# Physics and “reality”

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“Yes, everything in physics is completely made up – that’s the whole point”

Is it ever true, then, to say that an electron is ‘real’ when it’s in motion? If we believe that electrons are real things, have we just made up the wavefunction to make the math work out? Absolutely – that was, in fact, the whole point. We couldn’t get the equations to work if the electron was a solid, isolated particle, so we made up something that wasn’t, and then the numbers started making sense.

physics isn’t built around ultimate truth, but rather the constant production and refinement of mathematical approximations. It’s not just because we’ll never have perfect precision in our observations. It’s that, fundamentally, the entire point of physics is to create a model universe in math - a set of equations that remain true when we plug in numbers from observations of physical phenomena.

Another physicist’s take on physics describing behavior vs reality

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Posted (edited)
45 minutes ago, swansont said:

“Yes, everything in physics is completely made up – that’s the whole point”

Is it ever true, then, to say that an electron is ‘real’ when it’s in motion? If we believe that electrons are real things, have we just made up the wavefunction to make the math work out? Absolutely – that was, in fact, the whole point. We couldn’t get the equations to work if the electron was a solid, isolated particle, so we made up something that wasn’t, and then the numbers started making sense.

physics isn’t built around ultimate truth, but rather the constant production and refinement of mathematical approximations. It’s not just because we’ll never have perfect precision in our observations. It’s that, fundamentally, the entire point of physics is to create a model universe in math - a set of equations that remain true when we plug in numbers from observations of physical phenomena.

Another physicist’s take on physics describing behavior vs reality

Yes, up to a point. However I always dislike the tendency to make out physics is all about maths. Physical concepts come before, or simultaneously with, the maths. You have to describe an electron and its properties in words before you can do any maths involving it. So yes, physics makes mathematical models, but the building blocks that the maths connects and manipulates are concepts of physical entities and their attributes that are, of necessity,  described in words.

The writer quoted also seems to me to somewhat evade the issue about "reality" when she says the wave function is "made up". That suggests it is a fiction. However the fact that this made up maths fits the observations so well shows it is a model of reality that is pretty accurate. So while no one would claim a wave function "is real", the wavelike behaviour it describes does at least represent an aspect of reality.

Edited by exchemist
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To me, the funny thing about it is that every so often the mathematical model does suggest to us that the previous model in terms of inalienable properties A, B, C, etc. does suggest that we'd better drop say, C, no matter how cherished a property of this 'reality' it is. In QM, this 'C' could be 'position' or 'momentum.' In SR, it could be position and/or velocity, and in GR it could be the concept itself of an inertial system, or coordinates by themselves.

For lack of a better term, I would define this as a very ordered process of 'letting go' of anchors to what we think to be real.

x-posted with @exchemist

6 minutes ago, exchemist said:

Yes, up to a point. However I always dislike the tendency to make out physics is all about maths.

Agreed. But I think that's more an over-simplification that some people do when they don't understand time-tested principles like operationalism --the theory should have a counterpart in laboratory operations--, Ockam's razor --the theory should never create arbitrarily complicated constructs, and should be as logically simple as possible; it should produce falsifiable propositions --Popper--, etc.

I recognise that as a risk, but I think an acquaintance with some principles of the philosophy of science generally operate as a good antidote. If one is well-versed in the history of science, I think one can minimise the risk.

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Posted (edited)
1 hour ago, exchemist said:

I always dislike the tendency to make out physics is all about maths. Physical concepts come before, or simultaneously with, the maths. You have to describe an electron and its properties in words before you can do any maths involving it. So yes, physics makes mathematical models, but the building blocks that the maths connects and manipulates are concepts of physical entities and their attributes that are, of necessity,  described in words.

The writer quoted also seems to me to somewhat evade the issue about "reality" when she says the wave function is "made up". That suggests it is a fiction. However the fact that this made up maths fits the observations so well shows it is a model of reality that is pretty accurate.

The entire physics community has been evading the issue of "reality" (i.e. ontology) for over a century. Relativity and quantum mechanics suddenly made the question maddeningly difficult, so physicists copped out and gave up, saying "It's not our job. It's mere philosophy". Just like the fox and the grapes.

