# How does a photon carry energy in itself?

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The map might not be the same as the territory, but for some reason we need a map from abstract non-physical numbers to a physical representation of those numbers.

If someone thinks they might be able to "play around" with numbers, and not do something physical, I'd like to recommend them to an institution I know about; it isn't a university.

Slithy toves might or might not be physical; I've never seen or heard one.
I have no meaningful knowledge of slithy toves.
No? I connect several things to slithy toves. Names like Lewis Carroll, for instance.
Why is information in a different category than a slithy tove? Information has physical units attached, all I can attach to slithy toves, is logic.
If I say "The term 'slithy toves' appears in a poem by Lewis Carroll", is that information?

If it is information, then by your argument it is physical. Moreover, it has physical units.

What is physical about my statement above, and what are its units?

If the statement as a whole is information, and therefore physical, what about its parts? Are slithy toves physical after all? Is there any information content in "slithy toves"? What are the physical units of "slithy toves", then?

No? I connect several things to slithy toves. Names like Lewis Carroll, for instance.
But what kind of thing is it? Apart from the guy who wrote the words in a book.

What does it mean?

If I say "The term 'slithy toves' appears in a poem by Lewis Carroll", is that information?
You can say whatever you like. It has to all be information (whatever you say) because saying words makes them . . . wait for it . . physical.

That happens to also pertain to writing words. Or typing them. Or thinking them.
Typing the words slithy toves into a word-processing program in a browser doesn't make slithy toves physical; the words are though.

Now I have a question for you: is there a number that can't be written down?
Oh hell, I see I'll need to also ask you if you understood anything I've posted about the difference between information and meaning. So have you?

Is the following physical: *UI\@)&%%Mmk+=5

. . . ?

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arfa brane:

I fear we have drifted quite far from the question of whether energy is more than just a number. So far, in fact, that I don't think my answers to your latest questions are very important.

Meanwhile, you seem to be dodging my question about bottling energy. If energy is a "physical thing", I would have said that you ought to be able to bottle it. Now, however, I see that you want to define "physical thing" as "anything in physics that has physical units", which would automatically include a whole lot of numbers used in physics. Since we can't bottle numbers, I think the distinction I was trying to make has been lost from our discussion.

So, just to be clear: is it your claim that it is possible to bottle "pure energy", or do you agree with me that it is impossible? If it is impossible, I suggest that it is impossible because "pure energy" is not any kind of substance. Energy is completely unlike water, or steel, or even a box full of photons. What do you think?

Anyway, since you asked...
But what kind of thing is it? Apart from the guy who wrote the words in a book.

What does it mean?
It's a clever literary device, meant to be suggestive of a thing rather than declarative. The reader is left to imagine what "slithy toves" might look like, were they to exist "in reality" as something other than a literary invention.
You can say whatever you like. It has to all be information (whatever you say) because saying words makes them . . . wait for it . . physical.
We can split hairs all you like on this, really. For instance, I could argue that saying words involves moving a physical thing (your vocal cords) and producing vibrations (sound) in another physical medium (air). The sound is physical, but the words are an idea that we attached to particular vibrations. Ideas are not physical, the way I define it, but conceptual, like numbers.
Now I have a question for you: is there a number that can't be written down?
I suppose it depends on what you want. Do you require a particular notation? Is writing a precise description of the number (which specifies it uniquely) enough to count as "writing it down"?
Oh hell, I see I'll need to also ask you if you understood anything I've posted about the difference between information and meaning. So have you?
I don't think I bothered reading anything you posted on that particular point, to tell you the truth. It doesn't seem relevant to our point of contention.

Sometimes I think you forget that this is supposed to be a discussion, not your blog.

Ideas are not physical, the way I define it, but conceptual, like numbers.
But you can't explain how a concept or idea isn't physical. A concept in a brain/mind is physical James.
Unless you really believe you can conceive of something without a physical process ocurring in your brain; neurons firing etc.

But I see you'd rather not, um, think about that. Or think about what the difference is between information and whether it means anything.
It does if we decide it does, pretty much.

