4 ms·

But macroscopic decoherence (and therefore many worlds) is straightforwardly predicted by the Schrodinger equation. How is this philosophy?

chrischen 10y ago
Only one world of many is experimentally verifiable.
- ThePhysicist 10y ago
  The problem is that we need a convincing mechanism to explain how the irreversibility implied by the Copenhagen interpretation arises, which to my knowledge no one has come up with yet. What we understand so far is: * the measurement process can be described as an entanglement of a quantum system with a large external system, followed by a dephasing of the wave function that is caused by the huge number of degrees of freedom in the external system. * this dephasing decouples the individual terms of the wave function of the system that is being measured, thereby effectively suppressing any further quantum effects in those measured states. This is what we call a transition from a quantum state to a "classical" state. * the measurement process itself is not a discrete event: We can perform continuous weak measurements on a system's state, which will only partially collapse the wave function (there have been many experiments done on this e.g. by Serge Haroche's group and more recently with superconducting systems as well). * this whole process is completely reversible and can be described by the Schrödinger equation. Now, if we want to introduce irreversibility into this picture (which is required for the Copenhagen interpretation), we need a mechanism for it to arise. To my knowledge, no one has come up with a good theory for this, as it would require to modify the Schrödinger equation in a way that subtly depends on the characteristics of the system being measured and the measurement system. This mechanism would need to contain a variable A that would account for the size of the measurement system, as we need to preserve reversibility when the measurement system is small (i.e. has a small number of degrees of freedom), while destroying it when the measurement system is macroscopic. I'm honestly a bit surprised that no one makes this argument in favor of the many-worlds interpretation of quantum mechanics, as it's the only theory which accounts for all experimental evidence while not forcing us to invent a mechanism that "eliminates" the many realities that we don't want to accept, while in fact they arise naturally out of the theory. I think that many people just don't want to accept that the universe could work this way, even if it's the simplest and most straightforward explanation.
  - naasking 10y ago
    > I'm honestly a bit surprised that no one makes this argument in favor of the many-worlds interpretation of quantum mechanics, as it's the only theory which accounts for all experimental evidence while not forcing us to invent a mechanism that "eliminates" the many realities that we don't want to accept, while in fact they arise naturally out of the theory. I think you're projecting the existence of these worlds. Certainly you could view the equations that way, or you could view the particles as fundamentally real and obeying a non-classical law of motion, as in de Broglie-Bohm, which was actually the first the interpretation to correctly account for measurement.
gnaritas 10y ago
Math is not reality, sometimes it happens to describe reality, sometimes it doesn't, that makes math useful in doing science, but math is not science unless experimentally verified.
- Symmetry 10y ago
  You can't say that the Schrodinger equation hasn't been experimentally verified. The problem is that we can only practically test it on microscopic objects, which means that people can introduce ad hoc mechanisms like waveform collapse to say it doesn't apply for macroscopic objects. That's a very odd way of going about things. We can't actually observe galaxies over long enough timescales to be sure that gravity applies to them but their appearance is consistent with the existence of gravity so we don't even both to consider the possibility that there might be some separate force causing them to look that way.
  - gnaritas 10y ago
    > You can't say that the Schrodinger equation hasn't been experimentally verified. I didn't. I said math doesn't always predict reality, sometimes it's just interesting math. Some maths are also physics, some maths are just maths and have no bearing on physics.
- naasking 10y ago
  > Math is not reality, sometimes it happens to describe reality, sometimes it doesn't Conjecture. It seems self-evident that our reality reflects the structure of basic discrete mathematics, ie. if there are two apples, eating one leaves 1 apple. No amount of rationalization will refute this fact. The fact is, the basic structure of our world is mathematical in some way.
  - gnaritas 10y ago
    It's not conjecture, it's a fact; you're describing a case where it does match reality, that doesn't contradict what I said. There are plenty of maths that are self consistent but don't match anything in reality. Just because someone can come up with some self consistent math doesn't mean that math predicts anything in the real world. To further clarify > The fact is, the basic structure of our world is mathematical in some way. Yes, but that doesn't imply the inverse, that all maths are reflections of reality. Reality can be described by maths, but not all maths describe reality. Or to further simplify, physics is the subset of maths that describe reality, which necessarily implies that not all maths do.

chrischen 10y ago

Only one world of many is experimentally verifiable.

