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Do quantum events have no definite cause , a cause but the cause is unknown, they have no cause, they simultaneously have a cause and do not have a cause , there is a known cause, causes of events at the quantum and classical do not exist , or a combination of one or more these possibilities? that's about the limit of options I can come up with, any other thoughts would be welcome though.

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    Firstly, what is causation? See 'Is the idea of a causal chain physical (or even scientific)?' philosophy.stackexchange.com/questions/70930/… Most types of local hidden variable would conflict with local-realism, leading most physicists to feel they have been ruled out. See en.wikipedia.org/wiki/Local_hidden-variable_theory You forgot Many Worlds, where all quantum probabilities result in outcomes but their world-lines branch, preserving determinism but in a a larger cosmos
    – CriglCragl
    Commented Jun 12, 2023 at 11:50
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    On the standard interpretation, quantum collapse has no prior sufficient cause, aside from causes that determine possible eigenstates it is self-caused or "truly random".
    – Conifold
    Commented Jun 12, 2023 at 11:51
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    The answer to your multiple questions required me to take three years of physics at university and graduate level.
    – Boba Fit
    Commented Jun 12, 2023 at 13:37
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    I'm sure you can fit that amount of education in to a succinct answer suitable for stack exchange 😉
    – 8Mad0Manc8
    Commented Jun 12, 2023 at 13:50
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    So there is an uncertain outcome with an indefinite cause?
    – 8Mad0Manc8
    Commented Jun 12, 2023 at 14:51

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All quantum events have a cause, but the cause never determines the effect with absolute accuracy. That is because there is no such thing as absolute accuracy.

All quantum particles are described only as probability waveforms. There are no definite values until they are measured. All causes and effects are only probabilities. Macro scale events are averages of large numbers of quantum events.

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  • So the effect is to some degree determined by some cause and to some other degree determined by some other cause?
    – 8Mad0Manc8
    Commented Jun 14, 2023 at 17:08
  • Or more plausibly, the effect is to some degree determined by a cause and to some other degree not determined by a cause?
    – 8Mad0Manc8
    Commented Jun 15, 2023 at 1:04
  • I'm not sure if the word "determined" alone implies absolute accuracy. "Deterministic" and "determinate" do. Anyway, there is only one cause for each effect and both causal events have inaccurately known, indeterminate properties. Commented Jun 15, 2023 at 4:01
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There are multiple variants of quantum theory that are referred to as interpretations of quantum theory. Different variants make different claims about what is happening in reality and so make different claims about causes of events.

The Copenhagen and statistical interpretations claim that quantum mechanics doesn't describe reality and deny that any such description is necessary or desirable. One problem with this approach is that if you're doing an experiment then if there's no account of what's happening in reality it's unclear why you're doing the experiment since you're not testing whether quantum mechanics corresponds to reality because the theory claims it doesn't even matter whether such a correspondence exists. It's also unclear what it means to do the experiment correctly since you don't have a specific description of what's supposed to be happening in reality to which the experimental setup could correspond. Since there is a fundamental unsolved problem with these interpretations there's no point in considering them further.

In quantum mechanics in general a measurement will have more than one possible outcome and you're supposed to say they have a probability given by the Born rule. Some interpretations of quantum mechanics - collapse interpretations - claim that measurement is a physical process that changes the state and observables so they have only one value or a narrow range of values. The reason given for doing this is so that measurement results have well defined values. It's a bit unclear to me what these interpretations would say about causes, but here's a sympathetic account of this theory:

https://arxiv.org/abs/1204.4325

The pilot wave interpretation claims that there are particles in addition to the quantum state and observables. It's a bit unclear whether the quantum states and observables are actually supposed to exist in this theory and so it's unclear whether they cause anything, see

https://arxiv.org/abs/quant-ph/0403094

For a more sympathetic account of the pilot wave theory see

https://arxiv.org/abs/0811.0810

If we take quantum theory seriously as a description of what's happening in reality and don't modify it then each system exists in multiple versions that can interfere with one another under suitable circumstances, such as interference and entanglement experiments, see "The Fabric of Reality" by David Deutsch and

https://arxiv.org/abs/2205.00568

https://arxiv.org/abs/quant-ph/0104033

So in general more than one version of each event contributes to what happens. In addition, relative phases between different versions of the system and entanglement can affect the probabilities of outcomes so there is more to causality than just the existence of multiple versions of each system.

