Entities and attributes in science

Discussion in 'General Philosophy' started by James R, Mar 23, 2023.

  1. billvon Valued Senior Member

    No. It IS energy. You can say it is made of energy. That is less precide.
    Correct! It is energy.
    Light is, in fact, a form of energy. Specifically, light is electromagnetic radiation.
    For the fourth time now, light is energy. You can say light carries energy. That is less precise.
    Not at all.
    Light is energy.
    No. There are things that exist that are non-material - like energy.
    Of course. You could do so as well.
    There is no such thing as gravitational energy. There is gravitational POTENTIAL energy. And yes, you can detect it - but since gravitational potential energy is measured by both mass and distance (over short distances) then measuring that potential energy has two parts. First you measure the mass, then you measure the distance. You need both.
    I have answered this five times now. I have to conclude either you are trolling or are simply incapable of understanding this discussion.

    Have a good day!
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  3. origin Heading towards oblivion Valued Senior Member

    That is not correct, light is composed of photons and photons are not energy. Photons carry energy.
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  5. Guestfornow Registered Member

    Maybe whoever wrote the following has misinterpreted Einstein's paper on the photoelectric effect.
    Perhaps you can point out the errors for us all

    What you propose is that, after a photon loses energy it's still a particle. That isn't what we observe, though.
    Not when photons interact with charged particles, at least.
    Photons get redshifted and appear to lose energy, but there's a different kind of explanation for that phenomenon.
    Last edited: May 21, 2023
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  7. Guestfornow Registered Member

    If you asked me that question I would say it bothers me about the same as the non-material nature of time.
    I would add that I understand time fairly well, but I can't tell you what it is.

    Why are you trying to define energy beyond a conserved physical quantity? There are plenty of material and non-material things in physics, we don't know what a lot of them are but we understand what they do, or, what relevance they have if they don't do anything. Time doesn't do anything, it doesn't interact with particles.
  8. billvon Valued Senior Member

    Light is a form of energy. Again, you can say that light carries energy. That is not quite correct, though, although it's a common (minor) error. Everyone knows what you mean when you say it.

    If something carries something else then the two are separable. If, for example, a train carries coal, you can remove the coal and you still have the train. If you remove the energy from a photon, you have nothing. You have removed the energy (which is what photons are) and there is nothing left.
  9. origin Heading towards oblivion Valued Senior Member

    No, I didn't imply that or say that.
    I guess the same could be said of an electron. You can't remove the charge from an electron but it is still a particle. An electron is not pure charge.
    If photons are just pure energy, that would mean that energy has a spin of 1 and energy has momentum. That would not make sense.
    James R likes this.
  10. billvon Valued Senior Member

    Yep. And uncharged electrons are electron neutrinos - another form of lepton.
  11. Guestfornow Registered Member

    You're overthinking it.

    The energy of a photon is frequency-dependent, Take away the frequency and there is no photon. The frequency is of an oscillating field.

    So one takeaway is that oscillating fields are a form of energy. Pure energy doesn't make sense. Energy in a field does.
    Physics is about meaningful descriptions; it's also about what kind of questions are meaningful. These tend to be about what can be measured or more generally, observed.
  12. origin Heading towards oblivion Valued Senior Member

    I just agree with the physics community that clearly states that photons are not pure energy, which makes perfect sense to me.
    You are not disagreeing with just me, you are disagreeing with the consensus of physicist, which is fine, but I am on the side the physicists with this one.
    exchemist likes this.
  13. Guestfornow Registered Member

    Can you post a quote from that community to back up your argument?
    I don't know what "pure energy" might be.
  14. billvon Valued Senior Member

    I've never heard them described as pure energy either, just as I have never heard matter described as pure matter. Photons are, however, a form of energy.
  15. origin Heading towards oblivion Valued Senior Member

    Simply type into Google "is light energy?"
    Sorry for any confusion I caused by saying the word pure. What I was trying to say was that photons are not energy. A photon is a subatomic particle that has several properties and one of those properties is that it carries energy, it is not itself energy.

