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Contradiction between the show Cosmos and what someone here told me?

  1. Apr 22, 2016 #1
    In my thread titled "What does cold hydrogen gas emit at 1420 MHz?", physicsforums member blueleaf77 told me the following: "There are three main types of interaction between bound state electrons and photons: absorption, stimulated emission, and spontaneous emission. The first one involves annihilation of a photon to raise the electron state to a higher level. The last two, opposite to the first one, involve creation of a photon by decreasing the state of an electron to a lower level, and eventually to end up in the ground state."

    I just watched the Cosmos: A Spacetime Odyssey episode Hiding in the Light. In Hiding in the Light, the host Neil Degrasse Tyson explained how photons of light and the electrons of an atom interact with each other. Tyson said that when an electron absorbs a photon, the energy of the photon will cause the electron jump up to an orbital with a higher energy level. I've known that for over a decade. But then Tyson said that nobody knows why electrons drop down to lower energy levels. From what blueleaf77 told me, I thought that what causes the electron to drop down to a lower energy level is the electron's emission of a photon.

    What am I missing here? I learned about what blueleaf77 told me about the interactions between photons and electrons many years ago, but I forgot that information when I made the thread "what does cold hydrogen gas emit at 1420MHz". I thought that what blueleaf told me about an electron's emission of a photon causing the electron to drop to a lower energy level is correct.

    Who is correct, Neil Tyson or blueleaf77? Or are they both correct and i'm just missing something?
     
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  3. Apr 22, 2016 #2

    phinds

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    I think the correct statement is that the electron emits a photon BECAUSE it drops to a lower energy level so I see no conflict.
     
  4. Apr 22, 2016 #3
    I think I see your point here, but I want to clarify by putting the proper noun in place of the pronoun to be 100% sure. When you wrote the above quote, did you mean the following: "I think the correct statement is that the electron emits a photon because the electron drops to a lower energy level so I see no conflict" ? Is that what you mean?
     
  5. Apr 22, 2016 #4

    phinds

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    Yes, I thought that's exactly what I said.
     
  6. Apr 22, 2016 #5
    Phinds, the way blueleaf77 said it, it sure sounds to me like blueleaf77 was saying that the emission of the photon causes the electron to drop to a lower energy level, not that the electron drops to a lower energy level for unknown reasons and this causes an emission of a photon.

    Edited: I used the wrong word for the very last word of the post.
     
  7. Apr 22, 2016 #6
    No, it's not. You used the pronoun it instead of writing electron.
     
  8. Apr 22, 2016 #7
    The absorbtion of a photon causes an electron to absorb enough energy that the electron jumps to a higher energy level. Wouldn't it be logical to assume that the emission of a photon by an electron causes the electron to emit or lose enough energy that the electron drops to a lower energy level?
     
  9. Apr 22, 2016 #8

    phinds

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    No, I don't see why. The issue is WHY does the electron change back to a lower lever. That it emits a photon in doing so is a consequence, not a cause.
     
  10. Apr 22, 2016 #9
    You're just begging the question. What i'm saying is the following: How do you know that the emission of a photon is a consequence, not a cause?
     
  11. Apr 22, 2016 #10

    phinds

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    Yes, I see what you mean but it just seems natural to me that something causes the electron to change state and that causes the emission of a photon rather than the other way 'round.
     
  12. Apr 22, 2016 #11
    It doesn't seem natural to me. I always thought that the electrons went to higher energy levels and lower energy levels from absorbing photons and emitting photons respectively. It really surprised me when Neil Tyson said nobody knows why electrons drop to lower energy orbitals.

    DO you have any other evidence other than your intuition (and other than what Neil Tyson said in Cosmos) to support your argument that the emission of a photon is a consequence not a cause?
     
  13. Apr 22, 2016 #12
    What has always seemed natural to me is that the emission of a photon causes an electron to drop to a lower energy orbital. Here is my logic: The photons absorbed and emitted by electrons have energy. When an electron absorbs a photon, the electron also absorbs the photons energy and this causes the electron to have enough energy to jump to a higher energy orbital. When an electron emits a photon, the electron loses the energy of the photon, and this causes the electron to drop to a lower energy orbital. Ten years ago, I thought all that was a scientific fact believed by all physicists. The fact that in 2014 on the Cosmos show Neil Tyson said "nobody knows why the electrons drop to a lower energy level" makes me think that what I believed ten years ago was wrong. Although I still don't know how Tyson and other physicists know i'm wrong.
     
  14. Apr 22, 2016 #13

    phinds

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    Nope.
     
