Naked Science Forum
Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: Arthur Geddes on 21/04/2016 16:42:59
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We observe events compelled by fields; don't we? Has anyone actually seen a particle? Do we need duality or, are self-propigating waves enough?
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do particles actually exist? do fields actually exist? do waves actually exist?
I don't know and I'm not sure we can ever be absolutely certain what actually exists. However, scientific models that rely on the concepts of particles, waves and fields are all very useful. Often one can arrive at the same prediction by treating a system as particles or as fields, but it is usually much easier to do it one way over the other...
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Has anyone actually seen a particle?
Yes, the LHC sees them all the time. Earlier ways of seeing particles included the bubble chamber (https://en.wikipedia.org/wiki/Bubble_chamber).
Do we need duality or, are self-propagating waves enough?
Self-propagating waves are a good model where there are zillions of particles, with a wavelength much larger than the detector, so the underlying quantization is not significant.
So Maxwell's theory works very well for radio waves (many coherent particles of low energy, long wavelength), not so well for light (the photoelectric effect), and is not very relevant for gamma rays (few particles of high energy, non-coherent, very small wavelength).
Similarly, Einstein's theory of gravity produces useful predictions for gravitational waves the size of the Earth, but is not so useful when predicting events within micrometers of a black hole.
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I appreciate your consideration &, please bear with me while i delve into precise mechanism...
The particle perturbs the local pressure as it moves through the medium by what mechanism precisely?
I'm familiar with the Poynting vector (wikipedia.org/wiki/Poynting_vector) in E.M. propagation but, not how it relates to the photon structure. I'm also aware that subatomic particles are assumed to be of zero volume, which makes me wonder about mechanisms of interaction generally.
I'm also aware of potentially confusing the probability wave function, the statistics of 'finding' the 'particle,' with an actual wave-type definition of 'particle;' just to mention.
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Going back to the original post; it's easy for me to imagine the E field aspect of a photon as what moves the electron from orbital to orbital &, the magnetic aspect would alter the spin of the electron, i assume? No need for a particle if the fields are contained somehow.
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Elementary particles are assumed to have zero volume; to correct my error.
Thinking about the quantization of charge the nature of quantization generally; it seems reasonable to suggest that charge itself is the result of some harmonic function. Similarly quantization of spin wrt magnetic moment. Maybe?
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But first you label the dust 'particle' & then transpose that all the way down: i don't see any ground for that.
A nutron is not a particle; it's an assemblage of constituents. It has a volume because the constituents arrange themselves just so. Quantization suggests a quantum harmonic oscillator; a loop of some sort; not a particle.
It just seems to me the notion of 'particle' is dogmatically based on our experience of matter. I saw in another thread the observation that anything traveling at speed c experiences no volume so; to the photon, it has just as much energy per unit surface area throughout its length of travel to it (only one cycle, to it) but not to us: that seems relevant somehow.
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Reality is what we observe. Physics is how we describe it. We have good mathematical descriptions of macroscopic particles (billiard balls) and waves (sound, waves on water, whatever..). It happens that we can apply these descriptions to the observation of very small events, but sometimes the wave equation fits, and other times the particle equation is better.
Whether something "really exists" is the kind of question that intrigues philosophers. Predicting what happens next is much more important.
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We don't understand the interaction of billiard balls as an interaction of particles; scientifically speaking, it's an interaction of charges, mediated by force carrying photons, that derive rigidity from stable harmonics. No particles; mass but, no particles. I'm fine if it's just semantics but; if it's a supra-temporal elephant then; maybe particles are an illusion of resolving space-times. ...?
If particles are an illusion of particular being; describing the nature of the illusion will elucidate mechanism & facilitate understanding. If it's just semantics then, how is it helpful?
A supra-temporal shell of photon around its origin, static & of constant energy, comes to mind.
All of the spacetimes that are true are true at once.
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I'm familiar with the Poynting vector (wikipedia.org/wiki/Poynting_vector) in E.M. propagation but, not how it relates to the photon structure.