Without the discussion turning on this point of contention, I see I'm wasting my time trying to discuss the subject of what energy means with you.
Keep believing thoughts aren't physical, and that information has to mean something. I don't actually care (why should I). But stop lying about wanting to know what I think energy is, whether it's physically real etc.

arfa brane:

I see you again ducking and weaving and dodging the main question I asked you. This is ... what? ... the second or third time you've done that?

Can you show me a bottle of pure energy, or can't you?

If you can't, then in what sense is energy "physical"?
But you can't explain how a concept or idea isn't physical.
I think I already have, at some length.
A concept in a brain/mind is physical James.
Unless you really believe you can conceive of something without a physical process ocurring in your brain; neurons firing etc.
Conceiving of a concept requires physical processes to occur in my brain. That doesn't mean the concept itself is physical.

You're the first person I have ever come across who is seriously trying to argue, in effect, that the idea of X is as physical as X itself.

You can conceive of slithy toves. Does that mean slithy toves are "physical"? Where can I get one in a bottle?
But I see you'd rather not, um, think about that. Or think about what the difference is between information and whether it means anything.
Don't worry your pretty head about what I'd rather or rather not think. If you think the difference between information and whether it means anything is somehow relevant to this conversation, by all means explain why. Don't hold yourself back because you think it might be something I'd rather not think about, just to spare my feelings.
Without the discussion turning on this point of contention, I see I'm wasting my time trying to discuss the subject of what energy means with you.
Aren't we discussing our points of contention? Have I missed something?
Keep believing thoughts aren't physical, and that information has to mean something.
The first part: fine, I'll do that (thanks, arfa!). The second part: what do you mean keep believing? Have we discussed that at all? Perhaps you could try asking me what I believe, first. You know what they say about assumptions, don't you?
I don't actually care (why should I). But stop lying about wanting to know what I think energy is, whether it's physically real etc.
Okay. Have it your way. I did have a passing interest in trying to find out what you think energy is, but it sounds like you don't really know yourself, so the whole project is probably a waste of my time anyway.

Enjoy talking to yourself, once again. You must be getting used to it by now.

arfa brane:

I see you again ducking and weaving and dodging the main question I asked you. This is ... what? ... the second or third time you've done that?

Can you show me a bottle of pure energy, or can't you?

If you can't, then in what sense is energy "physical"?

I think I already have, at some length.

Conceiving of a concept requires physical processes to occur in my brain. That doesn't mean the concept itself is physical.

You're the first person I have ever come across who is seriously trying to argue, in effect, that the idea of X is as physical as X itself.

You can conceive of slithy toves. Does that mean slithy toves are "physical"? Where can I get one in a bottle?

Don't worry your pretty head about what I'd rather or rather not think. If you think the difference between information and whether it means anything is somehow relevant to this conversation, by all means explain why. Don't hold yourself back because you think it might be something I'd rather not think about, just to spare my feelings.

Aren't we discussing our points of contention? Have I missed something?

The first part: fine, I'll do that (thanks, arfa!). The second part: what do you mean keep believing? Have we discussed that at all? Perhaps you could try asking me what I believe, first. You know what they say about assumptions, don't you?

Okay. Have it your way. I did have a passing interest in trying to find out what you think energy is, but it sounds like you don't really know yourself, so the whole project is probably a waste of my time anyway.

Enjoy talking to yourself, once again. You must be getting used to it by now.
I wonder if, to clarify the point, it might help to discuss not energy but momentum. That, too, is something you can't bottle, is a calculated quantity that is conserved and does not seem to suffer from the "Star Trek" syndrome that often bedevils discussions of energy.

...but this suggestion presupposes you are discussing with a rational interlocutor.................

Can you show me a bottle of pure energy, or can't you?

If you can't, then in what sense is energy "physical"?
Why do I have to show you a bottle of pure energy to show you it's physical? Can you show me one of your thoughts?
Conceiving of a concept requires physical processes to occur in my brain. That doesn't mean the concept itself is physical.
That's quite a logical leap. How is the result of these physical processes not itself physical? How does that work?
You're the first person I have ever come across who is seriously trying to argue, in effect, that the idea of X is as physical as X itself.
Well, if X is physical, and the idea of X is also physical (but you don't believe that), then they are both as physical as anything . . . physical is.
You can conceive of slithy toves. Does that mean slithy toves are "physical"? Where can I get one in a bottle?

