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

[bluemoonKY]

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?

 

[phinds]

...I thought that what causes the electron to drop down to a lower energy level is the electron's emission of a photon.

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.

 

[bluemoonKY]

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.

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?

 

[phinds]

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?

Yes, I thought that's exactly what I said.

 

[bluemoonKY]

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.

 

[bluemoonKY]

Yes, I thought that's exactly what I said.

No, it's not. You used the pronoun it instead of writing electron.

 

[bluemoonKY]

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?

 

[phinds]

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?

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.

 

[bluemoonKY]

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.

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?

 

[phinds]

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?

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.

 

[bluemoonKY]

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.

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?

 

[bluemoonKY]

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.

 

[phinds]

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?

Nope.

 

[bluemoonKY]

Nope.

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?

 

[phinds]

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.

 

[bluemoonKY]

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


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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.

 

[bluemoonKY]

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.

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.

 

[bluemoonKY]

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).

 

[phinds]

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.

 

[bluemoonKY]

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?

 

[phinds]

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.

I was just the opposite. Didn't give a damn what anyone thought about me and wanted to get my money's worth so I asked most every question that popped into my head. Not everyone loved me because of it.

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?

No, I'm an engineer. It does what it does and my understanding it isn't going to change what it does and isn't going to give me any information that I feel I'll either (1) be happy about knowing or (2) find a practical use for. Don't take that attitude with everything but I struggle with a lot of this stuff and I prefer to pick my battles.

 

[bluemoonKY]

No, I'm an engineer. It does what it does and my understanding it isn't going to change what it does and isn't going to give me any information that I feel I'll either (1) be happy about knowing or (2) find a practical use for. Don't take that attitude with everything but I struggle with a lot of this stuff and I prefer to pick my battles.

I know what you mean, but you must have a modicum of curiosity and interest about this stuff or you wouldn't post about it so much.

I asked a physicist here about this on private message, and he told me that neither the emission of a photon nor the electron's dropping in energy levels are the cause of the other. How does he know this? The cause must come before the effect. And the emission of a photon and the electron's dropping in energy levels happens simultaneously. How does he know that the emission of a photon and the electron's dropping in energy levels happens simultaneously? Because if they didn't occur simultaneously, the law of conservation of energy would be violated. This physicist's explanation seems compelling to me.

 

[phinds]

I know what you mean, but you must have a modicum of curiosity and interest about this stuff or you wouldn't post about it so much.

I asked a physicist here about this on private message, and he told me that neither the emission of a photon nor the electron's dropping in energy levels are the cause of the other. How does he know this? The cause must come before the effect. And the emission of a photon and the electron's dropping in energy levels happens simultaneously. How does he know that the emission of a photon and the electron's dropping in energy levels happens simultaneously? Because if they didn't occur simultaneously, the law of conservation of energy would be violated. This physicist's explanation seems compelling to me.

I'm not so sure about that. The time between cause and effect can be essentially zero, I think, and not violate any conservation laws. That seems to be particularly possible at the quantum level but it's possible that's a misunderstanding on my part.

 

[bluemoonKY]

I'm not so sure about that. The time between cause and effect can be essentially zero, I think, and not violate any conservation laws. That seems to be particularly possible at the quantum level but it's possible that's a misunderstanding on my part.

Either you are misunderstanding what the physicist told me, or you made a typo, or I am misunderstanding you. I agree with the physicist that if two events happen simultaneously, then neither or the two events caused the other one. If neither of the two events caused the other one, neither of the two events is an effect of the other one either. How can the time between cause and effect be zero?

 

[phinds]

Either you are misunderstanding what the physicist told me, or you made a typo, or I am misunderstanding you. I agree with the physicist that if two events happen simultaneously, then neither or the two events caused the other one. If neither of the two events caused the other one, neither of the two events is an effect of the other one either. How can the time between cause and effect be zero?

I didn't say zero and certainly didn't mean to imply it. "Essentially" zero means really really small ... perhaps a Plank Time in this case.

 

[bluemoonKY]

I didn't say zero and certainly didn't mean to imply it. "Essentially" zero means really really small ... perhaps a Plank Time in this case.

It was one of the three possibilities I mentioned: I misunderstood you.

When I made the post, I did think for a moment that essentially zero might mean an infinitessimaly small amount of time, but I thought your meaning zero was more likely.

Very interesting point though.

 

[SteamKing]

In situations like this, the logical fallacy "post hoc, ergo propter hoc" must be considered (translation: "After this, therefore because of this").

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

In the absence of any detailed knowledge of what is occurring with an electron around the time that it emits a photon and then drops to a lower energy state, it is quite easy to make the connection: "Electron emits photon; therefore the drop to a lower energy state of the electron is because of this emission."

