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Heisengberg's Uncertainty Principle

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mikey4444 | 09:47 Thu 07th Mar 2013 | Science
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Can anyone explain in a relatively simple manner, that non-scientific people would understand, exactly what Heisenberg's uncertainty principle is ?

A simple example of how it might be used would also be welcome.
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Wasn't he the feller who put a cat in a box?
Sorry, I was thinking of someone else:

http://en.wikipedia.org/wiki/Schr%C3%B6dinger's_cat

oh come on, it has been updated to Schrodinger's Bank

Someone padlocked a wodge of fivers in a cash box
and invited people to bet on whether they were there or not

The discussion was meant to centre around if a bank says you are not in credit when you think you are,..... are you ? [in credit]

The winner of course was a bank director (named Fred the Shred) who said of course there is no money there - I am taking it for my bonus !

It is this sort of thing one learns on Maths with Finance courses.
The lectures are availavle on u-tube under the title - Why is everybody rich ?
I quizzed the brains of AB about this subject a couple weeks back and many of your responses are from the same head who tackled my posts. Even if you've attained some level of enlightenment about the issue, you might find the discussion about the implications of said principle on my thread a good read, if you have a spare 10mins :)

http://www.theanswerbank.co.uk/Science/Question1220621.html

http://www.theanswerbank.co.uk/Science/Question1221036.html

It seems contrary to common sense and I found it a difficult pill to swallow, but to understand and accept the observable evidence makes for a much more enjoyable journey into 'reality' :)
Common sense is based on both how we see the world and how we are taught to see it. If the HUP, Relativity etc. seem to defy common sense, that's because common sense is wrong, so we should perhaps be looking to address that in Schools. I've wondered if Science Education for most of the first 11 years or so is trapped in a 19th-century view of the world coupled with only using Newton's way of solving problems. While that works very well it fails utterly when trying to bridge the gap to Quantum Mechanics and what have you.

A far better approach is the so-called "Lagrangian Mechanics" that sadly relies on maths that is beyond High school. But the ideas behind it form a slightly different world view that leads more naturally to Quantum Mechanics. Things would I think be better if we based common sense on that, rather than Newton's Laws. Not sure how to fix this though, since as I say the Lagrangian school of thought is far more maths-heavy.
Jim,
I would say that there is a wide gulf between language and maths to explain natural events. It is for that very reason in fact that maths was invented. early philosophers and scientists needed to invent a new language to express in writing the calculations they were making in their heads. This allowed their theories and realisations to be taught to others, explained in neat equations and provide a framework build up (initially) with basic rules [+ - x /] which later increased in complexity as our knowledge grew.

I'm an etymologist by means of higher education and can defend the term 'common sense' simply by referring to it's use in context by the orator. Here's what the dictionary has to say (it highlights an interpretation you use for the phrase too);

"common sense, an inner conciousness unifying the five outer senses (obs.): average understanding: good sense or practical sagacity: the opinion of a community: the universally admitted impressions of mankind - Dictionary, W&R Chambers Ltd 1977

You seem to be using the last description of common sense as your ammunition to fuel the change of the application of the term, however you must include the first description of it in your argument. Common sense is simply the world we live in as per our sense of it. We know that one cannot be in two places at once, and location and speed through observation can clearly be tracked with time, so I know where the car is and how fast it's going s=d/t.

The quantum world teaches us that particles do have these properties and act differently when being observed or not. It's common sense that if we put a cat in a box with radio active material, a detector and poison, we must think that the cat could be either alive or dead. It is not common sense though to determine that the cat IS both dead and alive, and in every possible quantum state in between. That's merely common knowledge.

It is common knowledge that we don't live in a newtonian world now, people know about Einstein's research and the developments in CERN so I think it's wrong to say they aren't taught these ideas. One must learn to walk before running and learn the backlog history of scientific discovery before furthering their knowledge at higher education. "Standing of the shoulders of giants." - £2 coin (Isaac Newton)

I hope I've defended my interpretation of common sense fairly and politely :)

IHI
No problem with your post's tone and it's well-argued. But I do think you misunderstand the quantum world - although my understanding is almost certainly not right either. But I hope it's "more right" without being too rude about that. After all, I have studied it for longer!

Anyway, particles don't really act differently when being observed. It is just that the nature of observation is different in a quantum sense from how you would think of it classically. One analogy that I saw early on was the difference between the audience at a cinema and that at a theatre. In a cinema you are bound to watch impassively, but the theatregoers can actively interfere with the performance. But the underlying nature of the performance doesn't really change if you start heckling, even if events afterwards proceed differently.

It's not a perfect analogy of course, but then nothing ever is. Anyway.

