The quantum / macro border - 1 for GV et al
Discussion
I can get my head around the basics of the quantum universe and live in the macro world so can handle that ok ( but that fields stuff underlying it all still makes my brain smoke )
But what happenss at the border of the the two sets of rules. Is there a blur where the various equations start to overlap or is it a step jump between the 2 ?
Cheers, looking forward to some education.
But what happenss at the border of the the two sets of rules. Is there a blur where the various equations start to overlap or is it a step jump between the 2 ?
Cheers, looking forward to some education.
What a great question!
As to answering it in a satisfying way will test your comprehension though.
This is really a threshold question, I used to explain it this way:-
We are all able to understand what a threshold is, the most common one we encounter everyday is the one at our front door, one side of the threshold is outside and we are subject to the weather and the other side where we have an entirely different environment.
There is no real difference between the threshold of the Macro/Micro world and your own front door.
But the threshold of the M/M world is subject to some odd behaviour due to its place in the scale of things.
The most important of these is our own place in observing this threshold.
Now we've all heard of wave function collapsing as a result of observation and as an answer it pretty much says it all, but it really means little to most casual seekers of knowledge.
So what does this really mean?
To observe anything we need to utilise energy, we take energy in the form of EMR (electro-magnetic radiation) from or to the observation of what is already simply an EMR based effect.
This changes the threshold, to use our front door analogy again, it is as if you take that step through the door and the threshold moves past you at the same time and you are right in the house.
This is why we can't really 'see' the transition from Macro to Micro, you are either in the Macro or you are in the Micro, there is no 'cusp' that can be observed, because it is in 'midstep' (again using the front door analogy), so even carefully stepping back means you are suddenly outside completely.
That is the only way I have ever been able to explain wave function to students not immersed in deeper maths.
I hope that helps a bit.
As to answering it in a satisfying way will test your comprehension though.
This is really a threshold question, I used to explain it this way:-
We are all able to understand what a threshold is, the most common one we encounter everyday is the one at our front door, one side of the threshold is outside and we are subject to the weather and the other side where we have an entirely different environment.
There is no real difference between the threshold of the Macro/Micro world and your own front door.
But the threshold of the M/M world is subject to some odd behaviour due to its place in the scale of things.
The most important of these is our own place in observing this threshold.
Now we've all heard of wave function collapsing as a result of observation and as an answer it pretty much says it all, but it really means little to most casual seekers of knowledge.
So what does this really mean?
To observe anything we need to utilise energy, we take energy in the form of EMR (electro-magnetic radiation) from or to the observation of what is already simply an EMR based effect.
This changes the threshold, to use our front door analogy again, it is as if you take that step through the door and the threshold moves past you at the same time and you are right in the house.
This is why we can't really 'see' the transition from Macro to Micro, you are either in the Macro or you are in the Micro, there is no 'cusp' that can be observed, because it is in 'midstep' (again using the front door analogy), so even carefully stepping back means you are suddenly outside completely.
That is the only way I have ever been able to explain wave function to students not immersed in deeper maths.
I hope that helps a bit.
Edited by Gene Vincent on Tuesday 16th October 13:51
pointedstarman said:
I can see how GV's answer solves the observational issues (Heisenberg?) but not the mathematical issue. Is there a well defined point where you apply 'Macro' maths - Einsteinian? - and where do you apply quantum mechanics or do you try both and see which works?
Yes, the wave function is in reality a probability quotient, once, mathematically, the quotient is so small as to bring the basic quanta into play then we jump to quantum maths as our 'interference' precipitates it.It is a variable threshold that depends (largely, although not exclusively) the number of Quantum fields the item being looked at spans across, this is nothing to do with 'size' but much more to do with this interaction.
Gell-Mann and Feynmann did much of the work defining macro/micro cross-over back in the 60s and like much of their work it has remained almost completely intact since then.
Consider two situations, which are superficially similar: an electron travelling through a small aperture, and a football kicked through a doorway. We can easily describe the football's behaviour using classical physics, of the type Newton used. It's a macroscopic object. But we find we cannot describe the electron's behaviour successfully using those same equations.
Fortunately, we can bring our understanding of quantum mechanics to bear - great, now we understand the electron's behaviour. But why does the football obey one set of rules, and the electron the other? Well, actually, they both obey the quantum mechanical set of rules. But when things are large, or have lots of energy, the difference between the predictions of the two sets of rule is tiny. For the football, its deviation from the classical behaviour would be absolutely unmeasurable.
(Aside: when things are very large, or have enormous amounts of energy (i.e. on cosmological scales) then we run into trouble again.)
