
Video: Quantum Levitation - jasonadriaan
http://jasonadriaan.com/post/11595319387/the-future
======
MarkMc
Reminds me of a great quote by Benjamin Franklin:

"The rapid progress true Science now makes, occasions my regretting sometimes
that I was born too soon. It is impossible to imagine the height to which may
be carried, in a thousand years, the power of man over matter. We may perhaps
learn to deprive large masses of their gravity, and give them absolute levity,
for the sake of easy transport. Agriculture may diminish its labour and double
its produce; all diseases may by sure means be prevented or cured, not
excepting even that of old age, and our lives lengthened at pleasure even
beyond the antediluvian standard. O that moral science were in as fair a way
of improvement, that men would cease to be wolves to one another, and that
human beings would at length learn what they now improperly call humanity!"

\-- Letter from Benjamin Franklin to Joseph Priestly (8 Feb 1780), quoted in
"How Mumbo Jumbo conquered the World" by Francis Wheen

~~~
sans-serif
Benjamin Franklin would be delighted to know that he woefully underestimated
science's impact on agriculture.
[http://en.wikipedia.org/wiki/File:Wheat_yields_in_developing...](http://en.wikipedia.org/wiki/File:Wheat_yields_in_developing_countries_1951-2004.png)

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sbierwagen
Pure marketing. "Quantum levitation" is just flux pinning[1] as seen in all
"high temperature" superconductors. All you need a chunk of type 2
superconductor, a strong magnet, and some liquid nitrogen. Note the 852 videos
on youtube:
[http://www.google.com/search?q=superconductor+levitation&...](http://www.google.com/search?q=superconductor+levitation&source=univ&tbm=vid)

You can shell out 80 bucks and do it yourself:
[http://sargentwelch.com/superconductivity-suspension-and-
lev...](http://sargentwelch.com/superconductivity-suspension-and-levitation-
kit/p/IG0038153/) (LN2 not provided.)

There doesn't appear to be any novel physics here at all.

1: <http://en.wikipedia.org/wiki/Flux_pinning>

~~~
JangoSteve
> All you need a chunk of type 2 superconductor, a strong magnet, and some
> liquid nitrogen.

This isn't entirely accurate. A "chunk of type 2 superconductor" would just
show the Meissner Effect, which is different than "flux pinning". The Meissner
Effect is how superconductors essentially repel magnetic fields, resulting in
levitation; it wouldn't necessarily pin the levitating body in-place such that
it could follow some track for example.

Flux pinning occurs when _some_ magnetic fields penetrate the superconductor
in discrete "tubes" through the imperfections (along the grains) of the
superconductor. In order for flux pinning to happen, you must have an
extremely thin superconductor (in the case of the video, it's actually a
sapphire crystal wafer with a 1-micron thick coating of superconductor ceramic
material).

EDIT: Technically, you could also get flux pinning if you were to supercool
the superconductor (i.e. make it a superconductor) _while_ it's in the
magnetic field of the magnet.

~~~
iliis
I played quite a bit with the Meissner and the Flux pinning effect. But I was
never able to change a flux pinning "on the fly". You always had to reheat the
superconductor to something over the transition temperature and then cool it
down again inside a magnetic field (in the desired position). But then, it was
quite strongly locked in that position and would snap back to where it was
when moved.

So, I'm quite curious on how this works ;) Is it because it's a very thin
superconductor in this video?

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fybren
This is very cool. Another video with a bit of an explanation as to why -
<http://www.youtube.com/watch?v=VyOtIsnG71U>.

~~~
andrewflnr
Thanks. I'm not sure I understand the part about "quantum flux tubes". I take
it that they're leaks through flaws in the superconductor (which should
exclude the field entirely). Is the superconductor is being gripped or pinned
by these lines of force running through it, like a piece of cheese on a
toothpick? But that doesn't quite explain how it can move along a field.

~~~
JangoSteve
I think the magnets on the track piece may be arranged NSN like this:

    
    
      NNNNNNNNNN
      SSSSSSSSSS  ==>
      NNNNNNNNNN
    

Which allows movement as indicated. In the part of the video where it's just
locked stationary above a square magnet, it appears maybe the magnet as this
arrangment:

    
    
      NNN      NS
      NSN  or  SN
      NNN
    

Which locks it entirely in-place, not allowing movement. And then in the part
where it's spinning, I think maybe the magnet is S on the inside and N on the
outside or something:

    
    
          NN
         NSSN
        NS  SN
         NSSN
          NN
    

Allowing it to spin. But this is speculation based on my limited understanding
(but I noticed no one else was answering, so I thought I'd give a shot).

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sliverstorm
Quick question: If the object is the temperature of liquid nitrogen, how can
he touch it for so long?