Returning to the cat in the box problem, bear in mind that the cat itself is certainly capable of deciding whether it is alive or dead, so for the cat at least it is one or the other. For the man outside the box, he doesn't know until he opens the box and therefore it's one or the other, indeed a superposition of the two. Furthermore, this remains a thought experiment and one can simply invoke the idea of "classical limit" - that is, that this experiment makes sense only if you did it on quantum systems, which the cat is just not. So common sense at cat-scale prevails.

What this means in practice is that you can extrapolate upwards from Quantum mechanics to "common-sense" Newton's mechanics, but not the other way. The classical world and common sense is in some sense a subset of QM, but QM is the underlying truth (but not the end of the story!). Anyway, if common sense goes against a QM solution then it is certainly common sense that needs to change, at least when trying to understand the world more fully.
mibn2cweus: You opine. //Seems that the more we learn about the nature of the universe we live in - the less certain we become of our own existence within it.//, and yet if I'm not mistaken, don't you have absolute certainty in the non-existence of God?
Do you then favour a syllabus of education for secondary school pupils that focus's heavily on QM, that most will only have 5 years of lessons to build up to Newtonian principles? Might these children be at a disadvantage upon leaving school with this information when challenged about how the Moon orbits the Earth, Earth the Sun and the Sun the Galaxy. Plus one needs more complex mathematics to deal with QM, mathematics that would need to be taught to them too. But that subject you must agree, one cannot rush.

Teaching children Newtonian physics conforms (reasonably) to their common sense of how they perceive the world working. It's easier to make this our foundation syllabus and for those who wish to continue study in physics post GCSE, to then do so out of choice and commit to the mountain of knowledge they need to learn, regardless if you study the very big and then the very small. One should always study what they can observe initially. Without electron microscopes and particle smashers available in school labs, I don't see how one could expect 11-16 year old children to deal with these concepts.

I think the current structure is the only logical one... For now :)
I don't favour a rejection of Newtonian Mechanics entirely,or even at all, because it does indeed work very well for about 90% of people's needs if not more than that. Furthermore all the "better" (I think) ways to formulate physics are maths-heavy and it's too much to expect people who don't really enjoy maths to commit to learning so much for an end that they aren't interested in. Also Newton's mechanics is "easy" enough that you can actually start doing things in it very quickly.

What I do think is a good idea though is that there is a Disclaimer added of some sorts. Along the lines of "we can't use this approach for the Quantum Theory so don't try" or perhaps trying to introduce Quantum Mechanics in a less wordy hand-wavy manner that doesn't really explain what's going on at all.
IMO one discovers maths rather than invents it. If the universe didn't exist would maths ?
I really love the idea of a fuzzy universe....makes it more human
Naturally no it wouldn't. Maths was invented. It used the numerical systems of the day to quantify the world. Decimal winning as preferred system. Do you think that English was discovered rather than invented?
In one of the Terry Pratchett science books (One of then is "the Globe, the science of the Discworld) one of the science writers (Jack Cohen and Ian Stuart) sayd that the universe (our universe) doesn't care about the math. He says that you can't say that something is impossible because the math doesn't work. As a non mathematical person, I love this too.
No, but I don't see that as a fair comparison. Maths describe, for example, how a universe comes into being, it is from the equations we glimpse at some process that happens even without us, how that process must behave. Whereas languages only come with the need for higher lifeforms to communicate.
The reason one can not say that something is impossible simply because the math doesn't work, is because is something occurs and you can't yet describe it in the maths you know, the obvious assumption has to be that you've not discovered the right maths yet.
Oh this started up again didn't it?

There's certainly no way we should attempt to teach QM at GCSE level - it would be way too confusing and unnecessary

Quantum Physics is to some extent at A level - Einstein's photo electric equation, wave particle duality etc. and I'd say that was about right.

Trying to get a mathematical description at this level is way over the top.

Frankly there are a lot of topics that are taught in a particular way at a low level and then there's the 'right forget everything you were taught up to now' speech!

PS there's no way I'm getting into the Maths invented or discovered debate this time of evening!
But maths IS a language. It helps describe what we can't see or ever observe. Just like the word 'heaven' describes a state or place we cannot ever see (until death of course) yet it allows us to assign a term to a non-observable concept... Language is just the description of what is, what was and what might be. Maths, I argue, falls into that category....
Oh heck - yes I will

Maths is a language for describing patterns

Sometimes those patterns which maths can describe exist in the outside world and those patterns can be discovered through maths Geometry for example.

Sometimes those patterns only exist in our heads and the maths for those are essentially created although with those created axioms we can discover subsequent patterns that build on them.

I'm not convinced that you can 'discover' complex numbers for example.

:-)

The labels one uses in maths may be language, but the way maths work out is not from some arbitrary set of rules agreed upon, it is what it already is.

IMO complex numbers has to represent something "out there" or they would not be useful, so even if it is difficult to get one's head around what that might be the maths and reality are linked and already exist.

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