Irrational mechanics, draft Ch. 10
Spacetime oddities.
Greetings to all readers and subscribers, and special greetings to the paid subscribers!
Here’s a very early draft of Chapter 10 of my new book “Irrational mechanics: Narrative sketch of a futurist science & a new religion” (2024).
Note that this and the others draft chapters are very concise. At this point I only want to put down the things I want to say, one after another. Later on, when the full draft for early readers is complete, I’ll worry about style and all that.
10 - Spacetime oddities
The world described by the old physics is local. Things are nicely separated in space and time. Things happening here and now cause other things to happen at a later moment in a place nearby, without nonlocal interactions and without influences from the future to the past.
The new physics shows that this is not the case. So, strictly speaking, goodbye space and time. Borrowing Bertrand Russell’s words about neutral monism [Russell 2009] quoted in [Chapter 9], I think both space and time “are structures composed of a more primitive stuff.”
But space and time are integral parts of how we think, so when we try to reason about more primitive stuff that comes before space and time we must use our concepts of space, time, and motion.
We can’t visualize physical reality without the framework of spacetime upon which our intuition is based. But the weird spacetime oddities discussed in this chapter can help our intuition transcend space and time. Some inconsistencies are unavoidable because our language is not made to deal with things beyond space and time, but let’s do what we can. I think the spacetime oddities that I’m about to discuss point to the global workings of the cosmic operating system [Chapter 8].
Erwin Schrödinger said that quantum entanglement, the “spooky action at a distance” [Zeilinger 2010, Musser 2015] that troubled Einstein, is not one “but rather the characteristic trait of quantum mechanics” [Bell 2004].
Two quantum particles (or more complicated systems) that share a common origin or have interacted in the past are entangled: some measurable properties of one are correlated to the other regardless of the distance between them. For example it may be the case that, if the spin of one particle is found pointing in one direction, the spin of the other particle is found pointing in the opposite direction. This is indicated by the mathematics of quantum mechanics and confirmed by experiment [Bell 2004].
But how does the second particle know that the spin of the first particle has been measured and found pointing in one direction? One would think that the particles exchange some sort of signals. But experimental evidence shows that two particles can be entangled even when they are too far apart to exchange signals at the speed of light. One would conclude that the two particles exchange signals faster than light, but Einstein’s special relativity forbids that.
Quantum mechanics seems to indicate that entanglement can’t be used to send signals faster than light, so special relativity is safe from measurable violations. Or perhaps we haven’t been able to find ways to use entanglement for faster than light communications quite yet [Kaiser 2011], but one day we could. In any case, the tension between quantum mechanics and special relativity remains: something that is not limited by the speed of light is happening behind the scenes.
Instantaneous connection between remote particles would violate locality, which is a cherished assumption of contemporary physics. Locality means that everything happens locally. For example, a billiard ball must hit another billiard ball to move it. Fields propagate with local deformations of matter (e.g. sound waves in air) or spacetime itself, which move one little step a time. In quantum field theories, elementary interactions are often visually described with Feynman diagrams of fermions exchanging bosons locally.
But John Bell demonstrated [Herbert 1985, Stewart 1997, Stewart 2019] that there’s no way to make sense of entanglement without signals that “must propagate instantaneously” [Bell 2004]. In his introduction to Bell’s book, Alain Aspect notes that two entangled particles are “a single global quantum system, impossible to be thought of as two individual objects,” and Bell’s findings rule out “a physical reality localized in space-time and obeying causality.”
Entanglement “plays an even more central role in quantum field theory” [Carroll 2019]. As far as we can see, reality is strongly nonlocal behind the scenes.
There are entangled connections not only in space, but also in time [Musser 2016]. Entanglement seems independent of distance, “independent of which is earlier or later, etc.,” notes Anton Zeilinger [Zeilinger 2017]. “So quantum mechanics transgresses space and time in a very deep sense.”
David Mermin, the originator of the “Shut up and calculate!” quip, suggested that we shouldn’t “demand an explanation for the correlations” [Mermin 2016]. The idea that quantum correlations are elements of primary reality, and we shouldn’t try to explain them in terms of other things, is called the “Ithaca interpretation” and summarized as “correlations without correlata” [Wallace 2012]. I find the Ithaca interpretation a soberly minimalist interpretation of today’s quantum mechanics.
At the same time, today’s quantum mechanics could eventually be derived from a new theory that could help make intuitive sense of entanglement and nonlocality. The new theory would have to reproduce the nondeterminism of quantum mechanics.
Tim Palmer has speculated that strong fractal chaos could reproduce the nondeterminism of quantum mechanics [Stewart 1997, Stewart 2019]. Come what it may, if real numbers are processes that unfold in real time as suggested by Nicolas Gisin [Chapter 4], any mathematical model of reality based on real numbers would be nondeterministic.
A quantum particle can be a superposition of particles with different properties and even in different places, which interfere with each other. But entanglement with the rest of the world tends to remove interference effects. This “decoherence” process transforms amplitudes into probabilities. After decoherence, a particle that was here and there is here or there, but not here and there anymore [Ball 2018].
Well, here or there? Hugh Everett’s interpretation of quantum mechanics suggests that the particle is in one place in one world, and in another place in another world.