How do we measure faster than light speed ?

[Secular Sanity]

It was in relation to us.  I needed to say something about inertial frames to show that there is no absolute frame of reference and that objects are always measured relative to the position of another object.

Now explain how that is not a non-sequitur here:

Not us, as in you and I.

None of what you said here requires anything about "inertial frames" or "relative measurement". So are we about to the point in the discussion where you usually beg off by saying you were "just joking"?

I said two things.

It can be stored for a short time in the excited states of atoms.

BTW, a photon doesn't experience time or distance.

You said...

That's not exactly true. The photon, itself, cannot be stopped or stored. It's energy can be passed on to atoms which can later emit that energy again as a photon. It cannot be said to be the same photon.

I responded to your post, and then I added just a drop of inertial frames to my remark about the photon to show that the movement of anything can only be described relative to something else.

This thread hasn't even progressed anywhere near approaching how c is invariant in all inertial frames (and if you think the OP is there, you're deluded). Still sounds like you're just trying to pad your ego at the expense of helping anyone actually learn something.

Maybe the OP knows more than you think.  You go out of your way to make other people feel stupid, don't you?

I debate with others to hone my own thinking.

You’re sharping your skills like you’d sharpen a knife.  Why?

Again, your supposed "experience" of a photon is meaningless, because it is zero. It's not sad...a photon is not a widdle wost puppy...no matter how much your overactive emotions cry out to make a fanciful and personified story of everything. At least animals actually do have experience.

Hardy har-har!  You know that’s not what I meant.  Timeless eternity, isn't that what everyone is fighting for?

"Man alone measures time. Man alone chimes the hour. And, because of this, man alone suffers a paralyzing fear that no other creature endures. A fear of time running out."—Mitch Albom

But without time there’d be no journey.

[Syne]

None of what you said here requires anything about "inertial frames" or "relative measurement". So are we about to the point in the discussion where you usually beg off by saying you were "just joking"?

I said two things.

[quote='Secular Sanity' pid='7859' dateline='1479516645']
It can be stored for a short time in the excited states of atoms.

BTW, a photon doesn't experience time or distance.

And I addressed the first point, which doesn't require knowledge of inertial frames or relative motion (both very difficult concepts for laymen to understand). The second was an unnecessary non-sequitur, superfluous to answering the OP's question.

You said...

That's not exactly true. The photon, itself, cannot be stopped or stored. It's energy can be passed on to atoms which can later emit that energy again as a photon. It cannot be said to be the same photon.

Yep, because the OP specifically asked about "stopping light", and you're post did not make it clear that light, as light, cannot be stored. I have no idea why you can't bear to have your answers clarified...and with details you seem to agree with at that.

I responded to your post, and then I added just a drop of inertial frames to my remark about the photon to show that the movement of anything can only be described relative to something else.

Yeah, continuing your previous non-sequitur.

This thread hasn't even progressed anywhere near approaching how c is invariant in all inertial frames (and if you think the OP is there, you're deluded). Still sounds like you're just trying to pad your ego at the expense of helping anyone actually learn something.

Maybe the OP knows more than you think.  You go out of your way to make other people feel stupid, don't you?

You said yourself:

It doesn’t seem like you understand enough to form a proper question. Maybe you could start by asking just one question at a time.

If someone doesn't seem to know enough to form a proper question, why on earth would you expect them to understand inertial frames and relative motion?

I debate with others to hone my own thinking.

You’re sharping your skills like you’d sharpen a knife.  Why?

LOL. Read that again deary. I said "hone...thinking", not "sharpen...skills". Anyone seriously interested in science should always seek to make their thinking more rigorous.

[Secular Sanity]

The second was an unnecessary non-sequitur, superfluous to answering the OP's question.

Other people read the topics, too.  It’s is an interesting perspective and inertial frames explain why we observe photons moving and passing through space-time.  

https://www.youtube-nocookie.com/embed/5ELA3ReWQJY

If someone doesn't seem to know enough to form a proper question, why on earth would you expect them to understand inertial frames and relative motion?

It was meant to counter your discouraging remark.  

That is all gibberish.

I have no idea why you can't bear to have your answers clarified.

I’m fine with it, but your clarification leads to one of the most popular misconceptions regarding the speed of light through a medium, i.e., the absorption and re-emission process.

