Scientific consensus is hard to come by for many of physics’ hardest problems
The largest-ever survey of physicists from around the world – released today – shows a distinct lack of consensus across many of physics’ most important questions, from the nature of black holes and dark matter, to the still-incomplete unification of Einstein’s theory of gravity with quantum mechanics.
Even the best theory of the universe’s expansion, known as the standard model of cosmology or ΛCDM (Lambda Cold Dark Matter), did not attain majority support. This surprising outcome is perhaps due to results from the Dark Energy Spectroscopic Instrument (DESI) last year, which hinted that dark energy may change over time, in opposition to the standard model’s conviction that dark energy remains constant.
But that wasn’t the only surprising outcome. The survey doesn’t seem to find much agreement anywhere.
“The most striking result is how few of the ‘standard answers’ in fundamental physics command overwhelming support, with most falling short of a majority. The interesting point is not that physicists are confused. It is that the frontier is genuinely alive,” says Niayesh Afshordi, associate faculty member at Perimeter Institute and professor at the University of Waterloo.
Afshordi led the study in collaboration with coauthor Phil Harper and the American Physical Society’s Physics Magazine.
Majority consensus was achieved only on two points. First, contrary to most popular public understandings of the Big Bang, 68% of physicists agree that the Big Bang does not necessarily mark the beginning of time. Instead, it’s a theory that describes the evolution of the universe from a hot, dense state, and does not speak to time itself. Second, physicist narrowly agree (51%) that the early universe underwent a rapid period of expansion known as inflation.
Afshordi and Halper were joined by physicists Sean Carroll and Ghazal Geshnizjani to discuss the results of the new survey.
On other questions, consensus was much weaker. The leading explanation for dark matter, for example, suggests that it is neither a yet-undiscovered low mass particle or particles (17%), nor a modification to the theory of gravity (12%), but rather some combination of the many proposed solutions (21%).
The most likely solution to the problem of quantum gravity, meanwhile, remains string theory, but only 19% of physicists hold that view, with tough competition from both loop quantum gravity (12%) and the belief that gravity cannot be quantized at all (18%).
With all this disagreement, what does this survey actually mean for the future of physics? Afshordi is optimistic.
“Scientific truth is not decided by a vote. But consensus, or its absence, tells us where the evidence feels settled and where researchers still see room for radically different ideas. In this sense, lack of consensus can be a clue. It marks places where better data, sharper theory, or new connections between subfields may be needed. In the eternal words of the Canadian singer and songwriter, Leonard Cohen: ‘There is a crack in everything, that’s how the light gets in.’”
The results of the survey are outlined in an article today in Physics Magazine, and you can play with the results yourself on the survey’s online dashboard.
