Question

Do you favor the Copenhagen interpretation or the Everett interpretation? Why? Give details to support your answer.

Answer 1

Going by rational thinking, cannot support this interpretation. it is only a philosophical argument.
But as an axiom, it works in quantum mechanics, and do not affect any calculation in quantum mechanics since even if it is wrong,
the other side is nothing to do with the calculation in quantum mechanics.

According to the Copenhagen interpretation, physical systems generally do not have definite properties prior to being measured,
and quantum mechanics can only predict the probabilities that measurements will produce certain results. The act of measurement affects the system, causing the set of probabilities to reduce to only one of the possible values immediately after the measurement. This feature is known as wavefunction collapse.

This hypothesis says nature is inherently probabilistic — that particles have no hard properties, only likelihoods until they are observed.
Einstein once said, " Do you really think the moon isn't there if you aren't looking at it?"

According to the Copenhagen interpretation, properties such as the momentum of a quantum particle have no definite value until a measurement is made. Result of this was Heisenberg’s famous uncertainty principle, which said that measurement of a particle’s momentum limits the ability to find out its position, and vice versa. Many other pairs of observable quantities are governed by the uncertainty principle.

Let us imagine creating a pair of particles speeding away from each other, but with correlated properties–a position or momentum measurement on one particle would immediately tell you the position or momentum of the other.

Now the experimenter could choose to find either the position or the momentum of the first particle–without doing anything to it–by observing the second. This could only mean that the first particle had definite values of both properties all along because either property could be precisely inferred without any physical action being performed on that particle. The Copenhagen interpretation, by contrast, seemed to say that the second particle’s properties would only become definite after the first particle had been measured, even though the two particles were no longer in contact.

Copenhagen is what we observe in practice, but in reality, particles have definite positions that are governed by this whole extra elaborate guiding wave, which happen to be impossible to fully calculate.

Physics is not primarily about belief but is about being able to practically make calculations in-line with experimental observations.