Everything that is done is logged someway or somehow. Particles or something else to be discovered, will reveal traces of everything ever done. Luke 8:17
Sure. Now, still, it would be interesting to try and ascertain the speed of communication in these experiments. It should be equal to the speed of light, but the test is worth doing.
The current theory is that particles are waves, or rather localized excitations ('bumps') in a field. One of the surprising things from quantum theory is that these bumps have a finite minimum size, and they can only increase in multiples of that size; this unit is what we call 'a particle'.
This model seems to work (makes accurate numerical predictions, etc.) for all the known fields other than gravity, so physicists think there should be a 'graviton', ie quantum of the gravitational field. But they haven't been detected directly and we don't have a good mathematical theory of them (for a bunch of reasons I don't understand, but I think "gravity is really weak" and "gravity is nonlinear" are a good start)
I am not a scientist, but I can't stop me thinking that an old radio engineer would think about that article: "They are sending information by modulating polarization (indeed in a weird manner), so why the fuss?"
Or if you prefer, I am thinking some people are over interpreting what a "particle" means. BTW I like your comment, it reminds me the blog:
> The current theory is that particles are waves, or rather localized excitations ('bumps') in a field.
It might be more useful to think of it the other way around.
If you start with a quantum field which has an expectation value at every point in spacetime -- the electromagnetic field at its lowest energy, for instance -- then every departure from that fixed background is a perturbation of the field. The "quantum" part means that any perturbation takes on discrete values.
For example, perturbations of the electromagnetic field have discrete intrinsic frequencies and for any given frequency f they appear as 1 hf, 2 hf, 3 hf, 4 hf, ... but never 0.5 hf.
Those electromagnetic field perturbations (or excitations if you prefer, or in the case of our electromagnetic field, photons) localize when they interact -- the interaction is an all-or-nothing process and happens at a definite point in the universe, and the interaction produces a complete photon or consumes a complete photon.
We have promoted a wide range of classical field theories to quantum field theories by treating waves in the classical field as perturbations of the classical field's ground state, and we then quantize those perturbations. For example, a classical coherent electromagnetic wave with frequency f can be represented as a number of photons each with energy hf. Multifrequency electromagnetic waves just add more photons with different energies hf' or hf'', for example. Each photon's frequency hf, hf', hf'', and so forth determines the strength of the electromagnetic interaction that is carried.
In Quantum Electrodynamics or the Standard Model, when the frequency of a photon is extremely high pairs of non-photons can be produced (e.g. an electron and a positron). These pairs can go their separate ways, or mutually annihilate into a high-frequency photon. As the local energy-density increases we get more and more high energy photons, electron/positron pairs, and possibly other types of particles, all potentially existing locally for brief periods. To sort this out we use a mathematical procedure called perturbative renormalization, which essentially lets us declare some of these possible high energy interactions to be "marginal" or "irrelevant" to the physical system under study. This works very well in predicting experimental results up to very high energies.
General Relativity (GR) is a classical field theory. For decades relativists have worked with perturbatively renormalized gravity, which fixes a metric on a static spacetime background, and treats any perturbations of that metric (e.g. by the movement of a gravitational wave through the spacetime) much the same as we do with electromagnetism: a classical gravitational wave can be represented as a number of gravitons each with its own intrinsic frequency that determines the strength of the gravitational interaction it carries. Gravitons participate in all-or-nothing interactions that localize them.
There's a crucial point here though. Photons are a boson with spin 1, so they do not attract or repel or really interact at all with one another directly; they also do not electromagnetically attract electrons or positrons or other matter that feels the electromagnetic interaction; photons themselves have no electromagnetic charge. Gravitons are a boson with spin 2, so they attract like charge and repel unlike charge; they also carry a gravitational charge themselves. The whole particle zoo of the Standard Model has like gravitational charge, and so would only interact with one of the two possible charges of graviton in perturbatively quantized gravity; the other charge of graviton would be pushed away to infinity by the field content of the Standard Model (and also by the gravitons produced when the perturbations of the fields of the Standard Model propagate through the universe, and also by the gravitons produced when gravitons propagate through the universe).
