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Gravitational waves and the slow pace of scientific revolutions



Enlarge / For years people were not sure if the gravitational wave was a necessary product of the Theory of Relativity.

LIGO's detection of gravitational waves came almost exactly a century after Einstein's general theory of relativity and a subsequent work that mathematically describes the possibility of gravitational waves. At least that's the story of how it was presented to the public (including mine). And in some ways it's even true.

But the reality of how relativity has advanced to the point at which humans have assumed that gravitational waves are likely to exist and possibly be discovered is much more complicated than the simple narrative described above. This week Nature Astronomy details a group of science historians, from the beginning of relativity to the construction of LIGO. And historians show that ideas about scientific revolutions that bring about sudden, radical change sometimes lose their meaning.

Has your paradigm moved?

The popular view of scientific revolutions (as far as it exists) was coined by Thomas Kuhn. Kuhn described a process in which data gradually drives an existing theory into crisis, so that almost everyone can see that it does not work. After a time of crisis, a revolution takes place and a new theory emerges. The theory's ability to solve all the problems that triggered the crisis is quickly gaining support, and a new phase of the theory-driven Kuhn language, "paradigm-driven," is beginning.

On a certain level, this fits well with the history of relativity. Einstein's proposals have created a new paradigm of curved space-time, and they have solved a number of problems with Newtonian gravity, and have quickly received experimental support and acceptance. And less than a year passed before Einstein published a paper using the new paradigm for generating gravitational waves. The paper was wrong, but he published a more correct version a few years later. The revolution, which made discovery possible a century later, was completed.

But the historians (Alexander Blum, Roberto Lalli and Jürgen Renn) would like to protest about this paradigmatic parade. And they do so by focusing on the consequences of Einstein's formulation of the General Theory of Relativity.

(It is worth noting that the introduction does not support a Kuhn-like model of the revolution, people happily worked in the Newtonian framework even after problems arose with it and there was no clear period of crisis, even after Einstein developed a special theory of relativity: In some ways, the general relativity theory solved only a problem that Einstein himself had created by the introduction of the special theory of relativity] Do the wave

First of all, the gravitational waves did not emerge from Einstein's work He was asked by Karl Schwarzschild (of Radius Fame), his first work on them contained a mathematical error, and his corrected version worked only when the waves spread along a cylinder, while this paper serves as a basis for allegations that Einstein's Existence from gravitational waves, it was clearly an approximate solution in a simplified environment.

And that's where Einstein left it. His attention shifted to combining his version of gravity with electromagnetism. There was not really a community that grasped the subject at the time quantum mechanics was gaining momentum, and a World War interrupted the scientific community and redirected it to applied physics. According to historians, most of the relativity theory that took place during this period focused on the translation of existing, well-described physical systems from Newtonian mechanics into the Theory of Relativity. Less attention was paid to finding out which unique insights provided relativity theory about the universe.

The lack of a strong understanding of what relativism means also compounded problems like Einstein's mathematical errors. If math produced nonsensical things like singularities, it was not clear what that meant to us. Did not these mathematical abstractions have any foundation in reality? Would another mathematical approach provide a reasonable solution? Or was relativity simply limited in what she could successfully describe? In the absence of a robust understanding of the theory, it might be hard to say which of them was most likely.

So, while gravitational waves could come out of the right equation, there was not much interest in determining if they necessarily existed, let alone how we could discover them.

Outbreak

How did the field break out of this slack? The 1

950s saw strong government support for physics as a result of their successes during the war, which expanded the community of researchers. In addition, it has become increasingly clear that gravitational effects are needed to understand our growing body of data describing the universe and its evolution.

The theory of relativity also maintained the increasing internationalization of science and organized annual conferences for the entire field. Consensus emerged from the growing community: the remaining physical problems with the theory of relativity had to be worked out if a single research group had confidence in the work it did. The development of relativity problems was also considered as a necessary prerequisite for standardization with quantum mechanics, a problem that people were interested in working on.

The existence of gravitational waves was one of those problems and so it began to attract attention. An important breakthrough came at a conference where researchers (including Richard Feynman) recognized how the energy contained in gravitational waves can be replaced by better understood forms of energy in the rest of the universe. Another researcher discovered how to take mathematics that can describe electromagnetic waves and modify them to describe gravitational waves. The resulting mathematical structure was the genesis of the view that gravitational waves are waves in space-time, a perspective that has survived to this day.

Shaking Up

These and advances in other areas of relativity put them on a solid theoretical foundation. Blum, Lalli and Renn argue that back then, when the general theory of relativity was first introduced, people thought the consequences of relativity theory for the other theories they used to understand the universe. In the early sixties, historians argue, relativity could be seen as a direct impact on the behavior of the universe – no other theory is needed. This was the precondition for the belief that gravitational waves, as a necessary consequence of the theory, must have some physical manifestation.

This understanding was also needed to build models that told us how gravitational waves should look like the events that caused them. These let us remove real events from the noise as soon as we have a detector like LIGO with sufficient sensitivity to pick it up.

This 40-year trial does not go well with the revolutions described by Kuhn. There was no crisis and no period of frantic research as people tried to develop a new theory that could resolve apparent contradictions in the failed one. But historians argue that Kuhn is right: people who inhabit a relativistic world have a fundamentally different view of the universe and have difficulty sharing their perspective with someone in the Newtonian world.

Kuhn regarded this as fundamentally a language problem; Old terms got new meanings under the new paradigm. But historians seem to point out that the change of perspective is necessary for any kind of scientific progress. If people are unable to grasp the reality of a new theory and appreciate all its consequences, it is difficult for them to solve the implications of the theory sufficiently to make predictions – language changes are just a byproduct , Nature Astronomy 2018. DOI: 10.1038 / s41550-018-0472-6 (About DOIs).


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