That's not exactly true. The photon, itself, cannot be stopped or stored. It's energy can be passed on to atoms which can later emit that energy again as a photon. It cannot be said to be the same photon.

https://www.youtube-nocookie.com/embed/CiHN0ZWE5bk

https://www.youtube-nocookie.com/embed/YW8KuMtVpug

I never said they were the same photons, and I could be wrong, but I suspect that they might be, and this may be why the pattern is retrievable.  Although, there is some degree of energy transfer during the phase velocity, the photons are not absorbed.  

Whereas the phase velocity is slowed by the index of refraction, the group velocity is inversely proportional to the dispersion of the medium.  

"Only signal frequencies that lie within the narrow transparency window can propagate unabsorbed through the medium. Since the window width, as well as the group velocity, are proportional to the control intensity, the maximum pulse delay is inversely proportional to the pulse length to be slowed. (The proportionality constant depends on the optical density of the EIT medium.) It is therefore not possible to reduce the group velocity to zero with the technique described above. One more twist to the EIT bag of tricks is needed.

An essential characteristic of the technique used to stop light is that almost no photon energy or linear momentum is stored in the medium. They’re borrowed from the control beam in such a way that all other information that describes an entire light pulse is coherently converted into a low-energy spin wave.  The properties can be modified by simply changing the intensity of the control beam: if the control beam intensity is decreased, then the group velocity is further slowed. This also implies that the contribution of photons to the polariton state is reduced.

If the control beam is turned off after the signal pulse has been compressed into the EIT medium, two things happen: the polariton becomes purely atomic, and its group velocity is reduced to zero. The information originally carried by the photons is fully mapped onto the long-lived ground or spin states of the atoms.  The frequency spectrum of the polariton will narrow continuously as the pulse slows, so that it always remains within the transparency window. The stored light pulse can be easily retrieved by simply turning the control beam back on and re-accelerating the stopped dark-state polariton. For this reason, there is, in principle, no loss associated with the trapping procedure."...Source

[Syne]

It’s is an interesting perspective and inertial frames explain why we observe photons moving and passing through space-time.

So...you think that we cannot observe light from non-inertial frames? If we're in an accelerating frame, we cannot observe photons moving through space-time? Either explain why that would be so, or admit that inertial frames are not necessary to our observation of light.

I have no idea why you can't bear to have your answers clarified.

I’m fine with it, but your clarification leads to one of the most popular misconceptions regarding the speed of light through a medium, i.e., the absorption and re-emission process.

I never said a thing about propagation through a medium. Now you're just making shit up. Remember, you were talking about "stopping" light, not slowing light.

That's not exactly true. The photon, itself, cannot be stopped or stored. It's energy can be passed on to atoms which can later emit that energy again as a photon. It cannot be said to be the same photon.

I never said they were the same photons, and I could be wrong, but I suspect that they might be, and this may be why the pattern is retrievable.  Although, there is some degree of energy transfer during the phase velocity, the photons are not absorbed.

No, the pattern is retrievable because it is stored in spin excitations of the rigid atomic lattice of the crystal. As long as they allow those atoms to emit the energy before its quantum state becomes entangled with those of the atoms, in the process of decoherence, they can retrieve the pattern.

Seems you're now trying to equivocate the subject from "stopping" light to slowing light. If so, that is very intellectually dishonest.

[Secular Sanity]

So...you think that we cannot observe light from non-inertial frames? If we're in an accelerating frame, we cannot observe photons moving through space-time? Either explain why that would be so, or admit that inertial frames are not necessary to our observation of light.

The point was that everything always thinks of itself as stationary.  You don’t move with respect to yourself.  

That's not exactly true. The photon, itself, cannot be stopped or stored. It's energy can be passed on to atoms which can later emit that energy again as a photon. It cannot be said to be the same photon.

I never said they were the same photons, and I could be wrong, but I suspect that they might be, and this may be why the pattern is retrievable.  Although, there is some degree of energy transfer during the phase velocity, the photons are not absorbed.

No, the pattern is retrievable because it is stored in spin excitations of the rigid atomic lattice of the crystal. As long as they allow those atoms to emit the energy before its quantum state becomes entangled with those of the atoms, in the process of decoherence, they can retrieve the pattern.

Seems you're now trying to equivocate the subject from "stopping" light to slowing light. If so, that is very intellectually dishonest.

You’re right, but it was a misapprehension on my part, not deceit. Why do you always have to assume the worst in people?  It was an honest mistake.  All of the articles conflate the two subjects.  They never stopped light, but the articles make it sound like they slowed the light down enough to make it come to a screeching halt.

