The Train That Floats: How a maglev train flies on magnets
PHYSICS · 4 MIN
How does a train float on thin air at 600 km/h?
No wings. No wheels on the track. Just magnets, and a wire colder than outer space. You don't need to know any physics: we'll build it up from scratch, one simple idea at a time.
8 steps · 9 quick challenges
Step 1 of 8 · The ride
Meet the floater
Picture a train that never touches its track: no wheels on rails, nothing but air underneath. Let's work out how, one step at a time.
It's as fast as a small plane, yet once it's cruising, nothing touches the track. To see how, we only need one everyday thing: magnets.
- Rocket fast. In 2015, Japan's test train hit 603 km/h, the fastest any train has ever gone. At that speed, it would cross a football pitch in about half a second. It's like a passenger jet at take-off speed, but on the ground, with people sipping tea inside.
The record was set by the L0 Series on the Yamanashi test line in Japan, with people on board. Most high-speed trains carrying passengers today top out around 300 to 350 km/h.
So why can this one go so much faster? A big part of the answer is the next idea: once it's flying, nothing scrapes along the track.
- No scrape. When two surfaces touch and slide, they grab at each other and slow down. That grabbing is called friction. Normal trains fight it all day: steel wheels rubbing on steel rails. Try sliding in socks on carpet, then on a polished floor. Less grabbing means you glide further.
Friction happens because no surface is truly smooth. Zoom in far enough and even shiny steel looks like a mountain range, and the bumps catch on each other.
Once a maglev floats, wheel friction disappears completely. Only the air is still in the way, which is why the nose is long and smooth, like a bullet.
- Big trick. Every magnet has two ends, called north and south. Opposite ends pull together, and matching ends push apart. Hidden low on both sides of this train are giant magnets that use that push. Push two fridge magnets together the wrong way round and feel them shove back. Now imagine that shove holding up a train.
That invisible push or pull around a magnet is called its magnetic field. You can't see it, but you can feel it, and it reaches through air.
This train's magnets are special: they're made of wire kept almost as cold as outer space. Keep scrolling and we'll zoom all the way inside to see why.
- Record
- 603 km/h
- Place
- Japan
Did you know? Japan is building a real maglev line from Tokyo to Nagoya, and most of it runs through tunnels deep under mountains.
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Maglev is short for magnetic levitation. Levitation just means floating without touching anything, like a magician's assistant, but with real science instead of hidden wires.
A magnet is any object that can push or pull on other magnets (and on iron) without touching them. Every magnet has a north end and a south end. Opposites attract; matching ends repel.
Japan's maglev doesn't need wings to beat gravity. It uses magnetic pushes from the walls of its U-shaped track. It still has wheels for slow speeds, like a plane on a runway. The wow part begins once it's fast enough to lift itself clear.
The SCMaglev L0 test train set a 603 km/h record in 2015, with passengers on board.
Step 2 of 8 · The ride
The tiny air gap
If nothing touches the track, what's actually under the train? Let's drop down and look at the gap.
Once it's going fast, the whole train rises about a hand's width into the air. That sounds tiny, but it changes everything.
- Hand high. It floats about 10 cm above the track, roughly the width of your hand. Under the train, there's nothing but air. Like an air-hockey puck gliding on its cushion, except the cushion is made of magnetism, not air.
10 cm is actually a big gap for a maglev. Germany's Transrapid floated only about 1 cm up, so its magnets had to be adjusted thousands of times a second to keep it steady.
Japan's bigger gap gives more room for bumps in the track and even small earthquakes, which matters a lot in Japan.
- Wheels first. It starts off rolling on rubber wheels. The magnetic lift only gets strong when the train moves fast, so around 150 km/h the wheels tuck away. It's like a kite: standing still it flops on the grass, but run fast enough and it lifts into the air.
Why does lift need speed? You'll see in the next step: the push comes from the train's magnets rushing past the walls. No rushing, no push.
Planes work the same way: wings only lift once you're fast enough, so planes roll down the runway first.
- Less rubbing. No wheels on rails means no grinding, much less rumbling and far less wear. That's a big reason it can safely go much faster than normal trains. Think of a skater on fresh ice versus someone pushing a shopping trolley with a squeaky wheel.
- Gap
- ≈10 cm
- Lift-off
- ≈150 km/h
Did you know? At top speed, the train travels about 50 metres in the time it takes you to blink, while hovering a hand's width above the concrete.