The Poynting vector is a classical construct, based on Maxwell's equations.
You can also update it to match relativity.
However, it does not address the fact that, if you look closely enough, electromagnetic waves are quantized, ie particles like the photon.
So by all means use the Poynting vector where classical effects predominate (eg in a radio transmitter, or TV antenna cable, or a laser beam propagating through space), but be aware of its limitations.
Use quantum theory where it is more appropriate (eg to describe the generation of the laser beam, or the photoelectric effect when the laser beam hits a charged cathode in a vacuum tube).
pi*0²=1
I disagree. pi*0²=0, not 1.
Why not use some real maths? Like the Euler Identity (https://en.wikipedia.org/wiki/Euler%27s_identity): eπi +1 = 0
It has no relevance to the topic at hand - but that puts it on a par with "pi*0²=1".
At least it has the benefit of being correct...
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(eg to describe the generation of the laser beam, or the photoelectric effect when the laser beam hits a charged cathode in a vacuum tube).
There it is; why we maintain the notion of particle. The quantization can be understood from an harmonic perspective wrt the QHO; can't it?
A couple of problems with the particle notion:
-all of those virtual particles; i can get rid of them with a notion of a supra temporal field relative to the photon that is as valid as the real photon (event), i.e. they're the same thing. The 'perspective' of the photon has to be resolved with source & sink; i.e. in some sense, they are right next to each other.
-an exponential increase in virtual mass as entanglements propagate: resolved by understanding entanglements as just our experience of the source & the sink being in some sense right next to each other.
I dunno; why particles of zero volume when they can be 'particles' of spacetime?
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I have taken the liberty of cleaning this thread up somewhat. Please continue to discuss the validity and utility of particles here. If instead, you wish to debate the arithmetic invoked by TheBox, please find that here: http://www.thenakedscientists.com/forum/index.php?topic=66552.0
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(eg to describe the generation of the laser beam, or the photoelectric effect when the laser beam hits a charged cathode in a vacuum tube).
There it is; why we maintain the notion of particle. The quantization can be understood from an harmonic perspective wrt the QHO; can't it?
A couple of problems with the particle notion:
-all of those virtual particles; i can get rid of them with a notion of a supra temporal field relative to the photon that is as valid as the real photon (event), i.e. they're the same thing. The 'perspective' of the photon has to be resolved with source & sink; i.e. in some sense, they are right next to each other.
-an exponential increase in virtual mass as entanglements propagate: resolved by understanding entanglements as just our experience of the source & the sink being in some sense right next to each other.
I dunno; why particles of zero volume when they can be 'particles' of spacetime?
A few things:
First, let's not confuse the topic of particles with that of virtual particles--the latter is another way of describing fields and forces, while the former refers to units of matter.
Second, what's wrong with describing a very localized quantum of something that has both a position and a momentum (each not entirely determined) as a particle? Ultimately will we just get down to an issue of semantics, or do you believe that there is no such thing as a very localized quantum of something that has both a position and a momentum?
Third, I always get nervous when people talk about the "perspective of a photon." As far as I know, we really don't have a good way of describing the universe from the perspective of anything moving at c. (And, I know you didn't bring this up here, but I get the same feeling when people talk about the "perspective of a black hole"--these are just frames of reference we cannot intuit or observe...)
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The standard gravitational parameter u=Gm tells us that the whole mass of a system is not involved in the generation of gravity. This is because the constituent quarks of composite particles are a fraction of the total rest mass. Particles are strange things that can be modelled without actually observing them directly. Yes they do exist or we wouldn't.
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We observe events compelled by fields; don't we? Has anyone actually seen a particle? Do we need duality or, are self-propigating waves enough?
Neither particles nor fields can be "seen".
I'll assume that you're speaking of elementary particles such as electrons, neutrinos, photons, etc. The term particle is often used to refer to objects whose dimensions are small enough to be considered negligible for the purpose at hand. E.g. we use the particle approximation when we calculate the orbits of planets and satellites.
