The existence of a new kind of magnet has been confirmed
newscientist.com
newscientist.com
https://en.m.wikipedia.org/wiki/Magnetism#Types
And I am not sure it can be called a magnet. It's definitely a new kind of magnetic state
It's a new kind of magnetic medium that had not been previously observed. It is not something that can't be explained by our existing theory of electromagnetism.
> I am not sure it can be called a magnet.
It's an object that has magnetic properties. That's a magnet. It's a different kind of magnet from those we had previously observed.
Sometimes words are slightly ambiguous. This is not a hill to die on.
I agree that it is sometimes described this way, although as one commenter upthread said, such use of language is more common when physicists are talking among themselves, not when they are talking to the public.
The comments in this discussion indicate that I am by no means the only one who was confused by the original wording. So I think the change was helpful.
Div(B) = 0
And update it to say
Div(B) = sigma
Where sigma is a field describing the monopole density. Theres a ready "gap" in Gauss' law for magnetism where you can easily stick monopoles. Of course the divergence would be zero in the absence of monopoles, just as the divergence of the electric field is zero in the absence of electric monopoles, but decidedly non-zero when there's an electron around.
Not too many got the joke it seems :D
As far as I know there's no mathematical or physical reason to outright forbid magnetic monopoles. On the contrary, there is a well-known argument by Dirac that says that if they would exist then charge is quantised, which we know it is. This is one of the reasons people are still looking for magnetic monopoles.
∇⋅E = ρ(electric) / ϵ0
∇⋅B = μ0 * ρ(magnetic)
∇⨯E = -μ0 * J(magnetic) - ∂B/∂t
∇⨯B = μ0 * J(electric) + (μ0)(ϵ0)(∂E/∂t)
We could switch every physics textbook to using the above today, and the only difference would be setting ρ(magnetic) and J(magnetic) to zero when there are no monopoles in the problem.
[0] Griffiths Introduction to Electrodynamics 3E, Section 7.3.4
http://www.av8n.com/physics/maxwell-ga.htm
(or even just equations (3), which make symmetries more apparent)
> so close to zero that monopoles would be extraordinarily weak if they did exist
Why? I can't think of a reason why would this be the case? You are not solving Maxwell's equation for the universe. You can have divergence of electric field closed to zero because you have very low density (the field source) in the region you are studying.
So no, it was not explicitly ruled out by Maxwell's equations. It is not even ruled out because we did not explore the full phase space. And it depends on which monopole you are talking about (Dirac monopole, GUT monopole or EW monopole).
I also said "objects" in the GP to this post. There is no paramagnetism or diamagnetism in vacuum. You need an object made of an appropriate material. I would not insist on calling such an object a "magnet" if there is an objection to that.
However, what is described in the article is a kind of permanent magnetism; the term "magnet" applies to that in any case.
You are correct that this doesn't involve any changes to our understanding of electromagnetism in general; whether or not that means that altermagnetism is not a new type of magnetism is a matter of semantics. If I read in a paper or heard in a seminar that "altermagnetism is a new type of magnetism", I would not quibble with the language, though that phrase by itsself is almost tautologically pointless.
If you want a more technically meaningful phrase, I would propose that altermagnetism is a newly-discoved "magnetically ordered phase". Of course that doesn't fit so well in a headline.
Perhaps, but I think that when communicating with the public (as opposed to communicating with other physicists), "a new kind of magnetism" suggests something that isn't explained by our current theories, not just something that our existing theories predict but hadn't been observed before.
I would prefer this headline.
So a very nice discovery. Love how we keep finding strange new useful modes of matter at “the bottom”.
Computing substrates are far from reaching any kind of final form or limit.
https://phys.org/news/2024-02-altermagnetism-experimentally....
