B Schrodinger's Cat and The Universe

I had a question about Schrodinger's cat that extends to the universe.

First, I'm sure everyone knows the Schrodinger's cat set up so I won't repeat it. I will just ask, how can the cat be dead or alive prior to measurement? This measurement would be either atoms in the radioactive substance decay in an hour or they don't decay and the Experimenter opens the box.

Until this measurement occurs, how can we say the cat is dead or alive? Decoherence tells why you will see a dead cat or live cat but how can decoherence know which state to decohere to prior to measurement?

This leads to another question that I was curious about. What does Science say about the objective universe? For instance, we live subjective lives like I like spaghetti/I hate spaghetti. As far as I can tell these are subjective experiences.

An objective experience would be an Experimenter that measures which slit the particle went through.

My question is, what does Science say about that objective experience? Is it objective or is it just a subjective local experience and we're the end of observation in our local universe, therefore some superobserver could see a version of the Experimenter measuring the particle going through one slit and another version going through the other?

I remember reading in Nature about the death of local realism. So, does Science say our universe is non local and what we experience as Objective is really Subjective when connected to some wider universe that may be at thermodynamic equilibrium or is an isolated objective experience that's objectively real?

Does Science say anything when it comes to these questions?
 
Last edited:
14,991
4,652
... how can the cat be dead or alive prior to measurement?
It isn't. Schrodinger created the cat in a box thing to show how silly such a concept IS, NOT to show that that's actually how it is. Pop-science has been misrepresenting it ever since.
 

Demystifier

Science Advisor
Insights Author
2018 Award
9,741
2,782
Does Science say anything when it comes to these questions?
Science doesn't say anything. It is the scientists, not the science, who say something. On these questions scientists say a lot, but it is a controversial topic on which there is no mutual agreement between different scientists.
 
Decoherence tells why you will see a dead cat or live cat but how can decoherence know which state to decohere to prior to measurement?
This is how Quantum Mechanics differs from other areas of science: in other fields, we can explain phenomena by taking things apart and studying their components.

So, for example, we can explain the behaviours of Gases by considering them as many little atoms bouncing around.

But with QM, we cannot take it apart. There are no components. It's the "end of the line". The equations tell us what will happen but we can't say why.

There are "interpretations" of QM but they are only aids to our imaginations. So, for example, one "interpretation" says that opening the catbox will split the observer into 2 worlds. If you're comfortable with that (many aren't), you can imagine that to be your answer.

David
 
9,083
2,007
Does Science say anything when it comes to these questions?
What is the essence of science? Correspondence with experiment. I think if you cognate on the questions you asked its not the sort of thing that's experimentally testable. So science doesn't really say anything. That does not mean scientists do not have views on such things - but there is no general consensus.

Thanks
Bill
 

Demystifier

Science Advisor
Insights Author
2018 Award
9,741
2,782
This is how Quantum Mechanics differs from other areas of science: in other fields, we can explain phenomena by taking things apart and studying their components.
In that sense, QM is somewhat similar to psychology. (Or should I write ##\psi##chology?) Humans behave very differently when they know they are observed.
 
This is how Quantum Mechanics differs from other areas of science: in other fields, we can explain phenomena by taking things apart and studying their components.

So, for example, we can explain the behaviours of Gases by considering them as many little atoms bouncing around.

But with QM, we cannot take it apart. There are no components. It's the "end of the line". The equations tell us what will happen but we can't say why.

There are "interpretations" of QM but they are only aids to our imaginations. So, for example, one "interpretation" says that opening the catbox will split the observer into 2 worlds. If you're comfortable with that (many aren't), you can imagine that to be your answer.
Thanks for the response.

You bring up a good point and I had a question about interpretations. Wouldn't it make more sense to accept QM on it's face without interpretations? I know that would mean accepting what's called QM weirdness on a classical level but there's so many interpretations and the list keeps growing and the proponents of each of these interpretations will say they have evidence that there's is the correct one.

Copenhagen Interpretation
Bohemian Mechanics
Many Worlds
Many Histories
Quantum Bayesianism
Ensemble Interpretation
Objective collapse theories
Transactional interpretation
Cosmological interpretation
Quantum Darwinism


That's just some of them.

It seems to most of these interpretations are self imposed because Scientist don't like quantum weirdness. I read Penrose and his self collapse theory and he says at a certain point due to quantum gravity, the probabilities of QM collapse into one state. I think there has been objects that has past his threshold that has been put into Schrodinger cat states like the Cesium atom.

Wouldn't it be easier to accept QM as universal and we're just a subsystem of some larger system in thermal equilibrium therefore whatever happens in our subsystem isn't objective? If you accept QM as universal do you really need interpretations?
 
Interpretations are simply tools to help us think about QM - in particular, they help us to predict the results of new experiments.

Strange as it may seem, scientists who agree on all the known equations and predictions of QM, may disagree on what a given apparatus will do. They may even disagree on what it's doing when they have it working. Take, for example, the "delayed-choice quantum eraser". Some imagine that it's sending information backwards in time. Others think it's not doing anything unusual at all. It depends on your interpretation.

David
 
516
17
Interpretations are simply tools to help us think about QM - in particular, they help us to predict the results of new experiments.
If different interpretations lead us to make different predictions, then we've gone past interpreting.
 
