Note:- Make sure you have read my first article “The advent of Quantum Mechanics” as both are connected.
Hi guys so once again, here we are trying to understand QM, even if a little bit
. This article’s gonna be a bit rough as its more about understanding the 2 opposing views in the field of QM so I request you guys to please bear with me as I’ll try my best to simplify it. We are gonna start with Heisenberg Uncertainty Principle (HUP). The reason for that it is one of the core parts in the modern QM theory and this is in effect (what i think) where the two views started to brew up. I am going to tell you about the conflicting views of Heisenberg and Einstein which started with the HUP and eventually led to Einstein and Heisenberg (together with Bohr) on their separate ways in trying to solve the problems of Quantum Mechanics.
So if you remember correctly from my previous article, I told you how Heisenberg created matrix mechanics and Schrodinger came up with wave mechanics. But most of the physicists sided with wave mechanics as it was easy to visualize. In a letter to Wolfgang Pauli, Heisenberg wrote that he found this idea of visualization as “crap” . However he admitted that wave mechanics had an advantage of visualization but he was still against it. He thought to give his matrix mechanics a sense of visualization and thus ended up giving his uncertainty principle which has far greater and deeper implications than we are taught. If you guys are thinking why was Heisenberg so much against it, i've got an interesting story i read from the net (dunno if it's true or not as i didn't researched much about it.) According to it Heisenberg and his crew were all requested to give lectures in universities about Matrix mechanics and to be appointed as professors. His family was exerting pressure to capture one of the vacancies as older theoretical physicists were leaving and at the last moment Schrodinger pulled out his trump card, THE WAVE MECHANICS, :spiteful: [1].
So according to him questions like “What is the position of the particle”, “What is going on inside the atom”, “What is the path of the particle” are totally meaningless UNLESS one defines a specific experiment that measures that specific property, i.e. the sole act of measurement gives meaning to terms like “position”, “momentum” etc of the particle.
Have you ever wondered just why is it that we can’t measure position and momentum simultaneously... If you don’t know, well then be ready to get your answer. You can measure the position of a particle through an electron microscope but in order to know its position you first have to illuminate the particle by striking it with light or any other EMR. The thing is the smaller the wavelength, the greater the resolving power of the microscope and the greater the accuracy with which you measure the position. But since it’s a particle not a macroscopic object, if you strike it with high energy radiation it will cause a collision thus causing a change in its momentum. So at the instant you know its position i.e. at the instant light or more specifically a photon collides with particle its momentum changes and you can’t determine it simultaneously. But in actuality HUP isn’t “You can’t measure position and momentum simultaneously” it’s more “The more accurate you measure position, the greater spread or variance you get in momentum”. So we could use low energy photons to illuminate the particle… now the position is a little blurry but the change in momentum is less than the previous case, hence the spread in the values of the momentum will be less.
Now all of this is maybe a bit too technical. A great example I found while surfing online is, consider you are blind. You gauge the distances of the nearby object by throwing a rubber ball and having a feel for the time it takes for it to strike that object and reflect back to you. Think of the objects as having the same weight as paper. So you threw the ball, as soon as the ball strikes the object, it displaces… the ball comes to you so you know where the object was but you don’t know where it is now. The act of measuring or observing changed it. This is more commonly known as the “Observer Effect” and is often mixed up with HUP but it’s different. It’s just that the act of measurement changes the system. That’s what is actually happening above. The act of measuring the position changes its momentum. You get me? Oh and don’t confuse the Observer Effect with “Measurement problem” it’s something different.
Apart from that Heisenberg even thought that the sole act of measurement or observing gives existence to a value for that property. As stated by Heisenberg himself,
If this rings a bell for you good, if not let me explain. It has been an assumption from old times (maybe from Newton’s?) that there exists an objective reality i.e. a reality that is independent of us, whether we observe it or not it exists. It’s like saying “The moon exists” even if we can’t see it. This meant that everything had its own path, momentum etc it’s just that we don’t know because we have not measured or observed it yet. But now according to Heisenberg our act of observing gives meaning and creates a particular value for that property. It’d be like saying “The moon exists only if we see/observe it.” :crazy: Absurd ain’t it? These are actually the two different views in Quantum Mechanics.
