Why have so many physicists shrugged off the paradoxes of quantum mechanics? • Hacker News Board

Re: Why have so many physicists shrugged off the paradoxes of quantum mechanics?

#101

Post by frolig » Sat, Apr 20, 2019, 12:18 PM UTC

placebo wrote: post #93

jcoffland wrote: post #86

All human models of reality are flawed. It is improbable that our small minds will ever comprehend the nature of the universe in it's entirety. Each answer uncovers more questions, more paradoxes. That is not to say we should not continue to try to understand the world around us. Only that logic dictates that we proceed with humility.

> All human models of reality are flawed. Definitely. I wholeheartedly subscribe to this view ( https://en.wikipedia.org/wiki/All_models_are_wrong ). The thinking mind will always be confined to models. The way I see it, the questions posed here are an expected wall one will eventually hit when the mind attempts to explain something that is fundamentally inexplicable - i.e the nature of existence. My current intuitio…

The rise in visibility of subjective science (science of consciousness/spirituality) and integration of it with objective science will accomplish that.

Luckily the subjective sciences are already highly developed, just look at Kabbalah. You can read a thousand pages of it and you still won't understand a single word!

Re: Why have so many physicists shrugged off the paradoxes of quantum mechanics?

#102

Post by alkonaut » Sat, Apr 20, 2019, 12:26 PM UTC

What is the general feeling among theoretical physicists when it comes to breakthroughs in resolving these paradoxes? Decades ago there was great optimism about string theory and similar, followed by a long period of disillusionment . What is the guesstimates now for the next big breakthrough such as unifying gravity and QM? Is it seen as something achievable in the near/foreseeable future, or is it considered to be a far future achievement comparable to say interstellar travel (“we’ll get there if we aren’t extinct by then, but our current civilization will seem primitive by the time we do”)?

Re: Why have so many physicists shrugged off the paradoxes of quantum mechanics?

#103

Post by gus_massa » Sat, Apr 20, 2019, 12:30 PM UTC

atomack wrote: post #85

pdkl95 wrote: post #78

Earlier quoted context omitted.

3Blue1Brown has an extremely good explanation[1] of the intrinsic uncertainty, and why it's separate from measurement uncertainty. (the previous episode[2] is a recommended prerequisite for background on how the Fourier Transform works) > emerges through a different, as yet unknown, mechanism. In 3Blue1Bron's explanation[1], he shows how the intrinsic uncertainty is an inherent trade-off of trying to measure both pos…

Yes, I like these sources too. Good for building intuition. I would just add that Heisenberg-like here means that both systems share features of wave mechanics. Doppler type effects aren't quantum mechanical though. When I suggest the mechanism is unknown, I mean that Heisenberg uncertainty is a postulate of quantum mechanics. In other words the fundamental reason that quantum mechanics should appeal to wave mechanic…

I'm not sure about the historical part, but now the uncertainty principle is not an independent postulate. It's deduced form the non commutation of the operations to measure the position and the momentum of a particle. This can be done in the wave representation or in the matrix representation.

Moreover, similar calculations can be done with other measurements that don't conmute. One that is very important is the spin of a particle in the x, y, and z axis.

Another is the polarization of a photon in directions that are at 45°. For example, most of (all?) the experiments of the EPR paradox are done with polarization instead of position-momentum, because polarization is much easier to measure. https://en.wikipedia.org/wiki/EPR_paradox

Re: Why have so many physicists shrugged off the paradoxes of quantum mechanics?

#104

Post by Abishek_Muthian » Sat, Apr 20, 2019, 12:52 PM UTC

dave_sullivan wrote: post #97

Sylos wrote: post #35

Earlier quoted context omitted.

> This is a common error. Macroscopic "everyday" objects don't have a definite position and momentum. Macroscopic objects are quantum objects. But when the mass is big enough, the position and momentum can be defined simultaneously with an error that is so small that you can just ignore the uncertainty and approximate them as classical objects. To put this into simpler terms: Whenever we measure something, we need to…

I don’t think this analogy holds up. Consider the double slit experiment: throw a bunch of basketballs at a wall and see what pattern of hits they leave by looking at where they hit the wall. If the wall is being looked at (observed), we see one pattern. If we look away, conduct the experiment, then check it, we find another. To me that suggests the act of “observance” effects the probability distribution of likely s…

>Consider the double slit experiment: throw a bunch of basketballs at a wall and see what pattern of hits they leave by looking at where they hit the wall. If the wall is being looked at (observed), we see one pattern.

