At what point does an RF photon change to DC?

[Beamin]

Since RF is a photon and DC is bumping of electrons what happens at the transition at really low frequencies? If you have something at 1hz its a photon with very long wave length but what happens at 0.1hz? 0.00001hz? or one cycle for 13.8 billion years? Technically its not DC and therefore must be a photon?

[IanB]

You ask some really strange questions. You said: "Since RF is a photon and DC is bumping of electrons" -- but since this statement is inaccurate, the rest of the question really doesn't follow.

[Beamin]

You ask some really strange questions. You said: "Since RF is a photon and DC is bumping of electrons" -- but since this statement is inaccurate, the rest of the question really doesn't follow.

Its more of a thought experiment. Whats the lowest frequency you can have before it turns into DC? DC is electrons jumping from atom to atom down a wire. Put AC down that same wire and those jumping electrons start to give off photons. DC doesn't give off photons. So where is the transition? One the other end the highest you can oscillate a photon would be one plank length very high energy gamma rays that would probably have other properties at that energy. .

[IanB]

DC doesn't give off photons.

What about the filament of an incandescent light bulb?

[Doc Daneeka]

Our 'laws' for electricity eg at DC are just one model for what's happening. Models have a range of conditions where they are valid and elsewhere they aren't. You're kind of asking where does the model of electromagnetism as photons stop being valid and our DC model valid? It's not clear cut though. You can always model even ideal DC as photons if you take into account every electron - when they 'bump' into eachother they have a 'force' on each other by exchanging photons.

Don't take models literally, and also don't try to make models from analogy!

Our models of photons are accurate everywhere all the time (as far as we know so far). Our model for DC is only accurate when we think of current as a current density etc (not even considering individual electrons - we imagine current density as the averge result of a huge number of drifing electrons but beyond that we have noting to say about it - thats where the analogy breaks down)

It's not as if one model stops and another starts - one is a refinement of the other

[Beamin]

DC doesn't give off photons.

What about the filament of an incandescent light bulb?

That would be black body radiation from heat. So not generated by oscillations of AC current flowing and giving off " EMF waves". 

[helius]

All electrical and magnetic phenomena involve the action of photons, as they are the force carriers of the electric field. The radiation emitted from a bulb and from a long-wave antenna are the same: the only difference is that the photons from the light bulb have greater momentum, as it is proportional to their wave frequency. The current oscillations are still causing their emission in the light bulb, but instead of a radio-frequency, they oscillate at hundreds of terahertz—not from the input voltage, but from thermal motion.

Another way of answering is to pose a different question: at what point does an RF photon become light? And the answer is that there is a transitional band of energy with properties of both radio and light, called millimeter waves. At the low-frequency end, 0 Hz is a limit that photons can approach but never quite reach, as they would, by the Planck-Einstein relation, have zero energy, which is not allowed. The slogan of ultra-wide-band techniques, "DC To Daylight", must be understood as having DC as an exclusive, not inclusive, lower bound.

[T3sl4co1l]

Wave-particle fallacy.

A photon cannot have zero frequency; it would have zero energy and therefore would not exist.

But zero frequency can only exist for all time.

The known universe has only existed for a few attohertz.

There is no such thing as strictly zero-Hz DC.

No, DC is a convention, referring to the lowest frequencies in a circuit, usually the frequency band that's applying device bias.  Often, this band is exclusive of the AC signal, which lies in the middle (pass) band.  But often they overlap, as you can have DC coupled amplifiers which are therefore biased with overlapping ("DC") frequencies.



Tim

[Brumby]

Our 'laws' for electricity eg at DC are just one model for what's happening. Models have a range of conditions where they are valid and elsewhere they aren't.

This is the closest anyone has come (in my mind) to addressing the fundamental issue of the question.

You're kind of asking where does the model of electromagnetism as photons stop being valid and our DC model valid?

I wouldn't say "kind of".  I would say that it is exactly what is being asked.

