# Electron and the uncertainty principle

1. Dec 8, 2011

### austim14

I completly understand the uncertainty principle and why we cant pinpoint the exact location of an electron. but what if we could?? would it be important that would could find the location of an electrom? would we know more about atoms?

2. Dec 8, 2011

### eddybob123

The answer is no. The uncertainty principle is just an equation stating what actually happens. It also takes humans one step closer to a complete unified theory.

3. Dec 9, 2011

### joeypielago

i also thought about that when i studied the uncertainty principle, im wondering what diffrence could it make if someone could determine the exact location and momentum of an electron inside an atom?

4. Dec 9, 2011

### tyagi Anurag

wave function sci contain all the information about the moving micro particle and mode of sci square gives the probability of finding the particle........bcoz sci has no physical significance.

5. Dec 9, 2011

### Bobbywhy

Austim14:
It seems you do not have a complete understanding of the Uncertainty Principle. The position (exact location) of a particle CAN be known completely, contrary to what you posted.

“One striking aspect of the difference between classical and quantum physics is that whereas classical mechanics presupposes that exact simultaneous values can be assigned to all physical quantities, quantum mechanics denies this possibility, the prime example being the position and momentum of a particle. According to quantum mechanics, the more precisely the position (momentum) of a particle is given, the less precisely can one say what its momentum (position) is.”

http://plato.stanford.edu/entries/qt-uncertainty/

6. Dec 9, 2011

### Naty1

It would render our formulation of quantum mechanics obsolete and turn one of the most accurately tested theories upside down.

http://en.wikipedia.org/wiki/Uncertainty_principle

7. Dec 9, 2011

### mgervasoni

Isn't the electron's valence/ shell / layer a type of knowing where the electrons are?

8. Dec 9, 2011

### Staff: Mentor

No. It is simply a probability map of where it MIGHT be.

9. Dec 9, 2011

### mgervasoni

Do you happen know the experiments that support the uncertainty principle? I'd like to see if there's any other explanation, and if not, finally buy into quantum physics and stop being frustrated by it.

10. Dec 9, 2011

### DaveC426913

Well, all of them...

Actually, forget experiments, the thing you're typing on supports it. No electronic device in your house (or tens of millions of other houses) would work without it. It is the very basis of every transistor built in the last several decades.

11. Dec 9, 2011

### mgervasoni

It's the basis of every transistor built? How does my computer support it? Please back up these statements.

12. Dec 9, 2011

### DaveC426913

Transistors are semi-conductors. Modern semi-conductors take advantage of quantum tunneling (across an energy barrier). HUP explains quantum tunneling. No classical theory does.

13. Dec 9, 2011

### Staff: Mentor

14. Dec 9, 2011

### mgervasoni

This may seem stupid, but how do they know it's not a transfer of electrons from the barrier? I'm no physicist so please be nice ;) but can we say all electrons are universally the same?

Like if the barrier was a brick wall, and you thru a brick at it. The brick pushes one brick out to the other side and squeezes into it's place, giving the appearance of you throwing a brick through the wall, but really just transferring the brick [electron(s)]

15. Dec 9, 2011

### mgervasoni

They always show those images in the documentaries about quantum physics about some guy standing at a wall pushing and in quantum physics sometimes he would go through that wall. But it's not a guy and a wall.. They are atoms and electrons. Atoms make up everything, and electrons are in atoms. So its like a wall made of circles (electrons), squares (protons), and triangles (neutrons). If you push a whole bunch of circles against the wall some of the circles will go thru (or appear to go thru and just be transferring) and some of the circles will bounce off the squares (protons) and triangles (neutrons). I mean thats more accurate than how they analogize it on NOVA, but again, I don't know the mathematics, tests, and schematics behind it so maybe what I'm saying doesn't work?

