Are photons energy? What is energy, anyway?

Discussion in 'Physics & Math' started by origin, Aug 19, 2019.

Thread Status:
Not open for further replies.
  1. paddoboy Valued Senior Member

    Messages:
    27,543
    And after considering this pedantic argument further, instead of either calling a photon a " packet of energy" or a "carrier of energy" we could also consider a photon as simply an " energetic photon" but that's being pedantic.

    Please Register or Log in to view the hidden image!

     
  2. Google AdSense Guest Advertisement



    to hide all adverts.
  3. arfa brane call me arf Valued Senior Member

    Messages:
    7,832
    I'm waiting to see if James R or exchemist can explain how the power output of a radio antenna is calculated, given that electromagnetic radiation isn't a form of energy.

    I'd also like an explanation of what both of them think a "form" of energy actually is.
     
  4. Google AdSense Guest Advertisement



    to hide all adverts.
  5. Michael 345 New year. PRESENT is 72 years oldl Valued Senior Member

    Messages:
    13,077
    Pedantic - not so

    Colour of orange in the dark or under a blazing sun - it is the colour it is

    What colour is it PERCEIVED to be - depends on how it is lit up

    Please Register or Log in to view the hidden image!

     
  6. Google AdSense Guest Advertisement



    to hide all adverts.
  7. paddoboy Valued Senior Member

    Messages:
    27,543
    Actually an Orange in the dark has no colour.
    Colour in the first instant is determined by what part of the EMS is falling on that object, and what part of the EMS it actually reflects.

    Please Register or Log in to view the hidden image!


    This was part of a very lengthy long debate on a now defunct forum.
    https://www.scienceabc.com/nature/what-color-is-an-orange-in-the-dark.html

    What Color Is An Orange In The Dark?

    If you keep a ripe orange in one corner of your room that gets variable amounts of light as the day passes, you will see different intensities of the color orange on the piece of fruit. Perhaps the difference isn’t too evident for you, since you won’t be staring at the orange all day, but another exercise you can try is holding an orange in front of a bright torch. Believe it or not, but it will turn a bright flaming red!

    Put that same orange under a purple light and it will appear scarlet, but under blue light, it will appear brown. Has your orange turned into a chameleon? No, of course not, but why is it changing color? The orange will change color in all these situations because, as vision scientists put it, color is not a property of an object. Color exists in our head!
    more at link....


    PS, my apologies as this may seem to be off topic....

    Please Register or Log in to view the hidden image!

     
    Write4U likes this.
  8. Michael 345 New year. PRESENT is 72 years oldl Valued Senior Member

    Messages:
    13,077
    Is, the above, not what I expressed in far fewer words?

    Please Register or Log in to view the hidden image!

     
  9. Write4U Valued Senior Member

    Messages:
    20,076
    Would it be more correct to say "it depends on how the brain translates the perceived wavelengths into colors"?
     
  10. paddoboy Valued Senior Member

    Messages:
    27,543
    The above says that in the first instant, the "perceived" colour of anything depends on the EMS falling on it.

    Please Register or Log in to view the hidden image!

     
  11. Michael 345 New year. PRESENT is 72 years oldl Valued Senior Member

    Messages:
    13,077
    Seriously?

    Please explain the difference in concept behind the words expression (apart from spelling)

    Please Register or Log in to view the hidden image!

     
  12. Michael 345 New year. PRESENT is 72 years oldl Valued Senior Member

    Messages:
    13,077
    And my post
    ????

    please explain how the below is different

    Please Register or Log in to view the hidden image!

     
  13. Michael 345 New year. PRESENT is 72 years oldl Valued Senior Member

    Messages:
    13,077
    Found this dozzy worth a look

    The Longstanding Mystery of How Big a Proton Is May Finally Have Been Solved

    BY MIKE MCRAE

    SEPTEMBER 09, 2019

    ........the proton's radius at around 0.833 femtometres; a smidgeon off the 0.842 femtometres calculated by a landmark 2010 experiment.

    PLUS

    Unlike the convenient models of atoms in our text books, protons aren't like smooth little spheres. Lacking a distinct surface, the proton is instead a cloud defined by a threshold in its positive charge.

    PLUS (hopefully helpful re title of thread)

    Method number two is a little less aggressive, relying instead on detecting changes in an electron's energy levels as it orbits a proton

    https://www-sciencealert-com.cdn.am...zling-size-brings-us-closer-to-a-solid-answer

    Please Register or Log in to view the hidden image!

     
  14. Write4U Valued Senior Member

    Messages:
    20,076
    I don't believe we perceive colors at all. We perceive wavelengths which are translated into electro-chemical signals and when processing the information, the brain makes a best guess of what color these wavelengths represent.
    It's not always right .

    Remember the chess board with the two squares which are identical in color, but the brain is unable to see them as the same color.

    Please Register or Log in to view the hidden image!

