Does realism imply locality or vice versa?

[stevendaryl]

"it is not assumed but inferred." J.B.

I agree with Bell on this. Here's my argument:

Suppose we have EPR with anti-correlated spins. Suppose for the sake of the story that Alice measures her particle's spin along the x-axis slightly before Bob measures his particle's spin along the x-axis.

Immediately after Alice measures her result, it is 100% certain what Bob's result will be: The opposite of Alice's. So we have two possibilities:

1. Bob's result was determined before Alice performed her measurement.
2. Bob's result was indeterminate before Alice's measurement, but became determinate immediately afterward.

In case #2, Alice's measurement seems to have had an effect on Bob's particle: it made a transition from an indeterminate state, where both results (spin-up or spin-down) are possible, to a determinate state, where only one result is possible. So possibility #2 would seem to violate the rule that Alice's actions can have no result on Bob's particle.

So case #1 is left. Of course, Bell's analysis proves that case #1 can't be true, either. So I don't know where that leaves us.

So I think it's completely wrong to say that Bell assumed determinism. What he assumed was what he called local realism, that Bob's results, deterministic or not, only depend on conditions near Bob.

 

[Denis]

How about this clarification? "Local theories with speed of information transfer greater then c would best be named Einstein-nonlocal."

That would be fine.

"It is important to note that to the limited degree to which determinism plays a role in the EPR argument, it is not assumed but inferred. What is held sacred is the principle of 'local causality' -- or 'no action at a distance'. ... It is remarkably difficult to get this point across, that determinism is not a presupposition of the analysis."

I find this a bit vague, but if HE is saying that CFD is not employed in his original argument then HE is correct (to a "limited degree") in saying, "It is remarkably difficult to get this point across", Because, I, for one, disagree with HIM.

We have the Bell proof, which goes roughly in the following way:

EPR criterion + Einstein locality -> CFD in this particular situation -> Bell inequalities.

Is CFD "employed" here? It doesn't matter. What matters is that presentations of Bell's theorem which forget about the first part, and present the theorem as

CFD -> Bell inequalities

and therefore arguing that all you have to do is to reject a CFD assumption (as it would have been made) are wrong.

I see clearly where HE stealthily introduced CFD into HIS proof.

I can see only a part where he proves that CFD holds for the particular case of the spin components in this particular state. A proof which is based on the EPR criterion of reality (which, taken alone, gives almost nothing, because it contains the very serious and essentially unprovable condition "without in any way disturbing the system") together with a very strong notion of Einstein causality (which forbids any distortion in any way FTL).

What is the definition of speeding on Montana highways? / What is the criterion for speeding on Montana highways?
I you wish to quibble over the difference, feel free, but I won't.
After checking the historical record Alice inferred Dr. Bob was wrong. / After checking the historical record Alice assumed Dr. Bob was wrong.

There are precise and clear differences in the meaning. A definition gives you all what is necessary and sufficient to be what is defined, a criterion only some sufficient condition. (Therefore, in case of disagreement about the definition, one can nonetheless often find some criterion.)
"Assumed" means the property is listed in the "If ..." part of a theorem. "Inferred" means it is not in the "if ..." part of the theorem. It may be used in the theorem, but only after being in the "then ..." part of a prior part of the proof. (Therefore it matters only as far as you doubt the proof. But if the proof is ok, you can forget about it.)

 

[fanieh]

Simon and others who are not realist or antirealist. If Bell's Theorem was discovered by Bohr.. would we have all these debates about realism? Bohr is anti-realist.. so in the event it's called Bohr's Theorem and there is Bohr's Inequality violation.. then it's automatically dispensing with realism, is this a right thing to think? The reason we have all these debates is because Bell happens to be a Bohmian and so the whole realism issues come out? Remember Copenhagen or the orthodox interpretation is anti-realism.. so without Bell, we won't have all these realism, counterfactual definiteness, etc stuff right? And Bohr's Theorem will be automatically dispensing reality. Just to understand it by these perspective.

I really think dispensing reality is more logical. Imagine you have two pixels in the monitor screen, does it make sense the two pixels are directly communicating non-locally. It makes more sense the two pixels (let's say representing two particles light years apart in the program) are vivified by the computer software and electron guns or electronics. Therefore for the two pixels, they are correlated not by direct nonlocal communication but behind the screen (or behind the scene stuff). This is bonafide Copenhagen and orthodox interpretation is it not where particles don't exist before measurement and they are called into existence by higher reality. Or is this not the orthodox at all? What is it then?

