where does light from a torch go?

[OnlyMe]

No it's very easy. Just learn about photoreceptors. The action potential will not fire unless the stimulus is above threshold. One photon by itself will not trigger the action hillock. It takes a bulk of them, an actual wave, to cross threshold. Beyond that the pumping action of the wave must be sustained, or there is no visual perception. You can test this by pulse-modulating a light source. When the pulse becomes too narrow, you will no longer detect the light. The screen you are looking at does this. You only think the solid color of the text is not oscillating. It is. You just can't see it because it's designed to oscillate faster than the rate of visual integration. That rate, by the way, is anything faster than about 20 Hz. (It varies slightly from person to person.) (Or if your text is black the same rule applies to the background color, which you think is not flashing.)

From, http://math.ucr.edu/home/baez/physics/Quantum/see_a_photon.html

The human eye is very sensitive but can we see a single photon? The answer is that the sensors in the retina can respond to a single photon. However, neural filters only allow a signal to pass to the brain to trigger a conscious response when at least about five to nine arrive within less than 100 ms. ​

Which suggests that individual rods can detect single photons, but also that you are correct in that the act of perception requires more than a single photon.

However, the FAQ still explains the eye's ability to detect light as occurring via individual photons, rather than a wave... It just takes a minimum number of individual detected photons to reach the threshold of perception.

We don't see the wave character of light. That is something that we interpret from a series of unique interactions between a photon detector and the light it detects. Be that your eye or a CCD of some sort. Light interacts with matter in discrete quantifiable bits/quanta.., we call photons.

However, for dav57, your position is completely without any scientific merit. You would have us all believe that we are no more than an ostrige, for whom the world does not exist whilst we cannot see it. From the rabbit hole, to a head buried in the sand! Where will you try to take us next?

 

[dav57]

I agree entirely with you that my position is without scientific merit. But the weirdness of the Universe (and light in particular), along with experimental evidence, suggests that the observed behaviour of light has more to do with the observer than the source. Some experiments suggest that light waves appear to be able to foresee their future path before they even embark upon their journey. There are many mysteries surrounding light and I don't think text-book physics is going to uncover those mysteries.

I stand by my position that we don't "see" waves. We only detect the final transformation into photons where the wave is absorbed by a receiver. The double-slit experiment behaves exactly how I would expect it to. To me there is no weirdness there.

 

[dav57]

And like I say, the observer (always being in its own frame of reference) could only ever detect the incoming information/energy at a constant fixed rate regardless of the speed of the wave. Which is probably why the speed of light always appears constant. Again, that's what I'd expect.

 

[exchemist]

I agree entirely with you that my position is without scientific merit. But the weirdness of the Universe (and light in particular), along with experimental evidence, suggests that the observed behaviour of light has more to do with the observer than the source. Some experiments suggest that light waves appear to be able to foresee their future path before they even embark upon their journey. There are many mysteries surrounding light and I don't think text-book physics is going to uncover those mysteries.

I stand by my position that we don't "see" waves. We only detect the final transformation into photons where the wave is absorbed by a receiver. The double-slit experiment behaves exactly how I would expect it to. To me there is no weirdness there.

I agree the double slit experiment does imply the wavefunction of even a single QM wave-particle seems to explores space regardless of where the particle is detected. I tend to agree that the wave seems in that sense more fundamental than the quantised "particle"-sized lumps that we eventually detect at one location or another, on a statistical basis.

I do not however see why you think this involves the wave "foreseeing" a future path of the "particle". To me that implies there is a classical trajectory followed by a "particle", which is guided by a "wave" that somehow precedes it. I do not think that is right. We cannot know the trajectory, due to quantum indeterminacy, that's all. It is undefined.

Still less would I agree that the wave-particle does not exist until detected. That seems unnecessary, and thus perverse, to me.

 

[dav57]

"I do not however see why you think this involves the wave "foreseeing" a future path of the "particle"

That's what various delayed choice experiments tend to show - that the photon "knew" its final path before it began its journey.

"Still less would I agree that the wave-particle does not exist until detected."

Again, nobody has ever directly seen a wave, only the end result, which is a photon. Besides, if there was nowhere for a wave to release its energy on, what was the point in it starting out in the first place? Wouldn't that contravene the law of conservation of energy? i.e energy released but never going anywhere else?

 

[Russ_Watters]

Besides, if there was nowhere for a wave to release its energy on, what was the point in it starting out in the first place? Wouldn't that contravene the law of conservation of energy?

Still no.

i.e energy released but never going anywhere else?