In science we don't typically use the term exist. What we do is make observations and using logical induction formulate postulates from which we can generate theories. Starting with these postulates as premises we can then use logical deduction to arrive at proofs which can then be tested in the lab. If these observations are confirmed the lab then the we say that those postulates the postulates have gained support. Otherwise the postulates are either wrong. The theory then needs to be modified or tossed out.
The concept of particle that you're speaking of has an overwhelming amount of of experimental support. However there are those in the physics community who hold that particles don't exist and that only fields exist. I've seen this idea published in the American Journal of Physics, one of the most highly respected physics journals that there is. Then again another article in the same journal which holds that neither particles nor fields exist (what's a person to do? Lol!!) The references for those articles are
There are no particles, only fields by Art Hobson, Am. J. Phys. 81, 211 (2013)
http://scitation.aip.org/content/aapt/journal/ajp/81/3/10.1119/1.4789885
You can download this from: http://arxiv.org/abs/1204.4616
There are no particles, and there are no fields by Robert J. Sciamanda, Am. J. Phys. 81, 645 (2013)
http://scitation.aip.org/content/aapt/journal/ajp/81/9/10.1119/1.4812316
physics.uark.edu/hobson/pubs/13.09.a.AJP.pdf
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First, let's not confuse the topic of particles with that of virtual particles--the latter is another way of describing fields and forces, while the former refers to units of matter.
K.
Second, what's wrong with describing a very localized quantum of something that has both a position and a momentum (each not entirely determined) as a particle? Ultimately will we just get down to an issue of semantics, or do you believe that there is no such thing as a very localized quantum of something that has both a position and a momentum?
Nothing i suppose &, i definitely don't want to get hung up on semantics. Dr. Susskind mentions the standard model's assumption that elementary particles are of zero volume: i checked & it seems that's because (amongst other reasons, i suppose) the magnetic moment of an electron with spin is too large to be accounted for by a rotating charge, given the maximum size of an electron. I don't have a problem with using the word particle but, this zero volume thing has me looking for something else. Also; the complex statistics that gives the interference patterns, that these particles can interfere only with themselves; they take both pathways, unless we look: o.k. but, maybe there's a better way?
Third, I always get nervous when people talk about the "perspective of a photon."
Nervous is good here, i think.
As far as I know, we really don't have a good way of describing the universe from the perspective of anything moving at c. (And, I know you didn't bring this up here, but I get the same feeling when people talk about the "perspective of a black hole"--these are just frames of reference we cannot intuit or observe...)
General Relativity means we have to consider 'perspectives.' If the gravitational field is spacetime, we have to consider interacting spacetimes & relative shapes have to give consistent results. But then photons don't have their own spacetime... but they do relate events at source & sink(s)... But, nervous is good.
One of my Physics Profs was Werner Israel; he proved that black holes have no discontinuities: at least there's that.
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We don't understand the interaction of billiard balls as an interaction of particles; scientifically speaking, it's an interaction of charges, mediated by force carrying photons, that derive rigidity from stable harmonics.
Not sure what you mean by "understand" but we predict the motion of billiard balls with the principes of conservation of mass, energy and momentum, which seem to work at all levels. Force-carrying photons etc are merely models that we introduce to explain how the microscopic builds to the macroscopic.
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Force-carrying photons etc are merely models that we introduce to explain how the microscopic builds to the macroscopic.
This is one of the points that gets lost in translation. Can you write that in capitals please.
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Force-carrying photons etc are merely models that we introduce to explain how the microscopic builds to the macroscopic.
This is one of the points that gets lost in translation. Can you write that in capitals please.
O.K. so, instead of transposing the illusions of human experience all the way to the sub-atomic while ignoring the other 'direction,' i.e. not imposing a global coherence requirement on Being that we could call 'truth'; it is just as reasonable to suggest that everything is fields & that they can be everywhere permissible AND all at every single permissible location at the same time?
That about covers it. Thanks to all who contributed.