ThePhysicist 10y ago
The problem is that we need a convincing mechanism to explain how the irreversibility implied by the Copenhagen interpretation arises, which to my knowledge no one has come up with yet. What we understand so far is: * the measurement process can be described as an entanglement of a quantum system with a large external system, followed by a dephasing of the wave function that is caused by the huge number of degrees of freedom in the external system. * this dephasing decouples the individual terms of the wave function of the system that is being measured, thereby effectively suppressing any further quantum effects in those measured states. This is what we call a transition from a quantum state to a "classical" state. * the measurement process itself is not a discrete event: We can perform continuous weak measurements on a system's state, which will only partially collapse the wave function (there have been many experiments done on this e.g. by Serge Haroche's group and more recently with superconducting systems as well). * this whole process is completely reversible and can be described by the Schrödinger equation. Now, if we want to introduce irreversibility into this picture (which is required for the Copenhagen interpretation), we need a mechanism for it to arise. To my knowledge, no one has come up with a good theory for this, as it would require to modify the Schrödinger equation in a way that subtly depends on the characteristics of the system being measured and the measurement system. This mechanism would need to contain a variable A that would account for the size of the measurement system, as we need to preserve reversibility when the measurement system is small (i.e. has a small number of degrees of freedom), while destroying it when the measurement system is macroscopic. I'm honestly a bit surprised that no one makes this argument in favor of the many-worlds interpretation of quantum mechanics, as it's the only theory which accounts for all experimental evidence while not forcing us to invent a mechanism that "eliminates" the many realities that we don't want to accept, while in fact they arise naturally out of the theory. I think that many people just don't want to accept that the universe could work this way, even if it's the simplest and most straightforward explanation.
- naasking 10y ago
  > I'm honestly a bit surprised that no one makes this argument in favor of the many-worlds interpretation of quantum mechanics, as it's the only theory which accounts for all experimental evidence while not forcing us to invent a mechanism that "eliminates" the many realities that we don't want to accept, while in fact they arise naturally out of the theory. I think you're projecting the existence of these worlds. Certainly you could view the equations that way, or you could view the particles as fundamentally real and obeying a non-classical law of motion, as in de Broglie-Bohm, which was actually the first the interpretation to correctly account for measurement.

gnaritas 10y ago

Math is not reality, sometimes it happens to describe reality, sometimes it doesn't, that makes math useful in doing science, but math is not science unless experimentally verified.

Symmetry 10y ago
You can't say that the Schrodinger equation hasn't been experimentally verified. The problem is that we can only practically test it on microscopic objects, which means that people can introduce ad hoc mechanisms like waveform collapse to say it doesn't apply for macroscopic objects. That's a very odd way of going about things. We can't actually observe galaxies over long enough timescales to be sure that gravity applies to them but their appearance is consistent with the existence of gravity so we don't even both to consider the possibility that there might be some separate force causing them to look that way.
- gnaritas 10y ago
  > You can't say that the Schrodinger equation hasn't been experimentally verified. I didn't. I said math doesn't always predict reality, sometimes it's just interesting math. Some maths are also physics, some maths are just maths and have no bearing on physics.
naasking 10y ago
> Math is not reality, sometimes it happens to describe reality, sometimes it doesn't Conjecture. It seems self-evident that our reality reflects the structure of basic discrete mathematics, ie. if there are two apples, eating one leaves 1 apple. No amount of rationalization will refute this fact. The fact is, the basic structure of our world is mathematical in some way.
- gnaritas 10y ago
  It's not conjecture, it's a fact; you're describing a case where it does match reality, that doesn't contradict what I said. There are plenty of maths that are self consistent but don't match anything in reality. Just because someone can come up with some self consistent math doesn't mean that math predicts anything in the real world. To further clarify > The fact is, the basic structure of our world is mathematical in some way. Yes, but that doesn't imply the inverse, that all maths are reflections of reality. Reality can be described by maths, but not all maths describe reality. Or to further simplify, physics is the subset of maths that describe reality, which necessarily implies that not all maths do.