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Author Topic: How can Newtonian mechanics and quantum mechanics coexist?  (Read 15966 times)

Offline Soul Surfer

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Re: How can Newtonian mechanics and quantum mechanics coexist?
« Reply #25 on: 26/02/2012 10:09:16 »
Please do not give up Annie most of it is quite understandable by ordinary people it is just that some scientists like to enhance the air of mystery by choosing extreme examples ant putting them into the context of normal life.  For example from your replies you seem to think of waves as insubstantial things that are liable to fly off in all directions unheeded and particles as nice solid lumps that stick together and give solidity to materials.  the real point is that as I said earlier everything is all waves and particles all the time it is just the way you look at it that creates the difference.

Firstly let me clear up one important fact whatever people tell you the cup you are drinking your coffee from is going to stay being a cup for as long as you want it and not fly apart as a load of waves and drop the coffee in your lap (that is unless you drop the cup :)).  Physical laws stay the same as far as we are concerned.

Next about waves and particles.  We are all very familiar with electromagnetic waves.  These are in order of longest wavelength and lowest frequencies  Radio waves, microwaves,  infra red, visible light, ultra violet light, x rays, and gamma rays.

They are all exactly the same thing electric and magnetic fields oscillating and there is a continuous spectrum right from the lowest frequencies  the longest waves that is radio waves (remember long wave radio 1500 metres or fm radio 100 Megacycles that's about 3 metres )  right through the mid range of heat radiation which is measured in micrometers to gamma radiation where the waves can be less than the size of an atom.  The shorter the wave the easier it is to think of it as a particle however it is quite possible to measure radio waves as particles a good example is the 21cm wavelength radiation emitted by cold hydrogen atoms in the depths of space.  on the other hand the gamma rays are almost always thought of as particles but Mossbauer spectrometer measures them as waves to make incredibly precise measurements.

Now the wavelength of electrons protons and atoms involves more fields than just the electromagnetic but their wavelengths are very short so it is much easier to think if them as particles however with very low temperature and precise measurements it is quite possible to observe them as waves.  This does not in any way change the properties of things.

one of the problems nowadays there is so much science fantasy and so much very realistic computer generated graphics that it is possible to create images of anything happening quite easily.  This tends to cause some people to loose their grip on reality and start to think that the laws of physics can be bent and changed. This is just not true in our environment.
 

Offline wolfekeeper

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Re: How can Newtonian mechanics and quantum mechanics coexist?
« Reply #26 on: 26/02/2012 11:31:55 »
Curiouser and curiouser and through a glass darkly etc etc. My comment remains - re the average /reasonably educated person has no chance of ever making sense of it all and only the very favoured few are able to get even a glimpse of what it's all about. The Jest of God . . .(not that I believe in him/her . . .)
I suspect that that's true of practically everything. If you go along to watch a complex play at the theatre, you might think you understand it, but there may actually be a hidden meaning that is really what the play is really about. Or there may be bits which you didn't quite get but that didn't change the overall plot so you didn't bother about it, that an expert would know.
« Last Edit: 26/02/2012 19:05:29 by wolfekeeper »
 

Offline Geezer

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Re: How can Newtonian mechanics and quantum mechanics coexist?
« Reply #27 on: 26/02/2012 18:47:54 »
A frequent question is "yes, but why does it work that way?" Unfortunately, Science is more focused on "what it does" in ever greater levels of detail, and the greater the detail, the weirder it seems.
 