The cause and effect of spontaneous occurrences are hard to pin down, due to the random nature of the spontaneous occurrence, be it emission of a photon by an electron or the decay of a particular radioactive nucleus. For the particular phenomenon at hand, spontaneous emission of photons by electrons, a special field of physics called quantum electrodynamics (QED) studies such occurrences:

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

The physicist Richard Feynman won his Nobel prize for his work in this field.

Even though QED doesn't have all the answers, it does allow one to estimate the probability that an electron will emit a photon, and the behavior of a large number of such occurrences can be analyzed using regular statistical techniques, due to their random nature. Even though one can make certain calculations about spontaneous emission, the cause of the emission in the first place is still obscure.

Even if it wasn't, you would probably need a PhD. in QED to understand it.

 

[bluemoonKY]

In situations like this, the logical fallacy "post hoc, ergo propter hoc" must be considered (translation: "After this, therefore because of this").

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

In the absence of any detailed knowledge of what is occurring with an electron around the time that it emits a photon and then drops to a lower energy state, it is quite easy to make the connection: "Electron emits photon; therefore the drop to a lower energy state of the electron is because of this emission."

I agree. I am well aware of the Post hoc ergo propter hoc logical fallacy. Conversely, in the absensce of any detailed knowledge of what is occurring within an electron around the time that it emits and photon and drops to a lower energy state, it is also quite easy to make the connection: "Electron drops to lower energy state. Therefore, the emission of a photon is because of the electron's dropping to a lower energy state."

SteamKing, do you have any opinion on if there was just a plank time between the electron's dropping to a lower energy state and the emission of the photon, could the law of conservation of energy NOT be violated? This has implications on whether or not one of the two occurrences could have caused the other.

 

[SteamKing]

I agree. I am well aware of the Post hoc ergo propter hoc logical fallacy. Conversely, in the absensce of any detailed knowledge of what is occurring within an electron around the time that it emits and photon and drops to a lower energy state, it is also quite easy to make the connection: "Electron drops to lower energy state. Therefore, the emission of a photon is because of the electron's dropping to a lower energy state."

SteamKing, do you have any opinion on if there was just a plank time between the electron's dropping to a lower energy state and the emission of the photon, could the law of conservation of energy NOT be violated? This has implications on whether or not one of the two occurrences could have caused the other.

No, I don't. QED is rather out of my wheelhouse.

BTW, it's Planck time (for Max Planck, who proposed quantum theory):

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

Remember, very little is known about the structure of the electron. It's kind of a weird particle, since it can act as a particle or it can act as a wave, like light.

Physics is good at describing how something acts, but does less well at describing why something acts the way it does.

 

[DrDu]

The physicist Richard Feynman won his Nobel prize for his work in this field.

Methinks he wasn't the only one.

 

[DrDu]

But then Tyson said that nobody knows why electrons drop down to lower energy levels.

If he really said so, that's utter nonsense. As has been mentioned before, we can calculate the rate of spontaneous emission with fantastic precision using QED. While QED calculations are in deed involved, the main argument is easy to sketch: The electromagnetic field is a quantum object and as such the electromagnetic field is not completely absent even in the ground state (called vacuum). I.e. although the number of photons is zero in the vacuum, there is still an electromagnetic field present which perturbs the hydrogen atom and causes stimulated emission. Compare the electromagnetic field with the hydrogen atom: Also in the ground state of the hydrogen atom, the momentum and energy of the electron are non-vanishing and the 1s orbital has a finite size.

 

[DrDu]

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?

Apparently, you had bad teachers.

 

[bluemoonKY]

If he really said so, that's utter nonsense. As has been mentioned before, we can calculate the rate of spontaneous emission with fantastic precision using QED. While QED calculations are in deed involved, the main argument is easy to sketch: The electromagnetic field is a quantum object and as such the electromagnetic field is not completely absent even in the ground state (called vacuum). I.e. although the number of photons is zero in the vacuum, there is still an electromagnetic field present which perturbs the hydrogen atom and causes stimulated emission. Compare the electromagnetic field with the hydrogen atom: Also in the ground state of the hydrogen atom, the momentum and energy of the electron are non-vanishing and the 1s orbital has a finite size.

DrDu,I don't see how what you wrote in the above paragraph explains the cause of an electron's dropping to a lower energy level when it emits a photon. Maybe an expert could read what you wrote and understand how that explains the cause of an electron's dropping to a lower energy level, but what you wrote does not explain it to me. Could you break this down further or simplify it and explain how the above paragraph explains the cause of an electron's dropping to a lower energy level?

Edited to add this: The electromagnetic field causes stimulated emission of a photon, but what causes the electron to drop to a lower energy level? Does the emission of a photon cause the electron to drop to a lower energy level?

 

[phinds]

@DrDu, I'm curious about this as well. You seem to be implying that the drop in energy state is an effect and electron emission is a cause. Do we really know that for sure?

 

[Borek]

I wonder if it is not a matter of difference between "why" and "how". We can describe the process ("how"), but do we know "why" it happens?