Does commonsense really run counter to Quantum Mechanics?

Right, but it would not tell educated post-Galileans the same thing.

Or, perhaps what I'm really trying to say, though, is that common sense is what seems reasonable to me, but not to that ignorant dick over there.

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I have some sympathy with Feyerabend when people start talking about the (somewhat mythical) 'Scientific Method' as if it was the key to all knowledge. I'm more inclined to think that scientists (and everyone else) can use any method that they damn well please, provided that its use is justifiable in the context in which it is being employed. Statistics, mathematical and physical models, laboratory experiments, surveys, microscopic, telescopic and field observations, mathematical derivations and proofs... That's epistemological anarchy of a sort, I guess. It certainly pushes the question of how methods are justified to the forefront.

Definitely. I'm a big champion of 'common sense'. To me it basically refers to the world of the tables and the chairs in which we all live our lives, and to the ways in which we go about interacting with those middle-sized things while living those lives. No matter how outrageous somebody's metaphysical beliefs are, they all seem to drive their cars in the same way out on the road. They still eat food, try to get laid and shit like everyone else. They still get toothaches. That commonality is our starting point as human beings.

Physics started out as mankind's attempt to understand that world that we all live in. As time went on though, it's become more and more detached from that world of common experience, more focused on exploring its own concepts and mathematical formalisms which some physicists seem to believe are more real that the world around them. There's seemingly a tendency towards something like Platonic idealism among a certain kind of theoretical physicist these days. (I haven't seen it among experimentalists.)

Right.

They do in our experience, where things like friction and air-resistance exist. What Newton did was imagine an idealized and highly simplified situation where those complications don't exist. So physics started its movement away from the real world towards being a system of idealized abstractions interacting in precise mathematical ways. The pioneers of the scientific revolution discovered that simplifying things allowed far greater conceptual economy. A manageable set of basic physical principles could be combined in countless ways to account for no end of different physical situations.

I seem to remember that Feyerabend did well regarded work on the philosophy of QM in his earlier years, before his intellectual anarchism. He certainly wasn't unacquainted with physics.

Even if it isn't totally common-sensical, it isn't all that difficult to imagine the world around us in terms of the principles of classical physics working in various combinations. It's a lot harder with QM. Physicists' concepts like superimposed states or entanglement seem to be dramatically different from how we experience the middle-sized objects around us behaving.

Many prominent philosophers (and many physicists along with them) have opted for an instrumental interpretation of QM, where it's just an abstract formalism used to predict how experiments and observations will turn out. Of course it's possible to interpret QM realistically, as telling us something about how things really are down there on the micro-scale. If we go that way, we will seemingly have to admit that objects on the microscale (assuming that discrete objects even exist on the microscale) don't behave anything like billiard balls in our middle-sized world. That raises the problems of explaining not only how things really are down on the microscale (there are currently many different ways to interpret QM), but also of explaining the classical/quantum interface, of how it is that the things in our experience behave as they do, assuming that their atoms and micro-components are behaving in very different ways. How is it that classical physics 'emerges' from quantum physics as we consider larger and larger assemblages of atoms?

 

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Feyerabend is, of course, nice reading. But essentially he was only trolling the mainstream.

 

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You and I see more or less eye to eye on this somewhat mythical beast called the "scientific method" - I think we have discussed this before. And I do not quibble too much with your remarks about some theoretical physics getting far removed from everyday ways of thinking - as does some literary criticism, by the way. I was being a bit rude about Feyerabend because he set out deliberately to provoke, so he can damned well put up with a robust response. As with many academics of a rhetorical sort, it seems to me he pushes an idea with an element of validity beyond what it will sustain.

My main point, which I'm pleased to see you at least partially seem to acknowledge, is that what we call "common sense" depends on how we have been equipped intellectually. To the schoolboy who has learnt a couple of years of Newtonian physics (my 12 yr old son, for example), it is common sense that objects continue in a straight line at constant velocity if no forces act on them. That's because he has learnt to think about what forces act on bodies in practice, such as friction and air resistance on a bicycle, or whatever it may be.

