Physics and “reality”

[joigus]

1 hour ago, NTuft said:

So the f⁰ is the 0-th and f^k is the conventional. I don't have a handle on co-variant, contra-variant, vector indices or tensors here, I'd barely made a start on what I think is Einstein's vector convention. is the power gain/loss a boost? I ought to go through the sections I pointed at to get the details, but if you could explicate what this is saying I'd appreciate it; I don't even know what questions to ask.

The \( f^{0} \) comes from the 0 component of 4-momentum by differentiating wrt coordinate time. It's not to do with the usual gamma factor in Lorentz transformations. It's to do with a time-dependent gamma factor. The energy of a particle is \( mc^{2}\gamma \), but this \( \gamma \) is a function of time.

The power gain/loss for the particle is the time derivative of its energy, so that,

\[ \frac{d}{dt}\left(mc^{2}\gamma\right)=qu^{\nu}\left.F_{\nu}\right.^{0}=q\left(c\gamma F_{00}+\gamma v_{k}F_{k0}\right)=q\left(c\gamma F_{00}+\gamma\boldsymbol{v}\cdot\boldsymbol{E}\right) \]

\( F_{00} \) is zero, as F is a 2-rank antisymmetric tensor. Its non-diagonal elements are the electric and magnetic field. The zero component of the time derivative of 4-momentum is thereby the power. It's all beautifully wrapped up in space-time formalism. I've re-instated the gamma factors, but I might be missing some c factor and perhaps my initial definition of F (the electromagnetic tensor) had the wrong sign.

I'm sorry that I'm missing the main point in relation to physics and reality at the moment. Please, let me come back tomorrow and try to catch up with the finer points.

Edited March 8, 2023 by joigus
minor correction

[joigus]

Interactions, class of observers to class of observers transformations, thermal equilibrium. All of these are notions that require some kind of idealisation or another that is not real in any strict sense.

Interactions: Consider an electron. You want to study it in detail in the ultraviolet regime, you need to shoot something at it and, pretty soon, you excite the virtual degrees of freedom, and you have to worry about virtual photons and pairs that seem to come out of this --initially at least-- well-defined thing.

Lorentz transformations: You consider classes of observers that are at rest wrt each other and fill up all of space and time.

Thermal equilibrium: In order to rigorously define thermal equilibrium you need to go to the so-called thermodynamic limit. That is, all the extensive --additive-- variables are infinite.

So what's interesting to me is that, in order to study reality --whatever that is-- you absolutely must to take some distance from it, go to a theoretical framework that is not real in any meaningful way --it's just a convenient abstraction--, and draw your conclusions from there.

[Genady]

41 minutes ago, joigus said:

So what's interesting to me is that, in order to study reality --whatever that is-- you absolutely must to take some distance from it, go to a theoretical framework that is not real in any meaningful way --it's just a convenient abstraction--, and draw your conclusions from there.

What's even more interesting to me that it is so not only with science studying reality -- whatever that is -- but rather it is the only modus operandi we use to deal with reality, throughout our lives.

[joigus]

44 minutes ago, Genady said:

What's even more interesting to me that it is so not only with science studying reality -- whatever that is -- but rather it is the only modus operandi we use to deal with reality, throughout our lives.

I couldn't agree more. For every bundle of sensory input we receive, we build models in our minds, filled with switches and state variables, or whatever you like to call them.

Right now, in my mind, I picture @Genady's opinions and ideas, criteria, etc as --somewhat loosely-- some kind of a list with states of opinion, philosophical tenets and so on, that are perfectly defined as a series of 0s and 1s, so to speak. And you me, I'm sure. We work under such assumptions, and assign states, probabilities, etc to all these things.

There is no fundamental reason why this should be true. What's more, even if it happens to prove itself useful to a certain degree, there's no fundamental reason why this process could be continued till the last least little consequence for everything we experience.

[Markus Hanke]

1 hour ago, joigus said:

There is no fundamental reason why this should be true.

