“In fact, QFT[Quantum Field Theory] is constructed in such a way to explicitly preserve causality. Any QFT textbook devotes 10 pages of chapter 1 to explain why the square root of the Klein gordon equation does not make a good wave equation for a QFT – it cannot preserve causality.”
In physics, we speak of things happening based on mathematical laws. For example, two electrons are repulsed by the electromagnetic force and we can compute their path of motion. There seems to be a clear causal connection because the math is fully deterministic. In QM, the only difference is that the math is probabilistic rather than exact. No one is even sure that QM is indeterministic – Bohm’s interpretation might be right. Even if QM is non-deterministic, is it appropriate to say that things are happening without causes? We can use the Schrödinger/Dirac equation to make quite accurate probabilistic computations concerning the evolution of a system. We may not know when a particular radioactive atom will decay but we can use statistically large sets of atoms to accurately perform radiometric dating.
To be sure, there is a lot of controversy over how to interpret causation in QM (e.g., does the observer play a role?) but I don’t think QM really does away with the causal principle in the sense relied upon by the Kalam. The Kalam relies only on there being underlying reasons for things coming into being. If something happens in a manner that can be probabilistically predicted (as is always the case in QM), then it’s not a case of something being created without a cause from absolutely nothing. Things originating without causes could not be predicted even probabilistically!
Here is philosopher/Physicist David Albert on how Quantum Mechanics doesn’t explain the origin of the Universe from absolutely nothing: “The fact that some arrangements of fields happen to correspond to the existence of particles and some don’t is not a whit more mysterious than the fact that some of the possible arrangements of my fingers happen to correspond to the existence of a fist and some don’t. And the fact that particles can pop in and out of existence, over time, as those fields rearrange themselves, is not a whit more mysterious than the fact that fists can pop in and out of existence, over time, as my fingers rearrange themselves. And none of these poppings — if you look at them aright — amount to anything even remotely in the neighborhood of a creation from nothing.”
The Borde-Vilenkin-Guth theorem that I referenced in the previous blog indicates that spacetime cannot be extended into the infinite past. QM operates within spacetime so if spacetime is not eternal it is unreasonable to claim that quantum processes have been eternally in operation. Some physicists do speak of highly speculative theories of creating a universe out of the quantum vacuum but the quantum vacuum is not nothing – it’s just the lowest energy state of spacetime. It’s weird to think about spacetime not existing but such is the implication of BVG and the earlier Hawking-Penrose singularity theorems. This Scientific American article might be helpful in explaining how the Big Bang is not just describing expansion into “some imagined preexisting void.” The Big Bang is not dealing with expansion into preexisting space but the expansion of space.
For more details on the problems when some scientists speak about the Universe being created from absolutely nothing I highly recommend this blog by cosmologist Luke Barnes.
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