To take this question further, I would be travelling down a path that heads towards quantum mechanics and field theory.  If we then consider that what we call a photon is actually a localised disturbance in the electric and magnetic fields, then the limitations of the macro models that we use everyday become more apparent.

[Brumby]

The definition of "DC" is also something to look at.

If my computer is on 12 hours a day and off 12 hours a day - is the 12V rail (1) DC .... or (2) a sorry looking AC square wave with 6V offset and a frequency of 11.574µHz ?

[tom66]

The definition of "DC" is also something to look at.

If my computer is on 12 hours a day and off 12 hours a day - is the 12V rail (1) DC .... or (2) a sorry looking AC square wave with 6V offset and a frequency of 11.574µHz ?

It's a sorry looking square wave but we round that down to DC for most practical purposes.

I think when you start describing the on time of a square wave in seconds then frequency is not a useful measurement any more.  I would also describe it as DC that changes slowly, even though that's a contradiction.

[T3sl4co1l]

This is exactly why "DC" is contextual.  A seismic wave filter might be quite low frequency, whereas an RF amp might call 100s of MHz "DC".

Tim

[EEVblog]

Our model for DC is only accurate when we think of current as a current density etc (not even considering individual electrons - we imagine current density as the averge result of a huge number of drifing electrons but beyond that we have noting to say about it - thats where the analogy breaks down)

You could also view it as the lowest "AC" frequencies are just slight variations in that average result.

[Vtile]

DC is iquilibrium state. Every time you turn imaginary switch or disturb the equilibrium with outside force (ie. by moving the object in earth magnetic field or keeping it in place, but moon disturbs the magnetic equilibrium) or any other form be it hard or soft turn on or off the equilibrium is lost for x amount of time as you introduce a transition state of dV/dt or dI/dt. We also do consider that in this non-equilibrium state it is possible to have DC where energy is constant, moving in one direction and superimposed AC state mixed to it (AC or transition is working against and/or with the direction of steady energy flow). That kind of situation is ie. rectified sinewave that many times is described as pulsating or variable direct current. In reality the equilibrium is constantly disturbed, but in such a small scale that only physicist (or voltnuts) will worry about it

Also to be noted that frequenzy is independent from amplitude.

... Just kind of opening a bit of the swamp of terminology. Not trying to go to particle physics.

[Z80]

Your original question is a little poorly worded, but I think you are asking what is the lowest frequency electromagnetic wave is it possible to have which is an interesting question!  Well as said already not zero, so how low can you go in photon energy?  Unfortunately I'm not a nobel prize winning physicist, but a quick web search would suggest that there is no lower limit to photon energy emitted by a free electron, so infinitely low (but not zero) would be my guess.

[Vtile]

Interesting indeed. Also might be good to remember that all our units which we use to describe your surroundings are artificial, but scientifically agreed statics for now. In a few hundred years ago we still described the world with different kind of elements air and fire etc. and that were the scientific truth then. No one can guarantee that there will not be any further revolutions in those, when our general knowledge and understanding evolves. Scientific truth is per se only a social norm that also happens to allow predictions with that socially accepted norm.

edit. sorry I'm distracting  this to somewhere at direction of philosophy.

[Kleinstein]

Using the photon picture is implying a quantum mechanical view. Using the more like DC and also classical RF description is using classical electrodynamics.  AFAIK classical electrodynamics is compatible with quantum mechanics. So the classical electrodynamics is just a good approximation, that usually works well at low frequencies and allows for a much easier calculation. QM is supposed to be more accurate, but the math is so complicated that it is not really practical in many cases and would thus need approximate calculations. Classical theories can be seen as such approximations, though they are historically older.

However there can be exotic cases where even rather low frequency EM field should be treated in a QM way. One such example is "zero" field NMR - here a proton interacts with the earths magnetic field at radio frequencies in the low kHz range.

[Yansi]

The question should be: And when does the photon turn into photonicinduction?   

[hermit]

When the energy level drops below what is required to keep it at the speed of light.

Yes I made that up, but I like it and I'm sticking to it.   