We therefore say that, on large scales, the classical rules are a very good approximation to the quantum mechanical rules. This equivalency can be demonstrated mathematically for many different situations.
The classical equations are generally much simpler than the quantum ones, and so it is smart to use them where we can get away with it. Can we know in advance if we can get away with it? Well, not always, and, if you're a physicist, a good way to win science points is to make surprising things demonstrate behaviour that is clearly quantum mechanical.
Cheers,
Nick
Fortunately, we can bring our understanding of quantum mechanics to bear - great, now we understand the electron's behaviour. But why does the football obey one set of rules, and the electron the other? Well, actually, they both obey the quantum mechanical set of rules. But when things are large, or have lots of energy, the difference between the predictions of the two sets of rule is tiny. For the football, its deviation from the classical behaviour would be absolutely unmeasurable.
(Aside: when things are very large, or have enormous amounts of energy (i.e. on cosmological scales) then we run into trouble again.)
We therefore say that, on large scales, the classical rules are a very good approximation to the quantum mechanical rules. This equivalency can be demonstrated mathematically for many different situations.
The classical equations are generally much simpler than the quantum ones, and so it is smart to use them where we can get away with it. Can we know in advance if we can get away with it? Well, not always, and, if you're a physicist, a good way to win science points is to make surprising things demonstrate behaviour that is clearly quantum mechanical.
Cheers,
Nick
EliseNick said:
Consider two situations, which are superficially similar: an electron travelling through a small aperture, and a football kicked through a doorway. We can easily describe the football's behaviour using classical physics, of the type Newton used. It's a macroscopic object. But we find we cannot describe the electron's behaviour successfully using those same equations.
Fortunately, we can bring our understanding of quantum mechanics to bear - great, now we understand the electron's behaviour. But why does the football obey one set of rules, and the electron the other? Well, actually, they both obey the quantum mechanical set of rules. But when things are large, or have lots of energy, the difference between the predictions of the two sets of rule is tiny. For the football, its deviation from the classical behaviour would be absolutely unmeasurable.
(Aside: when things are very large, or have enormous amounts of energy (i.e. on cosmological scales) then we run into trouble again.)
Yeah, perhaps we could add to that by saying that the football which is made from a cohesive structure of tiny quanta was on or over the threshold suddenly behaves like it is not cohesive and each tiny quanta 'does its own thing' and because of that does not follow the trajectory prior to the threshold, so the nice straight kick turns into an erratic and slightly bizarre bounce around the room!Fortunately, we can bring our understanding of quantum mechanics to bear - great, now we understand the electron's behaviour. But why does the football obey one set of rules, and the electron the other? Well, actually, they both obey the quantum mechanical set of rules. But when things are large, or have lots of energy, the difference between the predictions of the two sets of rule is tiny. For the football, its deviation from the classical behaviour would be absolutely unmeasurable.
(Aside: when things are very large, or have enormous amounts of energy (i.e. on cosmological scales) then we run into trouble again.)
Gene Vincent said:
EliseNick said:
Consider two situations, which are superficially similar: an electron travelling through a small aperture, and a football kicked through a doorway. We can easily describe the football's behaviour using classical physics, of the type Newton used. It's a macroscopic object. But we find we cannot describe the electron's behaviour successfully using those same equations.
Fortunately, we can bring our understanding of quantum mechanics to bear - great, now we understand the electron's behaviour. But why does the football obey one set of rules, and the electron the other? Well, actually, they both obey the quantum mechanical set of rules. But when things are large, or have lots of energy, the difference between the predictions of the two sets of rule is tiny. For the football, its deviation from the classical behaviour would be absolutely unmeasurable.
(Aside: when things are very large, or have enormous amounts of energy (i.e. on cosmological scales) then we run into trouble again.)
Yeah, perhaps we could add to that by saying that the football which is made from a cohesive structure of tiny quanta was on or over the threshold suddenly behaves like it is not cohesive and each tiny quanta 'does its own thing' and because of that does not follow the trajectory prior to the threshold, so the nice straight kick turns into an erratic and slightly bizarre bounce around the room!Fortunately, we can bring our understanding of quantum mechanics to bear - great, now we understand the electron's behaviour. But why does the football obey one set of rules, and the electron the other? Well, actually, they both obey the quantum mechanical set of rules. But when things are large, or have lots of energy, the difference between the predictions of the two sets of rule is tiny. For the football, its deviation from the classical behaviour would be absolutely unmeasurable.
(Aside: when things are very large, or have enormous amounts of energy (i.e. on cosmological scales) then we run into trouble again.)
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