9,083
2,007
Wouldn't it make more sense to accept QM on it's face without interpretations?
Seems easy doesn't it? Trouble is the formalism has probabilities and while not usually discussed in books on probability, to make sense of it you need an interpretation of probability. John Baez discusses the issue here:
http://math.ucr.edu/home/baez/bayes.html

The bottom line is:
It turns out that a lot of arguments about the interpretation of quantum theory are at least partially arguments about the meaning of the probability!

In QM some kind of minimal interpretation is required. Formally though we have a pretty good idea what QM is about:
https://arxiv.org/abs/1402.6562

It's just a generalized probability model - likely the simplest after ordinary probability theory. But we have that sticky issue of exactly what is probability? There is also the issue of since its a generalized probability model about observations that occur here in the classical world, since everything is quantum, the classical world is quantum as well. It's circular - some even think incomplete because of it. Nonetheless a lot of progress has been made in resolving it eg:
https://www.sciencenews.org/blog/context/gell-mann-hartle-spin-quantum-narrative-about-reality

Thanks
Bill
 
Interpretations are simply tools to help us think about QM - in particular, they help us to predict the results of new experiments.

Strange as it may seem, scientists who agree on all the known equations and predictions of QM, may disagree on what a given apparatus will do. They may even disagree on what it's doing when they have it working. Take, for example, the "delayed-choice quantum eraser". Some imagine that it's sending information backwards in time. Others think it's not doing anything unusual at all. It depends on your interpretation.

David
Exactly,

I remember reading a Paper that said the wave function was real but non physical. Another Paper said the wave function is physical and yet another that says the wave function is neither real nor physical. All of these positions also can be used to say here's evidence for the interpretation you support.

So as I said, wouldn't it be easier to accept QM without interpretation. I was reading an article in Scientific American by Niayesh Afshordi is an assistant professor of physics and astronomy at the University of Waterloo, Robert B. Mann is a professor and former chair of physics and astronomy at the University of Waterloo and Razieh Pourhasan is a Ph.D. candidate at the Perimeter Institute who say our universe is the result of a Black Hole that collapsed in 4D space. It's called The Black Hole at the Beginning of Time.

https://www.researchgate.net/publication/264537601_The_Black_Hole_at_the_Beginning_of_Time

This would make things a lot easier. Our universe would be inside of black hole that collapsed in a 4D universe. So it would have a 3D event horizon. The wider system would be the 4D black hole in thermodynamic equilibrium and we would be a low entropy subsystem or a holographic projection of the information on the 3D event horizon. They say:

Of course, even as the holographic big bang resolves one giant question—the origin of our universe—it simultaneously raises a new set of mysteries. Foremost among them: Where did our universe’s parent universe come from?

For an answer to this puzzle, we might again turn to Plato. When Plato’s prisoners emerged from the cave, the light of the sun burned their eyes. It took them time to adjust to the brightness. At first, the prisoners were only able to make out shadows and reflections. Soon they could see the moon and the stars. Finally, they correctly concluded that the sun was “the author of all that we see”—day, night, season and shadow. Plato’s prisoners didn’t understand the powers behind the sun, just as we don’t understand the four-dimensional bulk universe. But at least they knew where to look for answers.
It raises new questions but it removes the need for interpretation of QM. QM would be universal and there's no need to translate QM into Classical Physics with interpretations. It's like you can play a new game called the interpretation game where you can match any discoveries in QM with the interpretation of your choice.
 
The bottom line is:
It turns out that a lot of arguments about the interpretation of quantum theory are at least partially arguments about the meaning of the probability!
Very good point. It seems all interpretations have different ways to look at probability. You also said:

[
In QM some kind of minimal interpretation is required.
Isn't this an impossible task though? Probabilities imply a basic level of uncertainty. It seems the debate about the nature of these probabilities and that's why there's so many interpretations.
 
9,083
2,007
Isn't this an impossible task though? Probabilities imply a basic level of uncertainty. It seems the debate about the nature of these probabilities and that's why there's so many interpretations.
Some interpretations like Ensemble are minimalist in that they simply give an interpretation to probability - in that case its frequentest.

Thanks
Bill
 

Lord Jestocost

Gold Member
2018 Award
335
205
Wouldn't it make more sense to accept QM on it's face without interpretations?
Yes!
There is an attitude towards quantum mechanics (QM) which might be termed “operationalism”. As characterized by A. J. Leggett: According to the adherents of this view, the whole formalism of QM amounts to nothing but a calculational recipe, designed in the last resort to predict the probabilities of various directly observed macroscopic outcomes, and the symbols occurring in it, such as the probability amplitudes, correspond to nothing in the “real world”.
By this way, one avoids to make the mistake to think about quantum phenomena with classical ideas. Classical concepts loose there meaning when thinking about quantum phenomena; thus, physics has to rely on a mathematical scheme and its unambiguous correlation with experimental facts.
 

Want to reply to this thread?

"Schrodinger's Cat and The Universe" You must log in or register to reply here.

Physics Forums Values

We Value Quality
• Topics based on mainstream science
• Proper English grammar and spelling
We Value Civility
• Positive and compassionate attitudes
• Patience while debating
We Value Productivity
• Disciplined to remain on-topic
• Recognition of own weaknesses
• Solo and co-op problem solving

Hot Threads

Top