Code: [Select]

      e? +  e+ ? ? +  ?


 

[CopperCone]

What is the lowest energy photon in free space?

During the transition from the hot compressed universe to a more relaxed one, what happened when the first large photons began to form? Are they on the edge of the boundaries of the universe? I.e. they gotta be old due to the lack of large radiators in the contemporary  universe compared to what could have been during the denser state.

A upper bound on wavelength might be the comparable to the dimensions of the universe by a few orders of magnitude?

During the hot dense phase, was there metastable low frequency radiators present ?

What are the largest ELF radiators present in the current universe?

Or is it the opposite, with almost no ELF forming in the early stages due to extreme temperature? I thought maybe as it cooled you might have some kind of massive lighting strikes inside of it.

[helius]

The photons emitted when the universe cooled from a plasma to its present state are what is called the microwave background. They are everywhere in the universe, not "on the edge", because the universe has no boundary. As light-speed particles, photons do not age: none are "older" than any others, although they may have traveled a long distance, emitted far in the past.

Electromagnetic waves do have a minimum frequency: inherent oscillations of the electrons in a plasma block lower-frequency waves from propagating. This is the reason that low frequency radiation cannot be detected from the Earth's surface, as the ionosphere oscillates at around 10 MHz. There is also plasma in the interstellar medium, which is much less dense. It oscillates at around 300 Hz: ELF waves below this frequency cannot travel far through the universe.

[CopperCone]

oh, so because the early universe in some duration was plasma, we can rule out it making ELF? I figured CMBR had a bell curve distribution focused around the microwave spectrum.

are there any cosmic sources of ELF? have any measurements been made?

[T3sl4co1l]

Try more basic, more conceptual, than that:

For a ~DC photon to be a reasonable concept, there must be a persistent bias or structure in the universe giving rise to it, for the better part of the age of the universe.

It also must be, not just that there was a source in the past, and will be a sink arbitrarily in the future, but that it's still present and ongoing, or at least was very recently (~billions of years).

Such a field could manifest as an electromagnetic bias in the universe.  It could be as basic as the cosmological constant, or dark energy: a pressure that permeates space, not really interacting with anything directly, but indirectly through its energy density, its effect on spacetime curvature.

That does assume some sort of origin for such a phenomenon, like charge imbalance.  Which is exceedingly unlikely to be the case (all observations point to a damned neutral universe).

But again, wave-particle fallacy.

The photon particle is just the quantized manifestation of the EM field.  It is the Fourier transform (frequency domain) representation of the transient waveform.  The definition of the FT is frequencies (sine waves) that exist for all times.  There is nothing necessarily causal or realistic about frequency domain, it's just another tool we use to work with these sorts of problems.  (And, as it turns out, most physical processes exhibit some sort of frequency dependency, or explicit frequency levels -- energy levels -- as a result of quantization.  So it is a very useful tool indeed!)

Speaking about frequencies over time is tricky at best.  It's much better to fall back to a transient model in that case.  The Schroedinger equation is just a differential equation, meaning, for given boundary conditions, it has some sort of solution; and if the boundary conditions are suitable, then that solution has quantized energy levels, and therefore frequencies and wavelengths.  You don't need to solve it in this way.  You can solve it the same as any other difference equation, like SPICE does: by integrating a small timestep at a time.  On the upside, you can solve for chaotic and non-analytic* conditions: you just keep on stepping, until you divide by zero or something!

*Though, they might be divergent, and attempts to make those divergent forms converge, may not be physically realistic.  (Or maybe they'll be too realistic**.)  Note that chaotic behavior is bounded, like a sine wave, and tends to be cyclical, but, the cycle rate is unbounded, so it cannot be analyzed with a mere Fourier transform.

**QED is solved analytically (and at a deeper level, not for given boundary conditions), so it's not by analogy with a transient solution.  But it does encounter infinite divergent sums.  These can be forced through (the series of partial sums diverges, but the infinite series can still be assigned a finite value, using renormalization), with the result being the most accurate physical theory we know to date.  So, that's fun, huh?

