Earlier, we noted that Eric Holloway argues for the new quantum mechanics find about particles influencing each other via time travel can be understood as showing that there is purpose in nature and a mind behind it. Here’s the open-access paper.

Our physics color commentator Rob Sheldon offers some thoughts on how to understand the quantum world and what the researchers are doing:

Mathematically, all QM experimentalists are agreed on the results. Where the disagreement lies is in the interpretation of the results.

QM State A and State B can be “entangled” in a “superposition” so that both precede the other. Does this violate causality? Not really, because causality is not a measurement you can make on state A and B. And if you can’t give me a Hermitian operator called “causality”, I can’t measure it, and what I cannot measure, I cannot describe.

So what is all this talk about QM violating causality?

It has to do with using a macroscopic word, “causality”, to describe the outcome of a microscopic QM measurement–it is a judgement, a translation, an inference. And like many of the inferences we make about QM, it is incomplete, contradictory, and subject to dispute. Once again, we are all agreed about the math, what we are not agreed upon is the English.

That’s because QM is all about microstates and their measurement, but not about macroscopic properties that you and I normally associate with everyday objects–smoothness, ripeness, tools like “hammer and nail” or biology like “chicken and egg”. So indeed we can entangle QM microstates, but can’t entangle chickens and eggs, and therefore using those terms creates a semantic muddle.

Let me try to explain this from the macroscopic side. In thermodynamics, we distinguish between “reversible” and “irreversible” processes. In a reversible process, such as bouncing two repelling magnets off each other, or two ideal billiard balls, the energy and momentum before the collision are identical to that afterwards. In an irreversible process, like bouncing two Toyota Camry’s in the fast lane, energy and momentum are lost in the process, turning into irreversible heat and metal strain. If we make a video of the two collisions, the billiard ball collision looks normal both forward and backward, whereas it is obvious in the Toyota collision which one is backward. What makes it obvious is the increase in disorder, or entropy, in the irreversible collision. Thermodynamics generalizes this common sense, by saying that given a video of unknown creation, the “arrow of time” is the direction in which entropy is increasing.

Okay, lets apply that to QM. Causality says there is an “arrow of time”, A–>B. How can QM destroy that?

Only by modelling a “reversible” system in which the entropy never changes so that B–>A, or A=B. In a rather direct sense, only “reversible” systems can be put into an entangled superposition in the first place, because changing energy forces changing time, (or conversely, changing time forces changing energy). That’s the definition of the Schrodinger equation–a time derivative on one side and an energy on the other. But if the entropy never changes, then in some concrete sense, the system doesn’t “age”, it always possesses its initial energy and momentum and information, which is to say, it doesn’t show causality in the first place, and we need a different word to describe that system.

Well, there’s a good reason these debates are endless, but I did my best…

Rob Sheldon is also the author of *Genesis: The Long Ascent* and * The Long Ascent, Volume II *.

*See also:* Eric Holloway: Quantum mechanics shows that our universe has purpose. He argues that a recent study shows that not only can two physically separated particles influence each other, they can influence each other through time and that it identifies a Mind behind the universe.