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Author Topic:   Is the “Fine-Tuned Universe” an Illusion?
Son Goku
Inactive Member


(2)
Message 53 of 61 (892150)
02-28-2022 7:36 AM
Reply to: Message 52 by AZPaul3
02-28-2022 1:08 AM


Re: Many Worlds
I'll take the statements out of order from your original post.
QM is internally inconsistent in it's definition of a measurement. What is a measurement? What happens when a measurement occurs?
This is not true. It's fairly clear in the theory what happens when a measurement occurs. There's a mathematical operation to describe how a measurement affects the state of the system.
The technical name for this mathematical structure is a Kraus operator, although when students take their first course in quantum mechanics we usually simplify it to something called a projection operator. The technical details don't matter so much for a forum post here, the point is more that it's fairly clear what happens when a measurement occurs, I've taught it several times and it pops up usually the first three chapters of an undegraduate QM book. If the theory couldn't describe how to deal with measurements it wouldn't be empirically valid.
Furthermore QM can be derived as a set of statements about measurements, i.e. its rules for describing measurements are in fact the core of the theory from which the rest can be derived. This is covered in recent books like Jochen Rau's "Quantum Theory: An Information processing approach" and D'Ariano's "Quantum Theory from First principles". It's even covered in detail in older books like Julian Schwinger's "Quantum Mechanics: Symbolism of Atomic Measurement" and Asher Peres' "Quantum Theory: Concepts and Methods".
So quantum theory has a very clear notion of what occurs upon a measurement and nobody has ever shown an actual internal inconsistency.
Some people don't like measurement being a primitive, but that's different from a mathematical inconsistency.
Copenhagen
....
But it is not a solid consensus of the discipline
.....
Objective reality has been "interpreted" to be incorrect by one school of QM
You said phrases like this a few times in your post.
"Copenhagen" usually refers to the specific approach to quantum theory discussed by Heisenberg, Bohr, Peierls, Pauli, von Weisacker, Ludwig, Born, etc. Essentially the understanding of the theory by the people who discovered it, as well as others after them such as Julian Schwinger.
I never specifically referred to this. In fact my favourite way of looking at the theory is that of the French physicist Roland Omnès called Consistent Histories. It doesn't really matter because although there might not be an exact consensus on whether literally every aspect of Copenhagen is correct, there is very little debate about a return to objective reality by people who discuss the fundamentals of quantum theory. It's not just one school that comes away from objective reality, it's virtually all of them. It's really impossible to understand how somebody could maintain it when you know the theory well due to results like the Kochen-Specker theorem, the Unruh effect and so on. That's why most people, even if they don't completely agree with Bohr, rarely argue for objective reality or measurement independent values.
Added to this is that the people that advocate a return to an objective reality have no working theory that actually matches observations.
In fact most of the people who disagree with Copenhagen think Bohr wasn't subjective enough.
The internal inconsistency shows the theory in not complete and needs to be adjusted
Again I have never seen this "internal inconsistency".
Fundamental levels? I submit we aren't there yet. We can make QM/QFT work so very well, exceptional accuracy, modern magic, but we don't know how measurement works or why it works. One view is to say hang the lot of it, reality doesn't matter, just shut up and calculate. Very productive but very inane.
I expect more. The smart guys have a lot more study to do.
Sorry AZPaul3 but I honestly view this as somewhat anti-scientific.
We physicists don't just think "reality doesn't matter". It's that we have seen a theory that jettisons objective reality, quantum theory, matches experimental results and there is no working theory that retains objective reality. Further as physics has advanced since Heisenberg's rejection of objective reality we have had to remove more and more elements of objectivity from our theories.
The realisation that reality lacks an objective description is an advancement in our understanding of reality. Going on about how a theory and the people who use it are "inane", have "more study to do" and you personally "expect more" is just anti-scientific rhetoric about a theory being poor because it doesn't match your metaphysical predilections regardless of how empirically successful it is.
Here is a video with a much better explanation of the issue involved. It is not a settled matter in the discipline.
I know both Hossenfelder, I have met her, and the experiment she is discussing. I'll only say:
(a) I don't see any reason why she is focusing on this experiment when the hundreds of experiments on the Kochen-Specker theorem, GHZ theorem, etc already show the existence of an objective description of reality is untenable. I don't think she analyses this experiment correctly. Ultimately her objection just amounts to that the experiment doesn't show a lack of objectivity at the human level. All of us know this. As I said above large scale features of the world are known to support an objective description. That's why Classical Mechanics works. The experiment does show however the lack of an objective description at the atomic level. One of hundreds that does so.
(b) She herself has started advocating nonsense like superdeterminism, an idea that involves rejecting basic aspects of scientific thinking. Again just because quantum theory doesn't fit her metaphysical preconceptions.
Again all I can say to you is look at the actual literature. Roland Omnes, Asher Peres, Bernard d'Espagnat, Werner Heisenberg, Rudolf Haag, all of them and several others have highly cited (thousands of citations) monographs explaining why you have to give up objective reality. To me it is a settled matter scientifically. It's only unsettled under the trivial criterion of "there exists some people saying otherwise in youtube videos and some pop science books". I mean then we could say evolution is not a settled matter in the discipline of biology due to the presence of creationist academics.
Edited by Son Goku, : Typos