 

[Zafa Pi]

I agree with Bell on this. Here's my argument:

Suppose we have EPR with anti-correlated spins. Suppose for the sake of the story that Alice measures her particle's spin along the x-axis slightly before Bob measures his particle's spin along the x-axis.

Immediately after Alice measures her result, it is 100% certain what Bob's result will be: The opposite of Alice's. So we have two possibilities:

1. Bob's result was determined before Alice performed her measurement.
2. Bob's result was indeterminate before Alice's measurement, but became determinate immediately afterward.

In case #2, Alice's measurement seems to have had an effect on Bob's particle: it made a transition from an indeterminate state, where both results (spin-up or spin-down) are possible, to a determinate state, where only one result is possible. So possibility #2 would seem to violate the rule that Alice's actions can have no result on Bob's particle.

So case #1 is left. Of course, Bell's analysis proves that case #1 can't be true, either. So I don't know where that leaves us.

So I think it's completely wrong to say that Bell assumed determinism. What he assumed was what he called local realism, that Bob's results, deterministic or not, only depend on conditions near Bob.

When I wrote "it is not assumed but inferred." J.B., I was taking it from, "It is important to note that to the limited degree to which determinism plays a role in the EPR argument, it is not assumed but inferred." in post #68. I assumed, or inferred (you choose) that Bell was thinking about EPR's argument, not his own. And I think EPR is loaded with determinism. And when Bell derived his inequality he uses CFD, which I consider a form of determinism.

 

[Zafa Pi]

There are precise and clear differences in the meaning. A definition gives you all what is necessary and sufficient to be what is defined, a criterion only some sufficient condition. (Therefore, in case of disagreement about the definition, one can nonetheless often find some criterion.)
"Assumed" means the property is listed in the "If ..." part of a theorem. "Inferred" means it is not in the "if ..." part of the theorem. It may be used in the theorem, but only after being in the "then ..." part of a prior part of the proof. (Therefore it matters only as far as you doubt the proof. But if the proof is ok, you can forget about it.)

I am happy for you finding such precision in the meaning of these words (ignoring the two pairs of sentences I provided in post #70).
But if you get to fret over these distinctions then so do I.

Usually people use "nonlocal" instead. But the term nonlocality is misleading, because local theories with speed of information transfer greater then c would have to be named nonlocal, which is a little bit Orwellian.

Orwellian usually refers to dystopian social issues. I think you should have used "Star Trekian"

 

[Demystifier]

Blaylock claims MWI is local.

As I explained in the paper, MWI is not non-local, but it does not imply that it is local. (I wonder what my avatar would say about that? )

 

[Demystifier]

Orwellian usually refers to dystopian social issues. I think you should have used "Star Trekian"

Maybe @Denis had the illogical Orwellian newspeak in mind, because "faster than light" is not the same as "non-local".

 

[Zafa Pi]

As I explained in the paper, MWI is not non-local, but it does not imply that it is local. (I wonder what my avatar would say about that? )

I accept anything you say about MWI, for two reasons:
1) You're smart and funny, in spite of sometimes defending some of your wrong opinions.
2) I put MWI in the same aesthetic garbage bag as superdeterminism, so have at it. (at least this is what this version of me thinks)

I think your avatar has a mean streak and never gave Frege a comforting hug.

 

[Demystifier]

1) You're smart and funny, in spite of sometimes defending some of your wrong opinions.

Having wrong opinions occasionally is a prerequisite for being smart. In a sense, it can even be derived from the Godel's theorems.

 

[Simon Phoenix]

Having wrong opinions occasionally is a prerequisite for being smart

I wish you hadn't used the word occasionally there. If simply getting things wrong was a qualification for being smart I'd be Gauss!

We all learn from our mistakes - so hurry up and make lots of mistakes

I think it was Weinberg who coined that. In a kind of similar vein I also like Edison's statement along the lines of "I haven't failed 10,000 times - I have succeeded in finding 10,000 things that don't work"

 

[Zafa Pi]

I wish you hadn't used the word occasionally there. If simply getting things wrong was a qualification for being smart I'd be Gauss!

