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> I'm curious, has any research been done on HOW they "choose" their state when observed? They do not. There is no "particle choosing", ever. What happens ins

> I'm curious, has any research been done on HOW they "choose" their state when observed? They do not. There is no "particle choosing", ever. What happens instead is that you (the observer) are also composed of particles. This is something that people are kinda willing to admit, but afterwards they deny the logical consequence... that the particles that create you can also be in more than one state at the same time. What happens instead is "entanglement", which means that certain options of one particle become connected to certain options of another particle. All options continue to exist, but only some of the relations between different particles exist. Specifically, when observe the particle, the option "particle going left" becomes entangled with the option (remember, you are also a system of particles) "you see the particle going left"; and analogically, the option "particle going right" becomes entangled with the option "you see the particle going right". Now each version of you observe one specific outcome... and can ask themselves 'what made the particle choose this specific outcome?' But there was no choice; it's just that the other movement of the particle is entangled with a different version of you. Yes, parallel worlds -- the true shocking discovery of the quantum physics. Actually, all physicists admit that parallel worlds exist on the microscopic scale, the only controversy is that half of them say "and it's the same on the macroscopic scale, too", while the other half goes "I can't believe in macroscopic parallel worlds, therefore there must be a magical thing called 'quantum collapse' which makes this madness stop before it gets too large". (The belief in quantum collapse in unfalsifiable, because no matter how large system of particles existing in parallel configuration you build, the possible counter-argument goes "but if you make it even larger, then it will finally collapse". And this goalpost can be pushed indefinitely.) Unlike in science fiction, the parallel worlds of quantum physics have the property that the more they differ, the less they can interact. If they only differ in position of one particle (one world where the particle goes left, another where it goes right, but everything else is exactly the same), there is a lot of interaction. But if they differ in hundreds of particles, the interaction is almost zero. The disappointing part is that you can never observe the parallel universe directly, because - again - you are composed of particles; even your very act of thinking means moving millions of particles in your brain around... so just the fact that you noticed a particle moving left has put millions of particles in your brain in a different position than if you would have noticed the particle moving right. The problems with thinking about quantum physics arise when we imagine that the microscopic scale is just like the macroscopic scale, only smaller. ("Particles are like oranges, only smaller, duh. Actually, they are more like waves on the lake. Anyway, must be the former or the latter, because those are the only options I am familiar with.") When instead, the macro scale is a statistical aggregate of the micro scale, so we can't observe e.g. things that get cancelled out by other things. Instead of trying to fit the micro scale into our everyday experience, the proper way is to study the micro scale by its own laws, such as probabilities being expressed by complex numbers, and then think how could our everyday experience arise from this, i.e. again, what laws would then govern huge systems of particles, such as ourselves.

posterboy 8y ago
> Actually, all physicists admit that parallel worlds exist on the microscopic scale No they don't. The many worlds theory is a very tentative suggestion. And even if that was a professional opinion, does it have any consequences for the theory or is it an after thought?
- Viliam1234 8y ago
  Many world theory is about what happens on macroscopic scale. Specifically, it says: "The world on the macro scale is still governed by the same laws of physics as on the micro scale, duh. There are no extra laws of physics (such as collapse) which would start to apply only when the number of particles involved in the experiment exceeds some unspecified threshold." And yes, there are people who agree with this, and there are people who disagree with this, even among the experts. But on microscopic scale, it is a general consensus that in the double-slit experiment the particle somehow goes simultaneously through both slits, i.e. that two different realities (different only in trajectory of a single particle) somehow got into superposition. The disagreement is only about "what will happen with this superposition, when more and more particles enter the game". Some theories say "at some moment, the superposition of multiple realities will somehow collapse, and only one reality will emerge victorious". Some theories say "the additional particles will also get entangled with the particles that are already there". The former predict that the observer will only see one outcome, because when the human brain is entangled, the collapse already happened and there is now only one reality. The latter predict that each observer will only see one outcome, because each outcome gets entangled with the version of observer observing that specific outcome. Both theories agree that at the end the observer will report to only see one outcome. I guess the experimental consequence of the no-collapse interpretations of quantum physics would be that quantum computers of arbitrary size will be possible. If you instead believe that an interaction with e.g. 1000 particles will collapse, that would put a limit on number of possible qubits. But of course, if someone would falsify that theory by building a larger quantum computer, nothing prevents you from saying "did I say 1000 particles? I actually meant 10000 particles!" and have the theory survive yet another day. Of course, you can also come up with a theory saying "the superposition of too many particles will collapse unless it happens to be inside of a quantum computer"; etc. But at that moment it should be obvious you are just making excuses. Now let me ask you in return: Is there any specific prediction of when exactly does the collapse happen? Was it ever experimentally observed to happen?

posterboy 8y ago

> Actually, all physicists admit that parallel worlds exist on the microscopic scale No they don't. The many worlds theory is a very tentative suggestion. And even if that was a professional opinion, does it have any consequences for the theory or is it an after thought?

Viliam1234 8y ago
Many world theory is about what happens on macroscopic scale. Specifically, it says: "The world on the macro scale is still governed by the same laws of physics as on the micro scale, duh. There are no extra laws of physics (such as collapse) which would start to apply only when the number of particles involved in the experiment exceeds some unspecified threshold." And yes, there are people who agree with this, and there are people who disagree with this, even among the experts. But on microscopic scale, it is a general consensus that in the double-slit experiment the particle somehow goes simultaneously through both slits, i.e. that two different realities (different only in trajectory of a single particle) somehow got into superposition. The disagreement is only about "what will happen with this superposition, when more and more particles enter the game". Some theories say "at some moment, the superposition of multiple realities will somehow collapse, and only one reality will emerge victorious". Some theories say "the additional particles will also get entangled with the particles that are already there". The former predict that the observer will only see one outcome, because when the human brain is entangled, the collapse already happened and there is now only one reality. The latter predict that each observer will only see one outcome, because each outcome gets entangled with the version of observer observing that specific outcome. Both theories agree that at the end the observer will report to only see one outcome. I guess the experimental consequence of the no-collapse interpretations of quantum physics would be that quantum computers of arbitrary size will be possible. If you instead believe that an interaction with e.g. 1000 particles will collapse, that would put a limit on number of possible qubits. But of course, if someone would falsify that theory by building a larger quantum computer, nothing prevents you from saying "did I say 1000 particles? I actually meant 10000 particles!" and have the theory survive yet another day. Of course, you can also come up with a theory saying "the superposition of too many particles will collapse unless it happens to be inside of a quantum computer"; etc. But at that moment it should be obvious you are just making excuses. Now let me ask you in return: Is there any specific prediction of when exactly does the collapse happen? Was it ever experimentally observed to happen?