You have suggested in the past that magnetism is caused by moving electrons being subject to Lorentz contraction.
If we consider a direct current in a copper wire, the positive copper nuclei remain in a fixed position while the electrons move along the wire with a small drift velocity.
Small though that drift velocity may be, the moving electrons are subject to a Lorentz contraction while the stationary positive nuclei are not..
The result is that the charge density of the moving negative electrons is greater than the charge density of the positive nuclei.
Now consider a positive test charge (q) moving parallel to the current carrying wire.
The test charge will be attracted towards the wire because the greater charge density of the moving electrons results in an attractive force that is greater than the repulsive force of the stationary positive nuclei, i.e., there is a net attractive force.
This is the origin of the magnetic Lorentz force - the force exerted on a charged particle when moving through an electromagnetic field.
Although the length contraction leads to a minute change in charge density, it has an appreciable relativistic effect when we consider that the total charge of all the conduction electrons in a metre long wire is tens of thousands of coulombs!
I'm sure some contributors will consider we are simply talking nonsense, Steve! 🤓
https://galileo.phys.virginia.edu/classes/252/rel_el_mag.html
We draw the coordinate system on the blackboard BEFORE we enter the "physical" "events". More exactly it would be the other way:
FIRST the events, THEN the rulers, scales.
I think, here, described thus, really the nonsense should become clear. The rulers, scales, the coordinate system, "space-time" are consequences, abstracts, aids, concepts, in order to describe and to interpret "world", "universe". Everyday concepts that have only come into the minds, and into the "world", in the course of life through individual perception and collecting, describing and categorization, abstraction and analysis, and through socialization. The RT are based on the fundamental mistake, not to recognize this and to reify these abstracts, aids, to introduce them into the "physical world" as objects.
... observation and description once put behind in their explanation;-)
Some method analysis, science;-)
FIRST the events, THEN the rulers, scales.
I think, here, described thus, really the nonsense should become clear. The rulers, scales, the coordinate system, "space-time" are consequences, abstracts, aids, concepts, in order to describe and to interpret "world", "universe". Everyday concepts that have only come into the minds, and into the "world", in the course of life through individual perception and collecting, describing and categorization, abstraction and analysis, and through socialization. The RT are based on the fundamental mistake, not to recognize this and to reify these abstracts, aids, to introduce them into the "physical world" as objects.
... observation and description once put behind in their explanation;-)
Some method analysis, science;-)
I decided to examine the concept of emergence.
Emergence describes the ability of individual components of a large system to work together to give rise to complex behaviour.
Understanding the behaviour of the constituent parts of the Universe may not be enough to predict the Universe, and we may have to consider the Cosmos as an emergent system that is greater than the sum of its parts.
A biological analogy would be that of a flock of birds. We may understand the behaviour of an individual bird, but be unable to predict the behaviour of the flock. The complex behaviour of the flock is greater than the sum of its parts and emerges from the interactions of the individual birds in the system.
Wikipedia sums it up well: "In science, emergence occurs when a complex entity has properties or behaviours that its parts do not have on their own, and emerge only when they interact in a wider whole."
https://en.wikipedia.org/wiki/Emergence
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Subjunctive, choose the form of possibility. Because both gravitational waves are not proved, therefore also their propagation, and also the proof is missing that EM can propagate in a "vacuum", "emptiness", "nothing". Especially since I suspect that behind this statement again the unscientific definition of "vacuum" is hidden, nothing with what in it and with potential and so - and ether we want to ignore mainstream-scientifically;-)
The photon is the carrier particle of the electromagnetic interaction and needs no medium in which to propagate.
The same would have to be true for gravitons if they exist.
What if I say that gravitatiional waves are vibrations in spacetime?
All of the above is tongue in the cheek, by the way!
Question: What if photons and gravity propagated through a vacuum using the same underlying mechanism? (Note, I am not saying the same method of generation since we know they are different)
A "photon" is a hypothetical particle introduced to dispense with "ether" as a light-bearing, wave-bearing medium so as not to have to abandon the R theses.
Richard Feynman, e.g.:
https://www.science.org/doi/10.1126/science.183.4125.601
Richard Feynman, e.g.:
https://www.science.org/doi/10.1126/science.183.4125.601
To compare gravity with electromagnetism, Bonsai, we would have to compare gravitons with photons. Trouble is, if they exist, gravitons would be almost impossible to detect, gravity being by far the most feeble fundamental force.
If gravitons are found to exist, it's perhaps not so much a matter of "what if" the two forces share the same underlying mechanism of propagation as "why wouldn't they".
P.S. I'm making this waffle up as I go along in order to avoid answering an unanswerable question! 🤓
If gravitons are found to exist, it's perhaps not so much a matter of "what if" the two forces share the same underlying mechanism of propagation as "why wouldn't they".
P.S. I'm making this waffle up as I go along in order to avoid answering an unanswerable question! 🤓
Well, I keep coming back to Dan Fleisch's comment about the underlying mechanism of an EM field propagating through a vacuum as a 'deeply philosophical question' that students should set aside and just focus on the equations for the time being. As I've said before, we are able to describe EM and gravity with exquisite precision, but in both cases, we do not know the underlying mechanism of how they actually propagate through a vacuum - in the case of gravity, I'me specifically talking about gravity waves here. We don't know what causes gravity to arise so that is another question still to be answered fully - QLG from what I've read still has too many holes in it to be considered the answer.
