Physics is Just a Model

[J_B_]

Since the wire is frictionless ...​

I had recalled the answer would be a cycloid, though I agree it's unintuitive.

Thinking about how the friction forces would act on the bead, I expect the answer would be the same with friction if those are only 3 choices: straight, circular, and cycloid (supposing the guiding wire is rigid). Has anyone ever tried to solve the problem with friction supposing the wire can take whatever shape needed? Does the answer deviate from a cycloid? If so, is the answer closed form, or would it require a numerical solution?

 

[J_B_]

Whether they are objectively testable does not make them objective reality. We model in terms of the limited senses we have in the limited dimensions we percieve.

This is more the sense in which I meant the OP. A standard reply would be that we can only perceive what we can perceive, and therefore we can't know if there is more.

But I was speaking of the fact that we know we are approximating reality. Among the many examples, one would be that we can know position OR we can know momentum, but we know we can't know them both simultaneously. Knowing that we only partially know a state is to know we are approximating is to know physics is only a model.

Another example might be pages of math about Lagrangian mechanics which knowingly ignores friction.

 

[Bob Crowley]

I'd have to differ about physics being "reality". I've just finished reading a book "Quantum Reality - The Quest for the Real Meaning of Quantum Mechanics - A Game of Theories" by Jim Baggott.

At one point he used the phenomena of red roses to illustrate that what we perceive as "reality" is in fact due to our minds, and not necessarily "reality" in itself.

"... You know what your own consciousness is or at least what if feels like. So what's the problem?

To answer this question it's helpful to trace the physical processes involved in the conscious perception of a red rose. Now, roses are red because their petals contain a subtle mixture of chemicals called anthocyanins, their redness enhanced if grown in soil of modest acidity. Anthoocyanins in the rose petals interact with sunlight, absorbing certain wavelengths and reflecting predominantly red light, electromagnetic radiation with wavelengths between about 620 and 750 billionths of a metre, sitting at the long-wavelength of the visible spectrum, sandwiched between invisible infrared and orange. Of course, light consists of photons but, no matter how hard we look, we will not find an inherent property of 'redness' in photons with this range of wavelengths. Aside from differences in wavelength (and hence energy, according to the Planck-Einstein relation), there is nothing in the physical properties of photons to distinguish red from green or any other colour.

We keep going. We can trace the chemical and physical changes that result from the interactions of photons with cone cells in your retina all the way to the stimulation of your visual cortex at the back of the brain. Look all you like, but you will not find the experience of the colour red in any of this chemistry and physics. It is obviously only when this information is somehow synthesized by your visual cortex do you have a conscious experience of a beautiful red rose...."

If my dog could speak and we had a conversation about red roses (the scent wouldn't interest him - he'd rather go and roll in something that's been dead for a week!), he'd wonder what the heck I was talking about. All he'd see is a something close to black. The "reality" of a red rose would be completely alien to him, or at least very different.

So what is "reality"?

Incidentally I've often claimed that the night my father died, he appeared in my room, hanging around the foot of the bed for most of the episode. He looked for want of a better term, "ghostly" in that I could see through him or focus on him. He was also only a pale white. But since "white" is a combination of all colours, then exactly what colour was his spirit? Or was that "white" a different ball game altogether? Since he was now pure spirit, with his dead body miles away where it would not be found for another four days, could photons even bounce off him?

So again, what is "reality"?

 

[durangodawood]

A demonstrative example illustrating the generation of evidence through the application of a test of MDR hypothesis was given in post#18.

Another might be say, when people say they can tell a stone exists independently from their minds. When they kick one, (their test for mind independence), and it hurts, they are inexplicably ignoring the fact that it is their mind that's telling them it hurts. (That's mind dependence, again).

The 'abundance' claim comes from the myriad of such simple examples. All that has to be queried is what someone means by something (or their descriptions of something) and the mind dependence evidence appears (with zip for mind independence).

Look we could go on ad-nauseum about this .. but I have no reason to 'push' this hypothesis/test/results. At the end of the day, one's preferred philosophical viewpoint (such as Realism), makes zero difference on the production of objective results anyway, (because all philosophies are posited on assumed true beliefs and science can't test these, so they're ignored .. and the testing process proceeds). Adjusting perspectives using various philosophical viewpoint however, highlights some of these rather surprising results and exposes untestable truisms people claim as being 'part of science' (and they demonstrably just aren't).

