# How does a photon carry energy in itself?

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The frequency is fixed. Both the electric and magnetic oscillations are equal and in phase. The only way this can change is if space gets stretched by cosmic expansion. Otherwise the fields are symmetric but orthogonal.
Does the spacetime stretching not compass the entire 3D volume

Question : If spacetime stretches does that not also stretch everything within it? And if so, does the stretching create an imbalance or will everything remain in the same frame of reference as when spacetime is smaller?

Would we become aware that everything is stretching, including ourselves?
And speaking of frequencies, would frequencies of all wave functions alter in a stretching spacetime.

Does the spacetime stretching not compass the entire 3D volume
Cosmic expansion is seen in the redshift of distant galaxies. Redshift is exactly the change in frequency of photons from such distant sources.
The redshift therefore gives a kind of metric (distance measurement).
If spacetime stretches does that not also stretch everything within it?
Yes, but only over very large distances, much greater than say, the distance from our sun to the centre of our galaxy or any galaxies in the local group. It has practically no observable influence locally.
And if so, does the stretching create an imbalance or will everything remain in the same frame of reference as when spacetime is smaller?
All the galaxies at the same redshift distance are comoving, so no. The galaxies aren't stretched, the distance between them and us is.
Would we become aware that everything is stretching, including ourselves?
And speaking of frequencies, would frequencies of all wave functions alter in a stretching spacetime.
No, and no.

Those electromagnetic oscillations in an electronic circuit propagate away from the circuit into the space around it in all directions.

In a conductor electrons don't have to move very far to generate a 'signal'. The currents in a circuit don't need to move at the same scale as say a pendulum. This is because the electromagnetic fields generated by an oscillating current are many orders of magnitude greater than the gravitational fields of a pendulum oscillating.

That means detecting gravitational signals is way harder than detecting electromagnetic signals.

But how do photons carry energy, isn't really the question. The question should be how is photon energy related to photons propagating.

The Sun provides the Earth energy, right?
Light from the Sun, which is photon, carry heats to the Earth.
How the particles of photon carry energy?

The Sun provides the Earth energy, right?
Light from the Sun, which is photon, carry heats to the Earth.
How the particles of photon carry energy?
Any wave carries energy, by virtue of the fact that a wave is a travelling displacement of a medium from its equilibrium position.

To displace the medium you have to do work on it (which is energy), and that energy is then carried by the wave as it travels.

In the case of light, it is a travelling disturbance in the electromagnetic field.

Light gives up its energy when it is absorbed. In the case of visible light*, when this happens it gives up its energy to an electron in the absorbing material, causing it to enter an excited (higher energy) state. This energy may then be further converted within the absorbing material in various ways, usually ending up as heat.

*In the case of EM radiation that is in other ranges of the spectrum, it may not be an electron but some other feature of matter that is excited.

A very common misconception about electrons is that a current is responsible for the transfer of energy to a circuit or say an electric motor.

If that was true you would have an alternating positive/negative flow of energy from an alternating current.

What actually happens is energy is transmitted by the electric and magnetic fields in the space around a current flowing back and forth in a conductor.

In the case of photons the alternating fields underline this; the energy of photons doesn't depend on their speed (or velocity) through a vacuum or a material.

Their energy only depends on how fast the electromagnetic fields alternate together.

If you think that's wrong you need to explain the photoelectric effect in some alternative way. Ok?

arfa brane:

So you're in a special group of people?
If you think that the group of people consisting of those who have a good understanding of the concept of energy is a special group, then I guess I am. You can call us "energy experts" if it makes you happier.
It must be quite a difficult misconception to explain, I guess, since you haven't offered one.
Not particularly. If you asked nicely, maybe I'd offer you one. Mind you, I have posted on this topic many times in the past on this very forum. Perhaps you just missed all of those previous posts.
He was. But what was he right about? I'm nowhere near convinced that you understood him.
He was right in saying that energy is just a number!
What about work? Is work "just a number"?
Now you're getting it!
If it is, why do so many, presumably educated people say it's a quantitative property that has to be transferred to a system? Can you explain how this "just a number" is transferred to a system? or is the system also "just a number"?
What is "transferred", exactly? As far as I can tell, you take a number from one column in your energy accounting ledger and you move it to another column, more or less. There's no "energy stuff" being physically moved from one place to another.
Also, if energy is a number ("just"), are different forms of energy an illusion? Heat and electricity are the same kind of number? Or are you saying heat and electricity aren't forms of energy; or should I say energy in the form of heat, and energy in the form of electricity, are just numbers?
Essentially, the different "forms of energy" that you mention are just separate columns in an energy accountacy ledger. The particular numbers and the ways they are calculated correspond, of course, to actual physical processes that are going on in various ways. For example, consider kinetic energy, the "energy of motion". The "stuff" is the molecules doing their thing. But the energy is just a number we associate with that molecular motion: we calculate E=(1/2)mv^2 for a molecule and get a number. We call that number the molecule's "kinetic energy".
What I'll say is there is an equivalence between energy and information; information is a physical thing, a physical thing is not "just a number".
Information is a physical thing? I think that information is a conceptual thing. In what sense is information physical?
For instance, tell me how the information content of this post you're reading manifests itself physically.
My car is not "just a number"; the air I breathe isn't either. You aren't a number, are you James?
None of the physical objects you mention are numbers and you know that I never claimed they were. I was talking about energy, remember?
Why do these "educated people" say the number in question has physical units?
Lots of numbers in physics have units. Having units, by itself, doesn't turn a concept into some kind of physical substance. Take a different example: the charge on an electron. It is a number that has units of Coulomb, for instance. Does that mean that charge is a substance that can exist independently of the electron it is associated with? No. Both the electron's charge and its energy (whatever kind of energy you like) are numbers we associate with the electron. They are useful numbers, but numbers nonetheless.
How many numbers are there with physical units? how many are there with no physical units?