Quote

The most common response I get when I talk about dark matter is: “isn’t this just something physicists made up to make the math work out?”

The author (like most other professional physicists) misses the point of the question by ignoring the word "just". People don't complain that dark matter is something physicists made up, they complain that it's just  something they made up, meaning it's not "real" in the sense that science is commonly expected to be (and was perceived to be in the 19th century). Many critics even explicitly make the analogy with epicycles as bad science that was motivated by religious narrow-mindedness.

Of course, many of them are motivated by "physics envy", i.e. frustration that the geeks of the world have been getting so much attention and legitimacy for the last few centuries, and a common counter-argument by science advocates is that critics are projecting their own narrow-mindedness onto scientists.

But the current mainstream counter-argument (which is repeated for the zillionth time in the article) is dangerous. It basically says it's okay to do bad science -- or at least shallow science -- until someone comes up with something better, and anyone who doesn't like it can go jump in a lake. But the bad science of string theory has been (or at least was recently) dominating theoretical physics research politically, suppressing more promising lines of research and wasting billions of dollars and the careers of thousands of bright theorists. Physicists risk a religious backlash if the community gets too corrupt and too dominated by unproductive pseudoscience.

Edited by Lorentz Jr
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I see a relation between models in physics and reality akin the relation between living organisms and environment. Models in physics evolve to fit their domains of reality, like organisms evolve to fit their environment.

Models in physics don't reflect or describe the reality, but they represent aspects of reality by being able to successfully work with it. Similarly, organisms don't look like their environment, but they represent aspects of the environment by being able to successfully operate in it.

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1 hour ago, exchemist said:

The writer quoted also seems to me to somewhat evade the issue about "reality" when she says the wave function is "made up". That suggests it is a fiction. However the fact that this made up maths fits the observations so well shows it is a model of reality that is pretty accurate. So while no one would claim a wave function "is real", the wavelike behaviour it describes does at least represent an aspect of reality.

Whenever this comes up, the distinction of what one means by real needs to be made: real as opposed to fantasy/fictitious, or real in the sense of physical existence vs concepts. These aren’t completely orthogonal thoughts, but the latter is a better description IMO. Much of physics is comprised of calculational conveniences. Math, for example, is conceptual, but it’s not fiction.

A photon or a phonon doesn’t need to physically exist to be useful to describe the relevant behavior. How would one tell if they do, since all we can do is look at experimental results? It’s like Plato’s allegory of the cave.

51 minutes ago, Lorentz Jr said:

The entire physics community has been evading the issue of "reality" (i.e. ontology) for over a century.

Bull. That you are unaware of discussion of the issue does not mean that it has been ignored or is being evaded. For a lot of physicists, the issue has no impact on them and the physics that they do. But some do study it (people working on foundations, for example)

55 minutes ago, Lorentz Jr said:

People don't complain that dark matter is something physicists made up, they complain that it's just  something they made up, meaning it's not "real" in the sense that science is commonly expected to be (and was perceived to be in the 19th century).

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Sabine has a nice take on all the physical reality of measurements in QM.  Getting past the Wigner's friend conundrum....

...The problem is now that according to Alice, the outcome of her measurement never was in a superposition, whereas for Wigner it was. So they don’t agree on what happened. Reality seems to be subjective.

Now. It’s rather obvious what’s going on, namely that one needs to specify what physical process constitutes a measurement, otherwise the prediction is of course ambiguous. Once you have specified what you mean by measurement, Alice will either do a measurement in her laboratory, or not, but not both. And in a real experiment, rather than a thought experiment, the measurement happens when the particle hits the screen, and that’s that. Alice is of course never in a superposition, and she and Wigner agree on what’s objectively real.

If that’s so obvious then why did Wigner worry about it? Because in the standard interpretation of quantum mechanics the update of the wave-function isn’t a physical process. It’s just a mathematical update of your knowledge, which you do after you have learned something new about the system. It doesn’t come with any physical change. And if Alice didn’t physically change anything then, according to Wigner, she must indeed herself have been in a superposition.

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Posted (edited)
1 hour ago, Lorentz Jr said:

The entire physics community has been evading the issue of "reality" (i.e. ontology) for over a century.

