Is light an electromagnetic wave?

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Is light an electromagnetic wave?

Postby Odal on October 18th, 2017, 6:46 am 

I am not going to comment on this model, but isn't the concept of a light wave going on indefinitely also a form of perpetual motion?
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Re: Is light/EM a form of perpetual motion?

Postby Braininvat on October 18th, 2017, 10:19 am 

A photon, while propagating, does not do work. Look up the concept of "work" as it used in physics. This work is the basis of a PM machine.
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Re: I thought perpetual motion and perpetual energy was a my

Postby Odal on October 18th, 2017, 10:24 am 

Braininvat » Wed Oct 18, 2017 6:19 am wrote:A photon, while propagating, does not do work. Look up the concept of "work" as it used in physics. This work is the basis of a PM machine.



A photon creates a chemical reaction in my eye, making me see things. Isn't that work?
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Re: I thought perpetual motion and perpetual energy was a my

Postby Braininvat on October 18th, 2017, 12:11 pm 

You were referring to a "light wave going on indefinitely." That is not what a photon being absorbed by retinal pigments is doing. It is being absorbed. It shifts the molecular structure of an eye pigment.
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Re: I thought perpetual motion and perpetual energy was a my

Postby Odal on October 18th, 2017, 12:21 pm 

Braininvat » October 18th, 2017, 3:19 pm wrote:A photon, while propagating, does not do work. Look up the concept of "work" as it used in physics. This work is the basis of a PM machine.


I see your point.
So, a magnetic wave creating an electric field... is not seen as work?
According to the Oersted experiment, the electric field will move a compass needle.
So, along the way, the wave will create work, or at least has the potential of creating work.
Would placing magnetic needles along a beam have an effect on its total energy?

I realize I have jumped again from one phenomenon to the other: from a beam of light to an electric current. They are of course all e.m waves, but I have no idea whether what I said really makes sense.
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Re: Is light/EM a form of perpetual motion?

Postby zetreque on October 18th, 2017, 10:42 pm 

Odal » Wed Oct 18, 2017 8:21 am wrote:
Braininvat » October 18th, 2017, 3:19 pm wrote:A photon, while propagating, does not do work. Look up the concept of "work" as it used in physics. This work is the basis of a PM machine.


I see your point.
So, a magnetic wave creating an electric field... is not seen as work?
According to the Oersted experiment, the electric field will move a compass needle.
So, along the way, the wave will create work, or at least has the potential of creating work.
Would placing magnetic needles along a beam have an effect on its total energy?

I realize I have jumped again from one phenomenon to the other: from a beam of light to an electric current. They are of course all e.m waves, but I have no idea whether what I said really makes sense.


To place the magnetic needle along a beam you are performing work. You also perform work to turn on an electric field and that electric field and current is losing heat energy.
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Re: Is light/EM a form of perpetual motion?

Postby Odal on October 19th, 2017, 6:26 am 

What I am trying to understand is how a light wave can go on indefinitely.
The discussion then shifted to the concept of work.
Let us say I am in empty space and turn a flash light on for a few moments. The (invisible) light beam will then go on indefinitely until it encounters an obstacle?
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Re: Is light/EM a form of perpetual motion?

Postby BurtJordaan on October 19th, 2017, 7:35 am 

If something emits an electron in otherwise totally empty space, it will also travel indefinitely. Light consist of massless photons and have even more reason the travel indefinably. If we view it in a cosmological sense, it is a little more complicated, where light can, but electrons can't travel indefinitely.
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Re: Is light/EM a form of perpetual motion?

Postby Odal on October 19th, 2017, 8:38 am 

Let us say we use femtography methods to register the path of a pulse in empty space. You are saying that we should be able to get a picture of the pulse somewhere along the path, after the pulse has been generated?

Allow me to clarify. A pulse is emitted that lasts a few nano or picoseconds. Somewhere at a distance, sensors are triggered after the pulse has finished emitting, but before it would reach the sensors.

The sensor should then register the pulse after that pulse had stopped emitting?

That would be a nice empirical experiment if practical at all, wouldn't it?
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Re: Is light/EM a form of perpetual motion?