As to your final question, that, I think, is one of the glories of my subject - physical chemistry. The short answer is "statistical thermodynamics". What that does is take the QM atomic scale behaviour and show how the bulk properties of macroscopic scale matter arise from it, perfectly naturally, as a result of applying statistics to assemblages of atoms or molecules. I often suspect that I, as a chemist, have less trouble bridging the supposed gap between QM and ordinary scale matter than my esteemed physicist colleagues. The chemist - in the end - has to explain what is going on in his test tube or vacuum line or whatever, which is usually inconveniently complicated for a physicist. Chemistry is full of semiquantitative or qualitative explanations, guided by physics, but putting up with the fact that real situations have too many variables to be calculated accurately. (I don't know whether you are aware, but the most complex system for which exact solutions of Schroedinger's equation can be computed is the hydrogen molecule ion - 2 protons and one electron. A sodium atom? - nucleus plus 11 electrons - forget it.)

 

I agree with Schmelzer on that one, though I think that the word 'all' is too strong.

'Common sense' isn't just proto-natural-science. It also embraces the natural logic that everyone uses in their everyday lives, the ideas of truth and falsity and the ability to employ logical implication. In other words, 'common sense' includes our innate human reasoning ability.

I'd say that natural logic and natural reason are our starting points. Then lacking any divine revelation, science tries to hoist itself by its own bootstraps, adding more and more elaborations to the conceptual and methodological raw material of common sense.

Again I agree.

I'm not really sure what "the scientific method" is or what the phrase means precisely. In secondary school, hypothesis testing is often presented to students as if it is 'the scientific method'. Make observations. Form hypotheses. Test them.

Of course, a moment's reflection reveals that wonderful and infallible method is just common sense's age-old trial-and-error restated.

 

Except we don't encounter relativistic masses or spooky action at a distance in our natural lives.
There was nothing common-sensical about time dilation due to velocity, or about quantum entanglement.

There was no way any amount of common sense could get us there; it required irrefutable data to force us to abandon our common sense.

 

To answer the thread title - yes, at least in some cases common sense runs counter to quantum mechanics. We usually assume the location of an object is well defined. The ability of particles to "jump" or "tunnel" empty space because of blurred location is counter-intuitive.

Same as for a particle going through two holes at once. We do not expect objects to be able to traverse two openings at the same time without splitting up and re-uniting. Yet, particles do just that.

The small scale world is weird like that.

Best, you give up you idea of objects, location, speed and think only in wave functions - while concepts like location and speed are getting blurry and useless, the wave function is the precise description of the object.

 

What is not common sense with clocks going slower when they move or when they are in a strong gravitational field. It is completely common sense. It is well known that rulers become greater with temperature. So what is strange if clocks go slower in a strong gravitational field? Our measurement instruments can be easily distorted.

Quantum theory is, indeed, strange. But strange does not mean impossible to understand. One should try hard to understand strange things. Scientists have not. Their rule was "shut up and calculate". Which is, clearly, not the advice of common sense. And also not the advice of the scientific method.

 

Posted by accident. Post deleted.

 

OK, fair enough, on reflection I do have to concede that wave-particle duality is something counter to what most people would think of as common sense. I've thought of it as a normal state of affairs for over 40 years, but I do have to accept I am in a small minority.

 

This is absolutely not the same thing. And by getting it wrong, you have demonstrated nicely that SR and GR are not common sensical, even to you.


SR and GR do not affect our measurement instruments, they affect our very existence.

If I heat your ruler, that does not make me actually 10% taller. Another ruler - or this one once it is properly calibrated - will show the error in the measurement.

If I go to A. Centauri and return at near c, I really am younger - by all accounts. It cannot be "corrected" (because it is not wrong); and it will not be contradicted by my clock or by any other clock. Same with GR. Astronauts really do age less than we down here on Earth. It's not a measurement instrument issue.

Thank you for succinctly making my point for me.

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No one said impossible to understand. They said not common sense.

You have mis-referenced this quote. It does not mean what you think it means. It is only valid in the very specific context in which it was uttered.

 

It is, of course, not what SR and GR spacetime interpretation tells us. It is what observation, interpreted based on common sense, tells us.