It seems to me, these are questions that need answering.
It seems to me, these are questions that need answering.
The burning question for me at the moment is why my laptop is failing to recognise that the (working) DC power supply is plugged in, resulting in the battery going flat and the device shutting itself down.
I've had to drag out my old Windows Vista laptop which, although built like the proverbial brick outhouse, runs at a
pace!Followers of this thread may be pleased to hear that my contribution rate is likely to decrease until such times as I purchase a new laptop.
To accept LQG (Loop Quantum Gravity), you have to do away with one of the central tenets of General Relativity - that spacetime is smooth.
LQG says that spacetime has structure on the smallest scales - a structure that would only be apparent on the level of the Planck scale - around a trillionth of a trillionth of a trillionth of a metre!
To detect spacetime structure on that scale, you'd need an atom smasher 1,000-trillion-times more powerful than the Large Hadron Collider - one about as big as our entire Milky Way galaxy!
The story continues here: https://www.space.com/end-of-einstein-space-time
Galu, I am a bit shocked that you post a link called "Was Einstein Wrong? The case against Spacetime theory." and featuring Doctor Sabine Hossenfelder, who is notoriously a Philosopher more than a serious Physicist these days:
https://en.wikipedia.org/wiki/Existential_Physics
You may encourage the anti-science skeptics, and you know who I mean! I see little need to worry or philosophise about Quantum Theories of Gravity. They only apply to the instant (T=0) of The Big Bang, and that was ages ago. We are very much at T>0 and General Relativity is just fine.
I don't know if this is a true story, but it is an entertaining one anyway:
A solemn Physics Professor at Harvard had become so fed up with philosophy majors attending his Origins of the Universe seminar that he finally posted a sign on his classroom door:
In my classroom, T>0.
For all enquiries where T=0,
please visit the Religion Department.
😀
I was going to talk about Dan Fleisch and the close relationship between Information Theory, Signal Processing, Waves and Laplace Transforms and Schrodinger's Equation, which is very Dan Fleisch, but will save it for another time, I think.
https://www.danfleisch.com/
One of my favourite things in signal processing, The Sinc Function, used in analog and digital, which is usually done with regular calculus. It seems very similar to Scrodinger's equation with his different notation, Bra-Ket.
But it does pertain to fields, and the current thinking is fields contain energy and momentum as much as particles do. The vacuum is not empty. The Higgs Field is spin 0, Electromagnetism is a spin 1 field, Gravity may be spin 2 if that approach is required.
@Galu. Puts on PC fixing hat: Your laptop may have a broken power socket, or the charger lead may have a break, usually at the plug which goes into the laptop.
https://en.wikipedia.org/wiki/Existential_Physics
You may encourage the anti-science skeptics, and you know who I mean! I see little need to worry or philosophise about Quantum Theories of Gravity. They only apply to the instant (T=0) of The Big Bang, and that was ages ago. We are very much at T>0 and General Relativity is just fine.
I don't know if this is a true story, but it is an entertaining one anyway:
A solemn Physics Professor at Harvard had become so fed up with philosophy majors attending his Origins of the Universe seminar that he finally posted a sign on his classroom door:
In my classroom, T>0.
For all enquiries where T=0,
please visit the Religion Department.
😀
I was going to talk about Dan Fleisch and the close relationship between Information Theory, Signal Processing, Waves and Laplace Transforms and Schrodinger's Equation, which is very Dan Fleisch, but will save it for another time, I think.
https://www.danfleisch.com/
One of my favourite things in signal processing, The Sinc Function, used in analog and digital, which is usually done with regular calculus. It seems very similar to Scrodinger's equation with his different notation, Bra-Ket.
But it does pertain to fields, and the current thinking is fields contain energy and momentum as much as particles do. The vacuum is not empty. The Higgs Field is spin 0, Electromagnetism is a spin 1 field, Gravity may be spin 2 if that approach is required.
@Galu. Puts on PC fixing hat: Your laptop may have a broken power socket, or the charger lead may have a break, usually at the plug which goes into the laptop.
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A "serious physicist" knew the games with e.g. a finger, which, held in front of the eye, lets see all kinds of strong light diffraction effects. These proved and physical, thus material, diffraction effects would have to be determined and subtracted e.g. at observations of the night sky, in order to prove afterwards e.g. a claimed "gravity diffraction", a non-material one.
Do yourself a favour and get one with a magnetic plug ;-)
https://www.apple.com/shop/buy-mac/macbook-air
//
In this case, she was being critical of LQG so listening to what she has to say in that context appeared valid.
I'm back on my faulty laptop at the moment. If left off, but plugged in, then when turned back on a few hours later it will indicate that it is "plugged in, charging". However, at some point during use today that indication is sure to disappear and the battery will discharge.
The power supply and its plug seems to be fine (and I have a backup that doesn't solve the problem). I've taken all the screws out of the laptop's base but danged if the thing will come apart - it must be clipped together in some cunningly fiendish way! There could be a fault with the laptop's power socket, but I was thinking there may be an electronic power management system that's working intermittently. Anyhoo - no worries - all is backed up and this laptop is long overdue for replacement.
The troubles can be from the battery going bad, fooling the charging management.
Try with a good battery or a new one.
Try with a good battery or a new one.