I don’t know about “fundamental”, but ultimately this reality-modelling machine is a result of the process of evolution. What this means is that its function is not at all to neutrally reflect “external reality as it is”, but rather to present us with a model of external reality that is specifically geared towards survival and procreation, and as such will be filtered, distorted, and pre-digested accordingly, with this goal in mind (pun fully intended).

For example - out in the jungles and savannahs where we originally came from, if you encounter other members of your species with whom you compete for limited resources, it is advantageous for you to have available a model that allows you to (at least to some degree) predict their intentions, mind-states, and possible future actions. Likewise with the flight path of an arrow, the weather, the behaviour of water in a river etc etc. If you have good models available that take sensory inputs, processes them, and generates something that allows for predictions of how your environment will evolve into the immediate future, you’ll simply have much better odds to do well and thrive, evolutionary speaking. So it’s actually not a surprise at all that things are as they are.

As a little aside: I, as being on the autism spectrum, am missing a part of this reality-modelling machine - when I encounter another human being, I am socially blind; I generally have no intuitive concept whatever about what kind of mind-state that individual might currently have, I might as well be looking at a stone statue. I don’t immediately know their intentions, nor can I easily tell how they will behave in the next few seconds. All I can do is make educated guesses based on experiences gathered during previous interactions I have had with people; but this takes an active and conscious effort, and sometimes I get it quite wrong. It’s called “mind-blindness”. This is part of the reason why autistic people often struggle with social interactions.

[joigus]

2 hours ago, Markus Hanke said:

I don’t know about “fundamental”, but ultimately this reality-modelling machine is a result of the process of evolution. What this means is that its function is not at all to neutrally reflect “external reality as it is”, but rather to present us with a model of external reality that is specifically geared towards survival and procreation, and as such will be filtered, distorted, and pre-digested accordingly, with this goal in mind (pun fully intended).

By "fundamental" I mean resting on minimal/general assumptions, although I know how slippery that concept can be.  

Yes, theory of the mind --understanding that others have minds probably like we feel we ourselves have minds, and acting accordingly-- is one of the most important adaptive pressures that shaped the evolution of the human brain. I don't have the sources at hand to assert this, by I know from the reasoned arguments of many scientists of human evolution I've sampled through the years.

2 hours ago, Markus Hanke said:

As a little aside: I, as being on the autism spectrum, am missing a part of this reality-modelling machine - when I encounter another human being, I am socially blind; I generally have no intuitive concept whatever about what kind of mind-state that individual might currently have, I might as well be looking at a stone statue. I don’t immediately know their intentions, nor can I easily tell how they will behave in the next few seconds. All I can do is make educated guesses based on experiences gathered during previous interactions I have had with people; but this takes an active and conscious effort, and sometimes I get it quite wrong. It’s called “mind-blindness”. This is part of the reason why autistic people often struggle with social interactions.

I am in no doubt that there must be a reason why Nature has kept the genes that give us autism, which at first glance looks like just a cognitive impairment. Look closer and more can be seen.

From my experience, from what I know from you, and others like you: Genuinely caring individuals, who suffer when they see conflict, generally devoid of manipulative intentions. Never foul players, sincerely concerned about problems, both human and technical, their own, and those of others. Hard workers, obsessive in a way that can be very productive, given the proper outlook, focus, and advise about how letting go when the time comes.

Sometimes we're discussing something and we're being petty and narrow-minded. And here comes Markus Hanke and shines his light. All the pettiness is dissolved. The problem is re-focused to what the problem is.

I guess that's why you lot are here for. Don't look now, but you activate us in a direction that --always in my experience, mind you-- usually is a good one.

[Markus Hanke]

16 hours ago, joigus said:

I am in no doubt that there must be a reason why Nature has kept the genes that give us autism

I can’t answer this, as evolutionary biology isn’t my area of expertise. It’s a difficult subject also because the autism spectrum is so broad - there are some like myself, with very few to no situational support needs, and then there’s a sliding scale of increasing severity right up to forms of autism that make independent living (never even mind independent survival) practically impossible. So it’s hard to generalise.