~~~
mechanical_fish
Leidenfrost effect:

<http://en.wikipedia.org/wiki/Leidenfrost_effect>

The stuff of which awesome party tricks are made. I have myself put a very
small amount of liquid nitrogen in my mouth and blown it out, although I then
heard that the guy who taught me that trick (Jearl Walker) cracked a tooth
doing that, so I never tried it again. And _for the love of god do not swallow
or you will literally kill yourself very painfully_ \-- see footnote 3 of the
above Wikipedia article.

I think I'll stick with dipping fingers briefly into LN, which is way less
stupid. Done that many times. Do not get it on your clothing, though, because
then you can't retreat quickly and the frost is going to bite!

~~~
martinkallstrom
"What was really astounding about Michael's case is that the liquid nitrogen
instantly expanded from a volume of about 3 or 4 cc's to about 3 or 4 liters
and then dissected into five separate body compartments"

Ouch. <http://www.wpi.edu/news/19989/nitro.html>

~~~
mechanical_fish
Yes, if this Wikipedia article had existed when I was a college senior I'd
never, ever have tried that particular party trick. ;)

Yet another example of how the web makes us much, much smarter.

I estimate that I used a tiny sip, not 3 or 4 ccs, but still. Crazy risky.

~~~
sliverstorm
A teaspoon is 5ccs. 3-4cc IS pretty much a tiny sip, unless you have excellent
lip-control.

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skeletonjelly
When I came into work this morning this was at the top of reddit.com/r/all
(got to get the procrastination out of the way first thing right!)

A guy spoke up regarding his father who works in the field. Currently doing
Q&A

<http://redd.it/lfsjn>

~~~
jmaygarden
Is there a layman's summary regarding the significance of that paper linked on
reddit?

~~~
sbierwagen
Completely irrelevant. It's a theory explaining how Type II superconductors
work, published five years ago, in a Chinese journal that has an impact factor
of 0.512 ( _Nature_ scores 30.98, for comparison.)

~~~
ehsanu1
What's the relevance of "impact factors"? I understand the basic idea behind
them, but I don't think publishing research in a low impact factor journal
should automatically make said research "completely irrelevant".

~~~
sbierwagen
It's completely irrelevant because it has little to nothing to do with the
original post, much like how you wouldn't link to a paper on algorithmic
complexity in a post about Facebook, because "they're both about computers."

Additionally, the author of the paper displays some worryingly crackpot-like
symptoms. He claims that it's "Nobel worthy", (!!) but Citebase can find _no_
citations.

I know nearly nothing about condensed matter physics, but skimming the paper
reveals that his theory doesn't really make any testable predictions, much
less the "grand slam" predictions that would result in a Nobel, like room-temp
superconductivity.

Impact factor is tremendously flawed, but as a quick sanity check, when you're
not sure if something makes _any sense at all,_ it is of great use.

~~~
blasdel
He cited it himself in two other papers :/

As far as crackpot symptoms, it looks like he's a biblical literalist too!

~~~
sbierwagen
Ah ha, you missed my very careful weasel wording! I said that _Citebase_ found
no citations, not that it actually _had_ no citations, mwa ha ha.

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colanderman
So, the electrical engineer in me says that this is because any movement of
the magnet would induce an electric potential in the superconductor. But
because such a potential would create an effectively infinite amount of
current requiring an infinite amount of work, the magnet is unable to move.

Or from a "cause-and-effect" viewpoint, movement of the magnet induces a
current loop in the superconductor, the creation of which creates an opposing
magnetic force.

Either way I believe this is the same principle behind electric motor braking
(e.g. when you short-circuit the inputs of a motor). I believe you would also
see a similar effect by dropping a magnet down a tube encircled with many (or
perhaps one spiral) loop of wire -- the magnet's descent will be slowed by
eddy currents in the loops.

Edit: Aha, this is just half the story. The superconductor is prevented from
spinning due to flux pinning: <http://en.wikipedia.org/wiki/Flux_pinning> (or
what the researchers call quantum trapping / quantum locking)

~~~
laughinghan
But, it clearly does not take an infinite amount of force to move the "locked"
superconductor, because you can adjust it by hand. The real question is, how
_much_ force does it take?

~~~
colanderman
Right, I believe this is a function of how much of the magnetic flux does not
encounter the superconductor. But IANAP, just a former EE, so I don't know
that this is 100% correct.

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mattyohe
Is this "quantum locking" just a rebranding of the Meissner Effect?

<http://en.wikipedia.org/wiki/Meissner_effect>

~~~
grannyg00se
Quoting a comment in the video linked to by fybren:

"This levitation is NOT due to the Meissner effect. It is﻿ negligible since we
use thin films. If it were the Meissner effect the field would get distorted
on a length scale of the diameter (~cm) and then two discs hovering above and
below each other would affect it other. Which is clearly not the case. The
discs are actually trapped in constant field contours rather than levitating."