If the basketball was of energy 1 quantum, if the energy used to observe is 1 quantum or more the (shining light to see the result in realtime) then the pattern is different due to interference. If we don't use any energy to see the result in realtime, then result is different due to non-interference.

Did what I say hold up?

Re: Why have so many physicists shrugged off the paradoxes of quantum mechanics?

#105

Post by exoesquitur » Sat, Apr 20, 2019, 12:57 PM UTC

jacobmoe wrote: post #100

wodenokoto wrote: post #80

Earlier quoted context omitted.

But isn't the reason why it is a fundamental problem, that fundamentally there is nothing smaller to throw?

No, under most interpretations of QM, things literally behave differently at that scale. Under Copenhagen, the wave literally collapses into a fixed position/momentum. The pre measurement wave isn't a statement of our ignorance of the system but rather a description of reality. The many worlds is even more serious in its quantum literalism. Far from pushing around the subject of your experiment with a too-big measuri…

To me, many worlds + time (as an inviolate observed vector) being merely a consequence of our inability to observe without moving foreward in time based on our entropic process driven cociousness, seems by far the most comprehensive explanation of observable phenomenon.

That observational uncertainty increases as the probability of direct interaction decreases (distance, time) strongly supports the hypothesis that observable phenomena are dictated strongly by the presentation and characteristic relationship of the observer to the phenomenon.

We know on the micro scale that all possible states exist simultaneously.

It seems logical, even axiomatic then that on the macro scale the same applies, but that we can only observe the bandwidth of states in which it is possible for us to exist to make the observation.

To claim that this state uncertainty is magically resolved in all cases and coherently for all possible observers into a single set of states seems an extraordinary claim requiring extraordinary evidence.

Re: Why have so many physicists shrugged off the paradoxes of quantum mechanics?

#106

Post by foldr » Sat, Apr 20, 2019, 12:59 PM UTC

throwawaymath wrote: post #55

paganel wrote: post #50

Earlier quoted context omitted.

> with an error that is so small that you can just ignore the uncertainty and approximate them as classical objects. I’d say that’s the gist of it, that we cannot “just ignore” the uncertainty because it’s too small, because if you do that then your model and the real world are indeed different. Also, at the end of it all what does “too small” mean? “Too small” compared to what? To a galaxy? To a super-nova? To a pla…

> To say nothing of the fact that comparing a number to physical stuff will eventually bring you head on against Zeno’s paradox, one way or the other. Zeno's paradoxes are soluble by basic calculus. Once you distinguish between countable and uncountable infinities, the problem of crossing a bounded interval in finite time ceases to be paradoxical. This is basically to say I don't think this is a particular problem fo…

>Zeno's paradoxes are soluble by basic calculus. Once you distinguish between countable and uncountable infinities, the problem of crossing a bounded interval in finite time ceases to be paradoxical.

They're not mathematically paradoxical, but that doesn't necessarily mean that the paradoxes are solved, because there's more than just math going on. A lot of the paradoxes hinge on the question of whether it is in fact possible to traverse an infinite series of positions in space or moments in time. I have no idea whether it is or it isn't, but the issue isn't settled by calculus. Calculus allows you to figure out what the result would be if such a traversal were to occur.

Re: Why have so many physicists shrugged off the paradoxes of quantum mechanics?

#107

Post by Tyr42 » Sat, Apr 20, 2019, 1:00 PM UTC

dave_sullivan wrote: post #97

Sylos wrote: post #35

Earlier quoted context omitted.

> This is a common error. Macroscopic "everyday" objects don't have a definite position and momentum. Macroscopic objects are quantum objects. But when the mass is big enough, the position and momentum can be defined simultaneously with an error that is so small that you can just ignore the uncertainty and approximate them as classical objects. To put this into simpler terms: Whenever we measure something, we need to…

I don’t think this analogy holds up. Consider the double slit experiment: throw a bunch of basketballs at a wall and see what pattern of hits they leave by looking at where they hit the wall. If the wall is being looked at (observed), we see one pattern. If we look away, conduct the experiment, then check it, we find another. To me that suggests the act of “observance” effects the probability distribution of likely s…

If you ever ran into a space leak in Haskell, you would see how having unresolved thinks can use more memory than eager evaluation.

