You left out what (IMO) is the best way to understand QM: the Transactional Interpretation (TI).
I've read many books about QM and the nature of reality ("Beyond Weird" by Phillip Ball, "Time Reborn" and "Einstein Unfinished Revolution" by Lee Smolin, "The End Of Time" by Julian Barbour, "A New Kind Of Science" by Stephen Wolfram, "Biocentrism" by Robert Lanza...), but nothing compares to this book about the Transactional Interpretation of QM by Ruth E. Kastner:
https://www.amazon.com/Understanding-Our-Unseen-Reality-Solving-ebook/dp/B00TZPIOM2
She uses clear analogies, explanations and formulas everyone can understand. I can't recommend it highly enough. It can really change the way you think about the universe.
The main idea is that spacetime is an emergent phenomena, created by all the energy transactions performed by quantum objects in the quantum realm. Everything we observe is prepared "behind the scenes" by wave exchanges that take place outside the spacetime realm.
In the Transactional interpretation, the concepts of change and momentum are more fundamental than those of space and time because, unlike the latter, the former always imply a relation between two entities, so there can be no energy exchanges without both an emitter and an absorber.
Kastner states that the current picture of the quantum world, that considers quanta evolving in spacetime, is incomplete and creates all the quantum riddles and paradoxes.
On the other hand, the Transactional Interpretation considers each spacetime energy exchange as the realization of one among all possible transactions between an emitter and all potential absorbers. The possibilities are handled in the non-observable quantum realm, and when virtual exchanges meet certain constraints, they are introduced into spacetime as real energy exchanges.
What materializes in spacetime each time is not a unique event, but two events (emission and absorption), separated by the spacetime interval that express the exchange of energy that took place between the emitter and the absorber. There are no single or isolated events happening in the universe. Any event has to be linked, at least, to another one in order to define a transaction, so they always emerge as linked pairs at the ends of any interval or exchange that develops in spacetime.
I, personally, have another reason to think TI really hits the spot: Five years ago, before even knowing the Transactional Interpretation existed, I reached the same conclusions starting from Special Relativity.
The same year Kastner published her book, I was wondering about the true meaning of the light speed constant, because, for me, a speed that doesn't change at all had to be different in nature to any other conventional speed.
So I was trying to imagine how light experiences our universe (the same thought that led Einstein to develop Special Relativity), when I realized that, precisely by applying SR, any quantum object travelling exactly at the speed of light would experience the maximum length contraction and time dilation possible, so it would "feel" no time or distance elapsed on its journey from emission to detection.
I thought this was remarkable, although I discovered later that it doesn't seem to astonish many physicists (it’s common knowledge that massless particles follow null geodesics in 4D, with no proper time associated.)
But for me, the fact that massless quanta know nothing about our space or time dimensions was really striking.
This insight triggered a "chain reaction" of thoughts that finally led me to reach some perplexing conclusions. For instance:
- Massless quanta can't feel empty space or vacuum. All the interactions they perform are related to the material world. They need the material world as the substrate to exist. They experience emission and absorption at the same time, so both emitter and absorber are essential parts of their existence.
- Only the whole spacetime interval we experience is fully equivalent to the single event they experience. They can not exist "partially", so any description of them as "evolving" in time is mistaken. There are no massless quanta "in flight". Wavefunctions are mental maps we use to track the constraints the material world imposes on their creation each time.
- They don't have intrinsic properties. All their properties or quantities come from the interval that elapsed for the material world. They express the spacetime conditions that took place during the interval we experienced.
- They are able to meet conservation laws and entanglement correlations because they feel no energy imbalances, no different times or places. Everything is an instant action/reaction event for them, with no space or time considerations whatsoever.
- Speed of light is the incredibly distorted way in which instantaneity gets mapped into the spacetime frame of reference of each matter observer, as dictated by her state of motion (SR) and that of her surroundings (GR).
- Time travel to the past is impossible. Speed of light is the limit for the "compression" of intervals into single events. Massless quanta can feel emission and absorption simultaneously, but there's no way to "reverse" the ordering of these events.
- It doesn't matter there's a speed limit in the universe, because quanta at the speed of light feel they're instantly teleporting at an infinite speed (since they feel all our spacetime interval at once).
- All forces mediated by massles quanta are "contact" forces, because the carriers that bring information/energy from place to place feel no spacetime elapsed. They behave like wormholes, connecting two different spacetime coordinates in no time (for themselves).
I could go on and on with the implications.
These insights (that light speed is equivalent to instantaneity or infinite speed, and that any spacetime process that develops at c is equivalent to an instantaneous event) were so fruitful that I decided to analyze the puzzles of Quantum Mechanics. To my surprise, I was able to find intuitive explanations for entanglement, nondeterminism, wave/particle duality, wave function collapse, Bell’s theorem, faster than light communication, EPR paradox, Scrhödinger’s cat experiment, double-slit experiment, delayed choice experiment… And each time I read about a new theory, mechanism or interpretation, the pieces still fitted together nicely (I had to change not a single comma when I discovered Relational Quantum Mechanics or the Transactional Interpretation).
In the end, I think this viewpoint works correctly because I reached the same key concepts exposed by Kastner for the Transactional Interpretation:
- Absorption is a fundamental part of any energy exchange.
- Both emission and absorption are required to define any transaction (massless quanta).
- Exchanges we observe as spacetime processes are, at the same time, instantaneous events taking place "outside spacetime" for the quanta involved.
Kastner's book is by far the most approachable reading about the true nature of reality and the inner workings of Quantum Mechanics I've ever seen. I'm really happy this new scientific description of reality is becoming widespread, as it resonates so nicely with my own findings.
If you also got interested on my own interpretation, you can read all about it here:
