Physicists create light out of nothing(abc.net.au)
abc.net.au
Physicists create light out of nothing
http://www.abc.net.au/science/articles/2011/11/17/3368920.htm#
10 comments
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.
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.
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".
If "nothing" doesn't mean anything, then the title doesn't mean much either.
Nothing is more important than life. The holes in donuts are nothing. Therefore the holes in donuts are more important than life.
Getting back to the pedantry of the op technically the holes of a donut are at minimum filled with vacuum and on earth with air.
So, are donut holes more important than life or not?! What's the bottom line, man!
It is only difficult, if you expressly go for ambiguity, and confusion. Lest I say spin, which is standard in physics.
'it means just what I choose it to mean — neither more nor less.
http://cdsweb.cern.ch/record/1127343/
'it means just what I choose it to mean — neither more nor less.
http://cdsweb.cern.ch/record/1127343/
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.
Can you put vacuum in a bottle in any more real sense than you can put darkness in a bottle, or cold, or dry?
Phrases found from a Google search for "put vacuum in"
"hand vacuum pump (the one that you can use to bleed brakes with) and hook up the line directly to the actuator and put vacuum in it"
"I was wondering if anyone has experimented with a vacuum pump or any other way to put vacuum in the crankcase."
"I believe VW uses an air pump to test the evap system instead of relying on engine vacuum to put vacuum in the evap system"
"I want to be able to put vacuum in and leave it but not sure why no suction?"
It seems that many people regard it as having a concrete meaning. (I saw little hit of a non-concrete meaning. The other cases I saw were things like "put vacuum in pool", in reference to a vacuum cleaner.)
There were 138 non-duplicate matches for "put darkness in". All were metaphorical, and most were due to a Biblical verse.
While there are some references to "put cold in", as in:
"If you put cold in the thermostat doesn't kick on until much later causing the water to freeze at a later time."
"it's identical to a regular hotwater tank so you have to put cold in to the drain and loop it back"
they are short-hand for "cold water". Otherwise the terms are either metaphorical, like "put cold in its place with this warm parka", or a reminder that chilling devices don't put cold in but rather take heat out.
The phrase "put dry in" only appears in context like "Get 2 [dog] bowls and put dry in 1", or "I didn't have fresh basil so I put dry in the mayo", where the "dry" refers to a preceding noun. (The one exception was the question "why would they want to put dry in their beer?".)
Thus, a haphazard search of the Google corpus reinforces my assertion that putting vacuum in (something) has a more real, concrete sense than putting darkness, cold, or dry in (something).
"hand vacuum pump (the one that you can use to bleed brakes with) and hook up the line directly to the actuator and put vacuum in it"
"I was wondering if anyone has experimented with a vacuum pump or any other way to put vacuum in the crankcase."
"I believe VW uses an air pump to test the evap system instead of relying on engine vacuum to put vacuum in the evap system"
"I want to be able to put vacuum in and leave it but not sure why no suction?"
It seems that many people regard it as having a concrete meaning. (I saw little hit of a non-concrete meaning. The other cases I saw were things like "put vacuum in pool", in reference to a vacuum cleaner.)
There were 138 non-duplicate matches for "put darkness in". All were metaphorical, and most were due to a Biblical verse.
While there are some references to "put cold in", as in:
"If you put cold in the thermostat doesn't kick on until much later causing the water to freeze at a later time."
"it's identical to a regular hotwater tank so you have to put cold in to the drain and loop it back"
they are short-hand for "cold water". Otherwise the terms are either metaphorical, like "put cold in its place with this warm parka", or a reminder that chilling devices don't put cold in but rather take heat out.
The phrase "put dry in" only appears in context like "Get 2 [dog] bowls and put dry in 1", or "I didn't have fresh basil so I put dry in the mayo", where the "dry" refers to a preceding noun. (The one exception was the question "why would they want to put dry in their beer?".)
Thus, a haphazard search of the Google corpus reinforces my assertion that putting vacuum in (something) has a more real, concrete sense than putting darkness, cold, or dry in (something).
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.
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.
A vacuum can be a robot. A political vacuum occurs after a revolution. A vacuum can be abhorred by nature. My vacuum has a dirty filter. In a vacuum, no one can hear you scream. Vacuum.
... uh, sorry, I got carried away.
... uh, sorry, I got carried away.
"Absolute" vacuum is not attainable due to fluctuations though, not due to some semantic ambiguity.
Then they should have said "vacuum" instead of intentionally using such an ambiguous word.
In music, the intervals of silence are often more important than the sounds themselves.
They are not more important; without the sounds there wouldn't be the intervals of silence.
Without the silence, you wouldn't have a melody.
We can go on discussing about how painting is about adding to a canvas, while sculpting is about taking away the parts you don't need.
Such discussions are pointless.
We can go on discussing about how painting is about adding to a canvas, while sculpting is about taking away the parts you don't need.
Such discussions are pointless.
It is very well possible to have a melody without silence. For instance using glissandi you can move from one note to another without an intervening break.
http://en.wikipedia.org/wiki/Glissando
http://en.wikipedia.org/wiki/Glissando
That's what I was saying -- neither is more important than the other.
So, it gets no semantics at all, then?
Correct, the semantics are simply nothing at all. :)
However, in the context of discussing this article, they also used the subheader "faster than the speed of light" for a paragraph describing how the physicists accelerated the mirror... and didn't go faster than the speed of light.
So it's kinda a poorly written article in general :)
So it's kinda a poorly written article in general :)
The sad thing is that for a lot of magazines and newspapers, the person who writes the article isn't the person who writes the headline or headers.
This often means no matter how good the writers understanding is of the subject, the headers always make the article look retarded. It would be like assigning a 12 year old to subheader Stephen Hawkings next book... the sad thing being the 12 year old would likely do a better job than the 40 year old who does this for their living.
This often means no matter how good the writers understanding is of the subject, the headers always make the article look retarded. It would be like assigning a 12 year old to subheader Stephen Hawkings next book... the sad thing being the 12 year old would likely do a better job than the 40 year old who does this for their living.
I suppose it is hard to write a pithy title that does a good job of summarizing what happened, but these titles definitely contribute to scientific confusion and ignorance.
Since I could sensibly say to my advisor "well, there's nothing in the environment, so it must be something in the device", I think 'nothing' is a perfectly valid word for describing a sufficiently low pressure vacuum. Especially if you are addressing a lay audience.
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.
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.
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?
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.
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.
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?
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?
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.
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.
um, did you mean electrons and positrons? afaik photons are their own antiparticles....
"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.
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.
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?
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.
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.
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.
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.
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.
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.
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?
> the spooky properties of quantum physics
Can we link to the actual research papers from now on? Pretty please? With sprinkles on top?
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.
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.
The reporter is probably referencing that to some extent but mainly in the sense that it goes against classical intuition.
Previous discussion, about 2 months ago: https://news.ycombinator.com/item?id=3252591
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.
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.
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.
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.