No, I can conceive of a guy called Charles Dodgson conceiving of a nonsense adjective and noun together; then physically representing them in a poem with physical words. Since the words aren't bound by some ridiculous rule that demands they have to represent something other than a nonsense adjective and noun.
I only have this information--adjective and noun--because of the rules of English grammar. I have to conclude that the pair of words do not refer to a real thing. Although they might; but given the writing style, the previous conclusion seems valid.

You're looking like something of an idiot, James.

How foolish is someone who actually believes thoughts aren't physical? After some neurons fire "signals" around, you have a thought left over. Where is it?

How dumb is believing that information has meaning? It doesn't; meaning is something you might, or might not, derive from information, that would depend entirely on how the information is encoded.

Ooops I shouldn't forget how rational James is, and his buddy exchemist. Lurch and Uncle Fester.

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Riiii . . . ight.
I get it. James believes that he can believe something without the physicality.
"Ideas are not physical, but conceptual".

But hang on, ideas are concepts. You conceive ideas, sure, but that's another way of saying you think of a solution to a particular problem.
You can see James doing this with the 'literary device' that explains Carroll's poem, and what he's doing.
Not that he needed to, it's obvious. Like balls on a dog.

So no, ideas and concepts aren't really different things. What though, about the fact humans conceive of themselves, or have "self-awareness". How is that not physical? It's a problem that needs a few ideas.

. . . it might help to discuss not energy but momentum. That, too, is something you can't bottle, is a calculated quantity that is conserved . . .

Here's what a poster at physicsworld said:
Galap said:
Momentum ends up being the quantity that is physically 'real' or 'meaningful', as it is conserved in all frames of reference in both relativity and QM. Both mass and velocity (the components that classically make up momentum) are not conserved and are interchangeable, etc. It is a measure in a way of how much stuff there is in a system.

Can you be bothered explaining what he means by "physically real" in his argument?
Since mass and velocity aren't conserved, are they not "physically real"?

Hoe does photon carry energy in itself?
By vibration?

Yes, in a way.

Somebody asked this very question in the Q&A column of this month's Astronomy magazine.

It's a very good question, since if photons have no mass, how can they have energy? If according to Einstein's E = mc^2, how can E have a value when m is zero?

The answer given was that E = mc^2 is not Einstein's full equation. It's just a special case version.

The full equation is E^2 = (mc^2)^2 + (pc)^2

where E = energy, m = mass, p = momentum and c = speed of light

The familiar E = mc^2 is the formula for a particle at rest

And E = pc is the formula for a massless particle

So the question becomes, how does a massless particle have momentum? In classical mechanics it wouldn't.

The answer the author in Astronomy gave is that it's a result of wave/particle duality.

A particle can simultaneously be thought of as a wave and while waves don't have mass they can have momentum. (Exchemist already discussed this in post #45)

Or something like that...

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Don't forget that whatever idea or concept you have about photons, it isn't physical.

Photons are physical but ideas aren't.
According to James R.

Of course his theory can't be physical either because theories are ideas.
James might or might not have . . . thought about how that casts a whole different light on physics.

In James' world, nonphysical ideas explain physics. Explaining quite how these ideas become printed words is then something you don't need to do.
You skip over why or how the printed characters appear and just publish your theory.

Somehow the nonphysical world of ideas gets transferred to physical paper, as physical symbols. Magic.

And in order to resolve any argument about energy and whether it's physical or not, you ask a particular question about putting energy in a bottle.

Even though the question-that-must-be-answered is posed in physical language, it's based on ideas which are a nonphysical language.

I can't really understand the intricacies, but James believes it. So who am I to doubt?

Or laugh?

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I think to understand (with or without physical thinking), what information and what energy represent "really", you need to understand what computers do with it.