Still isn't what happens.

 

[exchemist]

"I do not however see why you think this involves the wave "foreseeing" a future path of the "particle"

That's what various delayed choice experiments tend to show - that the photon "knew" its final path before it began its journey.

"Still less would I agree that the wave-particle does not exist until detected."

Again, nobody has ever directly seen a wave, only the end result, which is a photon. Besides, if there was nowhere for a wave to release its energy on, what was the point in it starting out in the first place? Wouldn't that contravene the law of conservation of energy? i.e energy released but never going anywhere else?

Two points:

1) this behaviour does not apply only to photons. It is true of electrons and other atomic scale particles too. It's just QM. So whatever speculations you want to entertain about particles not existing until observed must apply to electrons and other constituents of matter just as much as it does to the quantum of light. Are you happy with that?

2) Your last para strikes me as rather unintelligible. What do you mean by "if there was nowhere for a wave to release its energy on"? The wave "releases" its energy when it is absorbed, in the case of a photon. In the case of a particle with rest mass, such as an electron, the energy of its wave depends on its kinetic energy and, if it gives some of this up, its de Broglie wavelength increases.

So in all cases there IS somewhere else for the energy to go. I really can't follow your point here at all.

 

[Read-Only]

Two points:

1) this behaviour does not apply only to photons. It is true of electrons and other atomic scale particles too. It's just QM. So whatever speculations you want to entertain about particles not existing until observed must apply to electrons and other constituents of matter just as much as it does to the quantum of light. Are you happy with that?

2) Your last para strikes me as rather unintelligible. What do you mean by "if there was nowhere for a wave to release its energy on"? The wave "releases" its energy when it is absorbed, in the case of a photon. In the case of a particle with rest mass, such as an electron, the energy of its wave depends on its kinetic energy and, if it gives some of this up, its de Broglie wavelength increases.

So in all cases there IS somewhere else for the energy to go. I really can't follow your point here at all.

Ever since the third or fourth post, this thread has done nothing but degenerate. Dav, did you make it through high school ? It sure doesn't look like it. Even a 10th grade student knows FAR more about this simple topic than you do!

I completely agree with exchemist, you do not seem to understand the most simple things.

Who cares where the wave releases it's energy, or if it ever does?!? Once the energy is released it STAYS conserved - if it's released OR if it isn't. Can you not understand that?????????

 

[dav57]

...other constituents of matter just as much as it does to the quantum of light. Are you happy with that?

Yes.

 

[dav57]

Who cares where the wave releases it's energy, or if it ever does?!? Once the energy is released it STAYS conserved - if it's released OR if it isn't. Can you not understand that?????????

You should care. You should care because there are too many unanswered questions remaining. There is something deeper going on and you are unlikely to uncover the reasons while you're genning up on and preaching your textbook physics.

 

[exchemist]

You should care. You should care because there are too many unanswered questions remaining. There is something deeper going on and you are unlikely to uncover the reasons while you're genning up on and preaching your textbook physics.

This is crap, I'm afraid. Do you REALLY imagine the thousands upon thousands of physicists and chemists who work, or have worked, with QM every day for the last half century or more have somehow overlooked a violation of conservation of energy?

Of course not. There is no issue at all on this score, as evidenced by your inability to explain to anybody, after several attempts, where the alleged problem is.

QM has mysterious and unintuitive aspects to it, sure, but the conservation of energy has nothing to do with it.

 

[dav57]

Take this example - one of the experiments in the following link - the one involving polarising filters:

http://www.dhushara.com/book/quantcos/qphil/qphil.htm

They say erasing path "information" restores the interference pattern. They say that adding a polarising filter to one of the paths enables you to determine where the photon came from. As a consequence the interference pattern disappears. Err, yes, that's what I'd expect. Of course I'd expect the pattern to disappear but not because you can somehow determine the path. It seems to me that the insertion of a polarising filter actually blocks part of the wave (some of the light has now effectively been observed by the filter) which has completely unbalanced the two possible paths and thus interference is not possible because from what I can work out an interference pattern can only occur when the wave is equally and identically split.

They go on to say that inserting two more polarising filters restores the pattern because there is now no way to determine which path the photon went down. Well, firstly, photons don't travel at all. They are waves when they "travel". So they never go down one single path and I don't understand why anyone would try and determine which path something which doesn't exist is taking! Secondly, I would have thought there was a far simpler reason for the pattern restoring i.e. the two additional polarising filters now effectively block or "observe" the same polarised light as the first filter consequently only allowing through the rest of the "unobserved" light which is of similar characteristics and perfectly balanced in order to create an interference pattern. What's the big deal? Am I missing something?