    There is not much more I can add. Google the question "are photons energy" and check the results, I agree with the results from Google.
    exchemist and James R like this.
  16. Guestfornow Registered Member

    Well I actually did try what you suggest. The results, or some of them, say that light is a form of energy.
    You can check this yourself.
    One of them says the energy of a photon depends on its frequency; that's what I said.
    Do you still agree with the results from Google?
  17. Guestfornow Registered Member

    Ok. I agree that a photon has several properties.
    It propagates or moves at the speed of light--no surprise there. It has spin or polarization, it has momentum.

    What happens if a photon is absorbed? What properties remain that tell you a photon is not the momentum, not the polarization, not the energy from the oscillations of the field? What should I be able to observe after a photon is absorbed?
  18. billvon Valued Senior Member

    I am not a fan of using popular media to define science. Nevertheless I tried your experiment:

    Top results:
    "In fact visible 'light' is a form of radiation, which can be defined as an energy that travels in the form of electromagnetic waves." (ESA)
    "Light energy is a form of electromagnetic radiation." (scholarschools.com)
    "Light energy is a kind of kinetic energy with the ability to make types of light visible to human eyes. Light is defined as a form of electromagnetic radiation ..." (byjus.com)

    So all those hits agree that light is a form of energy. Two out of three say it explicitly.

    OK I tried that too. Results:

    "A photon (from Ancient Greek φῶς, φωτός (phôs, phōtós) 'light') is an elementary particle that is a quantum of the electromagnetic field, including electromagnetic radiation such as light and radio waves" (Wikipedia)
    "As quanta of light, photons are the smallest possible packets of electromagnetic energy." (Symmetry magazine)
    "A photon is a particle of light which essentially is a packet of electromagnetic radiation. The energy of the photon depends on its frequency" (energyeducation.ca)
    "Photons are simply discrete packets of light energy." (study.com)

    I agree with all the above. Light is made up of photons, and photons are quanta of EM energy.
  19. James R Just this guy, you know? Staff Member


    With so many sources getting this fundamentally wrong, it's no wonder that you and others have picked up the wrong message somewhere along the line and are now struggling with a misconception.

    Taking the quotes in turn:
    • The ESA one starts by saying light is a "form of radiation", which is fine. Radiation consists of particles. Light consists of particles (photons). But then it goes off the rails, claiming that "radiation ... can be defined as an energy that travels in the form of electromagnetic waves". Well, I suppose it can be defined like that, but defining it that way just opens a can of worms which will be an ongoing source of confusion and inspecificity. Claiming that energy can take the "form of" electromagnetic waves is just hopelessly muddled. Energy just isn't stuff. It has no form. You can't turn energy into light, or light into energy.
    • scholarschools.com makes the same mistake. If it just said "light is a form of electromagnetic radiation", everything would be fine, but instead it claims that light energy is electromagnetic radiation, which is just plain wrong. It's taking one property of electromagnetic radiation and pretending that's a complete description of the electromagnetic radiation. It ought to be obvious that it isn't anything like a complete description.
    • byjus.com is probably the worst example of the three. First, it conflates the difference between "light energy" and "kinetic energy"; that is, it doesn't even appreciate that these are different "forms of energy". Then it claims that kinetic energy has the ability to make visible light, which it (obviously?) doesn't. The last sentence is fine, although it's not really a definition so much as a deduction.
    Moving on...
    This is unproblematic.
    Pop science getting it wrong.

    A photon is not a packet of energy. You can't open the packet and see anything. You can't put energy in a packet, because energy is a concept.
    No problems here. Notice the form of words: "the energy of the photon". It doesn't claim the photon is the energy or the energy is the photon. It only says that it's possible to (conceptually)associate some energy with a photon. Of course, if doesn't say that explicitly.
    Just wrong, again. Pity any poor science students who rely on study.com.
    Logically, you can't, because they don't all agree with one another.
    Half right, but still half wrong, I'm afraid. Back to school with you!
  20. James R Just this guy, you know? Staff Member


    Welcome to sciforums. Did this discussion inspire you to sign up?
    Did you read through the whole thread? I have explained why several times, in some detail.