We talk about information, as signals, being lost during a transmission; copy an image and then copy the copy, repeat this process and the image starts to lose . . . visual information. Classical copying is a "lossy" process; transmitting information is an information copying process.

Bear with this line of thinking about physics, just a bit longer and maybe it will get somewhere near the "what is a photon" question, which is I think (haha, etc) what the initial thread question actually is asking.

So, logical reversibility and irreversiblility come into the frame of information loss. We now need to introduce the ideas of branching and merging, for physical paths in a logic circuit. So what the hell, use Boolean logic gates.

But, say, for a pair of photons, what can be done to illustrate a logic that spans reversibility (resp. irreversibility)? Is it possible (yes it is) to perform experiments that effectively branch and merge some logical property of photons? Well, I'd say polarization experiments could get you there.

You might be able to show connections between single and paired photons, in these experiments; the logic gates are of course, not Boolean but there is still a logic with a physical basis--mirrors and polarizers, say, lasers and photon polarization measuring devices. Quantum experiments open up the question of what the fundamental limits are, in order to compute something. But the inputs and outputs are determined (measured) by classical devices so we're halfway there (chortle . . . ).

Landauer proposed that logical irreversibility implies physical irreversibility. So can photon polarization experiments resolve whether this is true or not?
I know, I know, it's just a theory, right? How do you put a theory in a bottle ?

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R Landauer proposed that information is physical because it takes energy (as an 'input') to erase it.

Apparently there is new research that updates this: information is physical for . . . broader reasons.
It really does have to do with how information (its transmision and computation) is realised physically.
Erasure of information (i.e. loss), doesn't apparently require that heat is dissipated according to research in 2011.

Go figure.

Why do I have to show you a bottle of pure energy to show you it's physical? Can you show me one of your thoughts?
Can I show you evidence of processes in a physical brain that generate thought? Yes. Can I show you the thoughts themselves? No. Those can't be bottled. You can't bottle "pure thoughts" any more than you can bottle "pure energy".
That's quite a logical leap.
No. It's very old news. Plato wrote a lot about it, thousands of years ago. He talked, for instance, about a conceptual realm of pure mathematics, and the physical world. You should look him up.
How is the result of these physical processes not itself physical? How does that work?Well, if X is physical, and the idea of X is also physical (but you don't believe that), then they are both as physical as anything . . . physical is.
If I can't put it in a bottle, then it's not physical, in the sense in which I am using that word here.

You're trying to slime your way out of the simple point by redefining the word "physical" to mean something along the lines of "anything that is referred to in the field of physics". In that sense, momentum is physical, for example. But we can't bottle momentum any more than we can bottle energy or ideas.
You're looking like something of an idiot, James.
I'm running rings around you, so what does that say about you? Either you're a terrible judge of such things, or you're an even bigger idiot. Take your pick.
How dumb is believing that information has meaning?
Argument by babyish ad hominem attacks isn't working well for you. Maybe try something more mature. Just an idea.

As to the actual point, it should be obvious that some information is meaningful and some is not. Meaning is an assignation of importance or attention that we human beings assign to things. I don't know why you think this is at all relevant to this discussion.
Ooops I shouldn't forget how rational James is, and his buddy exchemist. Lurch and Uncle Fester.
No, you shouldn't. And didn't your Mum teach you any manners?

Here's what a poster at physicsworld said:

Momentum ends up being the quantity that is physically 'real' or 'meaningful',...​

Can you be bothered explaining what he means by "physically real" in his argument?
You didn't notice the scare quotes in that post, did you? Look at them. 'real'. 'meaningful'.

He was trying to tell you something, and you completely missed the message.

Don't forget that whatever idea or concept you have about photons, it isn't physical.
It has to be, if we accept your arguments. You say that ideas and concepts are physical, so if a photon is an idea or concept, that makes it physical in your book.
Photons are physical but ideas aren't.
According to James R.
Yes.
Of course his theory can't be physical either because theories are ideas.
Yes. You have to realise that "physical", in the sense I have been using that word, does not equate with "mentioned in the field of physics", like you're trying to define it.
In James' world, nonphysical ideas explain physics.
Yes. But good try there. I see how you're trying to muddy the waters. Good effort. Points for that.
Somehow the nonphysical world of ideas gets transferred to physical paper, as physical symbols. Magic.
Not magic. A person with a physical body can just grab a physical pen and write them down. Simple!
And in order to resolve any argument about energy and whether it's physical or not, you ask a particular question about putting energy in a bottle.

