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Why does everyone believe in particles?


Lorentz Jr
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1 hour ago, swansont said:

Why don’t atoms absorb part of the energy of an EM wave? e.g. a 2 eV emission hitting an atom that allows a 1 eV excitation.

They do, sometime. i.e. Compton scattering, or the photoelectric effect.

19 minutes ago, Lorentz Jr said:

I'm assuming you mean the energy of N photons, where hf < 1eV and Nhf = 2eV?

No. He meant that one photon with E=2eV strikes an atom that has electrons that can be excited by E=1eV.

23 minutes ago, Lorentz Jr said:

I just don't like a lot of things in modern physics, and I'm trying to make sense of them as well as I can.

..you should start from buying polarization filters, diffraction grating and double-slit setups, discharge tubes of various gases, prism (to split spectral and absorption lines) on eBay/Amazon/Ali-express or so..

https://www.google.com/search?q=how+to+build+cloud+chamber

"how to build cloud chamber" it costs less than 20 USD..

Instead of being a theoretical home-made scientist, become an experimental home-made scientist.

 

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12 minutes ago, MigL said:

Why do I picture your house to look like Dr Emmett Brown's house ( from Back to the Future ), Sensei ?

Because the Van de Graaff generator is right now in my rest room.. ?

1733862227_VanDeGraaff.png.c36d5b720e4f24cb96b193158b2cd53b.png

(no joke, really)

 

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3 hours ago, Lorentz Jr said:

Particles are entities by definition, and I'm suggesting that maybe matter isn't made of particles or entities of any kind at all. In other words, I'm saying that maybe there is no "they". Maybe matter is just ordinary, unquantized waves, and the particle side of the wave-particle duality is an illusion created by quantized interactions between waves in ordinary, unquantized fields. Is that consistent enough?

I like it, which means I'm tempted by its seductive promise of dispelling illusions.  And I'm open to such ontological flights, though I sometimes fly into the whirling blades of what, then, is a field, be it a field of force (a vector field) or a field of potential energy (a scalar field).  If everything that "is" is just a field perturbation, or a gradient, or a vector, what is being perturbed, waved, pointed, attenuated, quantized and so on?  What the heck are fields anyway? (Rhetorical question, don't answer)

I'm saying, mainly, that any metaphysics is possibly hopeless, and that maybe physics tends to attach a particle term to any quantized jiggle in the jello of reality because anything else feels like chaos and madness.  Even David Bohm couldn't get rid of solid particles.  Still, I'd love to look into any speculative take on a world of just waves.  

Edited by TheVat
Btfsplk
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But that is exactly what we're dealing with; nothing other than fields on top of fields.
Whether scalar ( value at a point ), vector ( value and direction at a point ) or even tensor ( for that pesky gravity field ), QFT is governed by Heisenberg, and so values at a specific point cannot be exact.
These small 'ripples' in the quantzed fied values must meet a certain threshold; below that threshold they are 'virtual', and if surpassing the threshold, they are 'real'.
It is foor convenience that we treat these field excitations as quantum particles.

See the sticky in Quantum Theory
"Matter is excitations in a field"
It i
 

Edited by MigL
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4 hours ago, Sensei said:

He meant that one photon with E=2eV strikes an atom that has electrons that can be excited by E=1eV.

Thanks. I don't have an answer to that, so maybe I need to back away from the whole "no entities" thing.

I still have this idea that a "particle detection" is where wave energy gets squeezed into a small space, and I don't see any point in calling that a "particle", and I don't see why there has to be any kind of point particle (or stringy or braney particle) between interactions. I would rather give up on particles than believe they can be in two places at once. So that leaves the idea of these mysterious, wavy little "quanta" that overlap each other in space and yet somehow remain separate "things". It's very strange.

Edited by Lorentz Jr
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As a general reminder, I think it is wise to remember that the concepts of ‘particle’ and ‘field’ are first and foremost mathematical models - to be precise, they are irreducible representations of symmetry groups. In physics, when we say that something ‘is’ a particle or field, then the verb ‘is’ should not be understood in a strictly ontological manner, but rather in the sense that these concepts are useful models for some observable aspect of reality. They are ways to make useful and functional models of the world, not irreducible ontologies.

Consider the following effects:

1. The Unruh effect: for a given volume of space, the number of particles contained therein depends on the observer. An accelerated observer will figure that the volume contains more particles than does an inertial observer, even though they are looking at the same 3-volume.

