Uncertainty of an Observable

[pmb]

Dear Fellow Physics Lovers,

 

I'm looking to put together a blog discussing Heisenberg's Uncertainty Principle and the some of its ramifications. The intent of the piece will be to educate people who have an interest in it, but limited knowledge of it. So that I can pitch what I say at the right level I need a better handle on what people think uncertainty is. I'd appreciate it if you would take a couple of minutes to write what uncertainty means to you in the context of quantum mechanics.

 

I'll wait a few days before I post in this thread again. At that time please let me know if you'd like my input on the definition. If you don't wish to wait then feel free to PM me. Thanks.

Edited June 13, 2012 by pmb

[Aethelwulf]

Uncertainty for me, is the lack of knowledge from an observer. Of course, the most basic explanation is that it requires two complimentary observables which are of course conjugate quantities, such as energy and time or momentum and position. However it holds a type of mysticism for me because it is the inability to predict the future based on the present - which means that ordered sets of events are hard to determine.

[md65536]

From an "interested but limited knowledge" perspective:

 

Uncertainty is the physical impossibility of measuring both of certain pairs of aspects to arbitrary precision.

The key point being that it is not that it is difficult to the point of impossibility to measure both precisely, but perhaps meaningless?

I would say that the reality of a thing is different depending on how you look at it, and if you look at it in a way that for example position can be very precisely known, then from that point of view, very precise momentum becomes physically meaningless?, and vice versa.

 

 

 

 

Also something about a wave

When I first accepted the idea that knowing one thing can prevent knowing another, I think it was explained in terms of a wave.

[Bill Angel]

It might help you to take a trip to the library:-)

I'm currently reading "101 Quantum Questions" by Kenneth W. Ford. Question 74 is "What is the uncertainty principle?" and question 75 is "How does the uncertainty principle relate to the wave nature of matter?". The author's explainations are aimed at readers who are intelligent and curious, and also willing to devote some time and effort in pondering his explainations.

[pmb]

It might help you to take a trip to the library:-)

Nah. I already know what uncertainty is. I learned what it was when I studied quantum mechanics in graduate shool. I don't want to say more than I already have so that I don't interfer with the responses.

[Bill Angel]

Nah. I already know what uncertainty is. I learned what it was when I studied quantum mechanics in graduate school...

I took three semesters of quantum mechanics in a graduate physics program (30 years ago) and back then also served as a teaching assistant in an introductory physical chemistry course. The course was basically an introduction to quantum mechanics for chemistry and biology majors. Now that I've mentioned my credentials the point I want to make is that I did nowhere near as good a job in getting across the basics of quantum theory to these undergraduates (in the sense of making it interesting) as the author of the book that I mentioned does, for the benefit of the interested but uninformed reader. My approach was typical of a physics major, i.e. "the Schrodinger equation explaines how things work at a microscopic level, and if you can't accept this, it's too damn bad and it's your problem!"

[pmb]

It might help you to take a trip to the library:-)

I'm currently reading "101 Quantum Questions" by Kenneth W. Ford. Question 74 is "What is the uncertainty principle?" and question 75 is "How does the uncertainty principle relate to the wave nature of matter?". The author's explainations are aimed at readers who are intelligent and curious, and also willing to devote some time and effort in pondering his explainations.

Do you have a scanner? If so then can you scan question 74 into a file and e-mail it to me? Thanks.

[imatfaal]

!

Moderator Note

I am not sure that scanning a section of a text to be emailed to another member would fall under academic fair usage - and as such, could we avoid such requests in the future please as they could be construed to be a request to breach copyright

[Aethelwulf]

If it is in an email, I should doubt it is in breach of copyright.

[pmb]

If it is in an email, I should doubt it is in breach of copyright.

Especially since its only a smal portion. I'll e-mail the publisher and author and ask for their permission.