One says that QM is a tool, things exist and have their own value, its just that we can’t observe them properly because the tool is inefficient and not complete yet.
The other says, no, its reality itself that is blurred and by observing it we give it existence or proper meaning.
Bear with me when I say, mostly the second idea is followed. The first one is known as “hidden variable theory”. I’m not going into detail as to what it is now, but I’ll touch up on that in the upcoming articles.
Hey wait a second, you guys aren’t thinking its bullshit, right? You aren’t thinking “How can observing gives existence to a Abuses will lead to ban moon. That is why "QM is Abuses will lead to banin AWESOME", just keep on reading. (sm2)
Back to where we were. So summing it up, according to Heisenberg measurement gives “meaning” and “existence” and this was the conflicting idea between him and Einstein. I’d like to paste a conversation of Einstein with Heisenberg[2] :
Heisenberg: "We cannot observe electron orbits inside the atom...Now, since a good theory must be based on directly observable magnitudes, I thought it more fitting to restrict myself to these, treating them, as it were, as representatives of the electron orbits."
"But you don't seriously believe," Einstein protested, "that none but observable magnitudes must go into a physical theory?"
"Isn't that precisely what you have done with relativity?" I asked in some surprise...
"Possibly I did use this kind of reasoning," Einstein admitted, "but it is nonsense all the same....In reality the very opposite happens. It is the theory which decides what we can observe."
If you notice the underlined parts, that is where the contradiction lies…Heisenberg thought that a theory should have only those properties that can be observed where as Einstein was of the view that a theory itself decides what we can observe. If you talk about me, I think Einstein here has the view that there is an objective reality, everything exists and a theory decides which things we can observe. If I think like that it supports the idea why Einstein later opposed the theory provided by Bohr and Heisenberg (more on this later.)
Phew… so that in essence was Heisenberg’s uncertainty principle, wanted to keep it short but it got big anyway. I don’t think I have space here to start a new topic so see you in the next article. I’ll probably talk about wave particle duality and measurement problem which is at the heart of QM.
- Umair Ahmed
Hi guys so once again, here we are trying to understand QM, even if a little bit
. This article’s gonna be a bit rough as its more about understanding the 2 opposing views in the field of QM so I request you guys to please bear with me as I’ll try my best to simplify it. We are gonna start with Heisenberg Uncertainty Principle (HUP). The reason for that it is one of the core parts in the modern QM theory and this is in effect (what i think) where the two views started to brew up. I am going to tell you about the conflicting views of Heisenberg and Einstein which started with the HUP and eventually led to Einstein and Heisenberg (together with Bohr) on their separate ways in trying to solve the problems of Quantum Mechanics.So if you remember correctly from my previous article, I told you how Heisenberg created matrix mechanics and Schrodinger came up with wave mechanics. But most of the physicists sided with wave mechanics as it was easy to visualize. In a letter to Wolfgang Pauli, Heisenberg wrote that he found this idea of visualization as “crap”
. However he admitted that wave mechanics had an advantage of visualization but he was still against it. He thought to give his matrix mechanics a sense of visualization and thus ended up giving his uncertainty principle which has far greater and deeper implications than we are taught. If you guys are thinking why was Heisenberg so much against it, i've got an interesting story i read from the net (dunno if it's true or not as i didn't researched much about it.) According to it Heisenberg and his crew were all requested to give lectures in universities about Matrix mechanics and to be appointed as professors. His family was exerting pressure to capture one of the vacancies as older theoretical physicists were leaving and at the last moment Schrodinger pulled out his trump card, THE WAVE MECHANICS, :spiteful: [1].So according to him questions like “What is the position of the particle”, “What is going on inside the atom”, “What is the path of the particle” are totally meaningless UNLESS one defines a specific experiment that measures that specific property, i.e. the sole act of measurement gives meaning to terms like “position”, “momentum” etc of the particle.