I’m speaking only for myself now, and perhaps those with similar profiles and predispositions as me. I think there might be an evolutionary advantage precisely because people like me don’t fit into the mainstream. For example, my sense of purpose, meaning, and well-being is not contingent upon social acceptance and belonging - things like how many friends I have, social gatherings and occasions, belonging to a certain group (or not), being around other people etc etc are simply of very little importance to me. This might at first glance sound like an evolutionary disadvantage, but think about it - it frees up enormous amounts of time and energy that can then be re-invested into other pursuits. I don’t know if there are statistics about this, but I bet that, among people who have made important contributions in their fields - the arts, sciences, literature etc etc - a disproportionally large amount might be found to be on the spectrum, or at least have autism-like traits of some sort or another. This is because such people are more likely to engage deeply in pursuits not directly concerned with survival and procreation (which is what social preoccupations are ultimately geared towards). I think society benefits from this kind of archetype - the ones who can stand on the sidelines, look back onto the mainstream from a more neutral and wider external perspective, and pursue “higher” things and unusual ways of thinking. I think there’s an evolutionary advantage for the group as a whole in having such individuals, because they function like a mirror that reflects back the forest when all you yourself are usually able to see is the trees, due to your own day-to-day involvement. Such individuals are often simultaneously despised (because they don’t fit in), and valued (for their contributions, often only posthumously), and sometimes burned at the stake; but whatever the case may be, their perspective is an important one. 

These are just some of my own thoughts, I’m making no claim to any academic truths here.

16 hours ago, joigus said:

Yes, theory of the mind

Yes, but it’s not just that - it’s a theory of the world, including the physics side of things. When we are building models in physics, then these are necessarily models of aspects of how the world appears to us. They are thus models of aspects of another model, namely the reality-model that our minds create for us. We all tend to agree on certain aspects of that generated reality simply because we all share a similar sensory apparatus (plus its extensions), and a roughly similar neurophysiological brain structure - thus the boundary conditions are similar, meaning the resulting reality-model is also roughly similar. The reality-model of an organism that evolved under sufficiently different boundary conditions may potentially be quite different from ours - an example from sci-fi literature that comes to mind are the heptapods in Ted Chiang’s “Story of Your Life”, whose minds do not employ the principle of temporal sequencing in constructing their reality-model. I know it’s just a story, but it’s an interesting example.

So what happens if the boundary conditions vary? I wrote about autism and social “mind-blindness” above - so what is actual reality here? Are social relations and intuitions real, irreducible aspects of the world - or are these contingent add-ons that your neurotypical brain artificially generates, and it is actually my own mind-blind autistic self who sees things as they really are? Or how about this - in addition to being autistic I am also a synesthete. Words to me have colour, texture, size, spatial orientation, and sometimes temporal extension. These, to me, are not associations (e.g. sky=blue), but intrinsic properties of the words themselves (so for me sky=off-white, smooth and cold like marble, angled backwards and to the right), like spin and charge for an elementary particle. For me this is so intrinsically normal that I am pretty much unable to imagine what experience would be like without these attributes - I only know intellectually that most people can’t experience this the way I do. So who perceives “actual” reality here - is the concept “sky” really smooth and cold, and you are all just blind to that? Or does my brain adds this on randomly? Who’s right and who’s wrong? Or is the entire concept of “reality” just a constructed idea, the meaning of which is strictly contextual?

Now think about the wider implications for physics - it makes models of a model. But how do we know, within how the world appears to us, what is an actual part of exterior reality, and what is an add-on by our brain? How can we distinguish, in the absence of having an external reference in the form of other reality-modellers against whom we can compare our reality? Do (e.g.) time and space really exist in the way we experience them, or are they just convenient representations to impose order onto a set of data, like the windows on the GUI of your computer? Are there other ways to structure that same information? Or are there aspects of exterior reality that are not being represented in our model at all, not even by deduction or induction, perhaps because they are irrelevant to our continued evolution? Does the way we do science thus say more about ourselves and how or brains make reality appear to us, than exterior reality?

I think these are important questions to consider not just in philosophy, but also in the foundations of science - just focussing on the model, while ignoring what the model is actually about, and who constructs it, might be misguided and eventually come back to haunt us. I don’t feel this is spoken about enough in the physics community, or even taken seriously. 