36 minutes ago, swansont said:

Bull. That you are unaware of discussion of the issue does not mean that it has been ignored or is being evaded.

Okay, I take back the word "entire". I know the subject has been discussed by Peter Woit, Jim Baggott, Sabine Hossenfelder, Lee Smolin, and Roger Penrose. My understanding is that they're still in a fairly small minority though.

1 hour ago, Lorentz Jr said:

People don't complain that dark matter is something physicists made up, they complain that it's just  something they made up, meaning it's not "real" in the sense that science is commonly expected to be (and was perceived to be in the 19th century).

36 minutes ago, swansont said:

I'm not sure what your point is, swanson.

EDIT: Oh, you mean they don't write the word "just"? I'm pretty sure they have the same complaint in mind. "made up" meaning "fake", as opposed to what the author of the article describes.

Edited by Lorentz Jr
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Posted (edited)
39 minutes ago, swansont said:

Whenever this comes up, the distinction of what one means by real needs to be made: real as opposed to fantasy/fictitious, or real in the sense of physical existence vs concepts. These aren’t completely orthogonal thoughts, but the latter is a better description IMO. Much of physics is comprised of calculational conveniences. Math, for example, is conceptual, but it’s not fiction.

A photon or a phonon doesn’t need to physically exist to be useful to describe the relevant behavior. How would one tell if they do, since all we can do is look at experimental results? It’s like Plato’s allegory of the cave.

Yes I agree it is about what one means by "real". I would contend that those calculational conveniences, and more importantly the concepts which we relate  to one another in our calculations, do in the end purport to tell us something about physical existence, i.e. what we think is real, even if they do not claim to be definitive. Otherwise why bother? I think the scientist must believe there is an objective reality out there to be modelled, or he or she would not make the models.

To borrow from St. Paul, we may "see through a glass darkly", but surely we have to think we are dimly perceiving something real, don't we?

Edited by exchemist
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Posted (edited)
20 minutes ago, exchemist said:

To borrow from St. Paul, we may "see through a glass darkly", but surely we have to think we are dimly perceiving something real, don't we?

It is a  faith but an overwhelmingly  convincing  one.

Does it make a point to ask whether "reality"  describes  something set in stone or something continuously changing ,even if imperceptibly.?

Off topic I find it more rewarding and satisfying  to weed out what is "unreal" than to home in on what may be considered essentially true.(well I don't have the intellect for the latter ,anyway)

Edited by geordief
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7 minutes ago, geordief said:

It is a  faith but an overwhelmingly  convincing  one.

Does it make a point to ask whether "reality"  describes  something set in stone or something continuously changing ,even if imperceptibly.?

Off topic I find it more rewarding and satisfying  to weed out what is "unreal" than to home in on what may be considered essentially true.(well I don't have the intellect for the latter ,anyway)

Ah well, what can be said to be "true" is another kettle of fish entirely. In science one tends to avoid bald truth statements. for the standard Popperian reason, viz. "truth" in science is only provisional. But the statements we make, with whatever caveats, are nevertheless about something that we think is real, I would say.

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3 hours ago, Lorentz Jr said:

Okay, I take back the word "entire". I know the subject has been discussed by Peter Woit, Jim Baggott, Sabine Hossenfelder, Lee Smolin, and Roger Penrose. My understanding is that they're still in a fairly small minority though.

Probably because it only impacts a minority of physicists. Atomic physicists tend not to discuss high-energy particle physics, and vice-versa. We tend to discuss topics close to our area of expertise. I’m not sure what is supposed to be surprising about this.

3 hours ago, Lorentz Jr said:

I'm not sure what your point is, swanson.

EDIT: Oh, you mean they don't write the word "just"? I'm pretty sure they have the same complaint in mind. "made up" meaning "fake", as opposed to what the author of the article describes.

My point is that you’re overreaching with your unsourced claims. They aren’t true.

3 hours ago, exchemist said:

Yes I agree it is about what one means by "real". I would contend that those calculational conveniences, and more importantly the concepts which we relate  to one another in our calculations, do in the end purport to tell us something about physical existence, i.e. what we think is real, even if they do not claim to be definitive. Otherwise why bother? I think the scientist must believe there is an objective reality out there to be modelled, or he or she would not make the models.

