Séadna
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Interpretations of QM:
So Complementarity blocks attempts to move beyond direct experimental or sense data. It does this by banning an extremely common aspect of human thought, using logic or reason to compose data gathered in different situations into a single mental model. It even prevents us from imagining the data we obtain in one experiment still exists but is unobserved when we make a different observation. As above if you chose to see colour from light it's invalid to even think the light has photons, since that's not how you chose to observe it.
Obviously this is a massive shift in the scope of physics which toward the end of the 19th century was aiming toward a complete fundamental description of reality. Now physics is a description of experiments or observations that can actually be performed, what to expect from them and nothing more. A particle is a type of click in our devices, not a "thing" which objectively exists. To quote Aage Bohr (son of Niels Bohr):
This is the understanding of quantum theory arrived at by the original inventors of the theory: Bohr, Heisenberg, Dirac, Pauli, Schrodinger, Born, Jordan, etc and is the one given in textbooks today. I'll give it its standard name: The Copenhagen Interpretation. However today we sometimes use the phrase "Participatory Realism" for reasons I'll explain in the next post.
The above post about Complementarity was quite long, but I wanted to make it because online essays and many popular books give a completely bizarre rendering of the Copenhagen Interpretation, taking about "waves" and "collapses" and stuff that has no real relation to it.
In the spoiler below I explain what the other Interpretations are and why I'm not going to use them to answer your question. It can be skipped if you're fine with ignoring them. I will stick to the Copenhagen Interpretation and explore the open questions within it today.
So Complementarity blocks attempts to move beyond direct experimental or sense data. It does this by banning an extremely common aspect of human thought, using logic or reason to compose data gathered in different situations into a single mental model. It even prevents us from imagining the data we obtain in one experiment still exists but is unobserved when we make a different observation. As above if you chose to see colour from light it's invalid to even think the light has photons, since that's not how you chose to observe it.
Obviously this is a massive shift in the scope of physics which toward the end of the 19th century was aiming toward a complete fundamental description of reality. Now physics is a description of experiments or observations that can actually be performed, what to expect from them and nothing more. A particle is a type of click in our devices, not a "thing" which objectively exists. To quote Aage Bohr (son of Niels Bohr):
Thus the clicks can be classified as electron clicks, neutron clicks, etc., although there are no electrons and neutrons
Vladimir Fock, one of the great Soviet physicists, on the common error or erroneous abstraction we tend to make that QM bans:The reality of atoms and the content given to this notion have remained issues ever since the concept of an atom was introduced. This question obtains a new content by the identification of reality with the world of experience and the recognition that, accordingly, there is no world of atoms underlying the macroscopic world.
Neglect of these considerations leads to an abstraction that we may call the absolutization of physical processes. If we accept this abstraction, it becomes possible to consider physical processes as occurring by themselves regardless of whether there is a real possibility of their observation....All of classical physics is based on the absolutization of physical processes.
This is the understanding of quantum theory arrived at by the original inventors of the theory: Bohr, Heisenberg, Dirac, Pauli, Schrodinger, Born, Jordan, etc and is the one given in textbooks today. I'll give it its standard name: The Copenhagen Interpretation. However today we sometimes use the phrase "Participatory Realism" for reasons I'll explain in the next post.
The above post about Complementarity was quite long, but I wanted to make it because online essays and many popular books give a completely bizarre rendering of the Copenhagen Interpretation, taking about "waves" and "collapses" and stuff that has no real relation to it.
In the spoiler below I explain what the other Interpretations are and why I'm not going to use them to answer your question. It can be skipped if you're fine with ignoring them. I will stick to the Copenhagen Interpretation and explore the open questions within it today.
Unsurprisingly not everybody likes the Copenhagen Interpretation. The original generation considered these conclusions obvious from the experimental data and Heisenberg discovered quantum theory by removing from the mathematics of classical mechanics the assumption of some objective description. However starting in the 1950s the new generation had physicists who wanted to find an old fashioned "objective" theory of physics that described what things are actually like, not just observations and experiences. This is what led to the alternate "interpretations" of quantum mechanics.
I have "interpretations" in scare quotes because it's a big mistake I see repeated online that all these different interpretations "give the same predictions" and thus are all equivalent. As I'll explain that's not the case.
There are in two types of alternative interpretations of quantum theory:
The second type, the modal theories that attempt to rewrite and redevelop quantum theory itself were mostly proven not to work by their own practitioners in the 1990s. This was really commendable as they had been working on these ideas for twenty years, but managed to refute their own work. The only Modal type theory still discussed today is the "Many Worlds Interpretation" as in the video TristramEvans posted above. The reason this wasn't refuted in the 1990s is that it's not well-defined what the idea actually is. Unlike most of these ideas it has never gotten to the point of being able to replicate even a small set of experiments.
For this reason I will set aside all of these alternative views, since they have never been able to replicate the predictions of quantum theory and the ones that managed to match some data are today experimentally ruled out.
I have "interpretations" in scare quotes because it's a big mistake I see repeated online that all these different interpretations "give the same predictions" and thus are all equivalent. As I'll explain that's not the case.
There are in two types of alternative interpretations of quantum theory:
- Hidden Variable theories. These attempt to come up with a new theory that replaces quantum theory and isn't restricted to observations.
- Modal theories. These attempt to rewrite quantum theory itself, i.e. take a subset of the same mathematics and redevelop it in a way that can be understood in a classical objective sense.
The second type, the modal theories that attempt to rewrite and redevelop quantum theory itself were mostly proven not to work by their own practitioners in the 1990s. This was really commendable as they had been working on these ideas for twenty years, but managed to refute their own work. The only Modal type theory still discussed today is the "Many Worlds Interpretation" as in the video TristramEvans posted above. The reason this wasn't refuted in the 1990s is that it's not well-defined what the idea actually is. Unlike most of these ideas it has never gotten to the point of being able to replicate even a small set of experiments.
For this reason I will set aside all of these alternative views, since they have never been able to replicate the predictions of quantum theory and the ones that managed to match some data are today experimentally ruled out.
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