# Accelerated Magnetic charge

1. Jan 12, 2009

### spidey

Accelerated electric charge radiates..so do accelerated magnetic charge,if it exist, also radiates?

I think it should also radiate as like electric charge..Any inputs on this..

2. Jan 12, 2009

Staff Emeritus
There is no such thing as a magnetic monopole - a single magnetic charge.

3. Jan 12, 2009

### clem

If there were one, it would radiate like an electric charge, but with different polarilzation.

4. Jan 13, 2009

### spidey

Absence of evidence does not mean evidence of absence

5. Jan 13, 2009

### DiamondGeezer

No it doesn't. If you discover a magnetic monopole then the Nobel Committee will certainly knock on the door.

But Maxwell's equations imply that magnetic monopoles do not exist.

6. Jan 14, 2009

Staff Emeritus
I'm sorry. I thought you were here to learn, not to lecture us. With platitudes.

You can never prove a negative. We can discuss the internal anatomy of unicorns or flying reindeer if you wish. After all, just because nobody has ever seen one doesn't mean one won't be discovered tomorrow. But it seems rather pointless.

Nobody has ever seen a magnetic monopole. In classical physics - where this message is posted - they do not exist. Classical physics - specifically the $\nabla \cdot B = 0$ piece of Maxwell's equations - is engineered so that the non-existence of monopoles is built right in.

But you know all that, right? So lecture away...

7. Jan 14, 2009

### spidey

In my first post i asked that question with keyword "if it exist"..i didn't say it exist..In my second post also i just replied you and again i didn't say "magnetic monopole exist"..I know noone has seen it before and dont know we will see it or not in future..Just out of curiosity i asked this question? Anyway i am not going to prove MM exist..I accept my defeat

8. Jan 14, 2009

### spidey

I don't have magnetic monopole..i have only dipole..Just i missed Nobel prize

9. Jan 14, 2009

### DiamondGeezer

I am not a giraffe and I can prove it.

I think you mean that you cannot prove a UNIVERSAL negative

10. Jan 16, 2009

### spidey

Why with different polarization? any reason

11. Jan 16, 2009

### JustinLevy

Because you would get the same solution as before, just with the E and B fields switched.

Speaking of whether magnetic monopoles exist:
I always thought magnetic monopoles were an interesting topic for discussing the scientific method with students. For example, how many magnetic monopoles would you have to see to consider that magnetic monopoles exist?

Most people answer 1. But historically, searches for magnetic monopoles have seen signals (there are two in literature I believe). But the signals were not repeatable, so we don't consider magnetic monopoles to have been discovered.

There are some theoretical niceties that we get if magnetic monopoles exist.
Wouldn't it be frustrating if we later find out they exist, and they are just rare enough that the original 'discovery' was just discarded? There will always be experiments which keep looking. Who knows, but I doubt they will find anything.

So how many magnetic monopoles would you have to see in the lab before you'd believe it? :)

12. Jan 16, 2009

### jambaugh

I think "imply" is too strong a word. For example the vacuum equations do not "imply" no charges at all exist.

Rather we should say "Maxwell's eqns. assume no magnetic charge."

13. Jan 16, 2009

### spidey

First of all, i have doubt between the magnetic charge and magnetic field...Just like particles have electric charge,they should have magnetic charge too...Have we ever calculated the magnetic charge of elementary particles..if elementary particles don't have any magnetic charge then magnetic monopoles cannot exist..but this again asks the question how can there be magnetic field without magnetic charge..

14. Jan 17, 2009

### jambaugh

I'd say 6. I'd need to see them produced in pairs and repeated a couple of times.

15. Jan 18, 2009

### JustinLevy

If Maxwell's equations are not convincing enough for you, then I'm not sure what to say.

And the elementary particles comment is really strange. The people performing magnetic monopole searches are not claiming the known particles have a magnetic charge. They are checking the possibility that there exist other particles that have a magnetic charge.