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The train doesn't float at the platform. At low speed it rolls on rubber wheels, just like a car.
As it speeds up, the magnetic push from the walls grows stronger. Around 150 km/h the push is strong enough to carry the train's whole weight, so it rises about 10 cm and the wheels fold away, like a plane's landing gear.
That small gap is plenty. If nothing is scraping along the track, there's no friction from wheels to fight, only the air.
A jumbo jet needs about 250 km/h to leave the runway. This train lifts off at around 150 km/h.
Step 3 of 8 · The track
Side-wall magic
That gap is the whole puzzle: something has to hold a 25-tonne train up across 10 cm of air. The answer is hiding in the track's side walls.
Watch it live: as the train's magnets sweep past, the wall loops light up and green arrows push the train up. The walls aren't powered; the train's own speed does it.
- Train magnets. Super-strong magnets sit low on both sides of the train, facing the wall. They alternate: north (red), south (blue), north, south. The pale blue lines are their invisible magnetic field reaching across the gap. Like holding a magnet near a fridge door: you feel the force before they ever touch.
Each car carries magnet units on both sides. They are far stronger than any fridge magnet: together, they hold up a train car full of people.
- Wall loops. The wall is lined with loops of plain copper wire shaped like an 8: a top loop and a bottom loop. They aren't plugged in. Watch them slide past: dark until a train magnet arrives, then glowing. Like a row of sleeping guards that only wake up when someone runs past them.
Each coil is shaped like an 8: a top loop and a bottom loop, wired so their currents flow in opposite directions.
When a train magnet passes right at the middle of the 8, the two halves cancel out and nothing happens. When the magnet is a bit low, the bottom loop pushes it up and the top loop pulls it up, so the train gets lifted back toward the middle.
- Push back. A magnet rushing past a loop shoves the loop's electrons round (the moving dots). That current turns the loop into a magnet: the bottom loop matches the train's pole and pushes up, the top one pulls up. Like a trampoline: the harder you land on it, the harder it bounces you back up.
This is called electromagnetic induction, discovered by Michael Faraday in 1831. A moving magnet near a loop of wire makes current flow, with no battery needed.
And electricity flowing in a loop always makes its own magnetic field. Nature arranges it so that this new field pushes back against the magnet that caused it. Here, that push-back is the lift.
The faster the train rushes past, the stronger the push. That's why it only floats at speed.
- Coils
- figure-8
- Track
- U-shaped
Did you know? Most power stations make electricity with the same trick that lifts this train: spin a magnet near coils of wire, and current flows.
Read more
Two simple rules make this work. Rule one: a moving magnet near a loop of wire makes electricity flow in the loop. Rule two: electricity flowing in a loop turns that loop into a magnet.
Put them together. The train's magnets rush past the wall loops (rule one), electricity starts flowing, the loops become magnets (rule two), and they push back on the train. Engineers call this electrodynamic suspension: lifting with moving magnets.
The figure-8 shape is clever. If the train sinks too low, the loops push it up; if it drifts sideways, the loops on the near wall push it back to the middle. It's like invisible hands on both sides.
The faster the train goes, the stronger the lift gets, until it settles at a steady hover.
Step 4 of 8 · The track
Surf the wave
So the walls hold the train up. But floating isn't moving. With no engine on board, what pushes it forward?
There's no engine on board. Instead, the track itself pulls the train forward, and the train surfs along like it's riding a wave.
- Pull ahead. A second row of coils, further back in the wall, is powered. Electricity turns a coil into a magnet. The coil just ahead of each train magnet becomes the opposite pole (red faces blue), so it pulls forward: gold arrows. Like dangling a carrot on a stick in front of a donkey: it always chases the pull ahead.
A magnet you can switch on and off with electricity is called an electromagnet. Scrapyard cranes use giant ones to lift cars, then drop them by flicking a switch.
- Push behind. The coil just behind each magnet gets current the other way, so it becomes the same pole (red behind red). Same poles push apart: orange arrows. Pull in front plus push behind: double the go. Like one friend pulling your sledge from the front while another pushes from behind.
- Wave ride. Watch the coil colours: the red-blue pattern ripples along the wall in step with the train. Switch it faster and the train speeds up; slow it down and the train brakes. Like a Mexican wave in a stadium: nobody runs, but the wave races round, and the train surfs it.