So the takeaway point is this: photons are just another conceptual tool, like the FT.  They are not a useful tool at very low frequencies.  They're not inapplicable, but trying to force meaning from such a view is a stretch at best.  One must always keep in mind that the physical laws must be consistent.  If classical E&M suffices to explain an observed field, then one gains little insight from repeating the same exercise in a higher (quantum) domain.

Tim

[Beamin]

Try more basic, more conceptual, than that:

For a ~DC photon to be a reasonable concept, there must be a persistent bias or structure in the universe giving rise to it, for the better part of the age of the universe.

It also must be, not just that there was a source in the past, and will be a sink arbitrarily in the future, but that it's still present and ongoing, or at least was very recently (~billions of years).

Such a field could manifest as an electromagnetic bias in the universe.  It could be as basic as the cosmological constant, or dark energy: a pressure that permeates space, not really interacting with anything directly, but indirectly through its energy density, its effect on spacetime curvature.

That does assume some sort of origin for such a phenomenon, like charge imbalance.  Which is exceedingly unlikely to be the case (all observations point to a damned neutral universe).

But again, wave-particle fallacy.

The photon particle is just the quantized manifestation of the EM field.  It is the Fourier transform (frequency domain) representation of the transient waveform.  The definition of the FT is frequencies (sine waves) that exist for all times.  There is nothing necessarily causal or realistic about frequency domain, it's just another tool we use to work with these sorts of problems.  (And, as it turns out, most physical processes exhibit some sort of frequency dependency, or explicit frequency levels -- energy levels -- as a result of quantization.  So it is a very useful tool indeed!)

Speaking about frequencies over time is tricky at best.  It's much better to fall back to a transient model in that case.  The Schroedinger equation is just a differential equation, meaning, for given boundary conditions, it has some sort of solution; and if the boundary conditions are suitable, then that solution has quantized energy levels, and therefore frequencies and wavelengths.  You don't need to solve it in this way.  You can solve it the same as any other difference equation, like SPICE does: by integrating a small timestep at a time.  On the upside, you can solve for chaotic and non-analytic* conditions: you just keep on stepping, until you divide by zero or something!

*Though, they might be divergent, and attempts to make those divergent forms converge, may not be physically realistic.  (Or maybe they'll be too realistic**.)  Note that chaotic behavior is bounded, like a sine wave, and tends to be cyclical, but, the cycle rate is unbounded, so it cannot be analyzed with a mere Fourier transform.

**QED is solved analytically (and at a deeper level, not for given boundary conditions), so it's not by analogy with a transient solution.  But it does encounter infinite divergent sums.  These can be forced through (the series of partial sums diverges, but the infinite series can still be assigned a finite value, using renormalization), with the result being the most accurate physical theory we know to date.  So, that's fun, huh?

So the takeaway point is this: photons are just another conceptual tool, like the FT.  They are not a useful tool at very low frequencies.  They're not inapplicable, but trying to force meaning from such a view is a stretch at best.  One must always keep in mind that the physical laws must be consistent.  If classical E&M suffices to explain an observed field, then one gains little insight from repeating the same exercise in a higher (quantum) domain.

Tim

I see where you are coming from but in my question the photon is a real wave/particle "thing" moving at the speed of light with a certain energy/wavelength and existing for some time (our time since it doesn't experience time). So when we slow the oscillation down to 1Hz a photon(s) is (are) given off. When we slow down to once an hour are there photons continually given off like a beam of photons? Or do the photons only manifest the instance the polarity switches? Also if the Hz is low enough how would the photons know they are really slow AC and to be given off? Like you have a 0.0000001Hz wave and you decide to shut off the experiment before the first oscillation then its just DC. So are the photons given off when it switches? How does the first photon of the first cycle know what wavelength to oscillate at? It can't just be some arbitrary wavelength it has to be 300,000,000,000,000 meters long (I might be off by a few zeros). But the second oscillation hasn't happened and may never happen. My brain experiment is breaking down without more knowledge about photon emission.   

