August 2025
Physicists disagree widely about what quantum theory means in the real world, according to a Nature survey. The view that quantum physics only reveals knowledge about the world, rather than actually representing physical reality, seems to have gained ground.
Schrödinger’s cat: both dead and alive? ILLUSTRATION: Gerald / Pixabay
The scientific journal Nature has surveyed more than 1,000 physicists about their views on what quantum mechanics (QM) means in the physical world. Interestingly, the physicists are in significant disagreement, despite the fact that QM has been around for a century (in fact, July 2025 marked its 100th anniversary).
The result may be an indication that mainstream physics still struggles to align with the elusive, almost nonphysical character of quantum reality.
The Copenhagen interpretation, entailing for example that a particle’s properties are not determined until observed, is broadly taught and almost viewed as standard. This interpretation was unsurprisingly held by the largest cohort of respondents in the survey, but still only by slightly more than a third – and half of those were unsure. Seventeen percent adhered to ‘epistemic explanations’, fifteen percent to the ‘many worlds’ interpretation and seven percent to David Bohm’s ‘pilot wave’ model.
The survey also asked whether there is a boundary between classical objects and quantum objects. The response was an even split between ‘yes’ and ‘no’, with ten percent undecided.
Regarding the famous double-slit experiment, a cornerstone of quantum theory, the physicists were asked whether they thought the electron passes through both slits when unobserved. The answer ‘The question is meaningless when asked about a quantum object’ was the most popular, chosen by almost half of respondents. Thirty-one percent answered ‘yes’, fourteen percent ‘no’ and six percent were ‘not sure’.
QM is probably the most successful theory in scientific history and has made much of the modern world possible. But there is a huge rift between applying the knowledge of how the quantum world works and understanding why. Physicist Nathaniel David Mermin coined the phrase “shut up and calculate”, which summarizes how QM largely has been approached in the last hundred years: to solve problems without delving into underlying philosophical interpretations. But the “why” won’t go away, of course.
According to the Nature article, which was also published with permission in Scientific American, there is a clear divide between researchers with a ‘realist’ view and those with an ‘epistemic’ view. The latter entails that quantum physics is concerned only with knowledge and information about the world, not necessarily with the actual world we experience. The ‘epistemic’ descriptions seem to have increased in popularity, judging by the results of a similar survey in 2016.
“How is it possible to disagree so strongly about the underlying world that quantum theory describes, when everyone does the same calculations?” Nature wonders. There are apparently different ways of viewing this divide. Carlton Caves, a theoretical physicist at the University of New Mexico, feels it is “embarrassing that we don’t have a story to tell people about what reality is”. Elise Crull, a philosopher of physics at the City University in New York, disagrees. People are taking the question of interpretations seriously, she points out, “and it’s not leading to chaos and it’s not embarrassing. It’s leading to progress, to creativity. There’s a kind of joy there.”
Nature sent the survey to around 15,000 physicists, and 1,100 responded.
Anders Bolling