We all learn from our mistakes - so hurry up and make lots of mistakes

I think it was Weinberg who coined that. In a kind of similar vein I also like Edison's statement along the lines of "I haven't failed 10,000 times - I have succeeded in finding 10,000 things that don't work"

The only thing I've learned from my mistakes is that I don't learn from my mistakes.

 

[Simon Phoenix]

The only thing I've learned from my mistakes is that I don't learn from my mistakes.

Lol - very Godellian

 

[Denis]

I am happy for you finding such precision in the meaning of these words (ignoring the two pairs of sentences I provided in post #70).

The meaning of these words may be quite vague and unclear, as suggested by your examples. But in this particular context, their meaning and the differences are quite clear and certain.

Orwellian usually refers to dystopian social issues. I think you should have used "Star Trekian"

The actual state of fundamental physics is imho a quite close to a dystopian scenario.

 

[Demystifier]

The actual state of fundamental physics is imho a quite close to a dystopian scenario.

So you don't believe that we already have the theory of everything?

 

[Denis]

The actual state of fundamental physics is imho a quite close to a dystopian scenario.

So you don't believe that we already have the theory of everything?

Sorry, I have forgotten to insert a "mainstream":

The actual state of mainstream fundamental physics is imho a quite close to a dystopian scenario.

Better?

 

[Demystifier]

The actual state of mainstream fundamental physics is imho a quite close to a dystopian scenario.

Can you elaborate?

 

[Denis]

Can you elaborate?

Fundamental physics has no experimental base, no conflict between observation and theory, thus, has only a few theoretical problems to be solved. This makes the domain highly speculative. This happens, in itself not a problem. The natural state of non-dystopian fundamental physics, and the optimal for finding the truth (given that in highly speculative domains most proposals will fail) would be a large number of very different proposals, each proposal supported by rather small groups.

What we see in reality are a very few directions: Strings, LQG, that is essentially already all. And this is a sociological problem: Even if you would have an alternative idea, you would have to recommend young scientists not to study it - because non-mainstream research, that means here everything outside strings and LQG, cannot offer grants and jobs, and make it much harder to publish, so you will be probably out of science after the actual grant finishes. Scientists have to follow established mainstream fads to survive as scientists.

And these mainstream fads, once in a position of power (control over grants), do not even have to care about progress. The main objections against string theory have been raised 10 years ago. Have you heard about a major progress which would have invalidated any of the objections? But string theory is alive yet.

So, even if somebody outside the mainstream would have developed an approach for a TOE, given these sociological aspects the probability is quite high that it would be simply ignored. If this is not close to dystopian, what is?

 

[stevendaryl]

When I wrote "it is not assumed but inferred." J.B., I was taking it from, "It is important to note that to the limited degree to which determinism plays a role in the EPR argument, it is not assumed but inferred." in post #68. I assumed, or inferred (you choose) that Bell was thinking about EPR's argument, not his own. And I think EPR is loaded with determinism. And when Bell derived his inequality he uses CFD, which I consider a form of determinism.

Here's the way I would put it: Bell (as did Einstein before him) was assuming a particular type of physical theory--locally realistic theories. These theories include both deterministic and nondeterministic theories, those that obey CFD and those that don't. So his notion of locally realistic theory does not assume determinism or CFD...However, you can show pretty easily that out of all the locally realistic theories, only CFD theories can predict perfect correlation/anti-correlation.

So given perfect correlation/anti-correlation, Bell had no need to consider nondeterministic locally realistic theories.

So it's not

• Locally realistic theory [itex]\Rightarrow[/itex] determinism

It's

• Locally realistic theory + observations of perfect correlation/anticorrelation [itex]\Rightarrow[/itex] determinism

An example of a theory that is locally realistic (in my opinion) but is not CFD would be a stochastic theory such as Brownian motion. If the world is nondeterministic, but the nondeterminism of distant parts of the world are independent, then that would be locally realistic. For example, I could have a nondeterministic theory of perfect coins, where flipping a coin nondeterministically results in heads or tails. But if this theory is locally realistic, then there would be no correlations between the results of distant coin-flips.

 

[stevendaryl]

Fundamental physics has no experimental base, no conflict between observation and theory, thus, has only a few theoretical problems to be solved. This makes the domain highly speculative. This happens, in itself not a problem. The natural state of non-dystopian fundamental physics, and the optimal for finding the truth (given that in highly speculative domains most proposals will fail) would be a large number of very different proposals, each proposal supported by rather small groups.