I'd rather learn some more about Langrangian mechanics .. Cheers

Yeah, I'm on the side of minimal realism for now. I absolutely accept that my mental concepts of the world may only match out-there reality in quite limited ways - the ways required for me to survive and reproduce. Minus that limited correspondence between concept and reality, I dont think Id have made it this far. Thanks for chatting.

 

[durangodawood]

I'd have to differ about physics being "reality". I've just finished reading a book "Quantum Reality - The Quest for the Real Meaning of Quantum Mechanics - A Game of Theories" by Jim Baggott.

At one point he used the phenomena of red roses to illustrate that what we perceive as "reality" is in fact due to our minds, and not necessarily "reality" in itself.



If my dog could speak and we had a conversation about red roses (the scent wouldn't interest him - he'd rather go and roll in something that's been dead for a week!), he'd wonder what the heck I was talking about. All he'd see is a something close to black. The "reality" of a red rose would be completely alien to him, or at least very different.

View attachment 296957

So what is "reality"?

Incidentally I've often claimed that the night my father died, he appeared in my room, hanging around the foot of the bed for most of the episode. He looked for want of a better term, "ghostly" in that I could see through him or focus on him. He was also only a pale white. But since "white" is a combination of all colours, then exactly what colour was his spirit? Or was that "white" a different ball game altogether? Since he was now pure spirit, with his dead body miles away where it would not be found for another four days, could photons even bounce off him?

So again, what is "reality"?

You could prick your dog with a red rose thorn and see his reaction. Is it similar to yours? Would you expect it to be? Does it indicate something real about the rose? Is your dog real?

 

[J_B_]

Minus that limited correspondence between concept and reality, I dont think Id have made it this far. Thanks for chatting.

Yes, it is a facet of philosophy that the odder ideas only seem relevant when burrowed into a comfortable chair next to a warm fire. It's a "no atheists in foxholes" kind of thing. When one is starving, one immediately accepts the reality of food. When the bus is bearing down on you, one immediately accepts the reality of unstoppable forces and their calamitous effect on the body.

 

[durangodawood]

Yes, it is a facet of philosophy that the odder ideas only seem relevant when burrowed into a comfortable chair next to a warm fire. It's a "no atheists in foxholes" kind of thing. When one is starving, one immediately accepts the reality of food. When the bus is bearing down on you, one immediately accepts the reality of unstoppable forces and their calamitous effect on the body.

Agreed. Tho Im very sympathetic to the idea that our sense concepts form from a quite limited spectrum of reality: the human scale experience. And, first-person, we describe our experience of things rather than the things themselves. But there's still things out there, obviously, and our concepts of them have some correct correspondence with them. A bus can be the end of the line for your genetic heritage. Anyone who thinks that fact about reality is a mind contingent belief is welcome to test it. (On second thought, please dont).

 

[SelfSim]

.. But there's still things out there, obviously, and our concepts of them have some correct correspondence with them. A bus can be the end of the line for your genetic heritage. Anyone who thinks that fact about reality is a mind contingent belief is welcome to test it.

Yes, it is a facet of philosophy that the odder ideas only seem relevant when burrowed into a comfortable chair next to a warm fire. It's a "no atheists in foxholes" kind of thing. When one is starving, one immediately accepts the reality of food. When the bus is bearing down on you, one immediately accepts the reality of unstoppable forces and their calamitous effect on the body.

So, introducing some contrast into this line of argument, (just for some dramatic effect), one might say that a dreamt bus cannot the end of the line for your genetic heritage, whereas a real one, will.
And this is how one's mind determines the difference, isn't it?

In other words, when one sees a moving bus that will not kill someone, one's mind calls that 'a dream'. When one sees a moving bus that will, one calls that 'reality'. So someone might think that is telling me 'what reality is', but all that demonstrates to me, (from a mind dependent viewpoint), is that person is telling me what we can all see they are telling me, ie: they are telling me what their mind means when they use the word 'dream', and what their mind means when they use the word 'reality'. I would see that is exactly what they are doing, no matter how profusely they might deny it.

