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Why would anyone believe such a thing?

bowsamic 3y ago
Because it’s very straightforward and has less assumptions and weird features than most other interpretations, and it has seen the most advancements in quantum fundamentals research
- Scarblac 3y ago
  Complete layman here -- does that theory say that every time a quantum effect does or does not occur, in fact both possibilities happen but in different worlds? The entire universe instantly splits up in two for every quantum event anywhere in it? Edit: I read more comments and no, it's not literally that.
  - bowsamic 3y ago
    Yes, it does mean that
- edgyquant 3y ago
  These are just mathematical tools we use to make predictions. Assuming they represent objective reality and somehow prove an infinite number of universes doesn’t seem very scientific to me.
  - bowsamic 3y ago
    I mean, that's obviously a huge matter of debate, but most of us physicists at least hope that our theories reflect objective reality in some way. Also, there are of course explicitly ontological aspects of quantum mechanics, such as PBR theorem and Bell's inequalities
  - goatlover 3y ago
    That's way too instrumentalist. The math also describes how atoms work and many other things. Modern physical understanding is based on those descriptions. Cosmology and nuclear physics would be useless without an understanding. How do the predictions work if they aren't in some way modeling the way reality is? Why does the technology based on them work? Instrumentalism gives no answers to those questions. Science is about understanding the world, and using that to make predictions.
    - edgyquant 3y ago
      They work because they use human logic which has evolved to understand the universe just enough to “work” and where that logic doesn’t work we use probabilities to ensure we’re only calculating the odds and deriving from there. You can devise probabilistic systems of equations to describe stock prices and account for when you could be wrong, but this is not you describing some objective set of equations the market emanates from. It working doesn’t mean it in anyway reflects some objective truth (if such a thing even exists.) It just breaks things down into small enough parts you can then model those parts and make predictions. This does not mean those small parts are “real” just that they are convenient ways to describe the flowing of energy for our purposes. > atoms work and many other things Atoms are still just a human created mathematical abstraction we use to describe and make predictions about matter. All there really is is energy and atoms are just a mathematical tool we use to study energy. This is quite literally the oldest debate in natural science and it seems like one half of the debate just decided they’re right a few centuries ago and stopped caring about the fact that’s not something they have (or can) ever proved. They’re tools, don’t get me wrong they are very useful ones, but the second you start pretending they’re anything else or that your interpretation of them is how reality really works you become just another religious zealot and that goes against everything science is supposed to be about.
      - goatlover 3y ago
        > Atoms are still just a human created mathematical abstraction we use to describe and make predictions about matter. All there really is is energy and atoms are just a mathematical tool we use to study energy. We can see atoms with electron microscopes. A mathematical tool to study energy doesn't say anything. A tool describing how chemistry arises from atomic structure does. > This is quite literally the oldest debate in natural science and it seems like one half of the debate just decided they’re right a few centuries ago and stopped caring about the fact that’s not something they have (or can) ever proved. Not proved, but imagine using this sort of argument against evolution being a true account of life's history on Earth. Of course it won't get everything right, but in general there is simply no other way to explain how life forms changed over time. Similarly, there's no other way to understand microscopic physics than quantum mechanics. Maybe a more complete theory combining gravity and QM would be more true, just like Newtonian physics was incomplete and superseded by relativity.
CraftingLinks 3y ago
Because that's what quantum mechanics in it's purest form tells us. Avoiding the many worlds requires tagging on extra stuff not in the equations.
- tsimionescu 3y ago
  Quantum mechanics tells us that, in order to predict the outcome of a measurement, we have to compute a specific probability based on the amplitude of the wavefunction. We can explain this probability as some kind of collapse, or we can explain it as some measure of the number of observers making the measurement in parallel "worlds". Neither is inherently closer to the math.
  - consilient 3y ago
    > Quantum mechanics tells us that, in order to predict the outcome of a measurement, we have to compute a specific probability based on the amplitude of the wavefunction Even this is already wading into interpretational waters. The math says nothing about whether a given POVM should be thought of as a measurement or an interaction (or both, or neither).
    - tsimionescu 3y ago
      Sure, it's not part of the math, but it is part of the physics. There is a very clear distinction in the theory between "interactions", governed entirely by the Schrodinger equation (or its relativistic versions, or QFT), and a "measurement", where you have the apply the Born rule not only to predict what the measurement device will show, but also to correctly predict what will happen in a subsequent experiment on the same particle. Without the Born rule, QM makes nonsensical predictions that don't explain what happens. Decoherence helps explain certain things directly from the math without appealing to the extra Born rule, but not fully, and not quantitatively (not the specific probabilities).
      - bowsamic 3y ago
        > Sure, it's not part of the math, but it is part of the physics. "the physics" here is a specific interpretation > Decoherence helps explain certain things directly from the math without appealing to the extra Born rule, but not fully, and not quantitatively (not the specific probabilities). You can derive the Born rule using decoherence