What we see in reality are a very few directions: Strings, LQG, that is essentially already all. And this is a sociological problem: Even if you would have an alternative idea, you would have to recommend young scientists not to study it - because non-mainstream research, that means here everything outside strings and LQG, cannot offer grants and jobs, and make it much harder to publish, so you will be probably out of science after the actual grant finishes. Scientists have to follow established mainstream fads to survive as scientists.

And these mainstream fads, once in a position of power (control over grants), do not even have to care about progress. The main objections against string theory have been raised 10 years ago. Have you heard about a major progress which would have invalidated any of the objections? But string theory is alive yet.

So, even if somebody outside the mainstream would have developed an approach for a TOE, given these sociological aspects the probability is quite high that it would be simply ignored. If this is not close to dystopian, what is?

I agree that progress on fundamental physics has been slow or even nonexistent in recent years. I actually don't blame the mainstream or the sociological aspects so much, though. To me, the situation is that we have an effective model, the standard model, that describes things so well that there is almost no observations that contradict it. Progress in physics happens when you see something that is incompatible with mainstream science. There was a golden age of fundamental physics during which every few years, a new particle was discovered, a new kind of decay. All those years of discovery led to the standard model. But now, we don't seem to be able to easily produce anything that isn't already predicted by the standard model.

There are certainly lots of puzzles left unsolved--explaining the large-scale structure of the universe, explaining why particles have the masses they have, explaining why coupling constants have the values they do, etc. And there is no shortage of people trying to explain these things. But their theories are little-better than speculation (speculation supported by really difficult mathematics, in lots of cases) if they don't predict a verifiable departure from the standard model.

 

[stevendaryl]

I accept anything you say about MWI, for two reasons:
1) You're smart and funny, in spite of sometimes defending some of your wrong opinions.
2) I put MWI in the same aesthetic garbage bag as superdeterminism, so have at it. (at least this is what this version of me thinks)

I think your avatar has a mean streak and never gave Frege a comforting hug.

I actually think that there is a sense in which MWI, Bohmian mechanics, consistent histories and the "minimal interpretation" (Copenhagen without objective collapse) are in some sense, basically the same theory. It's just different ways of describing the same thing, like the old fable about the blind men and the elephant.

 

[fanieh]

Simon and others who are not realist or antirealist. If Bell's Theorem was discovered by Bohr.. would we have all these debates about realism? Bohr is anti-realist.. so in the event it's called Bohr's Theorem and there is Bohr's Inequality violation.. then it's automatically dispensing with realism, is this a right thing to think? The reason we have all these debates is because Bell happens to be a Bohmian and so the whole realism issues come out? Remember Copenhagen or the orthodox interpretation is anti-realism.. so without Bell, we won't have all these realism, counterfactual definiteness, etc stuff right? And Bohr's Theorem will be automatically dispensing reality. Just to understand it by these perspective.

I really think dispensing reality is more logical. Imagine you have two pixels in the monitor screen, does it make sense the two pixels are directly communicating non-locally. It makes more sense the two pixels (let's say representing two particles light years apart in the program) are vivified by the computer software and electron guns or electronics. Therefore for the two pixels, they are correlated not by direct nonlocal communication but behind the screen (or behind the scene stuff). This is bonafide Copenhagen and orthodox interpretation is it not where particles don't exist before measurement and they are called into existence by higher reality. Or is this not the orthodox at all? What is it then?

In short. Without Bell, we won't have any of these problems about realisms, is it not? Bohr has already declared that in the absence of measurements of the positions of particles, there are no positions.

 

[Denis]

Of course, if you have no problem to reject realism without sufficient reason (say, if you think Bohr's opinion is sufficient to reject realism), then, indeed, you will have no reason to care about all these debates about realism. Once Bohr has declared this ... or maybe once Pope Benedict has declared this ...

I prefer to care about arguments. Those proposed, say, by Bohm, or Bell, or those papers one is forbidden to link here, not because of the authority of Bohm or Bell or those evil nonconformists, but because of the content of their arguments.

And the content which is relevant is that there exists theories and interpretation for everything which are compatible with realism.

