Q&A: Dark Matter and Multiple Universes
Dark Matter and Multiple Universes
Question
Hi Michi,
Let me start by saying that I’m not a physicist.
I read that one of the interpretations of the strange phenomena in quantum mechanics is the many-worlds theory.
According to Wikipedia, some of its advantages are an axiomatic and mathematically precise formulation; according to this interpretation, quantum mechanics is deterministic, realistic, and local. This interpretation does not require collapse of the wave function, and so on.
Its obvious drawback is the need to assume countless universes that nobody has seen or experienced consciously. And this drawback really does drive supporters away from it.
This drawback overshadows many advantages, and here on the site I saw that you also don’t connect with this interpretation (to put it mildly).
On the other hand, more than 85% (!) of the gravitation in the universe cannot be explained by the known mass. So they came up with the theory of dark matter, and we assume the existence of matter that nobody has seen or sensed.
In a podcast where you were a guest, you were asked about it, and you answered that you do believe dark matter actually exists.
My question is the obvious layman’s question: why do you reject the many-worlds interpretation because of this drawback, while at the same time accepting the existence of dark matter despite the same drawback?
Answer
Because the theory of multiple universes has no significant advantage whatsoever. It is mainly an empty word game.
As for dark matter, I see no similarity at all. If it is clear that there is a huge amount of mass in the universe, and that we do not see a substantial part of it, the conclusion is that there is dark mass. That is completely straightforward and in no way resembles fantasies about multiple universes.
Discussion on Answer
1. I haven’t read Wikipedia, but what you quoted here does not seem right to me, and in any case it is not really an advantage with respect to the question of whether this is the correct explanation. Also, you are not introducing determinism into quantum theory here; you are just hiding the indeterminism in the selection among worlds.
2-3. It is definitely common. Adding entities because of theoretical difficulties is a standard way science operates. By the way, that is not ad hoc. Ad hoc means that there are two competing theories, one of them runs into a difficulty, and you rescue it with ad hoc claims. But when there are not two competing theories, but rather one very successful theory, then if it has difficulties it is certainly reasonable to add entities and claims in order to “save” it. See my article on Ockham’s Razor and judging favorably: https://mikyab.net/%D7%9B%D7%AA%D7%91%D7%99%D7%9D/%D7%9E%D7%90%D7%9E%D7%A8%D7%99%D7%9D/%D7%A2%D7%95%D7%93-%D7%91%D7%A2%D7%A0%D7%99%D7%99%D7%9F-%D7%AA%D7%A2%D7%A8%D7%95-%D7%A9%D7%9C-%D7%90%D7%95%D7%A7%D7%94%D7%90%D7%9D/
By the way, many worlds is the best example of ad hoc additions. You add countless bizarre universes that nobody has seen and nobody can see because you have a difficulty in the theory. That is ad hoc in the bad sense of the word, and in my opinion it is also useless in every way. If it were useful, it would not be ad hoc, as I explained.
Hello,
1. When you say that the theory of multiple universes has no significant advantage, do you mean that you disagree that it really has the advantages listed in Wikipedia, or do you mean that you don’t agree that those advantages are significant?
To an untrained ear, “granting” determinism to quantum theory sounds quite significant.
2. Regarding gravitation, if 85% of the theory does not fit the amount of mass in the universe, then why keep holding on to it instead of looking for another theory or improving the current one? 85% is no small matter.
3. Is it common among scientists that when most of a theory does not fit reality, they add entities ad hoc?