2. The Aharonov-Bohm effect: there are measurable physical effects on charges due to an electromagnetic potential, even though the charges are located in a region where the electromagnetic field is absent (F=0).

So clearly, our naive intuitions of what ‘particle’ and ‘field’ might mean can be very misleading.

Ultimately, the question as to what exists in an irreducible way on the most fundamental level is very much open, in physics as well as philosophy. To me, it isn’t even clear what ‘exists’ and ‘most fundamental’ actually means, since these terms would need to be defined in a completely observer-independent way, which is difficult to say the least. Modern physics takes quantum fields and spacetime to be the most fundamental categories of (physical) existence that we know of, but there is certainly no claim that there couldn’t be something else that is even more fundamental - in fact, it is quite safe to claim that there most likely will be. There are also other ways to make models of what we already know - Rovelli’s relational QM, where the central category is a network of interactions rather than a collection of entities with given properties, is a good example.

With all that being said, particles and fields are far to useful as computational models in order to simply abandon them.

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15 hours ago, Lorentz Jr said:

Or maybe let go the idea that they're entities. They could be mere phenomena.

I think they have to be entities, because something continues to exist in between interactions. If that were not the case, we would be unable to predict the properties of the entity in the next interaction, which is what QM enables us to do with great success.  

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10 hours ago, Lorentz Jr said:

Please don't be mad at me. I know this all probably sounds hokey and ignorant, but I'm really not trolling. I just don't like a lot of things in modern physics, and I'm trying to make sense of them as well as I can.

Nobody is mad at you, we are just trying to guide your thinking so you can see for yourself.

 

1) Black body radiation.

I stick a poker in the fire and it glows red, then yellow, then white.

I don't see any quantum interactions here and you have specifically limited this discussion to quantum matters.

1) Photoelectric effect

Here there is an interaction because an electric current is produced when a light shines on certain materials. But there is nothing that suggests light needs to be a Field.
Swansont mentioned one of the characteristics of this effect that lead to the conclusion that this must be a quantum effect since classical EM wave thoery will not produce this effect, but a different one that is not observed in practice. Read the attachment I previously posted before you reply.

I don't think I have posted this analogy since you have joined but maybe it will help a bit.

Think of a stream bed with an smooth clay or sandy bottom.

The stream flows in steady parallel lines with no disturbances.

This is an example of a Field, called a flow field.

 

Now change the bed to a rocky bottom.

The flow changes and eddies appear around some of the rocks.

A few of these eddies are transient but many are persistent.

These all constitutes a disturbance in the field and involve greater energy due to the rotation of the fluid field at the eddy location.

Noone pretends that the eddies are points, they occupy real volume.

So within the field there can bee seen persistent disturbances, of higher energy than the surrounding general field.

These disturbances can be regarded as self contained entities, and if they relocate they move as self contained entities ie they have particle like characteristics

This is a very simple picture of the proposition 'a particle is a disturbance in a field'.

 

Does this help ?

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5 hours ago, Markus Hanke said:

As a general reminder, I think it is wise to remember that the concepts of ‘particle’ and ‘field’ are first and foremost mathematical models - to be precise, they are irreducible representations of symmetry groups. In physics, when we say that something ‘is’ a particle or field, then the verb ‘is’ should not be understood in a strictly ontological manner, but rather in the sense that these concepts are useful models for some observable aspect of reality. They are ways to make useful and functional models of the world, not irreducible ontologies.

This is stone-engraving material.

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11 hours ago, Lorentz Jr said:

I'm assuming you mean the energy of N photons, where hf < 1eV and Nhf = 2eV?

I was saying earlier, there would have to be a localized form of energy that mediates interactions, so fields wouldn't interact with each other directly. hf would have to be the quantization of interactions between the EM field and the intermediary.

N photons?

You’re the one saying that there are no particles. How can you invoke Nhf, which admits to the existence of particles?

Your proposal is that the EM energy is not quantized, so why can’t the quantized amount be absorbed, leaving the remainder? 

 

11 hours ago, Lorentz Jr said:

Please don't be mad at me. I know this all probably sounds hokey and ignorant, but I'm really not trolling. I just don't like a lot of things in modern physics, and I'm trying to make sense of them as well as I can.