[Brumby]

The point being made is that considering a photon to be a real "thing", discrete and self-contained, becomes a problem when you start stepping into the territory that you are trying to explore.

The concept of a photon as we commonly understand it is a useful tool that works pretty well in the day-to-day world.  It is, essentially, a "macroscopic" equivalent that allows for handling the phenomenon in practical situations, a fact further enhanced by some maths that support and describe related interactions.

What this concept does not do well is explain the actual physical mechanism involved.  The best explanation that I have encountered is the one I mentioned before - that a photon is a localised disturbance in the E&M fields.

I found this graphic - which shows how I visualise this (Yes, it's only a 2D "field".  It's not showing both the Electric and Magnetic components and the progress does show signs of dispersion.  It's not perfect, but it's the best I've found so far, OK?)


I equate the wavelength of the photon to the width of the disturbance (wave).  If you follow this down the path of longer and longer wavelengths, you will end up with very broad changes that seem almost smooth - but there is no true transition, no discrete change that can be pointed to.  This model allows for the frequency to get infinitely lower - and we can get to the point of asking ... well, what is DC?  This question has already been addressed, so I won't go into that again - but in terms of the above graphic, DC could be seen as the level of the field being raised across a broad region.

Now, this level may go up or down in time - but if it does, it's not going to do it across the entire field at the same time (remember, this field extends through the entire universe), so there will be some "localised" nature in those changes (even if that "locality" is the size of a planet).  Here we start getting back into the photon mindset - but, again, there is no hard and fast definition as to when this "change" occurs.


The best answer I can give to the original question is that the only way to provide any sort of an answer is to define an arbitrary point where the change occurs.

There are two major problems with doing that, though.  The first is that there will never be universal consensus on where that line should be drawn.  There is no physics which makes for a natural point of differentiation.

The second is - that such a differentiation does not reflect any real distinction between what physically happens on one side of any such line and what happens on the other.  Since this is the direction I felt was coming from your question, then all I can say is ... there is no answer - other than an arbitrary one.

[BrianHG]

Wouldn't a 0hz photon source just be a stationary magnet?

Damn, a stationary non-spinning Magnitar would be some bloody hell of a purely true all powerful 0hz photon source.

If you were to spin a magnet at 60 RPM would it not give you a 1 Hz signal?
If it does, then wouldn't slowing the magnet down to stationary create that actual DC photon?
Would this also mean that all stationary magnets in the universe, (I know nothing is truly stationary due to the expansion of space, motion of galaxies and ect) that we have something that many example material in the universe giving off what looks like a 0hz, or DC photon source?

I guess what I am trying to get at is an RF photon change to DC once it is a stationary magnetic source...

[T3sl4co1l]

I see where you are coming from but in my question the photon is a real wave/particle "thing" moving at the speed of light with a certain energy/wavelength and existing for some time (our time since it doesn't experience time). So when we slow the oscillation down to 1Hz a photon(s) is (are) given off. When we slow down to once an hour are there photons continually given off like a beam of photons?

Oh, hell yah.

Like, unimaginable numbers of photons.

When you flip a light switch, that's on the order of 10^20 photons per second.  With frequencies around ~5 x 10^14 Hz.

A 100W power amplifier at 1Hz is presumably ferrying around a quantity of photons in the 10^34 range, per second.

Physicists are happy to convert a summation into an integral when it's just billions of particles.  10^34?  That might as well be infinite.  Oh yah.  It's very "continuous", as a physicist might say.

More important is that there's no useful concept of photons confined within wires.  Photons are about propagating modes in free space.  Photons interacting with condensed matter is extremely complex.  Photons interact with pretty much every particle and quasiparticle (phonons, because electron-phonon and photon-phonon scattering are things) in that solid.  Casually tack on another 10^30 interactions in the course of the process!

