Long predicted
and long sought we have finally produced a magnetic monopole. Few had any doubt that we would although the
implications of the difficulty surely are meaningful as well. At least we have it and do know it is real.
As mentioned
this is predicted by quantum theory and is added confirmation. It also provides an excellent case of the
proposition that absence is not evidence of absence.
Thus ends an
eighty year research endeavor that was pursued actively throughout.
Physicists
Finally Made The One-Poled Magnet They've Been Missing For 80 Years
JAN. 30, 2014, 12:47 PM
Eighty years after they were first theorized,
scientists have just created an artificial magnetic monopole.
Monopoles were first conceived in their modern form
more than 80 years ago by Paul Dirac, one of the founders of quantum mechanics.
This discovery has some powerful implications for
physics.
Magnets — how do they work?
Every magnet that we have ever observed is a dipole
— it has both a north and south pole. If we draw magnetic field lines around a
magnet, we always see the lines curve around, joining the two poles.
If you cut this magnet in half, you are not left
with one north magnet and one south magnet, but instead two new double-poled magnets.
This goes on and on to the atomic level — you can
keep cutting the magnet apart, but each part will still have two poles. Even a
single spinning electron has both a north pole and a south pole.
That is how every magnet we have ever seen or
experienced works.
Until now.
Now, researchers at Amherst College in Massachusetts
and Aalto University in Finland have created a mysterious Dirac monopole in the
lab.
The monopole acts as a single-point source for a
magnetic field. The magnetic field lines stretch out from the monopole in all
directions, without the looping back seen
in a normal dipole.
Before the latest finding, researchers searched high
and low but never found a magnetic monopole in nature.
Monopoles for other physical forces are ubiquitous
in nature — electric monopoles exist all over the place. The protons and
electrons that are some of the basic building blocks of matter generate
electric fields centered on themselves without a corresponding opposite pole.
Finding the elusive monopole
The researchers used some high-tech lab work to
create their artificial magnetic monopole, which they published Jan. 30 in the journal Nature.
M.W. Ray et. al., Nature, 2014
The top row shows the scientists' experimental
results. The bottom row shows their mathematical predictions. The close
similarity between the two suggests that a monopole was formed. The vortex can
be seen as the dark spot in the center of the condensate.
Their first step was
making a Bose-Einstein Condensate — a small cloud of atoms cooled to a few
billionths of a degree above absolute zero.
The cooling process involves shooting atoms in a
cold gas with lasers, sapping the atoms of their momentum, and then carefully
manipulating the atoms with magnetic fields to slow them down even further.
At this temperature, the atoms are almost
stationary, and weird quantum effects start to happen. The atoms begin acting
very strange and form a new kind of matter — different from the solids,
liquids, and gasses we are used to.
The researchers then carefully applied finely tuned
magnetic fields to the strange matter, forming tiny tornado-like vortexes in
the fluid.
This animation, taken from a
YouTube video posted by the researchers at Aalto University, shows how the monopole is made. By carefully
balancing out external magnetic fields to move a point at the base of a vortex
into the middle of the condensate, the condensate itself begins to emit an
outward pointing monopole-style magnetic field.
The researchers call this the "hedgehog
configuration."
The mathematics that describe the theoretical
behavior of the Dirac magnetic monopole very nicely line up with what this
matter looks like in the hedgehog condition, the researchers said.
What's it all mean?
Being able to generate a monopole like this in a lab
has some serious implications for physics. When Dirac first hypothesized the
monopole in 1931, he realized that the existence of such a thing in nature
would confirm a
fundamental idea in modern physics — the quantum nature of electricity. This
means that electric charge can only exist as whole number multiples of some fundamental
basic charge — you can't have
something with one half the electric charge of an electron.
Various theories of the Big Bang suggest that in the
unfathomably high temperatures of the very early universe, exotic magnetic
monopole particles should have formed. Some of these particles should still
exist today, although they would likely be extremely rare. Finding a natural
monopole would help us better understand the conditions of the newborn
universe.
Scientists have searched for evidence of these naturally
occurring monopoles in places ranging from Antarctic ice to lunar rocks.
To date, these hunts for naturally occurring monopoles have all failed.
Making a synthetic monopole indicates that these
kinds of magnetic fields can exist without violating the laws of physics,
leaving open the door for a natural monopole. Future research into the
properties of synthetic monopoles could lead to new insights into how to find
these strange particles in nature.
1 comment:
all very interesting except that one is then left with the observation that the "magnetic field" is actually just an electric field seen through the lens of special relativity.
http://galileo.phys.virginia.edu/classes/252/rel_el_mag.html
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