QM is a really strange subject, and at some point I suppose you just have to accept "what it does" and run with it. That's why the people that work in this field are called quantum mechanics!! (footsteps running towards exit)
 
I think it's time for one of JP's favs
 
http://www.youtube.com/watch?v=wMFPe-DwULM
 
 
 

Offline annie123

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Re: How can Newtonian mechanics and quantum mechanics coexist?
« Reply #28 on: 26/02/2012 18:59:44 »
Yes, I've watched a lot of Feynman's videos and read the bio by L Krauss. And I agree that one doesn't have to be a genius to have a glimpse of what's going on when geniuses have helped to open the windows, but it's frustrating to know that reality is 'so hard to know' as Feynman puts it even at a basic level because so many people don't have the time or resources to even touch on the edge of it all. And quantum theories may be superceded or improved upon in the coming centuries (if we survive or for whatever survives). I know this is starting to get philosophical in terms of human purpose/satisfaction/self knowledge etc. so i won't go on. But despite knowing I'm hardly skimming the surface somehow it's still more exciting than most other things out there, and I guess I'm lucky to have 'the time and resources' to look at these things.I just think it seems rather sad that so many people don't have the opportunity to even start looking.Thanks  to all contributors.
 

Offline greeniemax

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Re: How can Newtonian mechanics and quantum mechanics coexist?
« Reply #29 on: 27/02/2012 10:45:14 »
Newtonian physics works on macro level and QM works on Quantum level, when you look at the world everything is logical and makes perfect sense, everything seems perfectly normal. When we look at Quantum level everything is weird and doesn't make logical sense, logic dies out.

1. Physicist say you other lay people are too stupid to understand what is being talked about, you have to learn high level math and it gives right answers...
2. Lay people say or people with little knowledge that it doesn't make sense, it could be all wrong if its not making sense.
3. Totally lay people don't even care because it doesn't bother them.

Everything though is fine till the point we think that where does it all change? When you talk about single atom does the law change or is it when you talk about multiple atoms? What happens when the laws change, this middle level actually has balanced laws something between two laws or is the change abrupt? Does this change over layer has its own law, in case it does how many layers are there?

The whole "science" we have today is based on "say" of few people, even if direction seems wrong same laws are followed without bothering about where we are heading or looking at alternative root, it doesn't matter just keep walking as long as you get answers right even if it involves 100 different constants.

People say "we are going the wrong way", scientist say "we study, this is why we know that we are going the right way" and still others don't care.

But a person who studies is better than a person who doesn't even though it doesn't apply to church but what the heck.
 

Offline wolfekeeper

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Re: How can Newtonian mechanics and quantum mechanics coexist?
« Reply #30 on: 27/02/2012 11:44:38 »
Newtonian physics works on macro level and QM works on Quantum level, when you look at the world everything is logical and makes perfect sense, everything seems perfectly normal. When we look at Quantum level everything is weird and doesn't make logical sense, logic dies out.
I don't know if any physicist has ever said that, only that everyday intuitions about how things are aren't much use.

Quote
1. Physicist say you other lay people are too stupid to understand what is being talked about, you have to learn high level math and it gives right answers...
It's not a question of stupidity, it's just a question of them not having studied it, and looked at the experiments.

Quote
Everything though is fine till the point we think that where does it all change? When you talk about single atom does the law change or is it when you talk about multiple atoms? What happens when the laws change, this middle level actually has balanced laws something between two laws or is the change abrupt? Does this change over layer has its own law, in case it does how many layers are there?
The many worlds theory (which Hawking says is 'trivially true' if quantum mechanics applies to the universe) doesn't seem to require any other layers; I'm not saying that there aren't any other layers, but we don't seem to need them, based on the experiments to date.

Quote
The whole "science" we have today is based on "say" of few people, even if direction seems wrong same laws are followed without bothering about where we are heading or looking at alternative root, it doesn't matter just keep walking as long as you get answers right even if it involves 100 different constants.

People say "we are going the wrong way", scientist say "we study, this is why we know that we are going the right way" and still others don't care.
There is no particular direction that scientists are going on; they just follow the clues they find, given by nature, and that takes them in particular directions with their theories; determined by nature. The whole point of science is to work out what nature is doing.

Scientists don't get to decide how nature works!!!
« Last Edit: 27/02/2012 12:00:15 by wolfekeeper »
 

Offline greeniemax

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Re: How can Newtonian mechanics and quantum mechanics coexist?
« Reply #31 on: 27/02/2012 12:32:01 »
I think that I can safely say that nobody understands quantum mechanics.
The character of physical law (Cambridge, USA, 1967) - Richard Feynman


If you claim you understand QM than seriously one of you is wrong, QM is something you can't understand its not logical, people who claim its logical should be simply asked to explain entanglement, with logic.