Postby BurtJordaan on October 20th, 2017, 3:23 am 

Odal » 19 Oct 2017, 14:38 wrote:Let us say we use femtography methods to register the path of a pulse in empty space. You are saying that we should be able to get a picture of the pulse somewhere along the path, after the pulse has been generated?

No, in empty space, femtography is not going to help you, because there is by definition nothing to scatter some photons towards your camera.

However, if you set up a number of cameras with properly aligned partly-silvered mirrors along the projected path of the light pulse, you can in principle record the path at any number of points you like. But what will be the purpose of such an expensive experiment?
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Re: Is light/EM a form of perpetual motion?

Postby Odal on October 20th, 2017, 6:03 am 

I was still not clear enough.
I am not interested in the path of the beam, but in its arrival.
I know that it seems evident that the pulse will reach the sensors even after the laser has stopped emitting. But I will remind you that it is only an assumption that has never been empirically confirmed.

So, once again, the pulse is emitted, and the sensor which is supposed to register the arrival of the pulse is triggered only after the pulse has stopped emitting.
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Re: Is light/EM a form of perpetual motion?

Postby BurtJordaan on October 20th, 2017, 7:14 am 

Every time a radar measures a distance, the return pulse arrives well after the transmitted pulse is completed. The Apollo laser ranging of the moon finds the return pulse arriving well over two seconds after the pulse has stopped emitting. If your issue is one-way tests, every time the speed of light is measured in space or on earth, the same thing happens.

Do you need more evidence?
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Re: Is light/EM a form of perpetual motion?

Postby Odal on October 20th, 2017, 7:31 am 

BurtJordaan » October 20th, 2017, 12:14 pm wrote:Every time a radar measures a distance, the return pulse arrives well after the transmitted pulse is completed. The Apollo laser ranging of the moon finds the return pulse arriving well over two seconds after the pulse has stopped emitting. If your issue is one-way tests, every time the speed of light is measured in space or on earth, the same thing happens.

Do you need more evidence?


Yes. I do not doubt that something, let us call it e.m waves keeps going on.
I am not sure the light we see when the pulse is emitted would survive after the pulse has stopped emitting.

Remember Hertz's experiments with e.m waves and sparks? There was one spark at the emitting coil, and then another at the receiving coil. I do not understand this as the spark traveling through space.
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Re: Is light/EM a form of perpetual motion?

Postby BurtJordaan on October 20th, 2017, 11:24 am 

Odal » 20 Oct 2017, 13:31 wrote:Yes. I do not doubt that something, let us call it e.m waves keeps going on.
I am not sure the light we see when the pulse is emitted would survive after the pulse has stopped emitting.

Remember Hertz's experiments with e.m waves and sparks? There was one spark at the emitting coil, and then another at the receiving coil. I do not understand this as the spark traveling through space.

Sparks are electrons/ions traveling through the air (i.e. electrical current). The accelerated particles then radiate e.m. waves that travel until they hit something that absorb them. That something can be at the edge of the observable universe.

I still do not understand your issue with light. Sparks emit light and other e.m. waves - they are not light themselves.
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Re: Is light/EM a form of perpetual motion?

Postby Odal on October 20th, 2017, 11:57 am 

BurtJordaan » October 20th, 2017, 4:24 pm wrote:
Odal » 20 Oct 2017, 13:31 wrote:
I still do not understand your issue with light. Sparks emit light and other e.m. waves - they are not light themselves.


Sparks emit light. That is why we can see them, like we see any other object that emits light. Even if it also can be said that it is not light.
I do not know how you understand light. all I know is that when we can see something it is because light is somehow involved.

Back to the experiment:
1) the pulse starts emitting
2) there is light coming out of the laser mouth which holds a piece of glass or mirror.
3) the pulse stops emitting
4) the sensors somewhere at a distance of the laser, but in the path of its possible beams, are turned on.

The question now is: would the sensors register the light created by the pulse after it has stopped emitting.

It is of course possible that the sensors react to the e.m wave reaching them and register the reaction as light.

For that we need to look more closely at Hertz' experiment.

We need sensors placed beyond both coils, and triggered after the first spark has crossed the gap.
Will the sensors register two sparks, or only the second one created by the second coil?