To even conceive of photons propagating in space, interacting with the vacuum only, one needs free space in which to propagate -- and a ~1Hz/1s wavelet cannot be reasonably said to be "free" until it has light-seconds of free space to do so.  That's a lot of interplanetary medium, or interstellar or intergalactic for that matter.  Perhaps out in the enormous voids between galactic superclusters, a photon of this wavelength could reasonably be considered "free"?  But such environments are, ah, rather inaccessible to science, so it's not a very useful question anymore.

I mention interactions, because the particle model is only useful on the most fundamental level, of single particle interactions.  It's simply not useful in any kind of bulk media.  Again, there's nothing important about the particle model.  The classical wave model captures everything of interest in this situation.

My brain experiment is breaking down without more knowledge about photon emission.

Because you're forcing far too much importance into a model, which is unreasonable to use for the situation.   Embrace the wave, let it wash over you (or through you, as the electromagnetic case may be).

Tim

[MrW0lf]

Glad to see less than religious viewpoints. It is important to understand that there is little to no understanding about inner workings. Only "black box" models that provide basic functionality spec for physics engine
If dig deep enough can find that basic spec is erroneous for tricky situations not handled in "common knowledge".
For example cannot be excluded that magnetic field is imaginary concept and exact same effects can be explained only by complex electric field interactions.
Also in quantum physics some "digital magic" can be explained using complex structures based on classical physics concepts in 3D interactions.
Problem is "complex" part. When theories emerged there was mostly no other computation power available than human brain which led to simplification and "helper concepts".
One simple example: if wind veeeeery long and thin air core solenoid it has solenoidal mag. field only from very close up. If measure from further away it has basically same field that straight wire, but different field propagation velocity. Now if think little about this some ideas may emerge how charges are moving in regular wire. However when take some random pic about "moving charges in a wire" you get funny balls with vectors parallel to wire.
There is no monopoly on truth so anyone in a shed may think & analyze & experiment and emerging theories have no less right to life than "official" ones.

[Zero999]

A photon of zero frequency will either have an electric or magnetic field, not both. Everything in the entire universe will be in the near field region and therefore experience the same, constant electric or magnetic bias.

As energy level goes down, the number of photons per second, for a given amount of power, increases, so it becomes increasingly difficult to count the photons individually. It's much easier to count the photons from a small UV laser, operating at 1000THz, than it is do with an RF transmitter working at 1000Hz.

[A Hellene]

Please, excuse my philosophical tangent but, are we talking about the Aitheric realm?

I am talking about ?? [Aither] (from the verb ? [aitho], meaning to scorch), this 'undetectable' fluid (see the latest theories of 'Dark Energy' / 'Dark Matter' that our eyes and testing equipment cannot seem to be able to be detecting) our universe is immersed into; this strange sea of charges, where the joules our power plants and batteries being send to us propagate into, via the wave-guides we call power cables? It is very well accepted today that the speed of the free electrons in a usual intersection of copper wire of 1.0mm2, for example, is a few centimetres per hour per Ampere... Taking it a step further, it seems to be giving an answer to what really happens around every electrical line carrying electric charges, the 'surface charges' which are tightly connected to electric fields while they should never be confused with the 'skin effect' that is relevant to magnetic fields and appears in cases of (high frequency, mostly) alternating current through a conductor.

Aither was firstly introduced by Plato in Timaeus and was briefly described by Aristotle as the [pempousia] (= ? ??), literally: the fifth element, or, as the Romans later called it, the Quintessence. This very realm was extensively supported later by Nikola Tesla's resonant coil single-wire transmission lines, widely known as they are colloquially being called, the Tesla Coils.

Even that more-than-famous plagiarist, the globally accepted (false-)god of science whose theories have been debunked, used to support the Aitheric realm before he chose to take the other path, along with the Cantorian gang (Georg Cantor, David Hilbert, Felix Klein, Ernst Mach, etc., with their miserably failed 'SetTheory' and the perennially failed 'Distorted Spacetime') that rewrote Physics by ruthlessly obliterating the (two-dimensional / flat space) Euclidean Geometry... Not to mention their same gang mates, Heaviside (that non-Academic tool who detested potentials and stated that they 'should be murdered from the theory'), Gibbs, and Hertz for reducing 12 of Maxwell's 20 equations with 20 variables each to four simple equations with just four variables, that we are taught now as Maxwell's equations even if they are not...