    I'm happy to answer questions.
    Light is not a form of information. Information, like energy, is a concept. Light is made of physical particles.
    Hmmm.... spacetime. Are you sure that's not a concept? And what about that curvature thingy you mentioned? That sounds like maths.
    It is a "thing". It's just not an entity, in the sense I have defined that term. It's a concept, an attribute.
    Yes. All that means is that if you calculate a number at the start of some process, you'll get the same number when you recalculate at the end of the process.
    The photons are absorbed in some way. As a result, some electrons move around a bit faster, or something along those lines. There is no "conversion" of photons to electrical energy. How could a particle possibly be "converted" into a number?
  21. James R Just this guy, you know? Staff Member

    I wrote "gravitational potential energy". Don't be petty.
    Why did you skip out on considering the matter of where the gravitational potential energy is?
    How disappointing of you to try an ad hominem attack. I really expected you would be among the last of the people here who would express his frustration by resorting to that kind of nonsense.

    If you're going to keep engaging with this, please do so in good faith. If you feel like you can't do that, it might be better to just walk away from it and take some deep breaths.

    If you had fully considered all the points I put to you and come up with arguments to refute them, then you might be on more solid ground. But to claim that I am incapable of understanding this discussion - which, I might add, you jumped into very late in the piece - is just silly nonsense. Do better.
  22. James R Just this guy, you know? Staff Member


    The main error is in the part that says "In the paper, Einstein proposes the existence of energy quanta, light particles now called photons,..."

    Yes, Einstein proposed the existence of energy quanta. I can't recall whether he introduced the word "photon" in his 1905 paper. But to confuse the energy quanta with photons is not something I think that Einstein did. That is a mistake made by whoever wrote that description of Einstein's paper.
    Typically, photons lose energy when they are absorbed, at which point they disappear. Also, don't misunderstand. All that happens to the energy when a photon disappears is that a number is moved from one column in somebody's energy ledger to a different column. The photon itself is not the energy. The energy was never the photon.
    Yes. You might like to consider the notion that photons have a frequency, too: a rather strange thing for a particle to have, you might say. Maybe this frequency thing is an attribute we use to describe the photon. Maybe the energy is somehow related to the frequency.... oh wait! E=hf for a photon. There's an equation, with some numbers! A number on the left called "energy", and two numbers on the right, called "Planck's constant" and "frequency".

    If, as some have claimed, a photon is energy, we might ask: where is the photon in that equation I just wrote down? Is the "E" the photon, perhaps?
    I'm not. I said energy is a number.

    It seems that lots of people don't like the idea that energy is a number, for some reason. But that's what it is.
    Okay. So what?
    The frequency is of an oscillating field.

    I take it that this frequency you mention can be described as an attribute of this oscillating field you mention? Something used to describe the oscillating field? Is it a number, by any chance?
    Are oscillating fields numbers?
    As a substance, it doesn't make sense. Because energy isn't a substance.
    Okay. So what?
    Right. And energy, generally speaking, lacks those properties - spin, polarisation, momentum.

    This ought to suggest to people that a photon is not energy, and energy is not a photon. But for some reason, there's a disconnect in understanding.
  23. Guestfornow Registered Member

    Where does the equation say energy is a number?

    The thing about qualitative statements, about saying you know what something is, is that it has to line up with what other people in the scientific community say. Suppose instead of energy and light, the subject is time. Is time a number, why does it move in the same direction, at an apparently (up to quantum measurements) linear pace? How do numbers flow?

    Can you tell us, since you know energy is a number? I maintain this is not what physics says about energy.
    It could be that it's an entirely human invention, but maybe time is too. Can you say?

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