To borrow from St. Paul, we may "see through a glass darkly", but surely we have to think we are dimly perceiving something real, don't we?

But the models are of behavior. How do you test for reality?

We can think there’s something real, but physics isn’t describing it. The physics we come up with allows us to calculate behavior we can observe. The more we dive into details the more abstract it gets. Or is reality “a continuous field of operators on an infinite-dimensional Hilbert space” as found in quantum field theory?

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7 hours ago, swansont said:

Whenever this comes up, the distinction of what one means by real needs to be made: real as opposed to fantasy/fictitious, or real in the sense of physical existence vs concepts. These aren’t completely orthogonal thoughts, but the latter is a better description IMO. Much of physics is comprised of calculational conveniences. Math, for example, is conceptual, but it’s not fiction.

I think that is also very true for other natural sciences, even if they are more conceptional rather than mathematical (as in Bio).

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Posted (edited)

Very much with you on this, Swansont.

Physical models describe what 'things' do, not what they are.
Our two most successful models make such accurate predictions that people, even Physicists,  start thinking they are describing actual 'reality'
They couldn't be farther from the 'truth'.

As you already stated, Quantum Field Theory decribes 'reality' as fields on fields, all on a fixed background stage.
General Relativity ( and  LQG ) go one better and take away the fixed background stage to be replaced by ( another ) geometric field, which can be affected by the other fields.

So where is the 'reality ?

Edited by MigL
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5 minutes ago, CharonY said:

I think that is also very true for other natural sciences, even if they are more conceptional rather than mathematical (as in Bio).

This is also true of many engineering disciplines where we tend to have greater exposure to more empirical formulae. This helps reinforce the impression that the science is data-driven: that the formulae are more of a convenient shorthand for expressing correlations observed in large to very large datasets. Sometimes the correlation is so clear and simple to suggest an obvious underlying mechanism that further data may confirm. But the rooting remains firmly in real observation. I don't see how lapsing into solipsism and questioning that reality is of any help to anybody.

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1 hour ago, MigL said:

Physical models describe what 'things' do, not what they are.

Nice way to look at it.

Though I would perhaps even go a step further and say that physics models describe how things relate to other things, wherein the term ‘things’ is to be understood in its most general and abstract meaning. So perhaps it would be far better to look at reality as a network of interactions and relationships, rather than a collection of ‘stuff’ that’s doing things.

It’s a bit like the concept of motion - it’s a very useful concept in order to describe certain aspects of the world, but it has no fundamental, ontological reality in and of itself, unless viewed as a relationship between things. I’d like to suggest that perhaps other aspects of reality are similar, though in less obvious ways.

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3 hours ago, Markus Hanke said:

Nice way to look at it.

Though I would perhaps even go a step further and say that physics models describe how things relate to other things, wherein the term ‘things’ is to be understood in its most general and abstract meaning. So perhaps it would be far better to look at reality as a network of interactions and relationships, rather than a collection of ‘stuff’ that’s doing things.

It’s a bit like the concept of motion - it’s a very useful concept in order to describe certain aspects of the world, but it has no fundamental, ontological reality in and of itself, unless viewed as a relationship between things. I’d like to suggest that perhaps other aspects of reality are similar, though in less obvious ways.

That view - of reality as a network of interactions and relationships - seems to fit well with Rovelli's relational interpretation of QM. But as it is those interactions and relationships that our mathematics models, such a view of reality implies that what we are doing (or should be doing) in science is to model a physical reality. And to go further, if we model interactions, there have to be some entities that interact, whether or not they can be said to have continuous existence in between.

I may be in a minority, to judge by the other comments from the physicists here, but I suppose I am a bit of a Baggotista on this, cf. Jim Baggott's slightly provocative book "Farewell to Reality". (Full disclosure: I worked with him for a while when we were at Shell. Admittedly  we are both chemists rather than physicists, which may colour our perspective.)

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I see a relation between models in physics and reality akin the relation between living organisms and environment. Models in physics evolve to fit their domains of reality, like organisms evolve to fit their environment.