  15. Apr 22, 2016 #14
    From lurking here and reading your previous posts here over the years, I'm sure that you're far more knowledgeable than I am about science (I'm a trucker not a scientist or engineer). I wonder if Neil deGrasse Tyson could tell me how he knows that the emission of a photon is a consequence of the electron's dropping to a lower energy level, not a cause.

    Could you give any thoughts on my logic in post #12? I mean, I know you disagree with my logic, but could you tell me anything else interesting?
     
  16. Apr 22, 2016 #15

    phinds

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    My logic is this: When the photon hits the electron, that's a positive action, not something passive, and it is therefore understandable in hindsight (now that we know) that this causes the electron to jump up in energy level. There is nothing spontaneous going on here.

    It seems to me that if the electron just randomly emitted a photon that would be a spontaneous event. Being a spontaneous event, one might expect it to occur to any electron at any time, other than if the electron is at the ground state. This does not happen. It only happens with electrons that have had their energy state bumped up. I therefore conclude that the assumption of a spontaneous event is incorrect.

    That leads to the conclusion that something OTHER than the emission of a photon must be causing the electron to drop back in energy level.

    Since we don't know what that something is, we cannot say that it is not spontaneous and of course if IT is spontaneous then we're back to the argument of why should not then the emission of a photon be spontaneous.

    I just have an unsupported gut feeling that it is more reasonable that we will find something that is NOT spontaneous that causes the electron to drop back in energy level. That is, there will be a discernible cause. A spontaneous photon emission does not see to HAVE a cause and that's why I don't like to use it, as causeless occurrence, as the cause of the energy drop.

    I understand that this line of reasoning can be looked at as circular. That is, perhaps we'll find some non-spontaneous cause for the emission of the photon and thus be able to assign it as the cause of the electron's energy drop, I just find this direction in the circular logic path to be less likely than the direction I propose.
     
  17. Apr 22, 2016 #16
    Phinds, that's very interesting. I would agree with you unreservedly, except that as you can see in my original post on this thread, blueleaf77 told me that there are two types of cases where electrons emit a photon: stimulated emission and spontaneous emission. Therefore, isn't blueleaf saying that electrons DO spontaneously emit photons?

    https://en.wikipedia.org/wiki/Spontaneous_emission

    From Wikipedia:
    Spontaneous emission is the process by which a quantum system such as an atom, molecule, nanocrystal or nucleus in an excited state undergoes a transition to a state with a lower energy (e.g., the ground state) and emits quanta of energy


    -------------------------------------------------------------------------------------------

    Edited to add this: A lot of weird, counterintuitive things happen when you get into quantum physics. I'm not so sure that our normal everyday rule of every physical action must have a cause applies on the atomic level.
     
  18. Apr 22, 2016 #17
    Are you sure that the only electrons that drop to a lower energy orbital and emit photons are electrons that have had their energy state bumped up? I don't remember ever hearing that or seeing that written before.

    Assuming for the sake of argument that the only electrons that drop to a lower energy orbital and emit photons are electrons that have had their energy state bumped up, maybe there is something we don't know that allows electrons that have had their energy levels bumped up to spontaneously emit photons but that thing we don't know does not allow electrons who have not had their energy levels bumped up to spontaneously emit photons. So I don't think we can definitively rule out that the emission of the photons is spontaneous.
     
  19. Apr 22, 2016 #18
    I just researched this more in-depth on physicsforums and found that on April 8, 2014, someone made a thread at physicsforums asking why electrons drop energy levels when they emit a photon. April 8, 2014, was just two days after the Cosmos episode aired in which Neil Tyson said nobody knows why electrons drop energy levels, so I suspect that the person who asked that question asked it in response to what Neil Tyson said on Cosmos.
    Nobody who responded on that thread could definitively prove why electrons drop energy levels, but most of the speculation was that the reason the electrons drop energy levels had something to do with quantum field theory (weird).
     
  20. Apr 22, 2016 #19

    phinds

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    Well, I do have to say that my opinions on all this are from a base of almost total ignorance, so ... not to worry if you disagree w/ me, and yeah I do see your point with the other references.
     
  21. Apr 22, 2016 #20
    To me, it seems like a lot of science at the atomic level seems to rely on a lot of uncashed checks. I took Inorganic Chemistry I and II at a university, and I didn't want everyone to hate me, so I didn't ask such questions there. If I asked my professors "How do you know this?" everytime I didn't know how something was proven through experiments, the class would have revolved around me and we would have moved through at a snail's pace.

    Before I posted this thread, had you ever wondered about what causes the electrons to drop to a lower energy level when they emit photons?
     
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