
Physicists create light out of nothing - ColinWright
http://www.abc.net.au/science/articles/2011/11/17/3368920.htm#
======
fragsworth
I have a great disdain for these kinds of BS titles, they cloud what really
happened and make me feel like I'll just get dumber than I already am if I try
to read the article.

That said, they didn't create light out of _nothing_ , they created light out
of the _vacuum_. The vacuum is _something_ \- at least its fluctuations are,
so they didn't create light out of nothing.

~~~
dmbaggett
I agree with your sentiment, but this is actually a matter of philosophical
debate. _Nothing: A Very Short Introduction_ by Frank Close is an enjoyable
treatment.

~~~
nsxwolf
But creating light out of quantum vacuum fluctuations and creating it _ex
nihilo_ in the theological sense are very different things. The title
indicates the latter occurred.

~~~
dmbaggett
Read the book. You may come away feeling, as I did, that it is rather
difficult to assign any semantics at all to the term "nothing".

~~~
dalke
While it is pretty easy to assign semantics to the term "vacuum". I can put
vacuum (or a very good approximation) in a bottle. I can pay someone to
provide a system which creates a vacuum. I can be killed by vacuum.

~~~
jodrellblank
Can you put vacuum in a bottle in any more real sense than you can put
darkness in a bottle, or cold, or dry?

~~~
derleth
Yes. Obviously, you just remove the air in the bottle and then there is a
vacuum (or as good of an approximation of it as you can obtain using your
techniques) inside the bottle.

~~~
pyre
Personally I would call that 'creating vacuum in a bottle' rather than
'putting vacuum in a bottle.' Putting it into a bottle implies that it was
something that existed outside of the bottle and it then transferred into the
bottle.

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stcredzero
From the article:

 _While the static Casimir effect does this in the three dimensions of space,
the dynamical Casimir effect does it in the dimension of time._

WTF!? This is the last line of the article. That's the most interesting line
in the whole thing, and it's totally unexplained and left hanging. What's with
the authors/editors? Science journalism is such fluff, that it's no longer
about interesting ideas, but contentless amazing sounding word salad.

~~~
noduerme
Yeah; that line struck me as well. Does this mean we're borrowing these
particles from the future? Hopefully not from the past...? Also, wouldn't this
qualify as a machine that outputs more energy than it uses?

~~~
pudquick
The reason one is called static and involves 3d space and the other is called
dynamic and involves time has nothing to do with stealing particles from the
future or creating a perpetual motion/energy machine.

What differs in these effects (in space and in time) is the electromagnetic
modes of the vacuum near the mirror(s).

<http://en.wikipedia.org/wiki/Normal_mode#Quantum_mechanics>

It's all about creating a differential - and the effect this has for static
vs. dynamic is different for each.

In the static effect, a differential is created in 3d space: two mirrors are
perfectly placed in parallel to each other with a gap less than that of a
photon's wavelength. In the vacuum fluctuation of space, virtual photons and
anti-photon pairs are created and annihilate each other all the time - but
this tiny gap keeps them from appearing between the mirrors. The end result is
a difference in the modes between the mirrors (total lack of any activity) and
outside them (normal vacuum fluctuations) which results in a pressure
differential (in 3d space) pushing the plates together (the static effect).

In the dynamic effect, a differential is created due to a change over time: a
mirror is moved at a velocity significantly close to the speed of light (in
this case, around 5%). Around the mirror, as always, the vacuum contains
photon and anti-photon pairs coming into existence and annihilating each
other. With a fast enough moving mirror, the mirror can change the ability of
the particles to annihilate each other. This represents a change in time over
the nature of the vacuum / space where the particles appear.

Thought example: Prior to pair formation, there is no mirror at coordinate
XYZ. Proton and anti-proton pair appears - and mirror is moving so fast, it is
now present at point XYZ, between the proton and anti-proton, faster than the
two could reach and annihilate each other. Now, instead of annihilation, the
proton is reflected by the mirror.

This is the dynamical Casimir effect. It is a change, over time, in the nature
of vacuum.

Yes, photons are being reflected ("created from nothing") in this effect - but
so are anti-photons, which quickly find some other photon to interact with and
annihilates the pair of them. There is no net gain of energy here - in fact
quite a bit is spent keeping the mirror moving at high speeds.

~~~
Karmadragon
Thank you for your summary! It makes much more sense than the original
article. It does leave me with a few questions, though.

