Whether you’re young or old, clueless about physics or studied it all your life,
magnets do feel a little bit like magic.
There’s something mesmerizing about watching an invisible force
make two pieces of metal leap together or fly apart.
But magnets aren’t just a quirky glitch of physics
that lets you hang pictures on the refrigerator.
Magnetism is a force generated whenever there are electrical charges whizzing around,
whether it’s the bits that make up the individual atoms
or swathes of electrons in electrical currents that power our devices.
And the bigger the electrical current, the more powerful the magnetic field!
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Given its deep link with electricity, it’s no surprise that magnets are a vital part
of modern technology, from computer chips to medical devices.
But sometimes a little magnet won’t cut it
when we want to give something a really big push or pull.
So, we got curious about what the strongest magnets humanity has ever created are.
Here are five of them, including one so powerful it blew up the whole experiment!
One reason we need crazy strong magnets is to peer inside the human body.
And there’s no better example than the whopping, 132 metric ton Iseult magnet,
developed by French scientists at the NeuroSpin research center
as a component of a very powerful MRI machine.
Is this the one that exploded?
You’re going to find out soon!
This enormous magnet needs to be cooled down to –271 degrees celsius!
Which is just two degrees above absolute zero, which is the coldest temperature possible.
It’s built for medical imaging to give scientists a deeper look
into the activity of the human brain.
We measure the strength of powerful magnets like this in units of tesla,
and the Iseult magnet clocks in at 11.7 tesla.
For comparison, a super strong fridge magnet is something like 0.01 tesla,
so we’re talking like a thousand times more powerful than that!
MRI machines work by making protons inside your body line up with a magnetic field.
Then the machine sends a pulse of radio waves
that pushes the protons out of alignment.
After the pulse is gone, the protons realign with the magnetic field
and give off their own radio waves.
And the MRI machine can use the pattern of those radio waves to construct an image.
Wild!
This sounds kind of freaky, but it’s totally harmless!
The thing is, small magnets don’t cut it for getting many of the protons
deep inside of your body to all point in the same direction,
which is why MRI requires such powerful magnets to do the job.
Ordinary MRI magnets are somewhere between 1.5 to 3 tesla, but more powerful ones
like the Iseult can give us a finer picture of what’s going on inside the body.
That’s because the stronger the magnet, the stronger the signal given off by the protons
as they realign with the magnetic field after that pulse of radio waves.
That helps resolve different features, like small blood vessels, more easily.
As for why the actual, physical magnet needs to be so huge and cold,
it comes down to how the magnetic field is generated.
As we mentioned, the stronger the electrical current producing the field,
the stronger the magnet.
So as well as having an electric coil big enough to pass a huge current,
cooling the equipment down lowers the resistance inside the circuit.
In fact, for certain materials, like the ones in the Iseult magnet,
the circuit becomes superconducting.
That means it has no electrical resistance whatsoever,
making it easier to drive a huge electrical current.
With this magnet’s absolutely beastly field, neuroscientists are able to study the
activation of really particular parts of a person’s brain inside the MRI scanner.
That gives us a much more accurate picture of what specific functions each of those
tiny regions of the brain do when it comes to the job of making you … you.
Including when it goes wrong.
By working out the functions of increasingly specific parts of the brain, researchers hope
to create new tools for diagnosing patients with neurological or psychiatric disorders.
So sometimes, big magnets need cooling down to operate.
But we can also use a powerful magnet to contain super high temperatures.
Which might even help produce clean energy!
In 2021, a team led by MIT and the startup Commonwealth Fusion Systems
developed and tested a magnet capable of reaching 20 tesla.
The goal is to use this kind of magnet to sustain nuclear fusion,
a carbon-free, safe source of energy
that produces much less radioactive waste than existing nuclear energy.
It’s the same process that powers the sun, where light elements like isotopes of
hydrogen fuse into heavier ones, but lose some small amount of mass overall.
That missing mass gets converted into energy,
as described by Einstein’s famous “E=mc^2”.
