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! [♪ INTRO] Thanks to Brilliant for  supporting this SciShow List Show! To keep building your STEM skills  and exploring beyond this video, you can check out Brilliant.org/SciShow.

That link will give you 20% off  an annual premium subscription! 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, which gives you 20% off an annual  Premium Brilliant subscription. Before you commit to a year with Brilliant, you can try it for free using that link  or by visiting Brilliant.org/SciShow.

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. [♪ OUTRO]