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(i love you)
Vsauce, I’m Jake and
nitrogen is a gas until it gets really cold.
Then it turns into...this....liquid.
In this state it has a temperature around -196 degrees celsius.
And these drops that are shooting off trailing vapor?
They’re literally boiling away into nitrogen gas, at room temperature.
And because nitrogen has a high evaporation expansion ratio, each drop expands to 700
times it’s volume in gas even though it was just a tiny drop.
Using a thermal camera we can see just how drastic the temperature change is.
Once our container is filled with liquid nitrogen it entirely becomes this deep blue.
You can even see the liquid nitrogen boiling away on the surface.
Where as in real life or with a regular camera, we can’t see it through the gas.
But we are here to levitate an object so what does liquid nitrogen have to do with magnetic
levitation?
Because you can make magnets levitate without it right now.
To demonstrate this, I’m going to use the Magnetic Levitator we made, and you can get
your own at our Curiosity Box website, but any two magnets will work.
If these two magnets have like poles facing each other, they repel each other.
It is the same principle for how maglev trains work.
And the opposite occurs if we flip the magnets around.
But what we’re doing here is not regular magnetic levitation or maglev.
It’s superconducting maglev, which is different.
First of all, let’s discuss superconductors.
A superconductor is a material that exhibits two incredible properties when it is cooled
below a so-called “critical temperature.”
The first is that they have zero electrical resistance: that’s why people study them
for use in electronics.
But more important for our purposes is the “Meissner effect”: which causes a superconductor
to completely expel magnetic fields when they enter their superconducting state.
What that means is that a superconducting material will actually levitate over a magnet
– even though the material itself is not magnetic.
Now, this is our superconductor a small disk made of Yttrium-barium copper oxide . Actually,
in this whole disk, the superconducting material is just a tiny sliver of crystal grown on
top of a stainless steel core, and covered by protective layers of silver and aluminum.
And when I say tiny sliver, it really is.
It’s just 3 microns thick.
30 times smaller than the thickness of a human hair.
And if I put a magnet next to it...nothing happens because it will only levitate when
it’s below that critical temperature.
WHich is why I drowned it in liquid nitrogen.
One of the most amazing things about superconducting levitation is what you see here – not only
does the disk hover above the track, but it can hover below it as well.
In fact, we can shape the track any way we want, and the disk zooms along, at exactly
the same height, no matter its orientation, with no friction or resistance.
That’s due to a phenomenon called “flux pinning” or “quantum locking.”
Basically, while the Meissner effect means that any superconductor will expel magnetic
fields, if you intentionally introduce some imperfections into the material, then a little
bit of the field can penetrate it, in discrete quantities called “flux tubes.”
Inside each of the tubes, superconductivity is locally destroyed, essentially trapping
a tiny bit of the magnetic field gets trapped inside the superconductor, pinning it in place.
And what I mean by that is that our superconductor, our disk, is quantum locked to the magnetic
field generated by this track.
That’s what allows our disk to go back and forth and upside down without falling off
or flying off either end.
It’s also what allows us to minutely adjust the superconductors orientation.
Now, to be entirely honest with you I don’t know how to end this episode so here is some
more cool levitation footage set to the song Flower Duet from Delibe’s opera Lakme..
And, as always, thanks for watching.