Because it’s very straightforward and has less assumptions and weird features than most other interpretations, and it has seen the most advancements in quantum fundamentals research

Scarblac 3y ago
Complete layman here -- does that theory say that every time a quantum effect does or does not occur, in fact both possibilities happen but in different worlds? The entire universe instantly splits up in two for every quantum event anywhere in it? Edit: I read more comments and no, it's not literally that.
- bowsamic 3y ago
  Yes, it does mean that
edgyquant 3y ago
These are just mathematical tools we use to make predictions. Assuming they represent objective reality and somehow prove an infinite number of universes doesn’t seem very scientific to me.
- bowsamic 3y ago
  I mean, that's obviously a huge matter of debate, but most of us physicists at least hope that our theories reflect objective reality in some way. Also, there are of course explicitly ontological aspects of quantum mechanics, such as PBR theorem and Bell's inequalities
- goatlover 3y ago
  That's way too instrumentalist. The math also describes how atoms work and many other things. Modern physical understanding is based on those descriptions. Cosmology and nuclear physics would be useless without an understanding. How do the predictions work if they aren't in some way modeling the way reality is? Why does the technology based on them work? Instrumentalism gives no answers to those questions. Science is about understanding the world, and using that to make predictions.
  - edgyquant 3y ago
    They work because they use human logic which has evolved to understand the universe just enough to “work” and where that logic doesn’t work we use probabilities to ensure we’re only calculating the odds and deriving from there. You can devise probabilistic systems of equations to describe stock prices and account for when you could be wrong, but this is not you describing some objective set of equations the market emanates from. It working doesn’t mean it in anyway reflects some objective truth (if such a thing even exists.) It just breaks things down into small enough parts you can then model those parts and make predictions. This does not mean those small parts are “real” just that they are convenient ways to describe the flowing of energy for our purposes. > atoms work and many other things Atoms are still just a human created mathematical abstraction we use to describe and make predictions about matter. All there really is is energy and atoms are just a mathematical tool we use to study energy. This is quite literally the oldest debate in natural science and it seems like one half of the debate just decided they’re right a few centuries ago and stopped caring about the fact that’s not something they have (or can) ever proved. They’re tools, don’t get me wrong they are very useful ones, but the second you start pretending they’re anything else or that your interpretation of them is how reality really works you become just another religious zealot and that goes against everything science is supposed to be about.
    - goatlover 3y ago
      > Atoms are still just a human created mathematical abstraction we use to describe and make predictions about matter. All there really is is energy and atoms are just a mathematical tool we use to study energy. We can see atoms with electron microscopes. A mathematical tool to study energy doesn't say anything. A tool describing how chemistry arises from atomic structure does. > This is quite literally the oldest debate in natural science and it seems like one half of the debate just decided they’re right a few centuries ago and stopped caring about the fact that’s not something they have (or can) ever proved. Not proved, but imagine using this sort of argument against evolution being a true account of life's history on Earth. Of course it won't get everything right, but in general there is simply no other way to explain how life forms changed over time. Similarly, there's no other way to understand microscopic physics than quantum mechanics. Maybe a more complete theory combining gravity and QM would be more true, just like Newtonian physics was incomplete and superseded by relativity.

CraftingLinks 3y ago

Because that's what quantum mechanics in it's purest form tells us. Avoiding the many worlds requires tagging on extra stuff not in the equations.

tsimionescu 3y ago
Quantum mechanics tells us that, in order to predict the outcome of a measurement, we have to compute a specific probability based on the amplitude of the wavefunction. We can explain this probability as some kind of collapse, or we can explain it as some measure of the number of observers making the measurement in parallel "worlds". Neither is inherently closer to the math.
- consilient 3y ago
  > Quantum mechanics tells us that, in order to predict the outcome of a measurement, we have to compute a specific probability based on the amplitude of the wavefunction Even this is already wading into interpretational waters. The math says nothing about whether a given POVM should be thought of as a measurement or an interaction (or both, or neither).
  - tsimionescu 3y ago
    Sure, it's not part of the math, but it is part of the physics. There is a very clear distinction in the theory between "interactions", governed entirely by the Schrodinger equation (or its relativistic versions, or QFT), and a "measurement", where you have the apply the Born rule not only to predict what the measurement device will show, but also to correctly predict what will happen in a subsequent experiment on the same particle. Without the Born rule, QM makes nonsensical predictions that don't explain what happens. Decoherence helps explain certain things directly from the math without appealing to the extra Born rule, but not fully, and not quantitatively (not the specific probabilities).
    - bowsamic 3y ago
      > Sure, it's not part of the math, but it is part of the physics. "the physics" here is a specific interpretation > Decoherence helps explain certain things directly from the math without appealing to the extra Born rule, but not fully, and not quantitatively (not the specific probabilities). You can derive the Born rule using decoherence