Edited March 10, 2023 by Markus Hanke

[martillo]

From the OP:

On 3/5/2023 at 3:07 PM, swansont said:

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

On 3/5/2023 at 3:07 PM, swansont said:

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.

I think the purpose of Physics is to describe the physical reality. 

Now, to describe something, whatever it would be, we always make some kind of abstraction and so a model always takes place. 

By physical reality I mean everything related to objects with their properties of shape, position, mass, energy, forces, etc. and their laws of interactions and behaviors. This means to not consider for instance the biological properties of the objects what is leaved for Biology. Similarly with Chemistry and all of the other Sciences. So, right at the beginning of a description we are making abstractions and so working with models. But more abstractions and so modelling are made to describe some physical reality. For instance we can consider the simple model of Earth as a round object with mass and consider just the center of mass to obtain its orbit around the Sun as another object with mass at its center applying the gravitational laws between objects with mass. Now if we want more accuracy in the trajectory of Earth we must consider other model with the gravitational effects of the moon and the other planets and so another model of the "reality" takes place.

A problem arises if some model gives a description that doesn't match with some direct experimental observation of something. Well, in this case the model would need to be improved or may be another model would be needed.

Physics is always involved in finding the right models to describe physical realities and that always implies the look for the truth.

 

 

Edited March 10, 2023 by martillo

[swansont]

1 hour ago, martillo said:

From the OP:

I think the purpose of Physics is to describe the physical reality. 

Now, to describe something, whatever it would be, we always make some kind of abstraction and so a model always takes place. 

Well, which is it? Are the models abstractions or are they describing reality?

 

1 hour ago, martillo said:

By physical reality I mean everything related to objects with their properties of shape, position, mass, energy, forces, etc. and their laws of interactions and behaviors.

Gravitational, electric and magnetic fields are related to such objects. They physically exist?

Electron holes and phonons physically exist?

1 hour ago, martillo said:

For instance we can consider the simple model of Earth as a round object with mass and consider just the center of mass to obtain its orbit around the Sun as another object with mass at its center applying the gravitational laws between objects with mass. Now if we want more accuracy in the trajectory of Earth we must consider other model with the gravitational effects of the moon and the other planets and so another model of the "reality" takes place.

If we can use approximations which we know are not reality, how is that reality?

 

1 hour ago, martillo said:

A problem arises if some model gives a description that doesn't match with some direct experimental observation of something. Well, in this case the model would need to be improved or may be another model would be needed.

Which means any model that can be improved isn’t describing reality. All models have limitations, so they fall into this category.

 

[joigus]

3 hours ago, Markus Hanke said:

I can’t answer this, as evolutionary biology isn’t my area of expertise. It’s a difficult subject also because the autism spectrum is so broad - there are some like myself, with very few to no situational support needs, and then there’s a sliding scale of increasing severity right up to forms of autism that make independent living (never even mind independent survival) practically impossible. So it’s hard to generalise.

I brought it up because I know the theme of so-called detrimental genes that can be a blessing in disguise for the group has been the subject of extensive study and discussion in medical science / biology. Examples I can remember are sickle-cell anemia --which in its mild version protects you from malaria--, schizophrenia --which in its mild version is thought to have played a role in shamanism--, etc. I'm sure there are others.

It could be the case for autism. I honestly don't know.

3 hours ago, Markus Hanke said:

Now think about the wider implications for physics - it makes models of a model. But how do we know, within how the world appears to us, what is an actual part of exterior reality, and what is an add-on by our brain? How can we distinguish, in the absence of having an external reference in the form of other reality-modellers against whom we can compare our reality? Do (e.g.) time and space really exist in the way we experience them, or are they just convenient representations to impose order onto a set of data, like the windows on the GUI of your computer? Are there other ways to structure that same information? Or are there aspects of exterior reality that are not being represented in our model at all, not even by deduction or induction, perhaps because they are irrelevant to our continued evolution? Does the way we do science thus say more about ourselves and how or brains make reality appear to us, than exterior reality?