-George


P.S. I am sorry for the unreadable characters, above, but the forum software seems that it still refuses to support Greek language characters...

[MrW0lf]

For me question is aether/physical vacuum/etc a substance or information about state of matter. Quantum teleportation for example is only about information Tx/Rx, so process as such is possible. Things also become interesting if go search for special cases where there are forces on charges but no net magnetic field - on quite macroscopic level. That also hints that there is information in space at location X,Y,Z just like with gravity. Objects know how to behave at specific point in space w/o any detectable delay.

[IanMacdonald]

At any time it feels like it. Look mate, we particles work to Quantum rules, so you humans with your deadlines and schedules can sod off.   

-and don't start about being him a wave either. They're entitled to join the union.

[CatalinaWOW]

While there is no conceptual reason I am aware of to deny very long wavelength, low energy photons there are other reasons that the concept is not very useful.  Scale reasons.  When the energy of a single photon is several orders of magnitude below the thermal noise the ability to actually observe the disturbance totally disappears.  Too bad because it would be interesting to watch the disturbance as something that takes hours to go by at the speed of light passes.

There are also boundary condition problems as the wavelengths approach the scale of the universe.  Just have to play in the much smaller sandbox we can really work with.  Drats, only about 20-30 orders of magnitude to play with.

[Beamin]

I guess my question is:

If you had a very long antenna with thousands of watts into it and a very long receiver antenna that could measure without noise and you turned the two on what would happen?

So you start at 100hz and start turning down the frequency what would you see on the receiver as you got down below 1hz? Would you see a continuous stream of photons (electrons from the antenna flowing into the receiver) or would you just see pulses as the moment the +and- switched back and fourth? How long would this pulse last? This is actually a doable experiment. And I'm sure if it wasn't done mathematical or smaller scale model have revealed the answer. Since 1hz is a long time given the limits of our technology when you shut off the transmitter when exactly does the photon beam stop?

I get what you are saying about how the photon shouldn't be looked at as a "thing" when you get near the limits like how an electron has mass but no size or a virtual particle is not a particle at all but rather a disturbance in it respective field that is out of phase with normal particles and therefore passes through them without consequence instead of amplifying or cancelling the "wave" of the real particle.

[T3sl4co1l]

Would you see a continuous stream of photons (electrons from the antenna flowing into the receiver) or would you just see pulses as the moment the +and- switched back and fourth? How long would this pulse last?

I already answered this: the stream is continuous, on the order of 10^30 / sec.

The photons are all in phase, and have a spectral and spacial extent corresponding to the bandwidth of the transmitter.

This is actually a doable experiment.

You're going completely the wrong way.

It is a doable experiment in the THz, where cryogenically cooled superconducting devices are sensitive enough to resolve quanta, while the frequencies are low enough for classical conductor and dielectric antennas to be useful.

It's even easier at optical frequencies, where quanta are nearly resolvable by eye (the human eye is something like 10-100 times too insensitive / noisy to properly resolve it), and easily measured as shot noise through various devices (photodiodes, PMTs, etc.).

There is most certainly no nonlinearity about the situation.  A beam is coherent, with well defined spacial and spectral extents.  There is no invocation of temporal events here.  Again, it's about frequency, not time.

Only very specific conditions can yield photon bunches that are temporally coherent: lasers are such an example.  Again, these are not harmonic processes, the waveform is always smooth and continuous.  The result is a tone burst or wavelet, which can also be represented as a superposition of frequencies over a range.

It is not meaningful to consider a very precise time event, because the wave is spread out over as much time and distance as its frequency implies.  Heisenberg uncertainty principle.  Which is also identical and equivalent to the duality between temporal and spectral uncertainty with the Fourier transform: the longer duration a wavelet has, the narrower (more precise) its spectrum is, and vice versa.  A sine wave has infinite temporal extent (it neither starts nor stops, at all), and zero bandwidth (perfectly known frequency).

