The problem with reductionism

exchemist said:
Yes but a number denoting what quantity? What does the number at each point in space signify?
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Where is a physicist when you need one?
If it is with an EM field then the strength of the electric field at that particular point, the magnetic field is the derivative wrt to that point as it runs perpendicular.
The gravitational field is a matrix with ten numbers (I think) at each point according to GR.
This relates to the amount of curvature with an associated mass. Higher the mass the more the curvature.
The Higgs field gives particles mass (not neutrinos) the stronger the coupling the higher the mass.

I'm sure you know all this!
 
Pinball1970 said:
Where is a physicist when you need one?
If it is with an EM field then the strength of the electric field at that particular point, the magnetic field is the derivative wrt to that point as it runs perpendicular.
The gravitational field is a matrix with ten numbers (I think) at each point according to GR.
This relates to the amount of curvature with an associated mass. Higher the mass the more the curvature.
The Higgs field gives particles mass (not neutrinos) the stronger the coupling the higher the mass.

I'm sure you know all this!
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Yeah but your description of the numbers in the EM field (they are actually vectors, as the field at each point has direction as well as magnitude) is self-referential. You are just saying the numbers express the field strength. That does not tell us what the field actually is.

It's not a force, as there is nothing for a force to act on, until you introduce a test object that is susceptible to the effect of the field. It's an immaterial thingie that exerts a force on a susceptible object. What's the thingie? And don't say it's a field! :biggrin:
 
exchemist said:
Yeah but your description of the numbers in the EM field (they are actually vectors, as the field at each point has direction as well as magnitude) is self-referential. You are just saying the numbers express the field strength. That does not tell us what the field actually is.

It's not a force, as there is nothing for a force to act on, until you introduce a test object that is susceptible to the effect of the field. It's an immaterial thingie that exerts a force on a susceptible object. What's the thingie? And don't say it's a field! :biggrin:
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You and I know that physics really is all about the mathematics. We are using words here and words will only take us so far.

There was a discussion on photons, what is it? A particle, wave or a mixture of the two?
One answer on another platform was, "an excitation in the EM field."
Another was "a massless particle in the standard model."
The third answer was just pure maths describing a wave function.

A physicist would give you a more satisfying answer if I try any further I will either just get it wrong or sound philosophical.
 
Pinball1970 said:
You and I know that physics really is all about the mathematics. We are using words here and words will only take us so far.

There was a discussion on photons, what is it? A particle, wave or a mixture of the two?
One answer on another platform was, "an excitation in the EM field."
Another was "a massless particle in the standard model."
The third answer was just pure maths describing a wave function.

A physicist would give you a more satisfying answer if I try any further I will either just get it wrong or sound philosophical.
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Indeed. I'm just intrigued by how the concept of the field in physics arose, its etymology and what people thought, and now think, it means. Faraday seems to have been the first to use the term, but I can't trace why he came up with that word, or how he originally explained what a "field" was supposed to be.
 
exchemist said:
Indeed. I'm just intrigued by how the concept of the field in physics arose, its etymology and what people thought, and now think, it means. Faraday seems to have been the first to use the term, but I can't trace why he came up with that word, or how he originally explained what a "field" was supposed to be.
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I will look into it, the concept of a mathematical field may have influenced it, if that was a thing then.
 
Pinball1970 said:
I will look into it, the concept of a mathematical field may have influenced it, if that was a thing then.
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I'll be interested to see what you come up with. It has always struck me as odd, and rather amusing, that physics apparently dislikes the concept of action at a distance, so models interactions via force-carrying virtual particles, yet at the same time it models these virtual particles as disturbances in a field - which, er, is a form of immaterial action at a distance! :?
 
exchemist said:
I'll be interested to see what you come up with. It has always struck me as odd, and rather amusing, that physics apparently dislikes the concept of action at a distance, so models interactions via force-carrying virtual particles, yet at the same time it models these virtual particles as disturbances in a field - which, er, is a form of immaterial action at a distance! :?
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Yep. IIRC it was also tied originally to a medium, like the aether, so that it would make more intuitive sense. Then M&M shot that down, just leaving the abstractions... lines of force, perturbations, knots of field strength.
 
TheVat said:
Yep. IIRC it was also tied originally to a medium, like the aether, so that it would make more intuitive sense. Then M&M shot that down, just leaving the abstractions... lines of force, perturbations, knots of field strength.
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Fields are treated as the ultimate source of all physical reality, according to current models, both matter and radiation. So it seems to me we should perhaps be asking ourselves what if anything we mean by these things, apart from the maths, which of course works a treat. But even back in Faraday's time, I wonder what he thought a field was.
 
exchemist said:
But even back in Faraday's time, I wonder what he thought a field was.
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I've read that my avatar for most of his life believed in the physicality of lines of force, i.e. that fields were not just locations of an action but were actual physical materials themselves. Faraday called the lines of force “tentacles” and would have gone to his grave believing in such if prevailing philosophy at that time had not rejected such unobserved entities and prompted him to, erm, discard his tentacles.