When you don’t present a consistent argument, it suggests you don’t have an actual model, which is a requirement for discussion in speculations. Not liking things in physics isn’t far from appeal to personal incredulity, which is a fallacy. If you’re not trolling, then stop doing things that look like trolling.

10 hours ago, Sensei said:

They do, sometime. i.e. Compton scattering, or the photoelectric effect.

The photoelectric effect does not do this, and if you can find an example if a 2 eV photon undergoing compton scattering off of an atom, please present it.

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16 hours ago, Lorentz Jr said:

Maybe matter is just ordinary, unquantized waves, and the particle side of the wave-particle duality is an illusion

12 hours ago, TheVat said:

I like it ... I'm tempted by its seductive promise of dispelling illusions. 

So am I. It's probably nonsense though. It can't even account for changes in state.

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any metaphysics is possibly hopeless

This is the depressing part. It's almost like "we're living in a simulation" is the only explanation that fits the data. If spatially distributed quantum entities really exist, my first thought would be that space itself is an illusion, because I can't imagine how else they could be implemented.

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the jello of reality

Speaking of jello, Angelo Bassi is doing interesting work. He looks for high-frequency EM noise left over from objective particle collapses. He says “You should remove the word ‘particle’ from your vocabulary,” and says quanta are like "gelatinous blobs that can spread out in space, split and recombine", or like octopuses that shrink when they're touched and then expand again.

https://www.nytimes.com/2020/06/25/magazine/angelo-bassi-quantum-mechanic.html

4 hours ago, exchemist said:

I think they have to be entities, because something continues to exist in between interactions.

That's a separate issue. Waves don't exactly "exist" the way solid objects do, but they can certainly continue to propagate when nobody's looking at them.

3 hours ago, studiot said:

1) Black body radiation.

I stick a poker in the fire and it glows red, then yellow, then white.

I don't see any quantum interactions here and you have specifically limited this discussion to quantum matters.

Well, Max Planck thought of it as a quantum phenomenon, and that seems reasonable to me.

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there is nothing that suggests light needs to be a Field.

I'm not trying to imply that QFT is needed to explain every quantum phenomenon. I'm just trying to minimize the looniness of my ideas by using existing theory as much as possible.

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Noone pretends that the eddies are points, they occupy real volume.

Okay, that's fine. There's a video where Sean Carroll says something to that effect about conversations among professional physicists, even though you hear the phrase "point particle" a lot in other contexts. And string theorists seem to take their stringy and braney "particles" or "objects" or whatever you want to call them pretty seriously.

2 hours ago, swansont said:

N photons?

You’re the one saying that there are no particles. How can you invoke Nhf, which admits to the existence of particles?

I should have written "equivalent", meaning the same amount of energy. I thought you were getting at how I would handle the photoelectric effect when there's enough total energy but not in a single photon.

Anyway, as I was saying to Sensei, I think I get your point now about dealing with interactions with random amounts of energy. I'm going to give up on my original idea and see what I can salvage from it.

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Not liking things in physics isn’t far from appeal to personal incredulity, which is a fallacy. If you’re not trolling, then stop doing things that look like trolling.

I'll try. Thanks for helping. 🙂

Edited by Lorentz Jr
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  • 1 month later...
On 11/30/2022 at 11:47 AM, studiot said:

Think of a stream bed with an smooth clay or sandy bottom.

The stream flows in steady parallel lines with no disturbances.

This is an example of a Field, called a flow field.

 

Now change the bed to a rocky bottom.

The flow changes and eddies appear around some of the rocks.

A few of these eddies are transient but many are persistent.

These all constitutes a disturbance in the field and involve greater energy due to the rotation of the fluid field at the eddy location.

Noone pretends that the eddies are points, they occupy real volume.

So within the field there can bee seen persistent disturbances, of higher energy than the surrounding general field.

These disturbances can be regarded as self contained entities, and if they relocate they move as self contained entities ie they have particle like characteristics

This is a very simple picture of the proposition 'a particle is a disturbance in a field'.

Does  your "stream bed" work as well as an analogy if there is no top and bottom   no rocks to cause perturbations  ,no gravity  and if the  various independent flows through the "stream" simply interact with each other?

Would "particles"/perturbations be formed the same way? And would  one perturbation lead to a cascade of other perturbations?

I am imagining an infinite number of very small streams,interacting with each other  .

 

Edited by geordief
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