 

[fanieh]

If realists are Demystifier, Denis
and anti-realists are DrChinese
what about the statistical essemblers like Bill Hobba and Vanhees71, are these considered Realists too or agnostics (neither realists or anti-realists)?

 

[Denis]

They have to decide themselves. But the statistical ensemble interpretation is not in conflict with realism. Realism is not determinism, thus, completely comfortable with a statistical description.

 

[OCR]

The only thing I've learned from my mistakes is that I don't learn from my mistakes.

HA! [COLOR=#black].[/COLOR] The only time I've ever been wrong, was once... when I thought I'd made a mistake ! [COLOR=#black].[/COLOR] [COLOR=#black].[/COLOR]

 

[forcefield]

So we have two possibilities:

1. Bob's result was determined before Alice performed her measurement.

So case #1 is left. Of course, Bell's analysis proves that case #1 can't be true, either. So I don't know where that leaves us.

I think what Bell proved was that the possible determinism was not like Bertlmanns' socks. I also think that Bertlmanns' socks type of determinism is close to Bohr's realism (whatever that is).

I am left with FTL effects assuming philosophical realism.

 

[Simon Phoenix]

Without Bell, we won't have any of these problems about realisms, is it not?

Isn't that a bit like blaming Newton for breaking the glass you've just dropped?

Anyway, there was already something of a sinking feeling regarding 'realism' well before Bell - I mean one only has to attempt (and usually fail) to understand Bohr's dense ramblings to see that a big spanner had already been chucked in the works regarding any 'classical' worldview. Bell just used it to tighten the nuts

 

[fanieh]

Isn't that a bit like blaming Newton for breaking the glass you've just dropped?

Anyway, there was already something of a sinking feeling regarding 'realism' well before Bell - I mean one only has to attempt (and usually fail) to understand Bohr's dense ramblings to see that a big spanner had already been chucked in the works regarding any 'classical' worldview. Bell just used it to tighten the nuts

Isn't that a bit like blaming Newton for breaking the glass you've just dropped?

Anyway, there was already something of a sinking feeling regarding 'realism' well before Bell - I mean one only has to attempt (and usually fail) to understand Bohr's dense ramblings to see that a big spanner had already been chucked in the works regarding any 'classical' worldview. Bell just used it to tighten the nuts

How do you relate the factorization or preferred basis problems in MWI to the realism/antirealism thing in Bell's? Conventionally, MWI supports realism.. but with the preferred basis problem and any solution, can it become anti-realism or still realism?

 

[Simon Phoenix]

How do you relate the factorization or preferred basis problems in MWI to the realism/antirealism thing in Bell's?

I don't.

Generally I try to think about MWI as little as I possibly can

 

[fanieh]

Are all MWI variants pro-realisms and pro-locality?
Or are there MWI variants that are non-local?

I think I read somewhere that BM is when you consider only a single branch of the MWI.. so does this mean MWI is fully realistic like BM?

 

[morrobay]

Are all MWI variants pro-realisms and pro-locality?
Or are there MWI variants that are non-local?

I think I read somewhere that BM is when you consider only a single branch of the MWI.. so does this mean MWI is fully realistic like BM?

Go Ask Alice

 

[Zafa Pi]

Here's the way I would put it: Bell (as did Einstein before him) was assuming a particular type of physical theory--locally realistic theories. These theories include both deterministic and nondeterministic theories, those that obey CFD and those that don't. So his notion of locally realistic theory does not assume determinism or CFD

I agree that Einstein and Bell (when deriving his theorem) assumed local realism (LR). But according to Wikipedia we have, "Local realism is a feature of classical mechanics and of classical electrodynamics" . (you will also find "realism, another principle which relates to the value of unmeasured quantities") And if you peruse the internet you find that almost all agree that classical mechanics is a deterministic theory.
Thus LR does not include nondeterministic theories. That is my position as well.

An example of a theory that is locally realistic (in my opinion) but is not CFD would be a stochastic theory such as Brownian motion.

Since CFD is an artifact of determinism you are saying that Brownian motion is not deterministic. That is false, it is Einstein baby and part of classical mechanics. I can say things like "When a particle of pollen is released at time zero and ends at position x after ten seconds, if instead it was released at time one it would be at some position y after ten seconds." Straight CFD.

For example, I could have a nondeterministic theory of perfect coins, where flipping a coin nondeterministically results in heads or tails.