I think this link provides Faraday's famous essay on the subject.

 
exchemist said:
I'll be interested to see what you come up with. It has always struck me as odd, and rather amusing, that physics apparently dislikes the concept of action at a distance, so models interactions via force-carrying virtual particles, yet at the same time it models these virtual particles as disturbances in a field - which, er, is a form of immaterial action at a distance! :?
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The idea of any field in physics is that it exists literally everywhere. At any given point in space (and time), the field has a particular value, or set of values, associated with it. For example, the electric field is a vector field, which means that every point in space has a particular vector associated with it at any given time.

Quantum field theory models fundamental particles as excitations of quantum fields. The fields themselves are literally everywhere, just like all fields are. An excitation is, more or less, just a point in space where the field has a non-zero value. If we're talking about the particular field that describes a particle - like an electron, say - then at most points in space the corresponding quantum field has a value of zero. At points where there is an electron, the field is non-zero.

Fields by themselves don't involve interaction at a distance. One point in a field doesn't affect other points in a field, directly. But a disturbance or excitation in a field can propagate from one place to another and can therefore carry information from one place to another. So, for instance, if a virtual photon propagates at the speed of light between two points in space, it can carry information about the electromagnetic force between two charged particles. This is not "immaterial action at a distance", exactly, because the model has an excitation literally moving across the intermediate space.
 
James R said:
The idea of any field in physics is that it exists literally everywhere. At any given point in space (and time), the field has a particular value, or set of values, associated with it. For example, the electric field is a vector field, which means that every point in space has a particular vector associated with it at any given time.

Quantum field theory models fundamental particles as excitations of quantum fields. The fields themselves are literally everywhere, just like all fields are. An excitation is, more or less, just a point in space where the field has a non-zero value. If we're talking about the particular field that describes a particle - like an electron, say - then at most points in space the corresponding quantum field has a value of zero. At points where there is an electron, the field is non-zero.

Fields by themselves don't involve interaction at a distance. One point in a field doesn't affect other points in a field, directly. But a disturbance or excitation in a field can propagate from one place to another and can therefore carry information from one place to another. So, for instance, if a virtual photon propagates at the speed of light between two points in space, it can carry information about the electromagnetic force between two charged particles. This is not "immaterial action at a distance", exactly, because the model has an excitation literally moving across the intermediate space.
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OK that's fair enough, but to say there is a travelling "excitation" in an immaterial entity called a "field" will seem to the layman very much like just a fancy way of saying action at a distance. What does one say a field is, to convince him it is physically real? Or does one fall back on an instrumental approach and say it's just how the maths works and it seems to give the right results?
 
Magical Realist said:
You seem to be saying that an emergent property can be traced to the combined behavior/properties of its subunits. I'm saying it is more than that, at least in the case of strong emergence. It is more than the mere sum of the parts. My favorite example is salt. The two atomic elements of chlorine and sodium, which in themselves are highly reactive and dangerous, combine to create common table salt. The properties of salt, its distinctive taste, solubility in water, ability to conduct electricity when in solution, and crystal structure, are not present in its two elements either discretely nor in summation. They are entirely new and surprising properties. Do we really understand how this happens? No.. We may certainly say that they are caused by the combination of chlorine and sodium. But we do not understand how salt's emergent properties rationally or necessarily follow, in a lawlike fashion, from this reaction,. That's why I said in the op that this becomes a matter of how we ultimately define understanding something. Is it enough to say they are just the magical combination of their components, without knowing HOW that combination results in the given properties? Or is there more to be discovered?
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No we know everything now. We should Just stop Science now.
 
exchemist said:
OK that's fair enough, but to say there is a travelling "excitation" in an immaterial entity called a "field" will seem to the layman very much like just a fancy way of saying action at a distance. What does one say a field is, to convince him it is physically real? Or does one fall back on an instrumental approach and say it's just how the maths works and it seems to give the right results?
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It's both, a photon is a real object and the field it propagates via is real also, the mathematics that describes it is an abstract construct.
There are no 0, 1's and 2's in the universe, we invented them but they represent a physical entity.

If you want to ask "but what is it?" Then we are back to questions such as what is an electron actually made of?

It's made of an electron, it is a fundamental particle and part of the SM of particle physics.

Perhaps an accelerator of the future will find it is composed of more fundamental particles or even validate strings? Until then.
 
A field is an immaterial substrate that is "everywhere"? What distinguishes it then from just being the spacetime continuum like gravity basically is?
 
exchemist said:
OK that's fair enough, but to say there is a travelling "excitation" in an immaterial entity called a "field" will seem to the layman very much like just a fancy way of saying action at a distance. What does one say a field is, to convince him it is physically real? Or does one fall back on an instrumental approach and say it's just how the maths works and it seems to give the right results?
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Since fields can't be detected directly, there's no way to tell whether they are physically real or just instrumentally useful, as far as I can tell.
 
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