrected version only worked if the waves propagated along a cylinder. Although this document serves as a basis for claims that Einstein predicted the existence of gravitational waves, it was clearly an approximate solution in a simplified environment.

And that's where Einstein left him. His attention has shifted to try to unify his version of gravity with electromagnetism. There was not really a community to tackle the problem at the time, as quantum mechanics was gaining momentum, and a world war was disrupting the scientific community and recentring it. on applied physics. According to historians, most of the work in relativity that took place during this period was focused on the translation of existing and well-described physical systems from Newtonian mechanics to relativity. It was much less about trying to determine what unique relativity brought about the Universe.

The lack of a strong understanding of what relativity meant also magnified problems like Einstein's mathematical error. When mathematics produced absurd things like singularities, we did not really know what that was telling us. Did not these mathematical abstractions have any basis in reality? Would another mathematical approach produce a reasonable solution? Or was relativity simply limited in what it could describe successfully? In the absence of a solid understanding of the theory, it might be difficult to say which one was most likely.

Thus, while gravitational waves could come out of the right equation, there was little point in determining whether they had to exist, let alone how we could detect them.

Breakout

How did the field emerge from these marasmes? The 1950s saw strong government support for physics as a result of its success during the war, which broadened the research community. In addition, it became increasingly clear that gravitational effects would be needed to understand our expanding data body describing the Universe and its evolution.

The relativity community is also committed to the growing internationalization of science. the entire field. A consensus emerged from the growing community: the remaining physical problems with relativity had to be solved if an individual research group had to trust the work they were doing. Working on the problems of relativity was also considered a necessary condition to unify with quantum mechanics, a problem on which people were interested.

The existence of gravitational waves was one of those problems and was beginning to attract attention. A major breakthrough came at a conference where researchers (including Richard Feynman) recognized how the energy contained in gravitational waves could be exchanged with forms of energy better understood in the rest of the world. l & # 39; universe. Another researcher has discovered how to take mathematics that could describe electromagnetic waves and modify them to describe gravitational waves. The resulting mathematical structure has been the genesis of the idea that gravitational waves are ripples in space-time, a perspective that has survived the present.

Revolting

These advances and other areas of relativity give it a solid theoretical basis. . Blum, Lalli and Renn argue that when general relativity was first introduced, people thought in terms of the consequences of relativity for other theories that they used to understand the universe. In the early 1960s, historians argue that relativity could be perceived as having direct consequences on the behavior of the Universe – no other theory needed. This paved the way for a belief that gravitational waves, as a necessary consequence of the theory, had to have a physical manifestation.

This understanding was also needed to build the models that told us what the gravitational waves would look like, based on the events that created them. These allow to draw real events from the noise as soon as we have a detector like LIGO with enough sensitivity to pick them up.

This 40-year process does not fit well with the revolutions described by Kuhn. There was no crisis and no period of frantic search as people scrambled to produce a new theory that could resolve apparent contradictions in failure. But historians say that there is one thing here that Kuhn was right: people who live in a relativistic world have a fundamentally different view of the Universe and would have trouble communicating their point of view to someone else. One in the Newtonian world.

a language problem; Old terms have taken on new meanings under the new paradigm. But historians seem to suggest that a change of perspective is necessary for any scientific progress. Unless people can inhabit the reality of a new theory and appreciate all its consequences, it is difficult for them to sufficiently solve the implications of the theory for making predictions – the language changes are only sub- products ] 2018. DOI: 10.1038 / s41550-018-0472-6 (About DOIs).