You’ve been wrong in the past.  Have you ever admitted it or apologized?

[Syne]

So...you think that we cannot observe light from non-inertial frames? If we're in an accelerating frame, we cannot observe photons moving through space-time? Either explain why that would be so, or admit that inertial frames are not necessary to our observation of light.

The point was that everything always thinks of itself as stationary.  You don’t move with respect to yourself.  

I thought you were trying to show how that wasn't a non-sequitur? Seems you've agreed it was.

That's not exactly true. The photon, itself, cannot be stopped or stored. It's energy can be passed on to atoms which can later emit that energy again as a photon. It cannot be said to be the same photon.

I never said they were the same photons, and I could be wrong, but I suspect that they might be, and this may be why the pattern is retrievable.  Although, there is some degree of energy transfer during the phase velocity, the photons are not absorbed.

No, the pattern is retrievable because it is stored in spin excitations of the rigid atomic lattice of the crystal. As long as they allow those atoms to emit the energy before its quantum state becomes entangled with those of the atoms, in the process of decoherence, they can retrieve the pattern.

Seems you're now trying to equivocate the subject from "stopping" light to slowing light. If so, that is very intellectually dishonest.

You’re right, but it was a misapprehension on my part, not deceit. Why do you always have to assume the worst in people?  It was an honest mistake.  All of the articles conflate the two subjects.  They never stopped light, but the articles make it sound like they slowed the light down enough to make it come to a screeching halt.

You’ve been wrong in the past.  Have you ever admitted it or apologized?

I never said it was deceit. So this "assume the worst" is just a strawman appeal to emotion. Equivocation (and even intellectual dishonesty) doesn't imply intent to deceive...it could just as readily be out of ignorance.

In the transparent crystal experiment, they did stop the energy of the light, and could retrieve the pattern as emitted light (new photons) within about a minute...before decoherence. The articles on the subject didn't conflate anything. They did stop the energy. I don't know what articles you're talking about that had anything to do with slowing light.

I have admitted to being wrong, even fairly recently (I think I recently told MR that he was absolutely right)...but you're just trying to poison the well. Good on you for taking another look and getting a better grasp of the experiment though.

[Secular Sanity]

In the transparent crystal experiment, they did stop the energy of the light, and could retrieve the pattern as emitted light (new photons) within about a minute...before decoherence. The articles on the subject didn't conflate anything. They did stop the energy. I don't know what articles you're talking about that had anything to do with slowing light.

I don’t think so.  They didn’t stop the energy from the original light pulse.  The energy from the original light pulse is absorbed, i.e., there is no more light pulse. Although, they were able to retrieve a copy of the pattern embedded in the atoms, they didn’t technically stop the light pulse.  

https://www.youtube-nocookie.com/embed/RIc5llW66sU

Let me ask you something though, Syne.  In the video at (1m56s) the narrator states that Lena Hau said that the atomic imprint of the light in the sodium cloud is a perfect copy embedded in atoms of the original light pulse.  It can then be stopped in free space in between the two clouds before moving on.  When it enters the second cloud another shot of the control laser expands it to its original size, shape, and speed.

I can understand how it could be stopped when it’s absorb into the sodium cloud, but how can it be stopped in the free space in-between the sodium clouds?

I have admitted to being wrong, even fairly recently (I think I recently told MR that he was absolutely right)...but you're just trying to poison the well.

Where?

I never said it was deceit. So this "assume the worst" is just a strawman appeal to emotion. Equivocation (and even intellectual dishonesty) doesn't imply intent to deceive...it could just as readily be out of ignorance.

Are you trying to say that my impression of you being a total dickhead is completely unfounded?

[Syne]

In the transparent crystal experiment, they did stop the energy of the light, and could retrieve the pattern as emitted light (new photons) within about a minute...before decoherence. The articles on the subject didn't conflate anything. They did stop the energy. I don't know what articles you're talking about that had anything to do with slowing light.

I don’t think so.  They didn’t stop the energy.  The energy from the original light pulse is transferred and absorbed. That light pulse technical vanished.  Although, they were able to retrieve a copy of the pattern imbedded in the atoms, they didn’t technically stop the light pulse.  