When you say the virtual particles are reflected, but quickly find another
pair and annihilate each other, are they pairing wth normal photons? And
because of the lack of anti-particles in our universe, isn't it more difficult
for the photons to pair, meaning that if this experiment was scaled
exponentially, the virtual photons would have an increasingly harder time
pairing, becoming more abundant and living longer?

~~~
ars
His explanation is partially wrong, which is why you have questions.

There is no such thing as an anti-photon, and if there was, then a photon
anti-photon pair would annihilate to produce - more photons!

Time in the quantum world is not completely logical, essentially these virtual
particles (they are not real particles!!) can not appear unless they already
managed to annihilate and vanish (i.e. the order of operations is not one
way).

The reason these photons do manage to exist is that the experiment provided
the energy necessary before the particles appeared. The "anti-photon" is not a
real particle, and does not need to find another photon to annihilate with.
It's more of a concept of energy, what it represents is missing energy, which
needs to be provided in order for the partner (the regular photon to exist).

The "missing/extra" energy pair can exist only for a short time, below the
Heisenberg uncertainty limit. If, in some way, you disrupt the annihilation of
missing and extra energy, the particles would not appear in the first place
(that's that out of order business I was talking about). But since the
experiment provided energy, the particles can appear, and then be split, and
the "anti-photon" uses the energy of the experiment to not exist.

You have probably heard of the momentum/location uncertainty pair - but there
is another: it's time/energy. So the more exactly you know how much energy
there is, the less you know about when it existed - that's why the particle
can have this out of order behavior - time itself is not properly defined for
it.

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jxcole
"Faster than the speed of light"

Though the underlying science is very interesting, I wish we could have less
sensationalized coverage. Nothing under this section title involves going
faster than light.

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tokenadult
Colin, was this submitted for disagreement? The comments here suggest that
this popular press account is missing some of the nuance that I usually expect
in articles you submit. Please help us out: what do you think about the
underlying physics being reported on here?

~~~
ColinWright
The reporting is poor, and people are right to diss it. But having written
extensively for semi-technical audiences, the kinds of criticisms being
levelled here are out of place. In this kind of article or publication there's
no point in splitting hairs in the title over the difference between vacuum
and "nothing". People who won't appreciate the difference will get turned off
by what they see as excessive nit-picking.

You need to get people to read. There's no point in having a fantastic finish
if no one gets there.

About the article, I think the phenomenon itself is amazing. The Casimir
effect is remarkable enough - completely at odds with classical physics and
yet trivally predicted by quantum physics, it's a great piece of evidence for
how weird the world is. To see it demonstrated using time as one of the
dimensions is brilliant.

OTOH, sp332 seems to have found the same story from another source, and in the
discussion there people are suggesting that the quantum explanation is out of
place and/or unnecessary, because it's more-or-less just like an antenna.
<http://news.ycombinator.com/item?id=3511341>

Then people just pick holes in the writing. I find that sad.

~~~
scott_s
I think you make an excellent point, which I take to be: let's all just apply
our popular-science-filter to the article and talk about the content, not the
words. I still think there's value in someone providing an explicit
translation. It may help to set the tone of the discussion by just stating up
front "Yes, the writing is poor. Here's what they should have said. Now that
we've established that, let's talk about the content." When I've submitted
stories and I wanted the discussion to go in a certain direction, I've tried
similar framing. (Although the stories didn't go anywhere. Ah well.)

With that said, can you provide more of an intuition for the Casimir effect?
Specifically, a better intuition for why is there are less fluctuations
between two plates than outside of them? Is it simply because there's so
little space between the plates, and hence less space for fluctuations? The
wikipedia article doesn't really provide this level of intuition.

~~~
ColinWright
Firstly, IANAQP, but here is my intuitive understanding.

When playing a bugle, high notes are all close together in pitch because with
short wavelength, adding one makes a proportionally small change. Playing
lower notes, the notes are further apart - there are effectively fewer notes
in the lower ranges because adding one extra wavelength makes a big difference
to the pitch.

Similarly the wavelengths of particles between the plates. When the plates are
far apart, pretty much every wavelength can appear between them, so things are
the same inside as out. When the plates are close together, fewer
particles/waves can appear between because their wavelength must divide the
distance, while the ones outside are still unrestricted. Then there are simply
more of them, resulting in a higher pressure.

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bdg
This is where I quit reading:

> the spooky properties of quantum physics

Can we link to the actual research papers from now on? Pretty please? With
sprinkles on top?

~~~
guelo
I believe "spooky action at a distance" is a term used by actual physicists to
describe some quantum phenomena. Though I don't know if the reporter used it
in the same sense.

~~~
lnguyen
Usually in reference to quantum entanglement. The quote is from Einstein (see
<http://en.wikipedia.org/wiki/Quantum_entanglement>)

The reporter is probably referencing that to some extent but mainly in the
sense that it goes against classical intuition.

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sp332
Previous discussion, about 2 months ago:
<https://news.ycombinator.com/item?id=3252591>

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WhatsHisName
Just a couple of points to consider. In the static Casimir effect the mirrors
cancel out virtual 1/2 wavelength standing waves so there is pressure outside
of the gap forcing the plates together. In the dynamic Casimir effect the
mirrors move fast enough to cancel out only half of the pair of virtual waves.
The other half whose energy is provided from the movement of the mirrors
remains.

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abecedarius
Background:
[http://en.wikipedia.org/wiki/Casimir_effect#Analogies_and_th...](http://en.wikipedia.org/wiki/Casimir_effect#Analogies_and_the_dynamic_Casimir_effect)

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ck2
_In practical terms that's impossible because it would take the output of a
nuclear power plant to accelerate a mirror to such high velocities_ [speed of
light]

No, in practical terms that's impossible because the mass of the mirror would
become unfathomable when it got within 10% of the upper speed of light.