String theory with 10 different ways to look at the world with 10 different formulation of same mathematical theory, logical?

I would personally love to understand QM, yes GR is simple and it is logical can be understood but QM please.



I would like to know what was expertise of Newton before he created Calculus and Formulation for Gravity? What was expertise of Galileo? I agree study of any subject is important but if you walk with rules that were given to you, you can never think out of the box because you automatically assume that rules given to you are correct. Lots of people give lots of weird theory that doesn't make sense but they can think out of the box for sure, unlike scientist.

So if there is no layer than where do the laws change? Where does the light was wave becomes photons? That is what I mean by layers, when the laws change from macro to micro where it happens? Does these law work for 1 atom, 2 atoms, 10 atoms or billion atoms? Maybe I'm bad at making my point clear but the laws have to change at some point, what is that point, do laws change abruptly or is there a middle layer of laws? I hope you understood what I'm trying to say.

Science considers whatever explained before as perfect flawless theories, no one has poked his nose to explain photo electric effect and keep light as waves, but science simply changed its understanding of elementary particles and take word of Albert Einstein for light to be photons even though that doesn't work in macro environment, because we can clearly see Doppler shift in light we never bother say how could color of a release photon change but we simply say it got elongated, how? No one bothers. Its a problem when we take older theories for their word of mouth values and try to apply them to current experiments, we don't know what's going on so it doesn't matter where we fit the results.
 

Offline wolfekeeper

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Re: How can Newtonian mechanics and quantum mechanics coexist?
« Reply #32 on: 27/02/2012 13:41:05 »
What does understand mean?

Did Newton understand his theory of gravity?

I mean his theory involved action at a distance. How did that work?

Now it's understood in terms of theory of curved space. How does space work?

I'm sure entanglement will be eventually understood in terms of simpler things, but just because we have entanglement that we don't understand in simpler terms, doesn't mean we don't understand quantum mechanics, or if we don't, Newton didn't understand gravity either.
 

Offline greeniemax

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Re: How can Newtonian mechanics and quantum mechanics coexist?
« Reply #33 on: 27/02/2012 14:03:09 »
I'm sure action at a distance is hard to understand if you think deeper because we "still" have no clue about it, we could say "gluons" are responsible for it but we still have no mechanism to say this is how it works.

We could say space-time is responsible for gravity but its something that would confuse the person at first but if you try to understand it, its not a problem its totally explainable, it gives reasons for why we feel gravity, why light bends and why planets have the orbits they do, but almost everything in quantum mechanics don't have any explanation of why they behave the way its does. For instance what produces light? What's the actual working mechanism behind it? Why less dense objects rise?

These things might be explained in QM but wouldn't make logical sense.
 

Offline wolfekeeper

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Re: How can Newtonian mechanics and quantum mechanics coexist?
« Reply #34 on: 27/02/2012 14:42:18 »
On the contrary, QM is perfectly logical, you just start with the right axioms, and you can derive the theory from it.
 

Offline greeniemax

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Re: How can Newtonian mechanics and quantum mechanics coexist?
« Reply #35 on: 27/02/2012 16:04:11 »
I'll give it another shot, I mean simple things like light doesn't make any sense in Young's Double slit experiment, when light behave's like particle it interfere with itself, which is impossible but if you put detector on slits you find them going through single slit.

The problem can't be solved logically, but if you accept these things as result it's perfectly fine and go ahead with the problem.
 

Offline wolfekeeper

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Re: How can Newtonian mechanics and quantum mechanics coexist?
« Reply #36 on: 27/02/2012 16:19:57 »
It can and is resolved logically, you just have to start with the right axioms.
 

