Scientists create light from vacuum | Hacker News Reader

Scientists create light from vacuum

physorg.com

53 pointseande11 comments

What!?

This is just incorrect. They aren't creating light from vacuum - they are simply creating light in exactly the same way that antennas create light.

Antennas create light (electromagnetic energy) by vibrating electrons at the same frequency of the light they want to create.

Here they are also vibrating electrons at the frequency of light. "several billions of times a second" - frequency of microwaves? Ghz. Exactly the same.

Accelerating an electron (actually any charged particle) creates light. For example: http://en.wikipedia.org/wiki/Synchrotron_radiation You can shake the electron, force it to curve, anything and it will radiate light.

I've often thought that this would be an awesome way to make a laser if you could find a material you can vibrate fast enough.

>I've often thought that this would be an awesome way to make a laser if you could find a material you can vibrate fast enough.

Isn't that a free electron laser?

Basically, yah.

Although I was thinking more of vibrating the electrons in place, the principle is exactly the same.

Umm, I'd like to give the scientists involved a benefit of the doubt. The probability that they don't know what they're doing is much lower than the probability that a popularized article about their study is incomplete and/or inaccurate.

The actual paper is available at arxiv and is quite readable: http://arxiv.org/abs/1105.4714

Well the actual experiment was awesome - full credit for that.

I just don't buy that you need to explain it using virtual photons that bounce of the mirror.

They do write:

"A mirror moving in a finite EM field then losses energy as the screening currents will emit EM radiation, as in an antenna."

And then say you need vacuum fluctuations to explain it still happening without an EM field. And explain it as the vacuum having a random EM field that is acting on the mirror.

I guess that's not quite the same as "virtual photons bouncing on a mirror". But since a charged mirror requires no extra field, and since their mirror basically is charge, I really don't see the need to bring in virtual photons here.

It would be very surprising if quantum mechanics didn't add up to the normal classical world we experience or to classical theories we use because they work. The story and explanations at the small level can have a totally different nature though.

Another way to put it might be this - you say "accelerating electrons creates light", but how? Classical electrodynamics is one explanation, but it cannot explain all related phenomena. At small enough levels, you find details (like photons appearing in pairs) that need a different sort of theory to explain it. What then would you say about the path integral explanation of a mirror that needs all sorts of particle creation and destruction, including particles moving backwards in time, to explain what the mirror "does" even when it isn't moving?

>What happens during the experiment is that the “mirror” transfers some of its kinetic energy to virtual photons, which helps them to materialise.

how is that different from just saying that their vibrating EM field radiated the energy (a vibrating EM field does radiates the energy and this radiation is photons by definition) without bringing in "virtual photons"

Is true that the energy put into the system (in the form of the dynamic mirror) must be the same or greater than the energy of the photons taken out? I don't think this is the "zero-point energy" or "reactionless engine" breakthrough that people on that page are hoping it is.

Yes. Bear in mind that each individual photons carries very little energy - the energy required to generate the described 'mirror' is enormous by comparison.

The main value of this is further experimental verification of certain aspects of quantum physics, as mentioned at the bottom of the article.

The energy is not in generating the mirror, but in shaking it. That energy is directly used to create the photons.

And the scientists said, "Let there be light!" And there was light.

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