That's a very good point. The brain is nothing but --it could be argued-- an organ evolved to map the world in certain ways. How it does that is subject to many variations. Some people count by projecting imaginary sounds in their minds, others do it by picturing images.

It's even possible that there were some kind of 'maximum common divisor', so to speak, that affects us all, neurotypical or not. In that case J.B.S. Haldane's words "Now, my own suspicion is that the universe is not only queerer than we suppose, but queerer than we can suppose" would be totally spot on as to what's given to us to know.

[Phi for All]

2 hours ago, martillo said:

Physics is always involved in finding the right models to describe physical realities and that always implies the look for the truth.

I think this stance is flawed in a big way. "How things really are" is quite different than "what we observe in nature". You're looking for proofs and truths and reality in a system that reveres theory for its resistance to deception and subjectivity.

[martillo]

2 hours ago, swansont said:

Well, which is it? Are the models abstractions or are they describing reality?

The point is that a description of some reality always involves some abstraction. Models are based on the abstraction considered. As more accurate the abstraction more accurate the description of the reality.

2 hours ago, swansont said:

Gravitational, electric and magnetic fields are related to such objects. They physically exist?

What physically exist are the forces not the fields. The fields are a mathematical construction that represents the forces that would act at some place if a particular object would exist at that place. The forces act over particular objects at the particular places where they exist. The fields are defined over the entire space.

2 hours ago, swansont said:

Electron holes and phonons physically exist?

Yes I think they do.

 

2 hours ago, swansont said:

If we can use approximations which we know are not reality, how is that reality?

The reality is known with more accuracy only as more accurate the observations are made. Follows more accurate abstractions and models developed to describe and explain them. As I said above the description of some reality always involve some kind of abstraction.

 

2 hours ago, swansont said:

Which means any model that can be improved isn’t describing reality. All models have limitations, so they fall into this category.

All models have limitations but they describe reality as they can. Of course some models fails in the description of some things and that's why new models surged along the entire history of Physics.

I would say that all models describes some reality to some degree of accuracy but sometimes some models are replaced by other ones more accurate.

 

1 hour ago, Phi for All said:

I think this stance is flawed in a big way. "How things really are" is quite different than "what we observe in nature". You're looking for proofs and truths and reality in a system that reveres theory for its resistance to deception and subjectivity.

I'm not sure if I understand you properly. If not  please let me know.

What we observe depends on how we observe, for instance, if we use telescopes or not and the accuracy depends on the kind of telescopes we use. Our observations of "how things really are" are always limited to some accuracy.

I consider theories as models to describe realities with some inherent level of accuracy. Some theories were considered right at some time but replaced by other better ones time after. Better theories will help better against those deceptions and subjectivities you mention.

The entire history of Physics is a look for "how things really are" (the truth) in all his areas...

[Genady]

7 minutes ago, martillo said:

What physically exist are the forces

Do we ever observe a force?

[martillo]

1 minute ago, Genady said:

Do we ever observe a force?

You can observe how the leaves of a tree moves with the force of the air on them...

[joigus]

Forces are not observables in quantum mechanics. Little wonder.

"Force" is a very derived concept.

How much force does a W boson exert on a neutron when it decays? Etc...

[Genady]

Just now, martillo said:

You can observe how the leaves of a tree moves with the force of the air on them...

I see leaves moving with the air, but I don't see any force. 

[swansont]

15 minutes ago, martillo said:

You can observe how the leaves of a tree moves with the force of the air on them...

IOW you observe behavior. The force of the air is inferred, but how do you know that’s the reality, and there’s not something else involved? How can you be sure it’s not invisible fairies moving the leaves?

[martillo]

51 minutes ago, Genady said:

I see leaves moving with the air, but I don't see any force. 

51 minutes ago, joigus said:

Forces are not observables in quantum mechanics. Little wonder.

"Force" is a very derived concept.

How much force does a W boson exert on a neutron when it decays? Etc...

30 minutes ago, swansont said:

IOW you observe behavior. The force of the air is inferred, but how do you know that’s the reality, and there’s not something else involved? How can you be sure it’s not invisible fairies moving the leaves?

