Physics and “reality”

[joigus]

6 minutes ago, martillo said:

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

That's why I didn't say concepts like "force" or "interaction" are sterile. I said your concept of "real" is:

19 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.

 

[Phi for All]

2 minutes ago, martillo said:

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?

Great! So it shouldn't be that hard for you to see that, unless we're somehow able to use ALL methods of observation available to us (and probably some we don't know about YET), we should never assume we know what's really going on. Physics observes how nature behaves, and it's counterproductive to the scientific method to claim what you're observing is Truth or Reality. We aren't looking for answers, we're looking for the best supported explanations. That's how theories can continue to improve.

[swansont]

33 minutes ago, martillo said:

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.

Experimental verification makes them valid. It’s not enough to say they are real. 

The EM force, for example, is mediated by virtual photons. IOW, the model uses something that it blatantly acknowledges are not real. 

[MigL]

You are standing on the ground holding a bowling ball, and it weighs about 12 to 16 lbs. It is a strain to hold it at arms length.

Now go parachuting while carrying that bowling ball; you will find it weighs nothing after you jump out of the airplane.
Yet you and the bowling ball are still falling due to gravity.
What happened to your force, Martillo ???

[joigus]

2 minutes ago, MigL said:

You are standing on the ground holding a bowling ball, and it weighs about 12 to 16 lbs. It is a strain to hold it at arms length.

Now go parachuting while carrying that bowling ball; you will find it weighs nothing after you jump out of the airplane.
Yet you and the bowling ball are still falling due to gravity.
What happened to your force, Martillo ???

!!!

[martillo]

48 minutes ago, MigL said:

You are standing on the ground holding a bowling ball, and it weighs about 12 to 16 lbs. It is a strain to hold it at arms length.

Now go parachuting while carrying that bowling ball; you will find it weighs nothing after you jump out of the airplane.
Yet you and the bowling ball are still falling due to gravity.
What happened to your force, Martillo ???

45 minutes ago, joigus said:

!!!

When I jump out I stop making force to the ball. We will be both in free fall...

 

53 minutes ago, swansont said:

Experimental verification makes them valid. It’s not enough to say they are real. 

The EM force, for example, is mediated by virtual photons. IOW, the model uses something that it blatantly acknowledges are not real. 

The proper model acknowledge to use something that is not real? I don't understand...

 

1 hour ago, Phi for All said:

Great! So it shouldn't be that hard for you to see that, unless we're somehow able to use ALL methods of observation available to us (and probably some we don't know about YET), we should never assume we know what's really going on. Physics observes how nature behaves, and it's counterproductive to the scientific method to claim what you're observing is Truth or Reality. We aren't looking for answers, we're looking for the best supported explanations. That's how theories can continue to improve.

I think I can agree. I don't get the point of disagreement...

Edited March 10, 2023 by martillo

[joigus]

7 minutes ago, martillo said:

When I jump out I stop making force to the ball. We will be both in free fall...

@MigL wasn't talking about your force on the ball. He was talking about gravity.

52 minutes ago, MigL said:

You are standing on the ground holding a bowling ball, and it weighs about 12 to 16 lbs.

 

52 minutes ago, MigL said:

you will find it weighs nothing after you jump out of the airplane.

(My emphasis.)

It weighed. Now it doesn't. Where's the force?

[martillo]

3 minutes ago, joigus said:

@MigL wasn't talking about your force on the ball. He was talking about gravity.

 

(My emphasis.)

It weighed. Now it doesn't. Where's the force?

The same force is acting in both of us, me and the ball and we are both accelerating towards the ground. I hope the parachute works fine! 😄

 

Edited March 10, 2023 by martillo

[joigus]

6 minutes ago, martillo said:

The same force is acting in both of us, me and the ball and we are both accelerating towards the ground. I hope the parachute works fine! 😄

What force? There is no force. It has disappeared. A reference change and it's gone. That's the essence of GR.

[martillo]

2 minutes ago, joigus said:

What force? There is no force. It has disappeared. A reference change and it's gone. That's the essence of GR.

How is that? The force didn't disappear. If I consider that I will not open the parachute and will smash in the ground! My frame is not an inertial one. It is being accelerated...

