IT'S ALL JUST PHILOSOPHY:

Bohr announced that resolving the wave-particle paradox required a new view of reality, in which both notions shared a role in explaining experimental phenomena. In experiments designed to observe waves, waves you would find, whether electrons or light. In experiments designed to detect particles, you'd see particles. But in no experiment could you demonstrate both at once. Bohr called this viewpoint the principle of complementarity, and it successfully guided the pursuit of quantum mechanics during the following decades.

More recently, as philosopher Slobodan Perović recounts in From Data to Quanta, Bohr's success has been questioned by some physicists and philosophers and even popular science writers (SN: 1/19/19, p. 26). Complementarity has been derided as an incoherent application of vague philosophy expressed in incomprehensible language. But as Perović's investigations reveal, such criticisms are rarely rooted in any deep understanding of Bohr's methods. Rather than Bohr's philosophy contaminating his science, Perović argues, it is his opponents' philosophical prejudices that have led to misstatements, misunderstandings and misrepresentations of Bohr's physics. 

[Q]uantum theory's success forces physicists to accept a number of uncomfortable truths. For example, it allows "spooky action at a distance" between entangled particles. This occurs when two particles become so deeply linked that a measurement on one instantly determines the state of the other, regardless of the distance between them.

Since then, physicists have studied spooky-action-at-a-distance in detail; it is straightforward to observe in a quantum optics laboratory. It is now even exploited in technologies such as quantum cryptography.

Another uncomfortable conclusion is that the quantum universe is governed by probabilistic behavior. At any instant, lots of different things could happen but the thing that actually happens is determined by probability, essentially on the roll of a dice.

This thinking forces physicists to the conclusion that our deterministic experience of the universe is an illusion. Indeed, there is little debate among physicists that the foundation of reality is fundamentally and weirdly probabilistic.

Except among a small group of theoretical physicists led by the Nobel Prize winner, Gerard 't Hooft. For them, the idea of determinism - that one thing leads to another - is sacrosanct. They say the probabilistic properties of quantum mechanics can all be explained by a set of hidden laws that sit beneath the surface of quantum mechanics.

Nobody has observed these laws at work but that hasn't stopped 't Hooft from trying to formulate what they must look like. 

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