16. Dec 9, 2011

### Staff: Mentor

See here: http://en.wikipedia.org/wiki/Quantum_tunneling

Mgervasoni, instead of simply questioning everything here on PF, it would be much more effective for you to pick up a book on Quantum Mechanics and read for yourself WHY it's like this. I highly recommend this one: https://www.amazon.com/Introducing-...8505/ref=sr_1_1?ie=UTF8&qid=1323484353&sr=8-1

It does a very good job of explaining not only the basics of quantum mechanics, but also the history of WHY QM was needed and the problems in Classical Physics. And it is extremely easy to understand. And the best part is that it is ILLUSTRATED! Many of the pictures are quite humorous and I thoroughly enjoyed this small book. Click the link and then you can look at some of the pages inside the book by clicking on the picture at the top left.

17. Dec 10, 2011

### mgervasoni

You're right, that's exactly what I should do and I thank you for a good recommendation on a book on QM as they can be hard to find. Thanks.

18. Dec 10, 2011

### mgervasoni

Also found some of the basic/first experiments for QM physics here: http://www.higgo.com/quantum/laymans.htm [Broken]

The answer "All of them" was perhaps the most non-educational and thought discouraging answer one could give. I was under the impression that a forum was a medium for discussion and learning, and I thought at a physics forum it would be full of intelligent answers and other sources than wikipedia, which in my opinion is garbage. If a contributor doesn't feel like giving any effort or time or joining a discussion, let it alone. Don't give short and unsupported answers to very interesting and awe-inspiring questions. It's as if someone has a brilliant thought and you point out he misspelt a word. In the information age we live in we should strive to give logical, meaningful, thoughtful answers and not get stuck in any one belief.
In the Dark ages no one questioned things. People would see a bridge, but no one would know how it was built. It's like a kid who eats his french fries and doesn't know they come from potatoes, because he wasn't taught. It's not his fault his teacher's are bad. If people spread their knowledge the world will be better. If people say "French fries are french fries, they come from McDonald's", we will suffer.

Last edited by a moderator: May 5, 2017
19. Dec 10, 2011

### mgervasoni

The thing a book lacks is dialogue. I start reading the books and asking.. well why? how did they know that? What are these experiments? Are there any other explanations? Maybe our idea of what light is, could be changed. Maybe we don't even truly understand gravity. That is why I joined the forum. I thought that was what a forum was about. If you think books > discussion, then we don't agree. I read books, and watch the MIT lectures, and have questions and come here to find answers and discussion. You don't have to stifle my thoughts. I think any respectable person who is in the field of physics should know the answers to these questions and easily explain them, or perhaps be asking them him/herself.

I'm not trying to "simply" question "everything". I am trying to have a discussion with people that know more than me, so that I learn. I'm not here saying anyone is wrong or acting like a fundamentalist zealot. What I am doing is purposing a question about the most basic principles in physics, so that I can have a strong foundation to grow on. If my questions bother you because they sound too simple, I understand. But you should understand that we don't know the answers. That we've never seen an atom so it's all intelligent guesswork. That the most intelligent physicist say we don't have gravity 100% figured out.

20. Dec 10, 2011

### DaveC426913

The problem is, there is no way a forum can provide enough info to you to have a two-way conversation with those who have been doing work in the field. The best a forum can do is say 'here's how it is, you can do further reading or you can take our word for it'.

There is just too much to know. The only way to have a two-way discussion at the level you're looking for is to go to school.

Either one learns the math and then studies Bell's Inequality Theorem and sees first hand that it demonstrates a profound truth about how QM must operate - or one has no choice but to take for it granted because that enough fine minds have come to that conclusion.

Last edited: Dec 10, 2011
21. Dec 10, 2011

### mgervasoni

I disagree. There might as well not even be a forum then. Unless it's here to answer people's homework questions.

forum |ˈfôrəm|
1 a place, meeting, or medium where ideas and views on a particular issue can be exchanged

Ok easy to disprove this: How about books like Bill Bryson's A short history of nearly everything? All you need is someone patient enough to explain things to you. A teacher doesn't have to be a college professor. You can be a teacher Dave, but maybe you're just no good at it or don't want to.