This take us on what is considered by "force"... 

I consider that objects exist in the Universe with laws that govern their behavior in it. You can see the objects but not the laws which are present but actually not visible. The laws determine that an object can interact with other one someway and the interaction is considered in Physics as "force". 

What you can actually see is the consequence of an interaction not the interaction itself because it is a law in the Universe, not an object.. 

 

 

 

Edited March 10, 2023 by martillo

[Genady]

6 minutes ago, martillo said:

This take us on what is considered by "force"... 

I consider that objects exist in the Universe with laws that govern their behavior in it. You can see the objects but not the laws which are present but actually not visible. The laws determine that an object can interact with other one someway and the interaction is considered in Physics as "force". 

What you can actually see is the consequence of an interaction not the interaction itself because it is a law in the Universe, not an object.. 

 

 

 

Fields are present in laws of physics. How they are not real but forces are real?

[martillo]

5 minutes ago, Genady said:

Fields are present in laws of physics. How they are not real but forces are real?

I didn't say they are not real. For me both fields and forces are real laws in the Universe and as laws they are not visible.

I consider the fields don't physically exist while the forces do. As I said, the fields are the mathematical representation of the force that WOULD act on an object if it WOULD exist at some place of the space. If the object exists the forces exists, not in the contrary.

 

[joigus]

26 minutes ago, martillo said:

I consider that objects exist in the Universe with laws that govern their behavior in it. You can see the objects but not the laws which are present but actually not visible. The laws determine that an object can interact with other one someway and the interaction is considered in Physics as "force". 

How do you know these laws are real, and not a part of your theory? Are meridians and parallels real, or just a cartographic artifact?

[Phi for All]

1 hour ago, martillo said:

Our observations of "how things really are" are always limited to some accuracy.

As others, including you, have noted, when you observe a phenomenon, you only know what can be observed by the methodologies you're using, and NONE of those methods could possibly tell you "how things really are". Observing tells you about certain behaviors, but doesn't tell you anything about reality. Watch a professional magician, and tell me your observations reflect what's really happening. 

[martillo]

1 minute ago, joigus said:

How do you know these laws are real, and not a part of your theory?

For the laws to be considered real they must pass the experimental verification following the scientific method, isn't it? But as I already mentioned models and theories evolved with time in the history of Physics for more accurate ones and I think is a process that hasn't reached an end if this could ever happen.

 

7 minutes ago, joigus said:

Are meridians and parallels real, or just a cartographic artifact?

They would be real but not physically existing. They would be a real mathematical artifact used in cartography.

[joigus]

1 minute ago, martillo said:

They would be real but not physically existing. They would be a real mathematical artifact used in cartography.

Then, a unicorn is real, as it is a real literary artifact used in story-telling.

Which leads me to think that you've expanded your concept of what's real to the point of rendering it completely sterile.

[martillo]

26 minutes ago, Phi for All said:

As others, including you, have noted, when you observe a phenomenon, you only know what can be observed by the methodologies you're using, and NONE of those methods could possibly tell you "how things really are". Observing tells you about certain behaviors, but doesn't tell you anything about reality. Watch a professional magician, and tell me your observations reflect what's really happening. 

I think all methods of observation tell us approximately how things are but sometimes they do not have enough accuracy to reveal how the things really are. Some times, as in the case of the magician, some features weren't observed by the method (for instance our direct visual perception) and we don't have the complete picture of what is really happening. So, some times if we need a more accurate description we must change our method of observation by a more accurate one. You may say this is something that never reaches and end and I think that some times we could reach an end while other times may be not. Physics' researches and developments continue, isn't it?

18 minutes ago, joigus said:

Then, a unicorn is real, as it is a real literary artifact used in story-telling.

Which leads me to think that you've expanded your concept of what's real to the point of rendering it completely sterile.

An unicorn do exist in literature but does not physically exist as objects in the real world, right?

I don't think these concepts are "sterile". They are helping to understand some things...

Edited March 10, 2023 by martillo