Most magnetic monopole searches aren't looking for production. They are just looking for existence.

If they could not be produced, would that up your personal requirement?

One of my requirements would not only be repeatability, but repeatability by another lab (see for instance the search for so called 'relic' free quarks ... there is a lab which has had repeatable finds, but no other lab has reproduced the findings).

So I guess I'd say 6 as well before I'd really start feeling comfortable considering the word "discovered" (3 from two different labs each). Although even two individual events seen by separate labs would cause quite a stir I believe.

EDIT: I'd only feel comfortable with such a low number here due to the simplicity of the search apparatus. If the discovery was made by a particle collider + detector ... well, I wouldn't be sure how to judge due to the complexity. I wouldn't be able to make a judgement myself, and would (like many others I assume) hope for consensus amongst those that specialize in that field.

Last edited: Jan 18, 2009
16. Jan 18, 2009

### jambaugh

Maxwell's equations have room for the contribution of a magnetic charge. (Just as Einstein's equations have room for a cosmological constant). Verifying ME's for electric charges and vacuum does not provide evidence for the absence of magnetic charge.

Compare this with say SR which equates FTL causality to time reversed causality and hence causal paradoxes. Thus confirmation of predictions of SR does in fact provide evidence for the absence of FTL causality.

Right. (I'm not sure to what "elementary particles comment you refer.?) I think its pretty simple to verify that known particles have no magnetic charge within a very fine degree of precision. The simple fact that the beam of an old fashion cathode ray oscilloscope doesn't skew under the influence of the electro"static" deflection field shows an electron's magnetic charge must be very close to zero. Obviously magnetic monopoles would be something new.

Well then assuming they could not be produced then they would be slow to decay and though rare they should be collectible. I would think then that in terms of production of observations one such particle can provide an arbitrarily large number of verifications.
So "one capture" or "three discoveries" wherein there are at least two sequential observations.

Yes. That's part of what my thinking is on the number "three". One lab produces and reproduces, a second lab confirms. However given the Pons-Fleshman debacle I'm inclined to "up" the threshold of certainty farther. I was quite embarrassed for my Alma Mater Ga.Tech. (and a bit proud of their quick retraction) when they "detected" neutrons.

I think we can learn from this that the more socially significant a scientific discovery the more rigorous our threshold of skepticism needs to be. Of course the ultimate mistake in the cold fusion business was the initial decision to call a press conference instead of the tried and true method of undergoing the peer review gauntlet.

17. Jan 20, 2009

### JustinLevy

That first part of my post was replying to a quote from Spidey, not from something you said.

He was doubting the existence of magnetic fields just because magnetic monopoles haven't been found (yet Maxwell's equations show that magnetic fields can arise from current or a change in electric field ... no magnetic monopoles are needed for magnetic fields).

Look at the quote of Spidey's I was replying to.
I think we're in agreement here. There was just a little miscommunication and you thought I was directing those comments to you.

Yeah, good points.

The cold fusion thing has always confused me because so many labs can reproduce the "apparent excess heat", but it has been clear for awhile now that it is quite doubtful it is fusion. Strange stuff. The whole scientific discussion of such investigations is tainted now, and people don't want to get involved, so we many never get a fully satisfying answer of what is going on. Oh well.

18. Jan 20, 2009

### jambaugh

Ah yes I see now. Pardon me...yes we're in agreement.

Just a thought. How would one go about checking if some of the cosmic rays are magnetic monopoles? Kind of like reading the serial number on a bullet in flight... but with the right detector I think it could be done. Hmmmm....nice problem. Differential currents induced in a wire grid?

19. Jan 21, 2009

### spidey

Electric charged particle takes circular motion in uniform magnetic field..so will magnetic charged particle take circular motion in electric field?

20. Jan 22, 2009

### jambaugh

That is the assumption under the duality that we are also using to define a "magnetic charge". Of course until we "see" one and test it . . .