They did stop (store) the energy of the light. I said "energy" because it was no longer light when stored. But I agree, they didn't "stop light", and I've been saying that from the beginning.

https://www.youtube-nocookie.com/embed/RIc5llW66sU

Let me ask you something though, Syne.  In the video the narrator states that Lena Hau said that the atomic imprint of the light in the sodium cloud is a perfect copy embedded in atoms of the original light pulse.  It can then be stopped in free space in between the two clouds before moving on.  When it enters the second cloud another shot of the control laser expands it to its original size, shape, and speed.

I can understand how it could be stopped when it’s absorb into the sodium cloud, but how can it be stopped in the free space in-between the sodium clouds?

The narration seems to be misleading.

"We demonstrate that we can stop a light pulse in a supercooled sodium cloud, store the data contained within it, and totally extinguish it, only to reincarnate the pulse in another cloud two-tenths of a millimeter away," said Lene Vestergaard Hau, Mallinckrodt Professor of Physics and of Applied Physics in Harvard's Faculty of Arts and Sciences and School of Engineering and Applied Sciences.
...
In her latest work, Hau and her co-authors, Naomi S. Ginsberg and Sean R. Garner, found that the light pulse can be revived, and its information transferred between the two clouds of sodium atoms, by converting the original optical pulse into a traveling matter wave which is an exact matter copy of the original pulse, traveling at a molasses-like pace of 200 m (600 ft) per hour. The matter pulse is readily converted back into light when it enters the second of the supercooled clouds -- known as Bose-Einstein condensates -- and is illuminated with a control laser. - http://www.photonics.com/Article.aspx?AID=28520

And even as a matter wave, it can still only be slowed to 600 ft/hr. So there's really no sense in which it could be said to be stopped, but as matter, it is slow enough to consider it practically stopped. BTW, nice find. I hadn't seen that research before. Very interesting.

I have admitted to being wrong, even fairly recently (I think I recently told MR that he was absolutely right)...but you're just trying to poison the well.

Where?

Check the thread "Classism in our daily lives".

I never said it was deceit. So this "assume the worst" is just a strawman appeal to emotion. Equivocation (and even intellectual dishonesty) doesn't imply intent to deceive...it could just as readily be out of ignorance.

Are you trying to say that my impression of you being a total dickhead is completely unfounded?

I'm saying that your emotional and fallacious arguments are irrelevant to anything but your fragile ego, and that your attempts at character assassination are willfully, intellectually dishonest. No one can fault you for ignorance, but you seem to think you can somehow win intellectual debate through emotional appeal. You should really have more faith in your own ability to make reasonable arguments.

[RainbowUnicorn]

question

if the laser is applied to the cloud, then surely the laser is making new light ?
"reincarnate " is a somewhat loose term and thus could be  "reincarnate " turnip.
if the reincarnate  part is bringing a template of wave form back into a photonic mass then maybe the mass is created by the laser, which in all intents and purposes is probably some type of attempt to use light as a form of data encryption rather than looking at light as a time/space property factor.
if ya gits me gist.

whats ya thoughts  around that ?

is it still light with no mass ? (i kinda assumed it is not as it is thus a wave print... (funded by xerox?kinda joking & not Re implications of actual usability)

it makes me feel that the nature of the spacial time factor of light has been left sitting on the shelf.

---

fibre optic real time encryption & decryption implications. thats pretty flash.

[Syne]

question

if the laser is applied to the cloud, then surely the laser is making new light ?

But the laser applied to the second cloud doesn't, itself, contain the information the messenger atoms do. From my understanding, it only provides the energy to make those messenger atoms emit photons in the pattern stored. So it is making new photons, but the laser photons only provide the needed energy.

"reincarnate " is a somewhat loose term and thus could be  "reincarnate " turnip.
if the reincarnate  part is bringing a template of wave form back into a photonic mass then maybe the mass is created by the laser, which in all intents and purposes is probably some type of attempt to use light as a form of data encryption rather than looking at light as a time/space property factor.
if ya gits me gist.

whats ya thoughts  around that ?

No such thing as photonic mass. But it isn't a question of mass...it's a question of information pattern. Yes, they hope this provides some new methods for quantum computing and encryption.

is it still light with no mass ? (i kinda assumed it is not as it is thus a wave print... (funded by xerox?kinda joking & not Re implications of actual usability)

it makes me feel that the nature of the spacial time factor of light has been left sitting on the shelf.

In between clouds, it's not light at all, just a pattern stored in atoms moving very slowly between the two sodium clouds. Within the clouds, it just works like refraction in glass, but on steroids. The speed of light is only c in a vacuum.