Which ones are "just numbers"?

Again, if energy is "just a number", can it be any number? can I decide which number or if the number has physical units?
There are lots of numbers with physical units and lots of numbers without them. All of them are numbers (or "just numbers", if you prefer). My point was/is that it is a mistake to start imagining that numbers are the same as physical objects or substances, which is what a lot of people do with energy (in particular). Numbers are concepts. If I have 3 sheep, the "threeness" is a property of the group of sheep - a conceptual property. There's nothing physically "threeish" about the sheep. We can't extract the threeness and bottle it. It's the same with the energy of the sheep.

I hope this helps clarify things for you.

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I hope this helps clarify things for you.
Thank you for that excellent clarification. Sciforums at its best!

What is "transferred", exactly? As far as I can tell, you take a number from one column in your energy accounting ledger and you move it to another column, more or less. There's no "energy stuff" being physically moved from one place to another.
So heating some water to make a coffee, is taking a number from one column and moving to another column?
But there's water, and there's heat from a source of heat; the water gets heated. Where are the two columns you say I need, so I can heat up the water?

Or say I start the engine in my car, it starts because a battery has electrical energy, and because the fuel has chemical energy. Where are these columns you mention? Why does your explanation seem so completely useless and counterfactual? I've never seen any of these columns. Quite likely that's because your idea is too simplistic. A five year old might be taken in, I guess. But five year olds grow up eventually.

Perhaps you might too, one day.

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Take a different example: the charge on an electron. It is a number that has units of Coulomb, for instance. Does that mean that charge is a substance that can exist independently of the electron it is associated with? No.

Why does this number not exist independently of the electron? What do you think it means, when there are numbers that are completely independent of physics, that really are just numbers and nothing else?

There are lots of numbers with physical units and lots of numbers without them. All of them are numbers (or "just numbers", if you prefer).
Well, that's complete bullshit James, sorry. You're a physics joke.

My point was/is that it is a mistake to start imagining that numbers are the same as physical objects or substances,
Then why do you make that mistake?
Information is a physical thing? I think that information is a conceptual thing. In what sense is information physical?
For instance, tell me how the information content of this post you're reading manifests itself physically.
Yes James; information is physical. I see you have some catching up to do.

If information was a concept, how would you transmit it or store it? Why would someone, as you just did, ask "how the information content of this post you're reading manifests itself physically". That's pretty asinine, you must actually be an idiot.

Good job. I hope you stay ignorant and never bother to question your knowledge of . . . anything at all. God help us all if you do.
You're an Aussie, right? That's pretty obvious too, you goddam moron.

Richard Feynman wasn't an idiot, but he probably didn't understand information in the modern sense either. Computer Science was in its infancy in the 1950's, in much the same way your understanding of it is.

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If I have 3 sheep, the "threeness" is a property of the group of sheep - a conceptual property.
It isn't "just" a conceptual property, you idiot.
The concept is in fact, information. Or I guess you could have a try at explaining how the concept exists in a brain without the three sheep, or three of anything (physical).
We can't extract the threeness and bottle it.
And "we" can't explain how the statement "three sheep" doesn't look like a bottle, I guess. It does contain, um, information though doesn't it?

Unless of course you don't have a big enough brain . . .

Really, the simple answer to the OP question is thus:

Photons carry energy from place to place for the apparently simple reason that they also carry information from place to place.

Except that information isn't really simple.
Information has entropy, and that concept isn't simple. If it was it would be as easy as . . . counting sheep.

I know there are some people (some of them are moderators here, but I'm not naming names) who don't appear to believe that they might still learn something.

If you happen to believe you aren't in that group, I can suggest studying information entropy. Also some category theory, maybe constructor theory.

Think on this one though. The concept of information, or the concept of numbers, are impossible without brains in the universe.

A concept in your brain/mind is information, it's encoded because it has to be. Concepts in human or other animal brains would not exist if life didn't exist.
Would numbers still exist? Would information that could be interpreted as numbers still exist? Would communication or computation exist?

That's what I think you could call an open question.

Thanks James for opening that door, and allowing me to demonstrate how ignorant you actually are.