Models in physics don't reflect or describe the reality, but they represent aspects of reality by being able to successfully work with it. Similarly, organisms don't look like their environment, but they represent aspects of the environment by being able to successfully operate in it.

This is very deep. If I understood it correctly, it's like what Swansont said about phonons. There are other examples: Defects in a crystal, different 2-dimensional modes that live on the surface between insulators (topological insulators.) These things live in a context: Surface phenomena, modes in a lattice, etc. They are not 'real' in the sense that you can take, say, a phonon and separate it from its context, and study it in isolation from everything else. You can't take any of these instances, isolate them, and study them independently of the embedding context. There are contingencies --I think that's the right word-- that define their 'being there.' If you dissolve the contingency, you dissolve the 'thing.'

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2 hours ago, exchemist said:

And to go further, if we model interactions, there have to be some entities that interact

I’m not so sure about this, because it doesn’t seem clear to me at all that/why there should be ‘something’ that is ontologically distinct from an interaction. If there is, then we have never observed it directly - any perception, any measurement, any experiment we can perform always boils down to interactions, at the most fundamental level. Even if there is ‘something’ there, then all we can ever see is the interface it exposes to its environment - and this tends to be highly contextual, especially in the quantum realm. Based on human intuition we tacitly and naturally assume that if there’s an interaction, there needs to be ‘something’ there that interacts, but I’m not so sure.

But of course, these are just philosophical musings of mine (even if they do, as you correctly observe, gel well with Rovelli et al), so I might well be entirely wrong

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1 hour ago, joigus said:

This is very deep. If I understood it correctly, it's like what Swansont said about phonons. There are other examples: Defects in a crystal, different 2-dimensional modes that live on the surface between insulators (topological insulators.) These things live in a context: Surface phenomena, modes in a lattice, etc. They are not 'real' in the sense that you can take, say, a phonon and separate it from its context, and study it in isolation from everything else. You can't take any of these instances, isolate them, and study them independently of the embedding context. There are contingencies --I think that's the right word-- that define their 'being there.' If you dissolve the contingency, you dissolve the 'thing.'

Thank you. Yes, this is my understanding.

Quantum fields represent / fit something out there (reality), like gazelles' legs represent / fit the terrain they live on.

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The Kantian distinction between phenomenon and noumenon still seems to serve physics with a guiding principle.  Phenomena, those interactions that are accessible to our senses (or enhanced senses), do not provide a window to the noumenon or thing-in-itself, i.e. that which exists independently of human senses (our measurements).

To borrow from @Genady s analogy, it's like observing gazelles roaming a landscape that is entirely invisible.  Everything we can postulate about the planet they live on is derived only from their configuration and movements.

The mystery inherent in this inaccessible ground of being is what drives some to religion and/or mysticism.  If everything we see is contingent, then is there that which is not contingent, that which is eternal and immutable and always true no matter how a big bang plays out?

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5 minutes ago, TheVat said:

is there that which is not contingent, that which is eternal and immutable and always true no matter how a big bang plays out?

I think it is called mathematics.

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I think it is called mathematics.

I think the question was about something more substantial.

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4 minutes ago, Lorentz Jr said:

I think the question was about something more substantial.

If it was, the question did not mention it. Mathematics answers what has been mentioned in the question.

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Posted (edited)
15 hours ago, Markus Hanke said:

Though I would perhaps even go a step further and say that physics models describe how things relate to other things,

I would have no problem taking that step also.
I only mention 'things' because the questions are always"But what is an electron, really ?" or "What is a photon ?" or possibly your favorite "But what is gravity, really ?".

3 hours ago, TheVat said:

If everything we see is contingent, then is there that which is not contingent, that which is eternal and immutable and always true no matter how a big bang plays out?

How would it make a difference ?
Everything we see ( contingent ) affects us through interactions.
That which is not contingent does not affect us through interactions.
IOW, whether it is there or not makes absolutely no difference to us, or the world around us.

Why is it needed in our models, and, by Occam, why is it needed at all ?
( argument applies to religion/mysticism as well )

Edited by MigL

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