The introduction of dramatically faster semiconductor memory chips pushed
bubble into the slow end of the scale, and equally dramatic improvements in
hard-drive capacity made it uncompetitive in price terms.[1] Bubble memory was
used for some time in the 1970s and 1980s in applications where its non-moving
nature was desirable for maintenance or shock-proofing reasons. The
introduction of flash storage and similar technologies rendered even this niche
uncompetitive, and bubble disappeared entirely by the late 1980s.> It was considerably more expensive than ROM chip-based boards and extremely sensitive to electromagnetic fields that could render the game unplayable.
You can find the start-up sequence of these on YouTube. It’s pretty…idiosyncratic. It took forever because it had to physically warm the memory up. Though I guess taking forever is irrelevant if you are turning on a machine only once in the morning. In fact, the music in the ROM it plays while starting up was named “Morning Music”.
That's a bold claim!
I found a NASA document from 1976 that expected bubble memory to reach about a terabit per cubic meter by the year 2000. And then you need over a hundred terabits for a library of congress. https://core.ac.uk/download/pdf/42884743.pdf
To be more specific in the case of magenetism, you can say that, for example, ferromagnetism arises from the alignment of magnetic moments into cohesive domains, where the individual magenetic moments arise on the atomic level from unpaired electrons in the d or f orbitals.
But if you poke at that (incomplete) answer a little bit, things start to get complicated. How exactly do magnetic domains align? What if there's a disruption in crystal structure? Are there other sources of magnetic moments? Where does the magnetic moment on an elementary particle come from? The answers to these questions get pretty complicated and questions like these motivate a lot of active scientific research.
My source is Feynman.
But which Fenyman?
You are confusing conceptual models of reality with reality itself.
The Scientific Method is used to construct an accurate, reliable, self-consistent, non-arbitrary representation of the world, which are models.
QED is one of the most stringently tested theories in physics. But it is a model and will never be proven as 'True', we just get more confident in he model after it passes test after test, after test, after test.
But it is still just the map and not the territory itself.
Feynman knew this well:
:magic smoke: n.
A substance trapped inside IC packages that enables them to function
(also called blue smoke; this is similar to the archaic phlogiston
hypothesis about combustion). Its existence is demonstrated by what
happens when a chip burns up -- the magic smoke gets let out, so it
doesn't work any more. See {smoke test}, {let the smoke out}.
Usenetter Jay Maynard tells the following story: "Once, while hacking
on a dedicated Z80 system, I was testing code by blowing EPROMs and
plugging them in the system, then seeing what happened. One time, I
plugged one in backwards. I only discovered that after I realized
that Intel didn't put power-on lights under the quartz windows on the
tops of their EPROMs -- the die was glowing white-hot. Amazingly, the
EPROM worked fine after I erased it, filled it full of zeros, then
erased it again. For all I know, it's still in service. Of course,
this is because the magic smoke didn't get let out." Compare the
original phrasing of {Murphy's Law}.
curl -fsSL https://jargon-file.org/archive/jargon-4.4.7.dos.txt | LC_ALL=C sed -n '/^:magic smoke/, /^:/{/^:mail storm/d;p;}'Are you telling me that this is not true?
∆ • B = 0
EDIT: See? Right there on the tin.
https://en.m.wikipedia.org/wiki/Maxwell's_equations
EDIT2: The meaning of this statement is that the sum of magnetic lines of force entering a frame is equal to those exiting; there are no magnetic monopoles.
Why these forces exist, we cannot know.
How these forces act is a question of physics and mathematics.
No exceptions.
There are ways that it is wrong, and ways that it is right.
...if you had said "why?" and not "how?" then you would be absolutely right.
1. Dr. Octagon (Kool Keith)
2. Insane Clown Posse
3. Bubb Rubb (also memetic) https://youtu.be/DYRDuOCKr2A
But it seems like a thin film of this stuff would be a good thing to skim an electron beam over, if you wanted some extremely short-waved photons.
Special relativity helps to explain why, even if you have a configuration that is purely electrostatic in one frame, it won't be purely electrostatic in other frames. But that's not the same as saying that all electromagnetic field configurations are that way. They aren't.
It cannot be reduced.
https://en.m.wikipedia.org/wiki/Duality_(electricity_and_mag...