Tim

[Doc Daneeka]

well another thing to think about is what you would see from an arbitrarily low frequency source of photons: as the frequency gets lower the energy in each photon gets lower. if you are transmitting with a constant power then the rate of photons must go up inversely with the frequency. As you turn down the frequency you get more and more photons and it will get harder and harder to tell them apart...

[hermit]

If I follow this correctly, and that is a big IF, this is really semantics used for models.  We have ways of measuring certain things and use these measurements to build models to predict behavior.  Photons travel by wave propagation.  So therefore, it will never be DC by definition.  Well, maybe fluctuating DC?  You can't separate the photon from its mode of propagation as if it were an electron and do a selective measurement at one point and proclaim that you know it's properties from that measurement.  It seems this is what you are trying to do.

I read a long time ago, before the WWW and have never been able to find the source on the web, that scientists were able to coax a single electron through a conductor if it was curved.  ie, wave shaped.  Even electron DC current may not be what you think it is.

[Beamin]

So I think you can answer my question:
We have the trans and receiver where the transmitter is controlled by a freq. gen that can make perfect sine waves and has a "pause or hold" button on it where when we press it the voltage is held at that position of the wave. Its a 20v 10A 200 watt transitter.

Our control is to turn the 1Hz signal on for 10 sec and we detect a 10 sec long radio signal of 1hz on the receiver.
So 0.0 -0.25 sec the signal gen goes from 0 to +10volts at 10 amps.
0.25-0.5 sec it goes from +10 to zero
0.5-0.75 sec 0 to -10v
0.75 -1.0 sec -10 to 0 and repeats for ten seconds

On our second run we do the same thing only at 0.25 sec we press the hold button.

On our third run we press the hold button at 5.25 seconds.

So we should see
Test #1 10 seconds of 1 hz signal on receiver
Test #2 0.25 seconds of 1hz signal  "
Test #3 5.25 "                          "
But we really should see:
#1 10 sec of signal
#2 no signal
#3 5 seconds of signal since the transmitter never made a full ac cycle after 5 sec.

Unless the photon only are produced(in time dimension) when a change happens like at the thresh holds where the cycle changes. You could change this to any frequency as long as you could press the hold button fast enough to catch it mid cycle and the resolution of you receiver was an order of magnitude better then the freq you are receiving.

[T3sl4co1l]

Again:

A 10s burst of 1Hz has a sinc(f) spectrum centered around 1Hz, with an uncertainty of about 0.1Hz (there's a factor of pi in there, too).

You can time the waveform, detect the peaks or zero crossings, and find that it's pretty damn close to 1.00Hz, sure -- but that's a special case.  A detector is a nonlinear process.  It's not general.  By using a detector, you destroy other information about the signal.  If you want its amplitude, for example, you have to start over, using the original signal.

The concept of photons lives in the frequency domain, so it's the spectrum that matters.

If you "pause" the waveform, then you are superimposing a wave burst (as above) with a DC offset (similarly windowed).  The resulting spectrum around 1Hz is identical.  What you've added is another sinc(f) term, centered around 0Hz (because it's a "burst" of DC).  Where the tails of those two spectra overlap (i.e., significant in the 0.5Hz range, 5th harmonic range as it were), the phase and timing matters, because of interference.  You'd have to run the numbers for that particular waveform to find out.

But in any case, this is all undergrad level signals analysis.  Fourier transforms.  Not even any need to invoke any physics.  All physics can tell you is that, yeah, there's an uncountable* number of particles going around, and you don't need to worry about it.

*In the practical sense, i.e., today, not only can we not design a detector for energy levels this small, but we can't design a detector capable of the rate (particles/sec), or count it in a reasonable time frame (10^30 requires around 100 bits -- a long int even on a 64-bit machine!).

Tim