[joigus]

2 minutes ago, martillo said:

How is that? The force didn't disappear. If I consider that I will not open the parachute and will smash in the ground! My frame is not an inertial one. It is being accelerated...

It's mainstream physics. It's been done to death. It's been measured to great precision. Knock yourself out:

https://en.wikipedia.org/wiki/Equivalence_principle

[TheVat]

11 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? 

It seems worth asking if other external reality modelers can always help us reliably.  Another being could appear to agree with us that we've come to a watering hole and that the water appears clear and smells fresh and potable.  But it could use different sensory models to arrive at those conclusions, while still using our shared language.  It might see "clear" as shimmering purple dots, and "muddy" as swirling pink fractals.   Our "blue" could appear orange to it.  It might also be able to perceive an electrical current running through the pond that was invisible to us (and potentially lethal) and the perception would be a moire pattern strobing from the pond surface that it called "bleeb" and struggled to communicate to us beyond that it was bad for us.  There could even be some holistic effect of large numbers of water molecules that the creature and its species perceive, and found adaptive, that remains utterly obscure to us and all our science.  Perhaps it is called "groove" and one reason we find a bath refreshing, in addition to holistic effects we do perceive like warmth, wetness, getting clean, is that water in our bodily cells get more groove.  Completely obscure to us, and science as we do it simply never looks in that direction.  

Anyway, thanks for a thoughtful essay on reality mapping, and slippery things-in-themselves. Or ding an sich as another modeling system might refer to them. 

[martillo]

1 hour ago, joigus said:

It's mainstream physics. It's been done to death. It's been measured to great precision. Knock yourself out:

https://en.wikipedia.org/wiki/Equivalence_principle

Right, my misconception was to say that in free fall the frame would be not an inertial one while it is. The situation is that in that frame I do not perceive any acceleration or gravitational force. No problem with that but the intention here is not to enter in GR theory. In this thread I consider this example of @MigL as similar to the case of the magician posted by @Phi for All in the sense that this frame alone does not let me perceive the complete picture of the real situation which would be me and the ball falling to Earth and that if I don't open the parachute I will be smashed to the ground, isn't it? So I just would say that a better observation to describe the situation would be to also consider the relative movement between me and Earth. In my frame I would see Earth accelerated to me and so a force would be acting on Earth now. The force didn't vanish, is just that because of the change of referential it is acting on Earth now (with a change in its observed magnitude of course).

Edited March 10, 2023 by martillo

[TheVat]

8 hours ago, swansont said:

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

(posted before reading the next eight hours of postings, so hope not to be redundant)  I think the key, with abstraction is to see it as a form of compression.  You could say, describe Idaho and I could laboriously recreate Idaho, simulating every tree and animal and rock and chewing gum wrapper etc. on an Idaho-sized stretch of Antarctica or the Sahara.   That would be a full and uncompressed description of the Gem State.  Or I could describe it by presenting a map, and a few facts as to its mountainous terrain and many potato fields.  Highly compressed, quite "lossy."  Hopefully the compressed description would provide an understanding of significant underlying patterns to the life and essence of Idaho, which would be congruent with anyone's experience visiting Idaho,  just as sound physics descriptions would show underlying patterns to the universe and its most fundamental attributes and dynamics.

If my dog eats canned beans and then farts all day, simply describing this provides no insight into the disturbing acoustic effects we experience.  Causality is obscured.  For that, we need description that goes down to the level of Bernoulli's principle, and the chemistry of fermentation of oligosaccharides.  Good description matches abstraction to its proper level, and compresses by removing what is extraneous to the understanding of "how it works" i.e. root causality.

8 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.

 

Yep!  Because models describe causal relations and patterns, not objects in themselves.  "Reality" then is nothing more than "what can be realized," and that is a compressed model/map of the noumenous territory.   Any reality beyond these causal maps is in a realm of  metaphysics and not physics.  

3 hours 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.

The word "real" endures so much abuse.  Which I suppose is how we get theorists who posit a "universe made of math."  Confusing mapping systems with the territory.