Edited by Son Goku, : Details


This message is a reply to:
 Message 52 by AZPaul3, posted 02-28-2022 1:08 AM AZPaul3 has not replied

  
Son Goku
Inactive Member


(1)
Message 54 of 61 (892163)
02-28-2022 3:57 PM


Experimental tests of Objective Reality
Actually for anybody wondering, just to provide a brief explanation how one can actually experimentally refute objective reality. It comes in two forms.
First of all, since quantum mechanics rejects the idea of an objective reality any experimental test in support of it is in a sense experimental evidence that objective reality is wrong.
However a more interesting case are the so called "no-go theorems". These are various mathematical proofs that show that a given experiment has to give results within a certain range if the idea of an objective description of reality is correct. The theorems have different names depending on the exact type of experiment they give constraints to, some examples include CHSH, GHZ, Kochen-Specker, Aravind-Mermin. The video by Hossenfelder concerns a recent such no-go result called Brukner's theorem.
When we have done these experiments the results break the constraints that follow from assuming an objective description of reality. Which means even if QM were wrong, objective reality wouldn't be right. The theory needed to replace QM would be another non-objective theory because these "no-go" experiments provide a test of objective reality independent of QM.

Replies to this message:
 Message 55 by Tanypteryx, posted 03-05-2022 9:30 PM Son Goku has replied

  
Son Goku
Inactive Member


(2)
Message 58 of 61 (892365)
03-06-2022 12:00 PM
Reply to: Message 55 by Tanypteryx
03-05-2022 9:30 PM


Re: Speed of Light = Speed of Gravity
If this doesn't make sense just say so and I'll phrase it differently.
We humans can easily imagine an object travelling from Earth to Mars faster than light say, because we picture space and time as seperated intuitively. We just imagine space as a thing that exists independent of time, i.e. there is the expanse between Earth and Mars that exists regardless of what time passes. Modern Physics* says this isn't true.
In modern physics the universe has a four dimensional shape that has "gaps" in it. If an ant wants to walk from one side of a doughnut to another it can't take a straight path simply because there is a hole in the middle of the doughnut, it has to go the long way round. Similarly you can't go from Earth to Mars FTL because that path passes over a giant "hole" in the universe's geometry and you have to take the "long way round", namely slower than light.
Moving at the speed of light is essentially taking a path that skims right along the edges of these gaps, so it is impossible to move faster than this. Only if you are massless can you do this, which both light and gravity are.
*I say Modern Physics rather than Relativity since I am taking the more complete picture from Quantum Field Theory.

This message is a reply to:
 Message 55 by Tanypteryx, posted 03-05-2022 9:30 PM Tanypteryx has replied

Replies to this message:
 Message 59 by Tanypteryx, posted 03-06-2022 1:46 PM Son Goku has replied

  
Son Goku
Inactive Member


(3)
Message 60 of 61 (892391)
03-06-2022 3:18 PM
Reply to: Message 59 by Tanypteryx
03-06-2022 1:46 PM


Re: Speed of Light = Speed of Gravity
OK, what are the "gaps"?
Holes as such in the shape of the universe. Like the hole in the center of a doughnut.
EDIT: A bit more detail. If you draw a 2D graph with time on the vertical axis and space on the horizontal axis then moving FTL at a constant speed is a line less then 45 degrees from the horizontal, i.e. covers more space than time. Although you can draw such paths modern physics says they don't really exist due to the universe's real geometry being different from this simple model. An FTL path is really like imagining a path along the surface of the Earth shorter than a great circle, i.e. invalid due to the true geometry.
So protons are just sitting there, not moving unless they are accelerated, but neutrinos seem to be always in motion at almost the speed of light. What gives them that speed or what accelerated them?
Neutrinos are usually given large kinetic energy at the moment of emission during a decay event.
Note that neutrinos are a bit more complicated than you'd think in that they either have a well-defined mass or a well-defined type (electron neutrino, muon neutrino, tau neutrino) but never both at the same time. So if you measure their type the result, which is probabilistic not determined, might be an electron neutrino but their mass remains undefined. If you measure their mass in some way (also probabilistic) their type is undefined.
but why do they both travel at the same speed?
Because they are both massless. Everything massless moves right along the "edge" of these gaps/shortest paths in spacetime. Since it's the shortest path through spacetime there's no quicker way to move than that. Humans can imagine shorter paths, i.e. FTL ones, because we don't correctly intuit the actual shape of the universe. It's like how there is no shorter way to move along the surface of the Earth than going along a great circle.
Edited by Son Goku, : More detail

This message is a reply to:
 Message 59 by Tanypteryx, posted 03-06-2022 1:46 PM Tanypteryx has replied

Replies to this message:
 Message 61 by Tanypteryx, posted 03-06-2022 4:29 PM Son Goku has seen this message but not replied

  
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