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In the Copenhagen interpretation, when I look at schrodingers cat, the wavefunction will collapse. After I have looked at it, no way to go back. Information is lost. In many worlds, I just become entangled with the system - and I could theoretically disentangle after. Like quantum computing going to a deterministic outcome in a certain basis.

Showing collapse happened is really tricky because of decoherence. Similar to unmixing coffee and milk. But all systems we have observed so far do not show wave function collapse (granted these systems are generally small, but otherwise decoherence starts messing about).

These are just fundamentally different theories. Not just an interpretation, physically different outcomes.

Does it not make any predictions? It states there is no such thing as wavefunction collapse. This means that if you entangle a state with a large system, in theory you could ‘disentangle’ it. Of course, this is no easy feat. But indeed quantum computing to me, is an example of this feat. We can entangle systems on a large scale, then use this feat to make calculations. Inspiration for quantum computing actually came from many worlds.

Many worlds is falsifiable, if you can show wave function collapse actually happens (not just decoherence). I believe that in the not so distant future we will get more and more proof that wave function collapse never happens. Quantum computing at scale to me is an indication that Everett was just right..

How would you define exactly ‘when gravity starts playing a role’. It always plays a role, from photons to planets.

And on the ‘every tick creates more universes’: we are completely fine with superposition in nanoscopic systems. It’s just uneasy to follow that conclusion to the logical end. Just my two cents. I think just because the conclusion seems hard to grasp, the reasoning to get there is completely sound..

"This rather fanciful interpretation of Quantum Physics has now become accepted by many theoretical physicists as being more satisfactory than the Copenhagen interpretation, despite the fact that the mechanism which causes the splitting of the Universe is not explained in any more detail than wavefunction collapse. As you can probably tell, I am in the minority of physicists who finds the Many Worlds interpretation dificult to accept, and not particularly illuminating."

I think these lectures are a good intro to QM. This statement feels very emotional though. Many-worlds just states there is no such thing as wave function collapse. The many worlds are a logical conclusion following. Copenhagen simply refuses to elaborate to when wave-function collapse happens, which to me is not a complete theory.

You could have some critique of many-worlds in relation to statistics, although I think many people have given quite satisfactory explanations.

Many worlds is just bare bones QM.. If any other theory is proposed, it should be falsifiable (like pilot wave theory for example). Doesn't mean it won't be difficult to measure.

I know, there's some tricky business with energy conservation (I'm not pretending I understand it all though). It is for me an easy analogy though. Even Hilbert space has to stick to some rules!

Yeah, this is also why I said many and not most :)

But I think if you ask experts (philosophers of nature, people into foundational quantum mechanics) most of them would be many worlds proponents.

I finished my masters in a quantum computing lab. The reality is that most physicists just don't care about foundational QM, and stick to the Copenhagen interpretation. To me the Copenhagen Interpretation does not even count as a complete theory. It just stays very fuzzy on when wave function collapse happens, which makes it impossible to falsify.

Not according to many worlds! I think nowadays many physicists think many worlds/an everettian view is most plausible

It’s not ‘all’ things that are possible, just things that are allowed within the laws of physics :)

Subtle difference, but energy conservation for example has to be adhered to.