Even though the question-that-must-be-answered is posed in physical language, it's based on ideas which are a nonphysical language.

I can't really understand the intricacies, but James believes it. So who am I to doubt?
It's okay. I can accommodate your slow learning process. I think you can get there, with a little more help.
R Landauer proposed that information is physical because it takes energy (as an 'input') to erase it.
What definition of "physical" is R Landauer working with?

Can I show you evidence of processes in a physical brain that generate thought? Yes. Can I show you the thoughts themselves? No. Those can't be bottled. You can't bottle "pure thoughts" any more than you can bottle "pure energy".
I see. But you say "pure thoughts" exist? Are they physical or is the brain they "occur in" the physical part?
In that sense, momentum is physical, for example. But we can't bottle momentum any more than we can bottle energy or ideas.
But momentum is physically real; it exists? Mass and velocity are too, right?
You're trying to slime your way out of the simple point by redefining the word "physical" to mean something along the lines of "anything that is referred to in the field of physics".
You're lying about what I'm trying to do, again.
As to the actual point, it should be obvious that some information is meaningful and some is not. Meaning is an assignation of importance or attention that we human beings assign to things. I don't know why you think this is at all relevant to this discussion.
And yet, you seem to be trying to tell me what energy means; and what momentum, or anything "referred to in the field of physics" means.
Are you not trying to do that, is it just what my naive, foolish mind thinks it can see in your obvious contempt for pretty much anything I post about . . . physicality?
You didn't notice the scare quotes in that post, did you? Look at them. 'real'. 'meaningful'.

He was trying to tell you something, and you completely missed the message.
What message is that James? Have you seen something more meaningful in that post than poor old me?
You say that ideas and concepts are physical, so if a photon is an idea or concept, that makes it physical in your book.
But James, a photon isn't an idea or concept. The idea or concept of a photon is an idea or concept. Are you stupid?
Not magic. A person with a physical body can just grab a physical pen and write them down. Simple!
I wonder what compels this person to grab that physical pen and write down ideas (which are physical). How do they remember what they were thinking when they grabbed the pen?
What definition of "physical" is R Landauer working with?
The same definition physicists use, of course. And the same as engineers who know how to build computers use.
Are computers physical? Let's wait and see what James has to say, it might be important.
/'yawn'

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arfa brane:

Your patronising assumption that whatever you say is important, while you yawn at the unimportance of anything I say, is just another manifestation of that lack of manners I pointed out earlier. This is who you are, I suppose.

Since none of this is important, then, I will be brief.
I see. But you say "pure thoughts" exist?
No.
Are they physical or is the brain they "occur in" the physical part?
The brain.
But momentum is physically real; it exists? Mass and velocity are too, right?
Momentum, mass and velocity are all concepts.
You're lying about what I'm trying to do, again.
The proof is in the pudding.
And yet, you seem to be trying to tell me what energy means; and what momentum, or anything "referred to in the field of physics" means.[
Are you not trying to do that, is it just what my naive, foolish mind thinks it can see in your obvious contempt for pretty much anything I post about . . . physicality?
Look, this was a very straightforward point, when we started. I said "energy is just a number; energy isn't 'stuff'". You apparently disagree. I no longer care why you disagree.
What message is that James? Have you seen something more meaningful in that post than poor old me?
Yes.
But James, a photon isn't an idea or concept. The idea or concept of a photon is an idea or concept. Are you stupid?
I was using your model, not mine. That's the source of the stupid, if you're looking for it.
I wonder what compels this person to grab that physical pen and write down ideas (which are physical). How do they remember what they were thinking when they grabbed the pen?
Wonder away.
The same definition physicists use, of course.
Nice attempt to dodge, again, but no cigar.
Are computers physical?
Yes.

Done.

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