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Consider the Model for Radioactive Decay (Did Curiosity Kill Schrodinger's Cat?)

This Wikipedia description is consistent with my memory of radioactive decay and the thought experiment known as Schrodinger's Cat:

Radioactive decay is a stochastic (i.e. random) process at the level of single atoms. According to quantum theory, it is impossible to predict when a particular atom will decay, regardless of how long the atom has existed.

Quantum interpretation of radioactive decay:

https://www.sciencedirect.com/topics/chemistry/radioactive-decay

Radioactive decay involves a transition from a definite quantum state of the original nuclide to a definite quantum state of the product nuclide. The energy difference between the two quantum levels involved in the transition corresponds to the decay energy. This decay energy appears in the form of electromagnetic radiation and as the kinetic energy of the products, see Element and Nuclide Index for decay energies.

What is the meaning or interpretation of Schrodinger's Cat thought experiment?

https://www.wtamu.edu/~cbaird/sq/2013/07/30/what-did-schrodingers-cat-experiment-prove/

In Schrodinger's imaginary experiment, you place a cat in a box with a tiny bit of radioactive substance. When the radioactive substance decays, it triggers a Geiger counter which causes a poison or explosion to be released that kills the cat. Now, the decay of the radioactive substance is governed by the laws of quantum mechanics. This means that the atom starts in a combined state of "going to decay" and "not going to decay". If we apply the observer-driven idea to this case, there is no conscious observer present (everything is in a sealed box), so the whole system stays as a combination of the two possibilities. The cat ends up both dead and alive at the same time. Because the existence of a cat that is both dead and alive at the same time is absurd and does not happen in the real world, this thought experiment shows that wavefunction collapses are not just driven by conscious observers.

Einstein saw the same problem with the observer-driven idea and congratulated Schrodinger for his clever illustration, saying, "this interpretation is, however, refuted, most elegantly by your system of radioactive atom + Geiger counter + amplifier + charge of gun powder + cat in a box, in which the psi-function of the system contains the cat both alive and blown to bits. Is the state of the cat to be created only when a physicist investigates the situation at some definite time?"

Since that time, there has been ample evidence that wavefunction collapse is not driven by conscious observers alone. In fact, every interaction a quantum particle makes can collapse its state. Careful analysis reveals that the Schrodinger Cat "experiment" would play out in the real world as follows: as soon as the radioactive atom interacts with the Geiger counter, it collapses from its non-decayed/decayed state into one definite state. The Geiger counter gets definitely triggered and the Cat gets definitely killed. Or the Geiger counter gets definitely not triggered and the cat is definitely alive. But both don't happen.

In this context we humans have a mental model for what causes the death of the cat. It is the radioactive decay of a single atom which may be located among a large number of atoms. If a single radioactive atom exists in the box with the living cat at time zero, then the stochastic radioactive decay (math) model does not give any indication of the probability of a dead cat at any future time. If a large number of atoms exist in the box with the cat, such as in a nuclear reactor, then we have a high probability of a dead cat in a very short period of time!

The concept of a quantum observer is not that a conscious human observer, or a conscious cat, causes the quantum event by the act of observation. The model is stochastic quantum energy transfer which gives good predictions when there are many atoms in bulk materials.

My model for stochastic process is Jiffy Pop popcorn. When I am young you could buy a pan of Jiffy Pop to heat on the stove. In the absence of heat nothing happens. Heat up the popcorn and the corn starts to pop at random with greater frequency and then reduced frequency until there are no more pop sounds. The model for an isolated radioactive decay or electron orbit decay is that it happens independent of the conditions in the surroundings. It is like one popcorn popping but without added heat or any other conditions and with no deterministic formula for when it will pop.