You could by employing QT, but not from CM.

I agree that it is impossible (even in principle) to find the initial position and velocity of all the atoms involved in pushing the poor pollen to and fro. Thus I'm inclined to believe, in the name of God, that determinism is a religion, without considering QT.

• Locally realistic theory + observations of perfect correlation/anticorrelation ⇒⇒\Rightarrow determinism

If the correlations you are referring to are those that come from measuring entangled photons, then then LR and the correlations are incompatible.
It's like saying X + notX ⇒ determinism or anything else.

 

[stevendaryl]

I agree that Einstein and Bell (when deriving his theorem) assumed local realism (LR). But according to Wikipedia we have, "Local realism is a feature of classical mechanics and of classical electrodynamics" . (you will also find "realism, another principle which relates to the value of unmeasured quantities") And if you peruse the internet you find that almost all agree that classical mechanics is a deterministic theory.
Thus LR does not include nondeterministic theories. That is my position as well.

I'm saying that's wrong. As Bell said, you can allow for nondeterminism in your theory and still have it be of the type that he was considering, but the problem is that you cannot predict perfect correlations and anticorrelations unless the theory is deterministic.

It's certainly correct that classical mechanics was deterministic, but you can generalize classical mechanics to allow for nondeterminism, and as long as the nondeterminism is local, it still won't violate Bell's inequalities.

Brownian motion is not a deterministic theory. Einstein may have believed that it could be explained in terms of an underlying deterministic theory, but it wasn't itself deterministic.

 

[stevendaryl]

Perhaps this is not worth arguing about, except that Bell made the correct point that determinism is a conclusion, not an assumption, and I have been trying to explain what I think he meant by that. An example of the type of theory that would count as a nondeterministic locally realistic theory would be a theory of nondeterministic cellular automata. Suppose that spacetime is actually discrete (maybe at the Planck level). Then you could describe the state of the universe in the following terms:

1. Divide up the universe into tiny little cubes of size [itex]L^3[/itex], where [itex]L[/itex] is some tiny length. Then a cell is specified by a triple of integers [itex](i,j,k)[/itex], which is the cell where [itex]i L \leq x \leq (i+1)L[/itex], [itex]j L \leq y \leq (j+1)L[/itex], [itex]k L \leq z \leq (k+1) L[/itex].
   
2. Each cell can be in one of a finite number of possible states: [itex]\sigma_1, \sigma_2, ..., \sigma_N[/itex]
3. Divide time up into discrete intervals, of length [itex]L/c[/itex].
4. Then describe the complete state of the world by a function [itex]S(i,j,k)[/itex], where [itex]i, j, k[/itex] range over integers, specifying the state of cell with label [itex](i,j,k)[/itex]
5. Describe the evolution of the state by a probability transition function: [itex]P(n | n_0 , n_1, ..., n_8)[/itex].

The meaning of the probability transition function is this: If at time [itex]t[/itex], you have a cell in state [itex]\sigma_{n_0}[/itex], and its 8 nearest neighbors are in states [itex]\sigma_{n_1}, \sigma_{n_2}, ... \sigma_{n_3}[/itex], then at time [itex]t + L/c[/itex], that cell will be in some state [itex]\sigma_{n}[/itex] with a probability given by [itex]P(n | n_0 , n_1, ..., n_8)[/itex].

This is a nondeterministic theory. But it is local in the sense that the next state of any cell depends only on the state of that cell and the states of cells that it is touching.

 

[Zafa Pi]

I said: "I agree that Einstein and Bell (when deriving his theorem) assumed local realism (LR). But according to Wikipedia we have, "Local realism is a feature of classical mechanics and of classical electrodynamics" . (you will also find "realism, another principle which relates to the value of unmeasured quantities") And if you peruse the internet you find that almost all agree that classical mechanics is a deterministic theory.
Thus LR does not include nondeterministic theories. That is my position as well."

I'm saying that's wrong.

Fine, then where is is the fallacy in: Wikipedia ⇒ LR is CM ⇒ CM is deterministic?
Your attempt at a nondeterministic LR theory with Brownian motion was wrong.

, but the problem is that you cannot predict perfect anticorrelations unless the theory is deterministic.

I don't understand. QT predicts perfect anticorrelations when the measurement are at the same angle/axis. QT is not deterministic.