    A and B are identical in color!
    It is impossible for the brain to see these two squares as being the same color. The brain always tries to correct for shadow and cannot override this internal adjustment process.
    (Its a survival tool)
     
    Last edited: Sep 9, 2019
  15. Michael 345 New year. PRESENT is 72 years oldl Valued Senior Member

    Messages:
    13,077
    Intriguing

    Slightly different answer to a slightly different question

    However as for not seeing colour (the check board is designed to deliberately trick the brain) not sure I would agree with the not seeing colour statement

    Not sure if experiments have been undertaken (to lazy to check) but I would design a test along the lines of using a known wavelength (say for discussion - green) - presenting said wavelength to the eye of the subject and document the response

    Now it has been said that your green might not be my green ie if I saw your green I would call it red (ieie different brains different perceptions but same response to NAME of colour) because of what I/you have been taught that (name green) is the correct response to the brains interpretation of that wavelength

    Again different to NOT SEEING COLOUR

    it's nearly 4:30 so have to go

    Thought of something I can try. Let you know how it turns out

    Holiday Bali in two days so how long it takes to check my idea depends on how holiday turns out

    Please Register or Log in to view the hidden image!

     
  16. Write4U Valued Senior Member

    Messages:
    20,076
    The board is designed to demonstrate the effect of shadow in our perception. It's our brain that tricks us.....

    Please Register or Log in to view the hidden image!



    Now that you KNOW the colors are the same, you will still not be able to perceive these two as being the SAME color.

    Please Register or Log in to view the hidden image!

    Your brain won't let you.

    This is why I really love the lecture by Anil Seth, explaining this phenomenon.

    Interestingly, the brain can very readily adapt to sound recognition and what may at first sound as garbled noise, can become clear with just a few audible clues. It's truly amazing!

    I'm posting another Anil Seth Lecture where he answers some of the same questions raised here on occasion.
    Can't do it here , so entered it in the Human Science forum under title; Anil Seth - Brainstorming
     
    Last edited: Sep 9, 2019
  17. paddoboy Valued Senior Member

    Messages:
    27,543
    The thing is, that we always see things on Earth under the same conditions in general with our star being a yellow dwarf G2V star.
    If we for example lived on a blue super giant star, the colour of an Orange would appear different.
     
  18. Michael 345 New year. PRESENT is 72 years oldl Valued Senior Member

    Messages:
    13,077
    Write4U likes this.
  19. paddoboy Valued Senior Member

    Messages:
    27,543
    Sydney Opera House under normal lighting conditions....

    Please Register or Log in to view the hidden image!


    Sydney Opera House under other lighting conditions....

    Please Register or Log in to view the hidden image!

     
  20. James R Just this guy, you know? Staff Member

    Messages:
    39,421
    Not really. I disagree with the guy on quora about all particles being "pure energy". Particles are excitations in quantum fields, yes, but that's not the same as "pure energy". The guy sounds reasonable enough that I think I could probably convince him of that with a brief conversation about it. It's not that he's exactly wrong, but he's using a metaphor without realising it. Like I said, it's a common mistake, and even physicists are prone to making it. To some extent, it doesn't matter if we're a little loose with the language, but when the question is this one it is actually important to get it right.
     
    Last edited: Sep 10, 2019
  21. James R Just this guy, you know? Staff Member

    Messages:
    39,421
    paddoboy:

    What I'm hearing is that you're not interested in whether you're right or wrong. As long as you walk away with your ego intact, you're content to be wrong. For you, this discussion ceased being about what is true some time ago. Now it's just about you trying to save face, at least as far as you're concerned.


    None of that addresses the question of whether photons are energy (they are not). There's no problem with anything in this quote, but it's irrelevant to our discussion.

    Okay so far. I wrote the same thing, above.

    Nup. Wrong! Back to school with you!

    Sloppy. Yes, the energy in light comes in discrete amounts. Those amounts are associated with individual photons. The mistake comes when you say that the photons are the energy, or vice versa.

    All fine, but irrelevant.

    Another error, even though it's a very common mistake. Energy and mass are not "perfectly equivalent". A certain amount of energy can be associated with a certain quantity of mass, but it is an error to think that mass is energy. If it was, we wouldn't need two different symbols with two different units, for starters. And besides, at this point the guy has forgotten about how he careful distinguished matter from light, earlier. He's muddled. He says light is energy. He says light is not matter. But then he says matter is energy, which would make matter and light the same thing. See? Muddled.

    Nup. More sloppy thinking. You can, for instance, convert mass into photons, but that's not the same thing at all, since neither mass nor photons are energy.

    From here on, it's just error compounding error.

    The sun turns some of its matter into photons, and there's energy associated with both the matter and the photons, but no matter is turned into energy. How could it? Energy isn't stuff that real physical things can turn into.

    I have no problem with anything there. Sounds like Dave is on the right track. Note that he nowhere says that photons are energy.
     