But that has some merit to it in that you can describe QC as merging equivalent paths and then sampling from a wave distribution afterwards.

One fun variant on the double slit experiment is taking a coherent laser beam (everything is in phase) and splitting it, sending it through two paths, A and B, then merging it and shining it on the wall.

If the two path lengths are equal, there is no effect from splitting it. But if we make B take slightly more time we can get a interference pattern. If we have it get shifted by half a wavelength the light will cancel out!

Now if you insert a polarizing filter along path B, when you merge the streams, you could tell with path the light came from, and the interference pattern disappears. This is not exactly measuring which path it took, but making it possible if you added a sensor to tell.

Observation is not required just making the streams distinguishable.

But now if we add another polarizing filter downstream we can erase the distinction between them, and now you get interference effects again!

Re: Why have so many physicists shrugged off the paradoxes of quantum mechanics?

#108

Post by dave_sullivan » Sat, Apr 20, 2019, 1:12 PM UTC

Abishek_Muthian wrote: post #104

dave_sullivan wrote: post #97

Earlier quoted context omitted.

I don’t think this analogy holds up. Consider the double slit experiment: throw a bunch of basketballs at a wall and see what pattern of hits they leave by looking at where they hit the wall. If the wall is being looked at (observed), we see one pattern. If we look away, conduct the experiment, then check it, we find another. To me that suggests the act of “observance” effects the probability distribution of likely s…

>Consider the double slit experiment: throw a bunch of basketballs at a wall and see what pattern of hits they leave by looking at where they hit the wall. If the wall is being looked at (observed), we see one pattern. If the basketball was of energy 1 quantum, if the energy used to observe is 1 quantum or more the (shining light to see the result in realtime) then the pattern is different due to interference. If we…

I could be wrong, but I have a different understanding on how all of that works. You keep talking about basketballs instead of waves or probability fields and I guess this is where we diverge.

Re: Why have so many physicists shrugged off the paradoxes of quantum mechanics?

#109

Post by atomack » Sat, Apr 20, 2019, 1:23 PM UTC

gus_massa wrote: post #103

atomack wrote: post #85

Earlier quoted context omitted.

Yes, I like these sources too. Good for building intuition. I would just add that Heisenberg-like here means that both systems share features of wave mechanics. Doppler type effects aren't quantum mechanical though. When I suggest the mechanism is unknown, I mean that Heisenberg uncertainty is a postulate of quantum mechanics. In other words the fundamental reason that quantum mechanics should appeal to wave mechanic…

I'm not sure about the historical part, but now the uncertainty principle is not an independent postulate. It's deduced form the non commutation of the operations to measure the position and the momentum of a particle. This can be done in the wave representation or in the matrix representation. Moreover, similar calculations can be done with other measurements that don't conmute. One that is very important is the spi…

It's a good point that uncertainty relations exist for all kinds of physical observables. But whether they're expressed as commutation relations or as in Heisenberg's original formulation, or whatever formulation you choose (wave mechanics, matrix mechanics, dirac representation, qft, or anything else one can think of) it's still asserted, rather than derived from an underlying set of fundamental physical objects and interactions.

Re: Why have so many physicists shrugged off the paradoxes of quantum mechanics?

#110

Post by scotty79 » Sat, Apr 20, 2019, 1:48 PM UTC

jacobmoe wrote: post #100

wodenokoto wrote: post #80

Earlier quoted context omitted.

But isn't the reason why it is a fundamental problem, that fundamentally there is nothing smaller to throw?

No, under most interpretations of QM, things literally behave differently at that scale. Under Copenhagen, the wave literally collapses into a fixed position/momentum. The pre measurement wave isn't a statement of our ignorance of the system but rather a description of reality. The many worlds is even more serious in its quantum literalism. Far from pushing around the subject of your experiment with a too-big measuri…

> The pre measurement wave isn't a statement of our ignorance of the system but rather a description of reality.

Post measurement particle is description of our ignorance not a description of reality.

It still evolves according to Schrödinger equation (which degrades to newtonian dynamics for sharp and narrow waves) but for historical reasons we choose to talk about it as it was little billiard ball, not still a wave just sharpened and narrowed down by intraction we call measurement.