Engineers call this a linear synchronous motor. Linear: a normal spinning motor unrolled flat along the track. Synchronous: the train moves exactly in step with the magnetic wave.
Slow the wave down, and the same coils help slow the train, turning its speed back into electricity.
- Motor
- linear
- Power
- track
Did you know? Unroll the electric motor spinning inside a fan and lay it flat along a track. That's basically what drives this train.
Read more
A normal electric motor (like the one in a fan) is a spinning ring of magnets chasing a circle of switching coils. Cut that circle open and lay it flat along the ground, and you get a linear motor.
Stations beside the track switch electricity in the wall coils on and off at exactly the right moments. Ahead of the train the coils pull; behind it they push.
Because the train and the magnetic wave stay in step, it's called a linear synchronous motor. Synchronous just means 'moving together', like dancers keeping time with the music.
The driving power is in the track, not in an engine on the train.
Step 5 of 8 · Inside the magnet
Peek inside
Lift and pull both depend on one thing: the train's magnets being incredibly strong. So what's inside one of them?
Let's zoom inside one of those train magnets. There's no lump of iron here, just a loop of very special wire.
- Special wire. The wire is niobium-titanium, a mix of two metals. At room temperature it's ordinary. Chill it enough, and it changes into something extraordinary: a superconductor. Like water that's just water, until it gets cold enough to suddenly become ice. Cold can change what stuff does.
The same kind of wire is inside hospital MRI scanners and the giant magnets of the Large Hadron Collider at CERN, the world's biggest science machine.
- Loop shape. It's wound into a flat racetrack shape, thousands of turns deep. Electricity runs around and around the loop, and every turn adds to the magnet's strength. Like one person pushing a roundabout versus a thousand: more turns of wire, more push.
- Cold flask. The coil lives inside a cryostat, basically a super serious flask that stops heat sneaking in from the warm world outside. It's a flask for your hot chocolate, but working backwards: keeping the cold in instead of the heat.
A flask keeps soup hot with an empty vacuum between two walls, so heat can't easily cross. A cryostat uses the same trick, plus shiny shields that bounce heat away like mirrors.
- Wire
- Nb-Ti
- Coil
- racetrack
Did you know? If you've ever had an MRI scan in hospital, you've been inside a magnet made with the same kind of wire.
Read more
Remember rule two: electricity flowing in a loop makes a magnet. So the train's magnet isn't a lump of iron at all. It's mostly a coil: lots of wire wrapped round and round.
More current and more turns mean a stronger magnet. The problem is that pushing lots of current through a normal wire makes it hot, and the heat wastes energy. That's where the special wire comes in.
The coil sits inside an insulated cryostat. Think of it as a super serious flask for one very chilly magnet.
The wire can carry a huge current in a loop without slowly wasting it as heat.
Step 6 of 8 · Inside the magnet
Super cold bath
We just saw the coil needs to be kept freezing cold. So how cold, and why does it matter?
For the magic to work, the wire has to be chilled to −269 °C. That's colder than anywhere on Earth, and we make it on purpose.
- What cold is. Everything is made of atoms, tiny building blocks that are always jiggling. Hot means they jiggle fast; cold means they jiggle slowly. At −273 °C they'd almost stop. This magnet is just 4 degrees above that. Like a classroom: hot is break time with everyone running about, cold is everyone sitting still in an exam.
−273.15 °C is called absolute zero: the coldest anything can ever be, because you can't jiggle less than not at all. Empty space between the stars is about −270 °C.
- Helium bath. Helium is the gas that makes party balloons float. Cool it to −269 °C and it turns into a liquid that can bathe the wire and keep it that cold. Like ice in a cool box keeping your drinks cold, but about 270 degrees colder.
Helium stays liquid at a colder temperature than anything else, which is exactly why it's used.
The train also carries small refrigerating machines that help keep the magnets cold during the whole trip.
- Wire changes. Down at about 4 degrees above absolute zero, something amazing happens: the wire's electrical resistance (its 'stickiness' to electricity) drops to exactly zero. Like a muddy road that suddenly turns to perfect ice: whatever slides along it stops slowing down.
- Temp
- −269 °C
- Coolant
- helium
Did you know? Cool liquid helium a little more, below −271 °C, and it becomes a superfluid that can creep up the sides of its cup and escape over the edge.