That’s kinda like the nuclear fission used in existing nuclear power plants,
which also convert mass into energy, but by splitting atoms, rather than fusing them.
The goal is to get fusion going on Earth,
in a way that gives us more energy than the amount we put into the process.
But that requires conditions not dissimilar from the core of the sun,
which is a very hot whirlwind of atoms called a plasma that needs to be kept stable
long enough for fusion to happen and sustain.
We’re talking, like, hundreds of millions of degrees!
There aren’t any solid materials that can withstand those kinds of temperatures,
but it is possible to suspend plasma in mid-air using, you guessed it, a magnetic field.
Which is why this kind of fusion is called magnetic confinement fusion.
That’s exactly what the magnet at MIT was developed to do.
Like Iseult, it’s the superconducting variety of magnet that helps produce
the huge current needed for a 20 tesla field.
The plans are for the reactor using this kind of magnet to go into operation in 2025
when maybe, just maybe, it will provide a proof of concept for usable nuclear fusion.
So, watch this space.
Things are getting exciting!
We don’t always have to chase the biggest individual magnet, either.
Sometimes, we can use a whole bunch of them working together
to achieve amazing things, like when we’re accelerating tiny charged particles.
And the granddaddy of all particle accelerators is the Large Hadron Collider, or LHC.
It’s a 27 km long ring of magnets outside Geneva, Switzerland.
Physicists designed it to accelerate protons to near the speed of light
so they can be smashed into each other inside detectors,
which provide us a sneak peek at the interactions of subatomic particles.
All of this tells us about the fundamental forces of nature of our universe,
like, for instance, the electromagnetic force.
Along that ring of the LHC are 9,600 magnets,
some of them 15 meters long, 35 tons, and producing 8 tesla on their own!
In scientific terms, that is a butt-load of big magnets.
Like the others we talked about, the LHC magnets have to be cooled down to
about 2 degrees above absolute zero, which allows them to become superconducting.
And superconducting circuits provide the huge electric currents
that generate those 8 tesla fields.
The point of all these magnets is to keep the protons inside the LHC
on track as they whizz around.
See, it takes an electric field to actually give the protons energy as they circulate
about the LHC, picking up more and more speed before they collide.
Electric fields are the close sibling of magnetic fields,
they’re also generated by electric charges and push and pull each other around.
But electric fields have some differences, and one of them is that they can give
charged particles kinetic energy, unlike magnetic fields which can
only change the direction of charged particles once they’re already moving.
At the LHC, electric fields are designed to give the protons
a kick in basically a straight line.
It takes the magnetic fields to provide the turning force to keep the protons
going around the ring, instead of slamming into the walls of the accelerator.
It’s like the magnets are the banked curves of the racetrack,
while the electric fields are each race car’s engine.
The other thing some of the magnets do is make sure the bunches of protons
stay squeezed together along their line of travel around the ring.
That makes it easier to slam them into each other inside one of the detectors.
And when these protons finally do collide, they break apart to produce all kinds
of exotic matter that can tell us about the fundamental laws of nature.
The crowning achievement so far is the Higgs boson discovery of 2012,
which confirmed our theories on how subatomic particles acquire mass!
Now, given the size of the magnets we’ve discussed so far,
you might get the feeling that bigger is always better.
Turns out, that’s not always the case.
In 2022, researchers at the Steady High Magnetic Field Facility in Hefei, China,
announced they had reached a 45 tesla magnetic field
with a magnet whose central component was no wider than a silver dollar.
Like the other magnets we’ve talked about, it has a whole bunch
of superconducting coils, but those only produce about 11 tesla of the field.
The star of the show is inside those coils,
where you’ll find another circuit that’s just 32 millimeters in diameter!
Unlike big coils, the tiny electromagnet inside has resistance
when the current flows through it.
Resistance means it takes a ton of power to keep the magnet going,
and, for sure, that makes it expensive to operate.
But, unlike a superconducting magnet, resistive magnets aren’t limited
in terms of the strength of the magnetic field they can produce.
So long as you keep pumping a bigger current through a resistive magnet,
its field will keep getting stronger and stronger.