In the case of an isolated atom subject to radioactive decay, there is no model for the proximate (human recognized) cause of the decay event. The model is that isolated radioactive decay is just a random event that can happen at any time. The decay event, however, may be the proximate cause of another quantum event, such as the increase of quantum energy states in the event detector.

The basic model for this concept is one quantum decay power coupled to one quantum absorption. This is conceptually identical to the physical coupling of two systems A and B. The systems A and B are power coupled if A can do work on B or B can do work on A. Since work, energy, and heat are equivalent there is energy transfer involved in a process of work involving two or more power coupled systems. In a complex quantum system (the universe of human experience) it is frequently not clear which quantum event is power coupled to any other particular quantum event. So the cause of any quantum event is either spontaneous energy decay or it is power coupled to some other quantum event that causes quantum energy increase. Photosynthesis is the scientific model where the Sun is emitting radiant energy associated with radioactive decay and the plants on earth are absorbing radiant energy as higher energy electrons that store electrochemical potential energy in organic compounds. Animals eat plants. Humans eat plants and animals. Therefore, humans are solar powered.


Hyperphysics - Failures of Classical Physics

http://hyperphysics.phy-astr.gsu.edu/hbase/qapp.html#c3

The link describes observations that were not explained by the theories of classical physics. In the context of explaining these observations with new theories probably the main principle was Conservation of Energy (First Law of Thermodynamics) shown under the following link:

http://hyperphysics.phy-astr.gsu.edu/hbase/thermo/firlaw.html#c1

Statistical methods with models for quantum states of matter and the quantum exchange of energy were developed. This is not so much a theory but a set of methods in which there are concepts of randomness mixed with deterministic models for states and changes of state and the development of power as instantaneous flows of work, energy, and heat.

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    I've known that cats are solar powered for a long time. You can see them recharging in sunny windows.
    – Scott Rowe
    Commented Jun 13, 2023 at 18:05
  • @SystemTheory So in the case of radioactive decay. The outcome is that half the radioactive atoms of a group will decay in some time. The decay is caused by radiated energy and the nuclide changes. If an atom is measured at a particular time the wavefunction determined by the shrodinger equation collapses and the superposition of being undecayed and decayed, falls to a definite state of either decayed or undecayed. However there's in no deterministic formula that enables you to determine when an atom will decay although if you attempt to measure or observe it you will get a definite outcome?
    – 8Mad0Manc8
    Commented Jun 15, 2023 at 13:35
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    The decay is caused by radiated energy and the nuclide changes. Spontaneous decay is not caused - it happens. Decay event means, in terms of our human models derived from observations, that the atom loses energy associated with a change in its microscopic states; and an equivalent amount of energy radiates away from the atom into the surroundings. The decay event can be seen as the cause of radiation and radiation can be seen as the cause of further absorption of energy by other atom(s). In Schrodinger's cat context the random decay event is the deterministic cause of the cat's death. Commented Jun 15, 2023 at 17:13
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    @8Mad0Manc8 If event B would not happen but for event A, then this pattern is called "but for" causation. The model for the nuclear decay event incorporates all the elements that we recognize as the loss of energy on a quantum level, the emission of Alpha and/or Beta particles, and the emission of electromagnetic radiation. The decay event does not really cause loss of energy or emission because these are related attributes of our model for this natural event. That it why I said decay seems to cause emission but really it is one event D with attributes of potential energy, kinetic energy, etc. Commented Jun 17, 2023 at 17:35
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    @8Mad0Manc8 There is a method, which I call The Physics Paradigm, and it is formalized in the study of Thermodynamics. The human observer imposes a real or imaginary boundary to draw a distinction between the system and its surroundings. A natural process is characterized as an interaction between the system and its surroundings. An isolated system does not interact with the surroundings so all interactions are internal. Conservation Laws (mass, momentum, energy, electric charge) apply for the isolated system or for the system + surroundings. Events happen! We impose physical and causal ideas! Commented Jun 18, 2023 at 15:20

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