  22. James R Just this guy, you know? Staff Member

    Messages:
    39,421
    arfa brane:

    Some people just can't stand being corrected. I'm tempted, on the basis of this incivility, to just stop interacting with you. People aren't pricks just because they disagree with you. Grow up.

    No. You can't create "stuff" from numbers.

    A photon, as I and others have already explained many times, is an excitation of the electromagnetic field.

    Your question is no different from asking where a water wave gets its properties from. It gets some of them from the nature of water itself. It gets others from the nature of whatever it is creating the disturbance that is the wave.

    Another error. A photon is an excitation of the field; it is not the field itself. Your statement is equivalent to claiming that a water wave in a pond is the pond.

    What is wrong is that whoever wrote that is hopelessly muddled about the difference between heat and radiation. Apart from that, the rest is sort of okay.

    You realise that wikipedia is full of errors, don't you? It's a publicly editable encyclopedia. It is only as accurate as its contributors. Mind you, apparently even the Encylopaedia Britannica gets some of these things wrong - again, it's only as good as its contributors. People make mistakes.

    Oh well, indeed. Maybe somebody will help correct them, like I'm helping by correcting you. Maybe you can take what you learn here and spread the knowledge around. Maybe together we can correct the internet, bit by bit.

    ---
    Regarding Schrodinger's Scientific American article, which you quoted, the first thing to realise is that he is writing for a popular audience, not that this excuses errors. Secondly, the article was apparently written in 1953, and Schrodinger did not have the benefit of today's understanding of quantum field theories and the like at that time.

    With that in mind, let's take a look....

    This is ambiguous. On the one hand, it can be read as saying that particles are a form of energy and there are other forms. On the other hand, Schrodinger might just be saying that energy can be emitted from the nucleus by many different processes. It's not clear which meaning he meant. If it was the former, then he was wrong; if the latter, then no problem.

    It's an understandable mistake he is making here - one that many physicists make. In practice, it doesn't make much difference if you pretend this is true. But, technically, it's wrong. Energy and mass are not one and the same. You can't make stuff from numbers.

    Fine.

    This is okay, but only if the word "radiation quantum" is understood to mean a discrete quantity of energy associated with a photon ("radiation"). An erroneous reading would be to interpret this as saying that energy (numbers) can somehow turn into photons (stuff).
     
  23. James R Just this guy, you know? Staff Member

    Messages:
    39,421
    arfa brane:

    What's confusing you?

    A bucket can carry water. Are you confused as to why the bucket is not the water? (Note: this analogy is imperfect, because energy isn't "stuff" like water is, but hopefully you get the point.)

    What do you find problematic about any of that? You're dismissing it, but you're not saying why.

    Are you telling me that you don't care how many good arguments I make, you're unwilling to believe me because I disagree with some "big name" authorities about certain subtle points?

    You need to understand that Science isn't a dogma. There are no High Priests of Science. Ideas stand or fall on their merits in science, not according to how many Nobel prizes you've been given - at least in the ideal practice of science.

    What you're telling me is that even though you can't put a coherent argument together to explain how a photon could possibly be energy, you're just going to go right on believing that's what it is, because it's some kind of article of faith for you, or because it will shake your faith in the Holy Men of Physics if you ever found out that they made a mistake or two.

    This is also precisely paddoboy's attitude here. He doesn't realise that Science isn't based on dogma and authority, either.

    Okay. That's all good. What's the relevance?

    Yes. I agree with all that.

    I haven't talked about most modern textbooks. I believe that so far we have discussed what one textbook says - one that you happen to have at hand. Nor have I made any comments about a university education in physics.

    I don't know where you're getting this stuff from. Not from anything I've said. How can we hope to identify errors in the literature if we don't consult it?

    I wouldn't put all the blame on them. People manage to mislead themselves. Also, this stuff isn't necessarily taught. People (even teachers) aren't always as careful as they should be in how they use the language, and as a result their students sometimes take away the wrong ideas.

    Electromagnetic energy doesn't have to be energy in order to have an energy associated with it. Energy is useful precisely because it's a good accounting system.

    I've already told you, but maybe I wasn't clear.

    We can talk loosely about different forms of energy - kinetic energy, potential energy, heat, spring energy, etc. What is really going on when we do that is that we're partitioning or assigning categories to some abstract quantity called the "total energy" of some system or other. We're saying we can associate X amount of energy with the mass in the system, and Y amount of energy with the motions that are going on, and Z amount of energy due to the relative distances between separate objects in the system, and W amount of energy with the orientation of the system in space, and so on and so forth. The usefulness of this partitioning is that when physical changes to the system occur we can move some energy from column Z, say, to column Y, and yet the total Y + Z (or X + Y + Z + W + ...) will remain unchanged if we've set things up carefully.
     
    Last edited: Sep 10, 2019
Thread Status:
Not open for further replies.

Share This Page