------
jeffool
On a more serious note, I'd love to find out more about just how much weight
they think this tech could support in the future. Those implications could be
insane.

~~~
geuis
Agreed. If the "floating" (I know its not actually floating in the traditional
sense) object could carry its own light-weight cooling system then you
wouldn't need to chill the entire unit to super cold temperatures. You might
only need to cool the superconducting layer.

~~~
Geee
The thing is, we are all waiting for room temp superconductors. That paper on
the Reddit post seems to have some breakthrough regarding this if I'm not
wrong.

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ars
Direct link: <http://www.youtube.com/watch?v=Ws6AAhTw7RA>

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atte
As a thought experiment, could the effect demonstrated here be used for a
transport system on a much colder planet with a much stronger magnetic field
(I do realize that these two properties tend to correlate in opposite
directions)? What about in our arctic regions, potentially over a magnetic
track to interconnect enclosed "settlements"? I'm guessing it would be less
cost-effective than other types of transport if even possible, but many times
cooler.

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ck2
Will this scale to train cars weighing a few tons each?

So if this was demonstrated live to congress, do you think they'd finally fund
a few miles of super-conducting trains for research?

~~~
shin_lao
Or they can cross the Pacific ocean.

<http://en.wikipedia.org/wiki/JR-Maglev>

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joshu
blogspam.

~~~
jasonadriaan
not exactly, I just posted it to tumblr. It would be blogspam if I were
running ads, but I don't.

~~~
JonnieCache
It's still blogspam even if you're only craving attention.

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Tichy
Hm, I remember getting excited about this about 23 years ago, when I was still
at school.

Can't help wondering if perhaps 50 years ago people were also getting excited
about it and expecting to see cool things to come out of it in the near
future.

Not saying that there couldn't, but I can't help feeling vary about the
"technology of the future claim".

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hugh3
Not particularly quantum mechanical.

Well, no more so than everything else you might happen to see in your everyday
life.

~~~
gwillen
Well, superconductivity is an inherently quantum phenomenon, more so than
other things in everyday life; see <http://en.wikipedia.org/wiki/Cooper_pair>
.

~~~
hugh3
Eh. _Solids_ are an inherently quantum phenomenon.

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Pointsly
Am I really the first one who immediately thinks about Hoverboards???

~~~
wicknicks
Wow! But that'd need magnets all over the ground!

~~~
thret
I think one magnetic half-pipe would be feasible, the question is could a
board be made that could support a small human?

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DanBC
Isn't there already a shortage of rare earth minerals, used to make strong
magnets? Is that going to be a problem for extending uses of this outside a
lab?

But: really cool video.

~~~
kokey
You could always use electromagnets.

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latch
how much force (if any) is required to break it off the track? Could that disk
be slingshotted around at hundreds of miles per hour and stay on tack?

~~~
simcop2387
I'd imagine whatever force is needed is proportional to the strength of the
magnets. Given that he can pull it off I can't imagine that specific setup
requires all that much force for it.

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Duckpaddle2
That has to be one of the most engaging conferences I have ever seen. The
science demos are just too cool. If I have the time I'm going next year!

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zerostar07
Quantum physics professors do that in their first lecture, it's getting old.

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DrData
Put this in a vacuum... perpetual motion?

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GraffitiTim
How does this work?

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coldarchon
At 1:30 the disc on the tracks stops without any outer interference, am I
missing something in the video?

~~~
camtarn
Yeah - when I saw that after watching the Take This Lollipop video, which is
an extremely well-done fake, I immediately lumped this one into the "cool
special effects, but not real" category.

So ... this is actually real? If so, that's pretty awesome :)

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marcamillion
Flying cars here we come?

~~~
rcthompson
Sure, but you can only fly at constant altitude along longitude lines. If I
understand the effect correctly.

~~~
michaelneale
This would have to be over a magnetic surface - like maglev trains
<http://en.wikipedia.org/wiki/Maglev> (which apparently are not technically
trains).

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bgramer
How much longer before we all drive landspeeders?

~~~
jeffool
Too long.