If they register two sparks, as we would if we were standing at the place of the camera, then that would definitely mean that the light emitted by the first spark traveled through space even after the spark ceased to exist.
Otherwise, we would have a very strong indication that the light emitted by the spark is only visible as long as the spark is active.
We can still assume that em waves will travel to the second coil and create a new spark.
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Re: Is light/EM a form of perpetual motion?

Postby zetreque on October 20th, 2017, 12:53 pm 

I'm a little bit confused too about what Odal is asking.

Does talking about the speed of light help?
Say there is a supernova 100 light years away. We won't see the flash and then cessation of the light until 100 years later.

Say you are looking at a light bulb in your room and someone waves their hand in front of it back and forth. The light is blocked momentarily causing you to see pulses. It's such a short distance though that the pulses or interruption in the light are huge.
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Re: Is light/EM a form of perpetual motion?

Postby zetreque on October 20th, 2017, 1:14 pm 

Odal » Fri Oct 20, 2017 7:57 am wrote:4) the sensors somewhere at a distance of the laser, but in the path of its possible beams, are turned on.


Would you be able to reword this step?
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Re: Is light/EM a form of perpetual motion?

Postby Odal on October 20th, 2017, 1:19 pm 

zetreque » October 20th, 2017, 6:14 pm wrote:
Odal » Fri Oct 20, 2017 7:57 am wrote:4) the sensors somewhere at a distance of the laser, but in the path of its possible beams, are turned on.


Would you be able to reword this step?


http://web.media.mit.edu/~raskar/trillionfps/

Imagine that the camera, or cameras, are not standing on the side, looking at the pulse as it progresses horizontally through the scene, but are located at the end of the path of the pulse.
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Re: Is light/EM a form of perpetual motion?

Postby zetreque on October 20th, 2017, 1:27 pm 

4) the sensors somewhere at a distance of the laser, but in the path of its possible beams, are turned on.

That sentence is incomprehensible to me. Are you saying there are sensors at the end of the beam at a distance?
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Re: Is light/EM a form of perpetual motion?

Postby Odal on October 20th, 2017, 1:31 pm 

zetreque » October 20th, 2017, 6:27 pm wrote:4) the sensors somewhere at a distance of the laser, but in the path of its possible beams, are turned on.

That sentence is incomprehensible to me. Are you saying there are sensors at the end of the beam at a distance?


Yes. What is so difficult about it? Once again, it is an extrapolation of the femtography experiments. Instead of filming the progress of the beam/pulse from the side, we film it from the opposite end to where it starts, from there where it will end up. I really do not understand what's so difficult to understand about this point.
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Re: Is light/EM a form of perpetual motion?

Postby Odal on October 21st, 2017, 1:23 pm 

Does this silence mean that you both have run out of arguments? Or simply that you are taking the weekend of?
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Re: Is light/EM a form of perpetual motion?

Postby zetreque on October 21st, 2017, 1:31 pm 

Yes. What is so difficult about it?


Well a good start would be comprehendable sentences, but I am waiting for more comments before commenting.

Light as a particle and a wave... When you move your hand over the beam of light between source and sensor it interrupts the stream of particles/waves as they travel at the speed of light.

I assume when light is absorbed and radiated via the change in electron orbitals the entropy of the universe increases therefore there is no perpetual motion.
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Re: Is light/EM a form of perpetual motion?

Postby Odal on October 21st, 2017, 2:09 pm 

zetreque » October 21st, 2017, 6:31 pm wrote:
Yes. What is so difficult about it?


When you move your hand over the beam of light between source and sensor it interrupts the stream of particles/waves as they travel at the speed of light.


The question is: what would be registered if the sensors were each time triggered after the pulse, and before the wave would reach them?

I understand you might find it difficult to understand the setting since the answer seems so obvious to you. But, although there are many reasons to consider the dual nature of light as a valid theory, there is not a single empirical proof of it.

If, using the femtography methods, we could devise an experiment that would prove beyond any doubt, that light itself, and not only electromagnetic waves in general, needs time to travel through space, that light indeed travels through space, then we would have finally an empirical proof.

let me remind you that it can be considered as being beyond any doubt that em waves, for example. radio waves, need time to cross a distance.