Offline wolfekeeper

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Re: How can Newtonian mechanics and quantum mechanics coexist?
« Reply #37 on: 27/02/2012 16:31:25 »
I mean, for example the idea that a light particle only goes through one slit is obviously wrong.

Feynman says that light particle behaves as if it goes ALL ways from the emitter to the receiver, including apparently crazy ways like going above the screen in a curve, and spiralling around in big arcs, and going completely the wrong way, and then coming back again... it's just that most of those crazy ways tend to cancel out, and he suggested a physically plausible way of adding them all up which gives the right answers; the photon carries a spinny thing that spins at a constant rate (depending on its frequency), and to add up all the routes you just add the spinny things together.
 

Offline JP

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Re: How can Newtonian mechanics and quantum mechanics coexist?
« Reply #38 on: 27/02/2012 17:31:18 »
The double slit experiment brings it back to your earlier point, wolfekeeper: what does it mean to "understand" the physics?  I think Annie's confusion comes down to the basic problem of having an intuitive grasp on the physics based on our life experiences.  I can watch objects move about under Newton's laws and I feel gravity everyday.  Even if I don't study Newtonian mechanics exhaustively, I can get understand what its models are saying intuitively from these experiences. 

But even in the simple two-slit experiment, the particle behaves like a wave and goes through both slits at once.  Even though we can intuitively understand waves and particles as separate things, we have no intuitive framework to understand something that can be both at once.  What physics training really gets you in this case is a very good understanding of the model, rather than an intuitive understanding of what quantum particles are.
 

Offline wolfekeeper

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Re: How can Newtonian mechanics and quantum mechanics coexist?
« Reply #39 on: 27/02/2012 17:43:14 »
I don't think Newtonian mechanics was even that intuitive, I mean, how many thousand years did mankind take to come up with it?

It's only intuitive to us because we were all trained in it as children. It wouldn't surprise me if we didn't start training school children in a qualitative understanding of QM eventually, and then it won't seem nearly so weird.

you know like: there's waves, there's particles, there's waveparticles!!! and all the kids will go: OK

I mean they won't completely get it, they probably don't completely get waves either, but it will break it to them gently, and when they do need to know it, it will have had longer to settle in.
« Last Edit: 27/02/2012 17:45:53 by wolfekeeper »
 

Offline yor_on

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Re: How can Newtonian mechanics and quantum mechanics coexist?
« Reply #40 on: 27/02/2012 23:56:36 »
I lean towards JP:s view. A good understanding of the model is foremost, and that never seems to end, does it? :)

As for the rest, I think everyone 'knew' about gravity even if the mathematics describing it was Newtons. Even babies can differ between a normal fall and a fall/curve that is 'wrong'. They've tested this with a white board using magnets and then letting them 'fall' correctly, versus using a magnet behind the board influence the object in front to take a 'wrong' course/curve. The way they measured was by measuring the babies eye movements, and see their movement to the 'right position' for a 'fall', versus the 'wrong' curve/fall that magnetic object in fact did
 

Offline greeniemax

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Re: How can Newtonian mechanics and quantum mechanics coexist?
« Reply #41 on: 28/02/2012 04:23:44 »
Wolfekeeper doesn't it ever occurred to you that we really need a different description of something that isn't explainable? You said that if children are taught QM they would simply say yes, but what if QM is wrong? What if there is no double state of Photon, electrons or atoms?

Still it doesn't matter if children say "OK"?

This is exactly what happens to people who go and study QM, even if they don't get it they say "OK", because if Feynman couldn't get it I'm sure others who say "We get it" are either lying or are totally lost. Its also a problem of society if a person is physicist and he/she says QM doesn't make sense than everyone in the Scientific society will attack that person, he/she would be considered dumb and stupid.

Maybe QM is right but scientist aren't even ready to look at other approaches where Quantum duality doesn't have to exist, no one want to risk explaining Photo Electric Effect in wave, because everything underneath will change and has to be change to understand another model.
 

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Re: How can Newtonian mechanics and quantum mechanics coexist?
« Reply #41 on: 28/02/2012 04:23:44 »

 

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