Read more
Temperature is really a measure of how fast the atoms in something are jiggling. When you touch a hot pan, its fast-jiggling atoms bash into the atoms of your hand and speed them up. That's the feeling of heat.
Cooling something means calming its atoms down. Liquid helium cools the coil to about 4 kelvin, which is about −269 °C, close to the coldest anything can be.
Keeping it that cold is hard. Heat always sneaks from warm places to cold ones, like water running downhill, so the magnet needs layers of insulation and constant cooling.
Four kelvin is only four degrees above absolute zero.
Step 7 of 8 · Inside the magnet
Current forever
At −269 °C the wire's resistance drops to zero. So what does that actually do to the electricity inside?
In a normal wire, electricity loses energy as heat. In this cold wire, it can race around a loop for years without slowing down.
- Normal wire. Electricity is electrons flowing through metal. But the metal's atoms are jiggling, and electrons keep bumping into them. Every bump wastes a bit of energy as heat. That's why your charger gets warm. Like rushing down a packed school corridor: you keep bumping into people and lose speed every time.
- Super wire. In deep cold, electrons team up into pairs that glide through the metal together. The atoms can't knock them off course, so no energy is lost. Like the whole corridor holding hands and moving as one conga line: nobody bumps, nobody slows.
These teams are called Cooper pairs. Put simply, the paired electrons move in step with the whole crowd, so the atoms can't knock them off course one at a time.
Heat ruins it. Warm the wire up even a little too much and the jiggling atoms break the pairs apart, and the resistance comes right back.
- Forever loop. Start the current once, then close the loop. With nothing slowing it, the electricity keeps flowing round with no battery at all, so the magnet stays strong. Like spinning a bike wheel in space: with no air and no rubbing, it would just keep spinning.
This is called persistent current mode. The magnets are charged up once, then left running on their own. No power cable is needed to keep the current going.
- Resistance
- zero
- Found
- 1911
Did you know? Superconductivity was found in 1911, when Dutch scientist Heike Kamerlingh Onnes cooled mercury with liquid helium and watched its resistance suddenly vanish.
Read more
Resistance is what makes a normal wire warm up. Picture electricity as traffic on a road: resistance is the potholes. Every pothole slows the cars and turns some of their energy into heat.
In a superconductor, the potholes vanish. Current can flow around a closed loop for years without losing any energy at all.
Superconductors have another trick: they push magnetic fields out of their inside, which can make a magnet float above them (see the photo). Japan's maglev, though, gets its lift mainly from the wall loops you met earlier.
Scientists have measured superconducting currents that kept flowing for years without fading.
Step 8 of 8 · Lift-off
Now it flies
Now zoom back out and join the dots: forever-current makes super magnets, and super magnets make the train fly.
Put it all together: freezing wire, super magnets, a speeding train and a clever track. The result is a train that flies.
- The chain. Cold wire carries electricity forever, so it makes super-strong magnets. Speeding magnets make the walls push back. Switching coils pull the train forward. That's the whole trick! Like a row of dominoes: cold leads to zero resistance, then strong magnets, then lift, then flight.
- Fast trip. The new line will link Tokyo and Nagoya, 286 km apart, in about 40 minutes. By today's bullet train it takes about an hour and a half. That's a 3-hour car drive squeezed into the time it takes to watch one TV episode.
- Clean ride. It runs on electricity, so the train itself puffs out no smoke. How clean it really is depends on how that electricity is made. Like an electric car: no exhaust pipe, but its power still has to come from somewhere.
- Trip
- ≈40 min
- Route
- 286 km
Did you know? At 603 km/h, the test train was going almost twice as fast as a Formula 1 car at top speed.
Read more
Let's rebuild it from scratch. Atoms jiggle less when cold. In super-cold niobium-titanium wire, electrons stop bumping into them, so electricity flows with zero loss. That makes the train's coils super-strong magnets.
As those magnets rush past the wall loops, they push electricity around them. The loops become magnets that push back, lifting and centring the train. Other coils switch on and off in a travelling wave that pulls it forward.
So the train isn't floating on air like a hovercraft. It's surfing a carefully timed magnetic system, and you now understand every link in the chain.
Maglev trains already carry passengers in China and South Korea, using different magnet designs.