Do you hear yourself? Fine minds came to fine conclusions in classical physics. Einstein didn't come up with what spawned into modern physics from studying Newton's math.. it was his ideas and imagination. I don't want to argue or have a conversation with you, there's no point. You see things totally different than I. Perhaps I'm not "in the field" like you are, or an expert. But I am an expert or "experienced" at one or two other things, one of which is piano; if someone asked me why there are 12 notes in a scale and if there could possibly be some in between notes we are missing, I would think.. wow what an odd and interesting thought. Perhaps there could be. Why are there 12.. why can't we squeeze a tone or two in there, etc. And no matter how much of an "expert" I thought I was at something, I would always rather consider myself a beginner. A beginner isn't brainwashed and told theories that he must take as fact for years. A beginner can learn and question and imagine. An expert is full of himself, thinks he knows it all and therefore will not learn anything new. In my opinion, it is much better to always consider one's self a beginner, leaving possibilities open and thinking "outside the box".

"In the beginner's mind there are many possibilities. In the expert's mind there are few."

22. Dec 10, 2011

### mgervasoni

and this thing we're having, although the subject has now changed from physics to the ability to discuss physics, is a discussion. Wouldn't you rather talk about physics than the inability to?

23. Dec 11, 2011

### Staff: Mentor

Nonsense. Einstein built his theory upon a framework of previous work by scientists before him, including Newton.

Not everything is known, and thus there are plenty of new things to be discovered. However quantum mechanics works, and it works beautifully and accurately. Even if a better theory is eventually discovered it wouldn't mean Quantum Mechanics is wrong. It isn't. You could still use it exactly as we use it today and it would be correct. Just like how we can and do use classical physics today even though we have GR and QM.

The real issue here is that you are looking for these "ulterior" explanations without a working knowledge of how things already work. THAT will get you nowhere. At the very least you need to know how things work just to be able to know whether something new is correct or incorrect. Einstein, Bohr, and all the scientists that worked on GR and QM had an depth knowledge of classical physics and were there at a time when problems were appearing. You don't have in depth knowledge and you aren't approaching known problems.

Now, as Dave has already stated, an online forum is NOT the place to learn the fundamentals. That's why we have books that delve into the math and the "boring" stuff as I like to put it. If you don't learn that stuff then you aren't learning the theory.

24. Dec 11, 2011

### eaglelake

Your basic assumption is incorrect! In quantum mechanics , we do pinpoint the exact location of an electron. In quantum mechanics we always assume that we have an ideal measuring device that measures the position with infinite precision. A quantum measurement is always perfect! When we measure the position we always know it "exactly". Of course, real measurement devices are inaccurate, but such inaccuracies have nothing to do with quantum uncertainty. The important thing is that quantum uncertainty is not the result of an inaccurate measurement.

This common misconception results from the language we use. We say "exact" or "accurate" when we should say "with certainty", which means if we repeat the position measurement many times, we always find the particle in the same position. "With certainty" means there is no uncertainty. I think we can help ourselves if we say "with certainty" to contrast with "uncertain", which means repeated measurements yield different results. For example, in the double slit experiment, in repeated measurements, particles are scattered all over the detection screen, but there is a dot where each particle hit the screen. Here, there is an uncertainty in position, even though we know the exact location of each particle!

Quantum uncertainty has nothing to do with the accuracy of a measurement. Rather, it has everything to do with our ability to predict the measurement result. If we can predict the result there is no uncertainty and we know the observable being measured "with certainty". But, in general, quantum mechanics is indeterminate and it predicts only the probability of getting a getting a particular measurement result. Uncertainty and probability and the indeterminate nature of quantum mechanics all go together.

25. Dec 11, 2011

### Runner 1

Actually, you CAN know both the position and momentum of a particle.

But if you repeat the experiment many times again, and do it exactly the same way that you did it the first time, you will find that the standard deviations of your results adhere to the equation:

$$\sigma_x \sigma_p \geq \frac{\hbar}{2}$$