And in the Hefei magnet, the tiny resistive magnet can be pushed
up to a huge 34 Tesla on its own!
Setups like these are called hybrid magnets.
They use a combination of the high-current capacity of resistive magnets
and low power needed for superconducting magnets to make the most intense,
stable magnetic fields we’ve ever created.
Recently, researchers implemented a few clever tweaks to this setup,
pushing the performance of the overall magnet to 45.22 tesla, just beating the previous
record holder at the National High Magnetic Field Laboratory in Florida.
One unique use of a magnet this strong is conducting experiments
on new materials for electronics, like carbon nanotubes.
Those are “tubes” of carbon, just one atom thick that are really good
at carrying electrical currents.
Because they conduct electricity so well and are extremely thin, in theory,
a computer processor made of carbon nanotubes instead of ordinary silicon
could be three times faster and energy efficient at the same time!
Since electrical currents and magnetic properties are intricately linked,
a powerful magnetic field like the Hefei magnet helps us study
the electric properties of carbon nanotubes.
So ultra strong magnets might help us take steps
towards more energy efficient electronics in the future.
Hybrid magnets are great because they produce strong but stable fields
that stick around long enough for us to do experiments with.
But what if we don’t care about stability at all?
What if we’re happy to throw everything into just making one heck of a magnetic field?
Well, in that case, it’s actually possible to achieve 1,200 tesla!
In 2018, a team of researchers at the University of Tokyo in Japan did just that.
The trick was starting off with a strong-ish field of 3 tesla
(which, remember, is very strong) created inside of a thin copper tube,
and then squeezing that field into a very small area.
Physicists call the amount of magnetism in a given region of space “flux density”.
The higher the flux density, the stronger the magnetic field.
So if you can “squeeze” the flux into a tighter space, you can increase the field strength.
This process is called electromagnetic flux-compression.
The University of Tokyo team achieved compression with a bank of electronic
components called capacitors, which store up a bunch of electric energy.
Surrounding the thin copper tube was a steel coil.
When all the energy stored up in the capacitors was released through 480 cables into
that coil, it created a massive magnetic field, causing the thin copper tube to implode.
So that first, 3 tesla magnetic field was suddenly squeezed into a much tinier space.
And that is what produced the unbelievably powerful, 1,200 tesla magnet.
If you want an idea of how insanely strong that is, the materials used in the set up
weren’t even made to withstand the force of magnetism produced by the field.
So the whole experiment literally, and intentionally,
exploded immediately after the field was produced.
Which is awesome… and totally impractical for most scientific purposes.
But, in this particular experiment, the whole idea was to see exactly how far things could
go with flux compression, so that explosion was actually the sign of great progress!
What’s more, even for the short time they exist, ultra strong magnetic fields like these
can help probe what happens to matter when under really extreme conditions,
like when subatomic particles like electrons get ripped off of atoms.
And with new frontiers of research available
thanks to powerful magnets like these, it’s no wonder that strong magnetic fields
are as attractive to scientists as they are to metals.
If you’re attracted to magnets, you’ll love Brilliant’s Electricity and Magnetism course!
This interactive course helps you learn about magnetic fields
and all sorts of physical laws that let them do their thing.
And with Brilliant, you’re actively learning.
The filmed demos in this course give you the chance
to see magnetism in action and apply the principles you’re learning
to better understand the devices you interact with every day.
But there’s so much to explore in the world that you interact with daily.
And Brilliant’s online learning platform offers guided courses
in way more than just magnetism.
You can take a range of courses in math, science, and engineering,
all with a focus on problem-solving.
To get started with Brilliant today, you can click the link in the description down below,
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Thanks to Brilliant for supporting this SciShow video
and thank you for sticking around to the end of it.
What an episode it was!
I have to just give some props to our team here.
Some of the most complicated ideas in science communication all compressed
into one video about the biggest and most awesome magnets in the world.
Thats amazing work!
So I’m really grateful to Brilliant for supporting it
and grateful to you for supporting it as well.
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