 

[dav57]

This is crap, I'm afraid. Do you REALLY imagine the thousands upon thousands of physicists and chemists who work, or have worked, with QM every day for the last half century or more have somehow overlooked a violation of conservation of energy?

Of course not. There is no issue at all on this score, as evidenced by your inability to explain to anybody, after several attempts, where the alleged problem is.

QM has mysterious and unintuitive aspects to it, sure, but the conservation of energy has nothing to do with it.

Ok, but you can't deny that the evidence so far strongly suggests that the observer plays a critical role in the outcome of how something is measured. Without an observer, there is no result. There is nothing. Light is a carrier of energy and information. It is observed and measured by whatever it falls on, whether that be an intelligent observer or simply a rock absorbing the light. In both cases energy is transferred within a closed system and conservation of energy is maintained. I can't help but wonder what happens to light shining outwards at the edge of our universe where even space-time doesn't yet exist. would our universe leak energy through a light beam that had nothing to transfer its energy to, or not? It's a question I doubt anyone could answer with confidence.

 

[exchemist]

Ok, but you can't deny that the evidence so far strongly suggests that the observer plays a critical role in the outcome of how something is measured. Without an observer, there is no result. There is nothing. Light is a carrier of energy and information. It is observed and measured by whatever it falls on, whether that be an intelligent observer or simply a rock absorbing the light. In both cases energy is transferred within a closed system and conservation of energy is maintained. I can't help but wonder what happens to light shining outwards at the edge of our universe where even space-time doesn't yet exist. would our universe leak energy through a light beam that had nothing to transfer its energy to, or not? It's a question I doubt anyone could answer with confidence.

I'ave already told you at least once there is NO EDGE to the universe. There is no way to get a light beam to go out of the universe to somewhere else. IT IS IMPOSSIBLE.

That being so there is NO PROBLEM. And I say that with confidence.

 

[dav57]

"There is no way to get a light beam to go out of the universe to somewhere else. IT IS IMPOSSIBLE."

In other words, every ray of light requires an observer or receiver otherwise it aint going anywhere. You just said so yourself.

 

[dav57]

Also, entangled particles exhibit principles of conservation of energy, even at a distance, and instantaneously too. Change one entangled particle and the other changes instantaneously, only because of conservation.

Is that a potential snippet of evidence that source and observer are somehow already connected prior to the release of energy from source to observer?

 

[Russ_Watters]

...genning up on and preaching your textbook physics.

This isn't just wrong, it's idiotic. "Textbook physics" *is* physics. What you are doing is ignorance and crackpot religion based idle speculation. Being wrong is one thing, but jeez, you're wronger than wrong. You're so wrong you don't even know what just being wrong looks like! If you improved your attitude greatly and started to learn just how wrong you are, you'd be considerably less wrong just for the understanding of how wrong you are.

I can't help but wonder what happens to light shining outwards at the edge of our universe where even space-time doesn't yet exist. would our universe leak energy through a light beam that had nothing to transfer its energy to, or not? It's a question I doubt anyone could answer with confidence.

I can confidently say the answer is simple: there is no edge to the universe, so the rest of the statement is gibberish. Again, it's wrong squared.

In other words, every ray of light requires an observer or receiver otherwise it aint going anywhere. You just said so yourself.

Still wrong and now you're purposely misconstruing other people's statements to try to twist them into agreement with you. That's trolling in addition to being ridiculously wrong.

 

[dav57]

So, Russ, what does YOUR explanation look like with regards to the mysteries of light?

 

[OnlyMe]

"There is no way to get a light beam to go out of the universe to somewhere else. IT IS IMPOSSIBLE."

In other words, every ray of light requires an observer or receiver otherwise it aint going anywhere. You just said so yourself.

No it only means that the universe expands with any redistribution of matter or energy. In this case light.

IF THERE WERE AND EDGE OF THE UNIVERSE

And

IF LIGHT TRAVELED OUTWARD FROM THAT EDGE.

The universe would be expanding with the passage of those photons. It creates no different issue for energy conservation than current expanding universe theories. And neither violates conservation laws.

 

[dav57]

Entangled particles connected over vast distances undergo mysterious, instantaneous change due to conservation laws. There appears to be no connection.

Why do you resist the same could apply (perhaps in a slightly different guise) to light source and observer? Why completely dismiss the fact that light could carry information/energy and follow conservation rules within a closed universe.