[Genady]

1 hour ago, martillo said:

Right, my misconception was to say that in free fall the frame would be not an inertial one while it is. The situation is that in that frame I do not perceive any acceleration or gravitational force. No problem with that but the intention here is not to enter in GR theory. In this thread I consider this example of @MigL as similar to the case of the magician posted by @Phi for All in the sense that this frame alone does not let me perceive the complete picture of the real situation which would be me and the ball falling to Earth and that if I don't open the parachute I will be smashed to the ground, isn't it? So I just would say that a better observation to describe the situation would be to also consider the relative movement between me and Earth. In my frame I would see Earth accelerated to me and so a force would be acting on Earth now. The force didn't vanish, is just that because of the change of referential it is acting on Earth now (with a change in its observed magnitude of course).

Imagine that instead of falling toward the Earth you are on a free trajectory around the Earth. You don't need a parachute, you are not going to hit the ground, Earth is not coming toward you, etc. And there is no force.

[swansont]

 

2 hours ago, TheVat said:

Yep!  Because models describe causal relations and patterns, not objects in themselves.  "Reality" then is nothing more than "what can be realized," and that is a compressed model/map of the noumenous territory.   Any reality beyond these causal maps is in a realm of  metaphysics and not physics.  

I thought the standard model described quantum objects. 

 

 

4 hours ago, martillo said:

The proper model acknowledge to use something that is not real? I don't understand...

Virtual photons can’t be detected. They do not exist.

[martillo]

1 hour ago, Genady said:

Imagine that instead of falling toward the Earth you are on a free trajectory around the Earth. You don't need a parachute, you are not going to hit the ground, Earth is not coming toward you, etc. And there is no force.

Well, in that case it depends on the theory (model) we are considering. Classical Physics would state that there would be a net centripetal force perpendicular to the trajectory producing the curvature in the trajectory around Earth. Relativity Theory would state there would be no net force and the trajectory is a geodesic in the curved space-time. Am I wrong in something? I'm saying this after a reading on the link @joigus posted to me. You are aware I know only the basics of Relativity Theory. By the way, I'm not questioning nor proposing any model or theory here, I'm just comparing the different approaches of those two models or theories.

 

25 minutes ago, swansont said:

Virtual photons can’t be detected. They do not exist.

Well, in that case I can only say that I think there would be a problem with the model. How something that do not exist could exert a force on something that do exist? I would agree with you when you mentioned in the OP the citation about that there are things just "made up" in Physics but not everything, I think...

Edited March 11, 2023 by martillo

[swansont]

—-

Special relativity tells you that it is not describing reality, since it can’t tell you if you are really moving or you are at rest. What you know us there is relative motion - something you can measure.

We have discussions about what is time, because there are questions about what it is at a fundamental level. Doesn’t sound like physics has described reality there. Similarly with mass. We have a functional physics definition, but that’s not telling us what it really is.

25 minutes ago, martillo said:

Well, in that case I can only say that I think there would be a problem with the model. How something that do not exist could exert a force on something that do exist?

That’s only a problem if you demand that physics be revealing reality.

25 minutes ago, martillo said:

I would agree with you when you mentioned in the OP the citation about that there are things just "made up" in Physics but not everything, I think...

No, not everything, but the acceptance of a model is based on whether it works - i.e. agrees with experiment, which means measurement of observed behavior.

[Genady]

3 hours ago, TheVat said:

That would be a full and uncompressed description of the Gem State. 

I don't think it will. For a full and uncompressed description, you will have to simulate not only "every tree and animal and rock and chewing gum wrapper etc." but also every molecule, atom, electron, etc., IOW, to simulate complete quantum state of the system. But - here comes the punch line - no cloning theorem tells us that this is impossible. Thus, abstraction is inevitable.

[sethoflagos]

5 hours ago, TheVat said:

I think the key, with abstraction is to see it as a form of compression.  You could say, describe Idaho and I could laboriously recreate Idaho, simulating every tree and animal and rock and chewing gum wrapper etc. on an Idaho-sized stretch of Antarctica or the Sahara.   That would be a full and uncompressed description of the Gem State.  Or I could describe it by presenting a map, and a few facts as to its mountainous terrain and many potato fields.  Highly compressed, quite "lossy."  Hopefully the compressed description would provide an understanding of significant underlying patterns to the life and essence of Idaho, which would be congruent with anyone's experience visiting Idaho,  just as sound physics descriptions would show underlying patterns to the universe and its most fundamental attributes and dynamics.