A moving bus might really bring about one's demise .. so the meaning is then added to our mind's model of what 'reality is'.

 

[sjastro]

I had recalled the answer would be a cycloid, though I agree it's unintuitive.

Thinking about how the friction forces would act on the bead, I expect the answer would be the same with friction if those are only 3 choices: straight, circular, and cycloid (supposing the guiding wire is rigid). Has anyone ever tried to solve the problem with friction supposing the wire can take whatever shape needed? Does the answer deviate from a cycloid? If so, is the answer closed form, or would it require a numerical solution?

Bernoulli’s problem is a very specific application of Lagrangian mechanics and based on conservative forces in this case gravity.
Friction is not a conservative force and if considered the principle of least action no longer applies.
You will not get a cycloid under these conditions.

In the case of conservative fields the generalized Euler-Lagrange equation is of the form.

L = T - V is the Lagrangian where T and V are the kinetic and potential energies respectively.
aₖ is the generalized time dependent coordinate and ȧₖ is the derivative with respect to time.
This form of the Euler-Lagrange equation is also known as Lagrange equations for motion.

The friction F in the form of a Rayleigh dissipation function which is velocity dependent can be introduced into the equation as

However as stated the principle of least action no longer applies.

 

[SelfSim]

.. There are enough paradoxes in these models to demonstrate they are not the underlying reality, however model development may assymptotically approach how some of it usually behaves

I could point to many - but take "does the moon exist before you look at it?"
The model of physics presumes as foundation that the universe is objective, causal and deterministic. Yet the quantum models derived from those assumptions violate all three of those tenets of the models foundation. Quantum physics attitude to this philosophical contradiction is "shut up and calculate". It is a useful model of what we percieve by senses. Not an objective reality.

Yes .. I see this line of argument being similar to the more common version of: 'The universe must exist in a form that matches our ability to make sense of it'.

One of the problems with saying that the predictability component of this implies a mind independent reality, is that, objectively, this means that the universe must exist in a form that matches our ability to make sense of it, and yet we can readily demonstrate that theories such as QM actually predict the opposite. It is contrary to our natural common sense. If, on the other hand, we see that our picture of the universe depends upon the way we are able to make sense of it, and the choices we make in how to model such, this issue goes away. However, as a consequence of which, the picture of Mind Independent Reality, (MIR), must go because what we have is a human dependent picture. This can be trivial or not, depending on the area of concern.

Hawking eventually got there. Having long postulated a fundamental theory of everything - his last book contradicted that at philosophical level by including the concept of "model dependent reality" - that is multiple irreconcilable models may be needed, requiring choice depending on circumstance. Whether Hawking realised he had blown his own philosophical foundation to bits is hard to say.

About Hawking: hard to say, yes.

Changing models from the idea of some 'theory of everything', to a more piecemeal approach, couldn't be a better demonstration of how 'what the really universe is', is entirely dependent on our mind's perceptions .. even in 'objective' science: (aka: provisional, contextually contingent, independently verifiable, etc). One might bring oneself to forgive Hawking, on these bases(?)

 

[SelfSim]

So what is "reality"?
..
So again, what is "reality"?

'What it is', doesn't seem to be as important to us, as the method by which we arrive at its meaning .. (ie: 'the how' .. and not so much: 'the what').
There are two methods I know of: belief or the scientific (objective) method.

 

[dlamberth]

'What it is', doesn't seem to be as important to us, as the method by which we arrive at its meaning .. (ie: 'the how' .. and not so much: 'the what').
There are two methods I know of: belief or the scientific (objective) method.

I know we've danced this song before, but there is another way of knowing reality. And that's by way of experience. No amount of belief or science can take the place of the direct reality experience when for instance riding in a plane that is crashing uncontrollably from 35,000 feet.

 

[durangodawood]

So, introducing some contrast into this line of argument, (just for some dramatic effect), one might say that a dreamt bus cannot the end of the line for your genetic heritage, whereas a real one, will.
And this is how one's mind determines the difference, isn't it?