Have you ever wondered just why is it that we can’t measure position and momentum simultaneously... If you don’t know, well then be ready to get your answer. You can measure the position of a particle through an electron microscope but in order to know its position you first have to illuminate the particle by striking it with light or any other EMR. The thing is the smaller the wavelength, the greater the resolving power of the microscope and the greater the accuracy with which you measure the position. But since it’s a particle not a macroscopic object, if you strike it with high energy radiation it will cause a collision thus causing a change in its momentum. So at the instant you know its position i.e. at the instant light or more specifically a photon collides with particle its momentum changes and you can’t determine it simultaneously. But in actuality HUP isn’t “You can’t measure position and momentum simultaneously” it’s more “The more accurate you measure position, the greater spread or variance you get in momentum”. So we could use low energy photons to illuminate the particle… now the position is a little blurry but the change in momentum is less than the previous case, hence the spread in the values of the momentum will be less.
Now all of this is maybe a bit too technical. A great example I found while surfing online is, consider you are blind. You gauge the distances of the nearby object by throwing a rubber ball and having a feel for the time it takes for it to strike that object and reflect back to you. Think of the objects as having the same weight as paper. So you threw the ball, as soon as the ball strikes the object, it displaces… the ball comes to you so you know where the object was but you don’t know where it is now. The act of measuring or observing changed it. This is more commonly known as the “Observer Effect” and is often mixed up with HUP but it’s different. It’s just that the act of measurement changes the system. That’s what is actually happening above. The act of measuring the position changes its momentum. You get me? Oh and don’t confuse the Observer Effect with “Measurement problem” it’s something different.
Apart from that Heisenberg even thought that the sole act of measurement or observing gives existence to a value for that property. As stated by Heisenberg himself,
The "path" comes into existence only when we observe it.
--Heisenberg, in uncertainty principle paper, 1927.
--Heisenberg, in uncertainty principle paper, 1927.
If this rings a bell for you good, if not let me explain. It has been an assumption from old times (maybe from Newton’s?) that there exists an objective reality i.e. a reality that is independent of us, whether we observe it or not it exists. It’s like saying “The moon exists” even if we can’t see it. This meant that everything had its own path, momentum etc it’s just that we don’t know because we have not measured or observed it yet. But now according to Heisenberg our act of observing gives meaning and creates a particular value for that property. It’d be like saying “The moon exists only if we see/observe it.” :crazy: Absurd ain’t it? These are actually the two different views in Quantum Mechanics.
One says that QM is a tool, things exist and have their own value, its just that we can’t observe them properly because the tool is inefficient and not complete yet.
The other says, no, its reality itself that is blurred and by observing it we give it existence or proper meaning.
Bear with me when I say, mostly the second idea is followed. The first one is known as “hidden variable theory”. I’m not going into detail as to what it is now, but I’ll touch up on that in the upcoming articles.
Hey wait a second, you guys aren’t thinking its bullshit, right? You aren’t thinking “How can observing gives existence to a Abuses will lead to ban moon. That is why "QM is Abuses will lead to banin AWESOME", just keep on reading. (sm2)
Back to where we were. So summing it up, according to Heisenberg measurement gives “meaning” and “existence” and this was the conflicting idea between him and Einstein. I’d like to paste a conversation of Einstein with Heisenberg[2] :
Heisenberg: "We cannot observe electron orbits inside the atom...Now, since a good theory must be based on directly observable magnitudes, I thought it more fitting to restrict myself to these, treating them, as it were, as representatives of the electron orbits."
"But you don't seriously believe," Einstein protested, "that none but observable magnitudes must go into a physical theory?"
"Isn't that precisely what you have done with relativity?" I asked in some surprise...
"Possibly I did use this kind of reasoning," Einstein admitted, "but it is nonsense all the same....In reality the very opposite happens. It is the theory which decides what we can observe."
If you notice the underlined parts, that is where the contradiction lies…Heisenberg thought that a theory should have only those properties that can be observed where as Einstein was of the view that a theory itself decides what we can observe. If you talk about me, I think Einstein here has the view that there is an objective reality, everything exists and a theory decides which things we can observe. If I think like that it supports the idea why Einstein later opposed the theory provided by Bohr and Heisenberg (more on this later.)
Phew… so that in essence was Heisenberg’s uncertainty principle, wanted to keep it short but it got big anyway. I don’t think I have space here to start a new topic so see you in the next article. I’ll probably talk about wave particle duality and measurement problem which is at the heart of QM.
- Umair Ahmed
Spoiler: show
Spoiler: show
Spoiler: show
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