However, as far as light is concerned, contemporary science believes that light is an em wave, but has been, until now, unable to prove it.

It is certainly a very strong assumption, and the belief is far from irrational, but it is still only a belief.

It is still possible that em waves create light phenomena at the start and the end, without that light itself has to travel through space.

My proposal for such an experiment is to prove (or disprove) the fact that light is not a side effect, an epiphenomenon as it were.
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Re: Is light/EM a form of perpetual motion?

Postby zetreque on October 21st, 2017, 2:15 pm 

What about fiber optics communication?
Doesn't it send pulses of light and has a sensor on the other end?
If a sensor detected light as instantaneous, then that would not work.
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Re: Is light/EM a form of perpetual motion?

Postby Odal on October 21st, 2017, 2:17 pm 

zetreque » October 21st, 2017, 7:15 pm wrote:What about fiber optics communication?
Doesn't it send pulses of light and has a sensor on the other end?
If a sensor detected light as instantaneous, then that would not work.


That is a circular argument. We are talking about an electric current that creates light effects in its path. The light effects can never precede the cause.
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Re: Is light/EM a form of perpetual motion?

Postby Odal on October 21st, 2017, 2:20 pm 

Odal » October 21st, 2017, 7:17 pm wrote:
zetreque » October 21st, 2017, 7:15 pm wrote:What about fiber optics communication?
Doesn't it send pulses of light and has a sensor on the other end?
If a sensor detected light as instantaneous, then that would not work.


That is a circular argument. We are talking about an electric current that creates light effects in its path. The light effects can never precede the cause.


May I remind you that nowhere am I claiming that the sensors would detect light instantaneously. On the contrary:

1) The sensors detect the pulse after it has stopped emitting, because the pulse needs time to reach the sensors.
2) the sensor does not detect the pulse because it has stopped emitting.
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Re: Is light/EM a form of perpetual motion?

Postby zetreque on October 21st, 2017, 2:21 pm 

Odal » Sat Oct 21, 2017 10:17 am wrote:
zetreque » October 21st, 2017, 7:15 pm wrote:What about fiber optics communication?
Doesn't it send pulses of light and has a sensor on the other end?
If a sensor detected light as instantaneous, then that would not work.


That is a circular argument. We are talking about an electric current that creates light effects in its path. The light effects can never precede the cause.


It might help to put some definitions to your question. You are now talking about the conversion of one form to another. Not light independently.
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Re: Is light/EM a form of perpetual motion?

Postby Odal on October 21st, 2017, 2:23 pm 

It might help to put some definitions to your question. You are now talking about the conversion of one form to another. Not light independently.


I am posing the question whether light should be considered as an em wave, and whether we can answer this question empirically.
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Re: Is light/EM a form of perpetual motion?

Postby zetreque on October 21st, 2017, 2:30 pm 

Odal » Sat Oct 21, 2017 10:23 am wrote:
It might help to put some definitions to your question. You are now talking about the conversion of one form to another. Not light independently.


I am posing the question whether light should be considered as an em wave, and whether we can answer this question empirically.


Electrons changing orbitals produce a photon.

Electrons are electricity. Photons are light.
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Re: Is light/EM a form of perpetual motion?

Postby Odal on October 21st, 2017, 2:40 pm 

zetreque » October 21st, 2017, 7:30 pm wrote:
Electrons changing orbitals produce a photon.

Electronics are electricity. Photons are light.


I am not discussing Quantic Optics, but simply what we, humans and biological creatures in general, experience as light.
Back to Hertz: a spark is created. We see the spark, whatever the theory says on electrons and photons.
Then we see another spark. Is it the same spark, or is the same effect?
I think that is quite important.
So, when a pulse stops emitting, and the sensor still registers it, then we could say that our sensation of light has one and the same cause. With the naked eye we experience it as instantaneous, with very fast cameras we see that in fact it takes time for the visual sensation to be created in our brain.

But what if nothing is registered once the pulse has stopped emitting?

That sounds very improbable, if not implausible, but proving it would nevertheless mean progress in our knowledge.
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