Summarizing Many-Worlds Theory

A new paper summarizes many-worlds:

Revolutionizing Quantum Mechanics: The Birth and Evolution of the Many-Worlds Interpretation

The Many-Worlds Interpretation (MWI) of quantum mechanics has captivated physicists and philosophers alike since its inception in the mid-20th century. This paper explores the historical roots, evolution, and implications of the MWI within the context of quantum theory. ...

One common critique of the MWI is its apparent lack of empirical testability. Critics argue that the MWI’s postulate of multiple parallel universes is inherently unobservable, making it difficult or impossible to distinguish experimentally from other interpretations of quantum mechanics. ...

Another criticism centers on the ontological status of the branching worlds in the MWI. Critics question whether the proliferation of parallel universes is necessary or justified, arguing that it introduces unnecessary complexity and violates principles of parsimony [32].

Yes, those criticisms are devastating.

One of the key impacts of the MWI is its resolution of the measurement problem in quantum mechanics. Unlike other interpretations that invoke wavefunction collapse or hidden variables to explain the transition from quantum to classical behavior, the MWI provides a deterministic and unitary description of the evolution of the quantum state. According to the MWI, measurements are merely instances of branching within the multiverse, with each possible outcome manifesting in a separate branch.

Saying that we just see one branch is no more satisfying that saying that we just see the collapse. It fails to solve the measurement problem in the same way. One theory says the wavefunction collapses, and the other says it splits into branches. The differnce is that MWI posits the existence of zillions of other branches we do not see.

Furthermore, the MWI has profound implications for our understanding of quantum superposition and entanglement. In the MWI, superposition is viewed as a fundamental feature of quantum systems, with different branches of the multiverse corresponding to different states of the system.

We do not see those other branches, so they cannot explain entanglement.

Moreover, the MWI has led to new insights into the nature of probability in quantum mechanics. In the MWI, probabilities arise from the relative frequencies of different outcomes across multiple branches of the multiverse, rather than from inherent randomness or observer-dependent collapses of the wavefunction. This perspective offers a coherent and objective interpretation of probability in quantum mechanics, resolving longstanding debates about the nature of quantum uncertainty.

Here it goes off the rails. The MWI folks have never been able to make sense out of different branches having different frequencies or probabilities. They cannot calculate probabilities that way.

Additionally, the MWI raises philosophical questions about the nature of consciousness and free will. If every possible outcome of every quantum measurement occurs in a separate universe, then every possible choice or decision is realized in some branch of the multiverse. This perspective challenges traditional views of free will as the ability to choose between alternative possibilities, suggesting that free will may be illusory or relative within the context of the MWI.

Nothing good has come out of those questions.

It is an embarrassment that modern Physics takes this nonsense seriously. It is like a child's fairy tale. You get to imagine whatever you please, with no connection to reality.

The biggest failure is its misunderstanding of science and probability. Science is all about figuring out what can happen, and what is likely. You get the probability by maybe enumerating equally likely events, and dividing the count of predicted events by the count of all possibilities. Or something similar. MWI throws that all out the window, says all possible events are real, and refuses to say that any worlds are more likely than any others. It cannot give probabilities. It is profoundly contrary to the scientific method, and cannot be used for anything but stimulating a philosophical discussion.