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[ 3.1 ms ] story [ 26.0 ms ] threadhttps://en.wikipedia.org/wiki/No-communication_theorem
Or is there still some kind of theory of "graviton" particles, spoiling this idea?
This model seems to work (makes accurate numerical predictions, etc.) for all the known fields other than gravity, so physicists think there should be a 'graviton', ie quantum of the gravitational field. But they haven't been detected directly and we don't have a good mathematical theory of them (for a bunch of reasons I don't understand, but I think "gravity is really weak" and "gravity is nonlinear" are a good start)
> One of the surprising things from quantum theory is that these bumps have a finite minimum size
How do physicists know that this is a property of waves themselves, and not of their interactions?
Or if you prefer, I am thinking some people are over interpreting what a "particle" means. BTW I like your comment, it reminds me the blog:
https://profmattstrassler.com
It might be more useful to think of it the other way around.
If you start with a quantum field which has an expectation value at every point in spacetime -- the electromagnetic field at its lowest energy, for instance -- then every departure from that fixed background is a perturbation of the field. The "quantum" part means that any perturbation takes on discrete values.
For example, perturbations of the electromagnetic field have discrete intrinsic frequencies and for any given frequency f they appear as 1 hf, 2 hf, 3 hf, 4 hf, ... but never 0.5 hf.
Those electromagnetic field perturbations (or excitations if you prefer, or in the case of our electromagnetic field, photons) localize when they interact -- the interaction is an all-or-nothing process and happens at a definite point in the universe, and the interaction produces a complete photon or consumes a complete photon.
We have promoted a wide range of classical field theories to quantum field theories by treating waves in the classical field as perturbations of the classical field's ground state, and we then quantize those perturbations. For example, a classical coherent electromagnetic wave with frequency f can be represented as a number of photons each with energy hf. Multifrequency electromagnetic waves just add more photons with different energies hf' or hf'', for example. Each photon's frequency hf, hf', hf'', and so forth determines the strength of the electromagnetic interaction that is carried.
In Quantum Electrodynamics or the Standard Model, when the frequency of a photon is extremely high pairs of non-photons can be produced (e.g. an electron and a positron). These pairs can go their separate ways, or mutually annihilate into a high-frequency photon. As the local energy-density increases we get more and more high energy photons, electron/positron pairs, and possibly other types of particles, all potentially existing locally for brief periods. To sort this out we use a mathematical procedure called perturbative renormalization, which essentially lets us declare some of these possible high energy interactions to be "marginal" or "irrelevant" to the physical system under study. This works very well in predicting experimental results up to very high energies.
General Relativity (GR) is a classical field theory. For decades relativists have worked with perturbatively renormalized gravity, which fixes a metric on a static spacetime background, and treats any perturbations of that metric (e.g. by the movement of a gravitational wave through the spacetime) much the same as we do with electromagnetism: a classical gravitational wave can be represented as a number of gravitons each with its own intrinsic frequency that determines the strength of the gravitational interaction it carries. Gravitons participate in all-or-nothing interactions that localize them.
There's a crucial point here though. Photons are a boson with spin 1, so they do not attract or repel or really interact at all with one another directly; they also do not electromagnetically attract electrons or positrons or other matter that feels the electromagnetic interaction; photons themselves have no electromagnetic charge. Gravitons are a boson with spin 2, so they attract like charge and repel unlike charge; they also carry a gravitational charge themselves. The whole particle zoo of the Standard Model has like gravitational charge, and so would only interact with one of the two possible charges of graviton in perturbatively quantized gravity; the other charge of graviton would be pushed away to infinity by the field content of the Standard Model (and also by the gravitons produced when the perturbations of the fields of the Standard Model propagate through the universe, and also by the gravitons produced when gravitons propagate through the universe).
Con...
Is this true?
As far as I've ever been able to determine, this was an assumption built into the model, not something empirically demonstrated.