As if this would change something. Of course, if measurement devices are distorted, it is also their very "existence" which is distorted, the rulers really become bigger. We could use, as well, bones as rulers. They would also become bigger. And we also become bigger. There is no subdivision of the world into measurement devices and really existing things.

The only difference is that temperature influences different materials differently. Instead, we have the same influence of velocity and gravity on everything, as measurement instruments as everything else. Instead of having different influences of the same cause (velocity/gravity) on different materials. If the more complex variant is not in contradiction with common sense, why the simpler variant should be? There is only one point, namely that in this case one can become confused by pseudo-philosophical talk about the very existence.

That there is a difference between time and clock time follows from the point that we can, nonetheless, see that different circumstances influence clocks differently. The travelling clock, and the clock in a strong gravitational field, are slower, we can see this by comparing them after some time. The twin paradox is a paradox only for those who confuse clock time with time.

Does common sense tell us we will never see something we don't understand easily? It always told the people who are afraid of the unknown to stay home, because at other places strange things can happen.

About "shut up and calculate":

You think so? Explain what you think is my error. This name for the minimal interpretation was originally satirical, and such satirical names work only if they allow different interpretations.

 

That was the rule of a small subset of scientists. Perhaps a subset of one.

In practice, scientists do a lot of metaphysics.

 

Unfortunately, your interlocutor believes that all the effects of GR are merely effects and, despite there being no way in principle to detect the true length of a ruler, he believes that there is nonetheless such a thing.

This, he must claim, is common sense.

 

The twin paradox is only a paradox for someone who confuses "paradox" for "scenario".

A "clock" in GR is only a physical process, any physical process and not even a regular one. In GR, for a clock to go slower means that an arbitrary physical process in one situation does not evolve as far as it would in a different situation. We test this by looking at certain regular physical systems that are very similar.

What does it mean that there is an optimal, natural, or true rate of evolution for an arbitrary physical system? GR suggests that there is no such thing.

 

They do, because the subdivision between physics and metaphysics is very problematic. But they have to sell it as something physical. There has been some improvement during the last years, different interpretations of quantum theory are more and more allowed. But there was a sufficiently strong prejudice against discussing them.

Yes. And is there anything in contradiction with common sense, if there is no such thing?

 

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.

When a derivative is taken it brings down the tangent vector,

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, of the loop,

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. So we have something like

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.

However, as

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is anti-symmetric in the indices

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and

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this vanishes (this assumes that

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is not discontinuous anywhere and so the tangent vector is unique). Now let us go back to the loop representation.

We consider wavefunctions

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that vanish if the loop has discontinuities and that are knot invariants. Such functions solve the Gauss law, the spatial diffeomorphism constraint and (formally) the Hamiltonian constraint. Thus we have identified an infinite set of exact (if only formal) solutions to all the equations of quantum general relativity![12] This generated a lot of interest in the approach and eventually led to LQG.

 

It is pretty obvious that you have no idea what that means.
When you copy something with out giving credit to the real author that is called plagiarism, which is frowned upon on this forum

 

Is it still plagiarism if it was copied verbatim from Wiki?
https://en.wikipedia.org/wiki/Loop_quantum_gravity
(about /3 the way down, just above "Geometric operators, the need for intersecting Wilson loops and spin network states")

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I'm against common sense!
Being told that something is common sense is more or less meaningful, and the name of a very silly book by the traitor Thomas Paine.
The claim that something is common sense is very frequently a demand to accept the conjecture of the claimant because he/she can offer no more solid evidence for his/her opinion.
Being told to use ones common sense is more or less useless.
Explain how you would use it in relation to spelling for example. It certainly does not work if it implies something like expectation or governance by rules. Doctor Johnson made a mistake over the spelling of the word gauge and we have had to spell it wrong ever since.
Explain how you would use it in relation to social customs. Does it offer a mechanism capable of explaining their diversity, or the seeming oddness of (say) Japanese to outlanders.
If something is logical, then spell out the series of logical propositions which lead to the conclusion and offer them for scrutiny -- and don't call it common sense, which adds precisely nothing and obscures the superior claim of being based on logic.
I'm with QM! Down with common sense!