well................ I'm not going to argue with an incredibly vague reference but magnetism inQuote:
Originally Posted by PhilosopherStoned
a ferrous metalmatter is associated with the alignment of the electrons in themetalobject. We could get into a whole discussion about the symmetry of fundamental particles, photoelectric effects and the unification of electromagnetism but.... no. All I'll say is;
http://carlbrannen.files.wordpress.c...abmn.jpg?w=700
OH!.....:lol: dur.... you should have said that from the beginning :roll:Quote:
Originally Posted by Xaqaria
:?
To be honest this is a pretty bizarre post. tommo basically said 'torsons'. In what sense is that an explanation of anything, haha... he didn't even define what a torson is or wtf it does.Quote:
Originally Posted by Xaqaria
I thought magnetic fields are caused by any moving charge (so a stream of protons would do it)... and the magnetic field around a wire is caused by the movement of electrons, not their alignment... photons are always the carriers though (the force being electromagnetic).Quote:
Originally Posted by Xaqaria
I'm only just starting Maxwell's equations so I could be wrong.
In what sense is "electrons" or "photons" an explanation of anything?Quote:
Originally Posted by Xei
I assume he was trying to point out that we basically just know nothing about how magnetism happens except that electrons cause it.
Except that isn't true.
Yeah, we can understand magnetism only as far as we understand why there are positive and negative charges that attract and repel each other and, if the field theory is right, why every point in space is caused to possess a direction of force near these charges. As far as I know, these "facts" are where the "just is" border of our knowledge begins.
Photons "mediate" the electromagnetic force. I could cook up some matter that was nothing but protons bound together by the strong force, e.g. an atomic nucleus, and an observer moving past it would measure a magnetic field. As far as the diagram goes, could you explain what the letters are? The squigly lines are usually photons in Feynman diagrams. This looks like a feynman diagram turned on its side in which case that would be a photon decaying into an electron and a positron which then reunite, anhilalate, and produce another photon.
EDIT:
Also, how is the exact title of the book, together with the name of one of the authors "vague"? Also, it's common knowledge that photons carry the electromagnetic force. So I'm really not saying anything weird here...
Its vague because you basically just said "read this book". Without having read the book or having enough time to read the book before posting (unless you think this conversation won't have gone anywhere in the next month or so) I have to take it on faith that the book addresses this topic and contradicts what I said. You didn't offer any actual information from the book so there is no real argument there.
Yeah, the feynmen diagram is a photon becoming an electron and positron, and back again. My point was that fundamental particles are interchangable, or exhibit "symmetry".
To xei, the short answer is; I don't know? I was talking specifically about an object that exhibits magnetism like a bar of magnetized iron, and not a magnetic field caused by charge flow. I'm sure they are related, but it has been so long since I've had formal teaching on the subject that I can't recall exactly how and I'm feeling too lazy to go look it up before posting so that I could appear smarter than I actually am.
Edit: okay okay, my deep seeded need to not be wrong kicked in, a short quote from wikipedia to show what I was refering to with my initial post about electrons;
and then a little more pertaining to what I said about the electrons being aligned:Quote:
In magnetic materials, sources of magnetization are the electrons' orbital angular motion around the nucleus, and the electrons' intrinsic magnetic moment (see electron magnetic dipole moment).
Quote:
Ordinarily, the enormous number of electrons in a material are arranged such that their magnetic moments (both orbital and intrinsic) cancel out. This is due, to some extent, to electrons combining into pairs with opposite intrinsic magnetic moments as a result of the Pauli exclusion principle (see electron configuration), or combining into filled subshells with zero net orbital motion. In both cases, the electron arrangement is so as to exactly cancel the magnetic moments from each electron. Moreover, even when the electron configuration is such that there are unpaired electrons and/or non-filled subshells, it is often the case that the various electrons in the solid will contribute magnetic moments that point in different, random directions, so that the material will not be magnetic.
However, sometimes — either spontaneously, or owing to an applied external magnetic field — each of the electron magnetic moments will be, on average, lined up. Then the material can produce a net total magnetic field, which can potentially be quite strong.
That's just saying that magnatism works because there's a bunch of little magnets all pointing in the same direction...
The explanation is that photons are mediating the electromagnetic force. They are the guage boson associated with electromagnetic fields.
Explaining the book in a post is not reasonable. Since you are interested in science, I would highly recommend reading it. The chapter "The Strange Symmetry of Light" is the relevant one. Briefly, there are "gauge fields" associated with the electronomagnetic field such that if the gauge field is given, then the electromagnetic is uniquely determined. But there are more than one gauge field that can be given for any given electromagnetic field so we can never measure the difference between them. Hence the laws of electromagnetism are "invariant" under a gauge transformation and the photons arise from this.