In other words, when one sees a moving bus that will not kill someone, one's mind calls that 'a dream'. When one sees a moving bus that will, one calls that 'reality'. So someone might think that is telling me 'what reality is', but all that demonstrates to me, (from a mind dependent viewpoint), is that person is telling me what we can all see they are telling me, ie: they are telling me what their mind means when they use the word 'dream', and what their mind means when they use the word 'reality'. I would see that is exactly what they are doing, no matter how profusely they might deny it.

A moving bus might really bring about one's demise .. so the meaning is then added to our mind's model of what 'reality is'.

If they are just telling you stuff about the contents of their mind, how they create meaning, etc, then why would you ever heed them if they told you youre about to get creamed by a bus? Seems to me they are also telling you about a real thing headed your way that could end you.

Or, the bus could blindside both of you. The contents of neither of your minds really matter one way or the other in this sad case.

 

[J_B_]

Agreed. Tho Im very sympathetic to the idea that our sense concepts form from a quite limited spectrum of reality: the human scale experience.

Agreed.

 

[SelfSim]

If they are just telling you stuff about the contents of their mind, how they create meaning, etc, then why would you ever heed them if they told you youre about to get creamed by a bus?

The precautionay principle might kick in motivating me to put what they say to the test) and check for myself again).
They might possibly have a view that I didn't(?) I (likely) may have a dissimilar way of perceiving that situation .. All mind dependent stuff here .. no problem for mind dependency and zip evidence for mind independent reality.

Seems to me they are also telling you about a real thing headed your way that could end you.

Yes .. your, (and their), different mind's models there.
(I just tested your meaning of your hypothetical there .. more contributions to the 'abundance' notion of evidence for mind dependence .. zip for the other).

Or, the bus could blindside both of you. The contents of neither of your minds really matter one way or the other in this sad case.

And so the remaining minds there have that mean: 'a sad case' .. (more evidence for the abundant pile there .. with zip for the other).

As I said previously, this goes on forever .. (its kind of boring and tedious after a while).
I'm not trying to prove myself 'right' in any of this .. I may well be wrong .. but that isn't what matters .. its the 'How' here that matters .. its a scientific test you see .. (in a science forum, talking about Physics)

 

[SelfSim]

Agreed.

'Our senses' is a mind model too. Its a testable one having objectively testable meanings for its parameters/definitions.

 

[durangodawood]

The precautionay principle might kick in motivating me to put what they say to the test) and check for myself again).
They might possibly have a view that I didn't(?) I (likely) may have a dissimilar way of perceiving that situation .. All mind dependent stuff here .. no problem for mind dependency and zip evidence for mind independent reality.
Yes .. your, (and their), different mind's models there.
(I just tested your meaning of your hypothetical there .. more contributions to the 'abundance' notion of evidence for mind dependence .. zip for the other).
And so the remaining minds there have that mean: 'a sad case' .. (more evidence for the abundant pile there .. with zip for the other).

As I said previously, this goes on forever .. (its kind of boring and tedious after a while).
I'm not trying to prove myself 'right' in any of this .. I may well be wrong .. but that isn't what matters .. its the 'How' here that matters .. its a scientific test you see .. (in a science forum, talking about Physics)

I must be missing something. Youve got all mind and no bus here as far as I can tell. But sometimes the bus wins.

 

[SelfSim]

I know we've danced this song before, but there is another way of knowing reality. And that's by way of experience.

'Experience' here, is 'the How' .. takes a mind to accumulate experience and give your knowledge that meaning you have for 'reality' there though, eh?
(Yet another test passed ..)

No amount of belief or science can take the place of the direct reality experience when for instance riding in a plane that is crashing uncontrollably from 35,000 feet.

Yes .. fear is what you have that experience mean .. (more mind dependence there).

 

[SelfSim]

I must be missing something. Youve got all mind and no bus here as far as I can tell. But sometimes the bus wins.

'Bus' is a testable model .. a pretty objective one, I might add. And when they move, one attribute of that model could be 'sadness' (under certain circumstances). 'Force' may be another .. depends on the the scientist's choices when it comes to making useful predictions there.

 

[durangodawood]

'Bus' is a testable model .. a pretty objective one, I might add. And when they move, one attribute of that model could be 'sadness' (under certain circumstances). 'Force' may be another .. depends on the the scientist's choices when it comes to making useful predictions there.

So our poor friend got hit by a testable model? And an attribute of the model did him in?