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Think on this one though. The concept of information, or the concept of numbers, are impossible without brains in the universe.
Yes, the concept is. The functional exchange of information is very much possible without the antropomorphic concept.
The entire field of chemistry is based on the exchange of elementary information.
A concept in your brain/mind is information, it's encoded because it has to be
Yes, if you believe that people conceptualize reality.
But a concept is not a physical thing at all. It is an emergent imaginary quality of neural information processes.

FFS

And that abbreviation conveys physically conceptual information?
That was a conceptual imaginary motivation. I don't think it helped your argument in a positive way.

arfa brane:

So heating some water to make a coffee, is taking a number from one column and moving to another column?
No. When you heat water, you cause the water molecules to move around, rotate and vibrate more, by doing something that causes those molecules to jiggle around. In an electric kettle, for instance, the water is placed in contact with some hot metal, and the metal atoms physically bump into the neighbouring water molecules. Notice that, in this description, the word "energy" does not appear.
But there's water, and there's heat from a source of heat; the water gets heated. Where are the two columns you say I need, so I can heat up the water?
If you like, you can open your energy ledger and describe the process as some electrical energy being moved to the column corresponding to kinetic energy in the heating element, then moved to the column corresponding to kinetic energy of the water molecules. The temperature of the water is a measure of the average kinetic energy of the water molecules. To find it, you could, in principle, look at how fast the water molecules are moving and then grab your calculator to fill in the "kinetic energy" column in your energy ledger. Then, by the miracle of averaging, combined with some calibration, you get a temperature reading out. Alternatively, you could just stick a (calibrated) thermometer in the water.
Or say I start the engine in my car, it starts because a battery has electrical energy, and because the fuel has chemical energy. Where are these columns you mention?
Those columns are the ones you're labelling "electrical energy" and "chemical energy". The physical processes that start your car are not the same thing as the energy numbers you write down.
Why does this number not exist independently of the electron? What do you think it means, when there are numbers that are completely independent of physics, that really are just numbers and nothing else?
There are numbers in physics and numbers outside (e.g. I have 3 sheep).

I can bottle a sheep (if I have a large enough bottle), but I can't bottle the number "3".

You can settle our little dispute very quickly right now, if you can produce a bottle of "pure" energy for me. Can you do that, or not? If not, why not?
Well, that's complete bullshit James, sorry. You're a physics joke.
Ah, an attempt at argument by ad hominem insult. Poor show, arfa brane. Can't you do any better than that?

What happened to you, man? I always thought you were more capable than this.
Then why do you make that mistake?
Yes James; information is physical. I see you have some catching up to do.

If information was a concept, how would you transmit it or store it?
If I get out my HB pencil and write down my name, say, then the information is "stored" in the graphite markings on the paper. The graphite and paper is the physical storage medium of that information. But by themselves, graphite markings on paper are just that. The information in my name is entire conceptual: the idea that those markings represent sounds in a language, that this particular combination of phonemes represents a proper name, etc. All of that is entirely in your head; none of it is in the graphite.
Why would someone, as you just did, ask "how the information content of this post you're reading manifests itself physically". That's pretty asinine, you must actually be an idiot.
Clearly, you're hopelessly confused and the only refuge you can find lies in insults. Try to come up with an actual argument or two. That would be more constructive. Also, just as a hint: if you expect somebody to converse politely with you, you ought to try practising some politeness yourself. Otherwise you come across as a crass bore.
Good job. I hope you stay ignorant and never bother to question your knowledge of . . . anything at all. God help us all if you do.
You're an Aussie, right? That's pretty obvious too, you goddam moron.
Personal insult not enough for you? Now you feel like you need to insult an entire nation of people? Does that make you feel better about your failings?
Richard Feynman wasn't an idiot, but he probably didn't understand information in the modern sense either. Computer Science was in its infancy in the 1950's, in much the same way your understanding of it is.
Feynman, as it turns out, was a very bright guy. He gave a very interesting talk about miniaturisation and information storage, years ahead of its time. You should look it up. You might learn something.

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And that abbreviation conveys physically conceptual information?
That was a conceptual imaginary motivation. I don't think it helped your argument in a positive way.
I don't think your earlier post helped either.
In any way.

I suppose I should ask, although the answer seems to be readily apparent, have you done any formal study of information theory, or of neurological science?

And, do you realize you're saying you know something that neither of those subjects predicts or theorises, in any way shape, or form?

Your idea is "just" an idea with no evidence or research to support it?

Otherwise known as a speculation. One that seems to be based on imagination?

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And, do you realize you're saying you know something that neither of those subjects predicts or theorises, in any way shape, or form
And here I thought that James just confirmed my understanding of the subject of conceptualization.
The information in my name is entire conceptual: the idea that those markings represent sounds in a language, that this particular combination of phonemes represents a proper name, etc. All of that is entirely in your head; none of it is in the graphite.
I agree with that. Don't you?

Tegmark had a similar analogy. His wife's name was inscribed in his wedding ring and that represented a durable form of information. However, if he had inscribed his wife's name in a puddle of water, the information would have been lost immediately. In any case the concept that is represented in either activity is "marriage". An exchange of vows!