The strong, weak, and electromagnetic fields are all gauge theories and the symmetries under the gauge transformations give rise the the gauge bosons which mediate the respective forces, 1 for EM, 3 for weak and 8 for strong.
electrons aren't just little magnets (well they are but...) its their angular momentum that plays the biggest role in macro scale magnetization. I don't know what we are even arguing though... photons do transmit electromagnetic forces, but I really don't see how that is any more of an "explanation" of magnetism than "the angular momentum of electrons" or "intrinsic magnetic moment". It seems to me that the concept of spin is more fundamental to any explanation of magnetism than the force carriers.
I'm confused... surely with small velocities we can assume non-relativistic space, but in this situation it seems to be that the existence of a magnetic force depends on the frame.Quote:
Originally Posted by PhilosopherStoned
I am not entirely sure I understand your question, and therefore I will probably not be able to answer it.Quote:
Originally Posted by Xei
However magnetic force is dependant on particles moving in relation to each other, as given by the formula for the Lorenz Force (which is electromagnetic force)
F = q(E + (v x B))
Assuming there's no electric field, the formula is reduced to
F = q(v x B)
Where q is an electric charge, v is the velocity of the particle with charge q and B is a magnetic field. This clearly shows that magnetism can only exist between particles that move in relation to each other.
As far as I can understand, though, it should be independent of your frame of reference.
I worded that statement poorly. I've been thinking a lot about local measurements so I pictured an observer moving past the nucleus with a test charge. The motion would lead to the magnetic field but all observers moving non-relativisticly would measure it.
What are your favourite simple things that science just cannot explain?
What was there before the Big Bang and what triggered it?
If space-time was created at the moment of the Big Bang, the question of what came "before" is meaningless. Causality came after the Big Bang.
Such a simple question huh?
This thread failed because everyone posted complicated shit.
Because pretty much every simple thing has already been explained.
Haha yeah seriously, the original point was WAY missed. "What happened before the universe" is NOT a simple, observable thing.Quote:
Originally Posted by tommo
I was thinking more about things like the shower curtain effect, which amazingly, is still not understood. There are all sorts of hypotheses about it, but no conclusive answer has been reached. this isn't because science can't, it's just there are more important things to do.
I think Crooke's Radiometer has only been solved conclusively very recently (if at all - I THINK they finally got to the bottom of that one, but am not sure).
I heard somewhere (haven't tested myself) that if you take two pieces of polarized material (e.g. 3d glasses from the theater), and hold them at 90 degrees (such that no light passes through), and then interpose a THIRD piece in between the two at a 45 degree angle, it becomes clear again, and that scientists have no clue why. I have yet to test this myself, and I have yet to find out if it's true that scientists have no clue why.
But I love these simple little unknowns. :) That was the original point of the thread hehe.
Basic quantum mechanics. Definitely true. Definitely understood. The light coming out of the first polarizer is definitely in the state that's polarized at the angle of the first polarizer. When the second polarizer is introduced at 90 degrees to the first one, the chance of measuring the photon in that state of polarization is 0. It's definitely polarized at a right angle to the second sheet because of the first polarizer. Hence zero photons get through.Quote:
Originally Posted by Replicon
However when you introduce the third sheet between them, then each photon coming out of the first sheet has a 50 percent chance to be measured as polarized in accordance with the third sheet. The ones that are measured to be aligned with the third sheet (i.e. the ones that get through) are now definitely polarized at 45 degrees relative to both the first and second sheet. Hence when they hit the second sheet, they have a 50 percent chance of getting through. So in all, with the three sheets lined up right, you get 25% of the original photons. This is not "clear" but it is see through.
Here's a cool one
The Oh-My-God Particle
I hope you enjoy this film shown on BBC 2 entitled, 'What Happened "Before" the Big Bang'Quote:
Originally Posted by Spartiate
http://www.youtube.com/watch?v=_bGx3UB-Slg
Part 2 Deleted due to complaints from the BBC ???
http://www.youtube.com/watch?v=c7vTQ3Z9fmY
http://www.youtube.com/watch?v=wH-GmZaJxLY&list=PL479413265B9FB954&index=4
http://www.youtube.com/watch?v=cSCMEO0Z3M0&list=PL479413265B9FB954&index= 5
http://www.youtube.com/watch?v=SzgcSxBIMGM&list=PL479413265B9FB954&index= 6
Laura Mersini-Houghton.... wow.