This is very good. 

How's this for low-loss compression?

Quote

In Xanadu did Kubla Khan
A stately pleasure-dome decree:
Where Alph, the sacred river, ran
Through caverns measureless to man
     Down to a sunless sea.
So twice five miles of fertile ground
With walls and towers were girdled round;
And here were gardens bright with sinuous rills
Where blossom'd many an incense-bearing tree;
And here were forests ancient as the hills,
Enfolding sunny spots of greenery.

— Samuel Taylor Coleridge, "Kubla Khan", 1816 edition

On a human level science can never compete with this. For those who think it can, the closing stanza of another poem springs to mind:

Quote

And on the pedestal these words appear:
"My name is Ozymandias, king of kings:
Look on my works, ye Mighty, and despair!"
Nothing beside remains. Round the decay
Of that colossal wreck, boundless and bare
The lone and level sands stretch far away.

 

— Percy Shelley, "Ozymandias", 1819 edition

 

[Markus Hanke]

7 hours ago, TheVat said:

It seems worth asking if other external reality modelers can always help us reliably.

Not reliably of course - I would hazard a guess and say that evolutionary pressures on other inhabitable worlds will be broadly similar to our own, so any sentient race that evolves there will likely evolve a reality-model that is also broadly similar to ours. Based on what we see here on Earth, nature tends to come up with similar solutions for similar problems. Nevertheless, even small differences might help us get a better understanding of our own concept of reality, and how it might relate to a possible ding-an-sich external reality.

As an aside, I would also conjecture that the more different a species’ reality model is from ours, the harder it would be to establish mutual communication. Arguably, if the models are sufficiently different, there might come a point at which no meaningful communication is possible at all, because we’d share too few fundamental categories.

[joigus]

11 hours ago, TheVat said:

The word "real" endures so much abuse.  Which I suppose is how we get theorists who posit a "universe made of math."  Confusing mapping systems with the territory.

Yes, that's something I've said at least a couple of times on these forums.

I still think @MigL's example was brilliant. Why it --initially at least-- didn't have any effect on @martillo is beyond me. 

I liked your picture of "describe Idaho."

What happens, the goings-on, happenstance, reality --if you will-- is a consequence of laws --some known, some unknown-- plus accidents. Quantum mechanics --among other theories-- has taught us that, even at the simplest level, accidents creep in, no matter how much we desire to control this "flow of details."

Accidental is not incidental, it's an essential part of the brew.

[swansont]

11 hours ago, TheVat said:

You could say, describe Idaho and I could laboriously recreate Idaho, simulating every tree and animal and rock and chewing gum wrapper etc. on an Idaho-sized stretch of Antarctica or the Sahara.   That would be a full and uncompressed description of the Gem State.  Or I could describe it by presenting a map, and a few facts as to its mountainous terrain and many potato fields.  Highly compressed, quite "lossy."  Hopefully the compressed description would provide an understanding of significant underlying patterns to the life and essence of Idaho, which would be congruent with anyone's experience visiting Idaho,  just as sound physics descriptions would show underlying patterns to the universe and its most fundamental attributes and dynamics.

 I can go and visit Idaho. Grab a potato. Have bugs plastered all over my car (which is what happened when I drove through the state)

[MJ kihara]

Real is what is there,around you but u don't want to see it, finally ur left to be consumed by your own imaginations when the brain start distintergrating cause of age...maybe AI will take over to show us what is real,and personalise a cocoon for every one of us,where we will be swimming in wild imaginations.

[joigus]

7 minutes ago, MJ kihara said:

Real is what is there,around you but u don't want to see it, finally ur left to be consumed by your own imaginations when the brain start distintergrating cause of age...maybe AI will take over to show us what is real,and personalise a cocoon for every one of us,where we will be swimming in wild imaginations.

I'd like to think your contribution here is just a wild imagination of mine, but probably bot.