Does the Heisenberg cut exist?

[John Clark]

Many quantum interpretations such as Copenhagen (but not Many Worlds) claim there is a "Heisenberg cut", a dividing line between the quantum world and the classical world, but it's getting harder and harder to find where that dividing line is. At first they claimed quantum mechanical behavior was limited to sub atomic particles but then it was discovered that buckyballs, which are composed of 60 carbon atoms, did too. And now in Wednesday's issue of the journal Nature experimenters report they have detected quantum behavior in silica nanospheres that have a diameter of 120 nm and contain approximately 60 million atoms, and they were able to detect it even at room temperature. 

I don't think the Heisenberg cut exists, I think everything behaves quantum mechanically.

High-purity quantum optomechanics at room temperature

 John K Clark    See what's on my new list at  Extropolis

38g

[Brent Meeker]

On 8/7/2025 4:03 AM, John Clark wrote:

Many quantum interpretations such as Copenhagen (but not Many Worlds) claim there is a "Heisenberg cut", a dividing line between the quantum world and the classical world, but it's getting harder and harder to find where that dividing line is. At first they claimed quantum mechanical behavior was limited to sub atomic particles but then it was discovered that buckyballs, which are composed of 60 carbon atoms, did too. And now in Wednesday's issue of the journal Nature experimenters report they have detected quantum behavior in silica nanospheres that have a diameter of 120 nm and contain approximately 60 million atoms, and they were able to detect it even at room temperature. 

I don't think the Heisenberg cut exists, I think everything behaves quantum mechanically.

Bohr's point was that there must be instruments and records which behave classically, otherwise science is impossible; no one could agree on observations.  His position was that the Heisenberg cut has to exist.  Much later it was discovered that decoherence provides a mechanism for the cut.  But Bohr's point still holds.  In fact surprisingly small things, like many biological molecules behave classically.

Brent

High-purity quantum optomechanics at room temperature

 John K Clark    See what's on my new list at  Extropolis

38g

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[John Clark]

On Thu, Aug 7, 2025 at 4:49 PM Brent Meeker <meeke...@gmail.com> wrote:

>> I don't think the Heisenberg cut exists, I think everything behaves quantum mechanically.

 

> Bohr's point was that there must be instruments and records which behave classically, otherwise science is impossible; no one could agree on observations. 

If you and I wouldn't agree on an observation then you and I must be in different worlds, and so we never meet or contact each other in any way. 

 

> His position was that the Heisenberg cut has to exist. 

He believed it must exist because otherwise things would be odd, not paradoxical, just odd.  But quantum mechanics is odd! 

> surprisingly small things, like many biological molecules behave classically.

Yes if you're only interested in approximate behavior, but as the years go by and our experimental techniques become more and more sensitive those "small things" keep getting larger and larger. And now it's up to 60 million atoms. 

 John K Clark    See what's on my new list at  Extropolis

e..

[Brent Meeker]

On 8/7/2025 2:36 PM, John Clark wrote:

On Thu, Aug 7, 2025 at 4:49 PM Brent Meeker <meeke...@gmail.com> wrote:

>> I don't think the Heisenberg cut exists, I think everything behaves quantum mechanically.

 

> Bohr's point was that there must be instruments and records which behave classically, otherwise science is impossible; no one could agree on observations. 

If you and I wouldn't agree on an observation then you and I must be in different worlds, and so we never meet or contact each other in any way. 

Or we're in a world where there's decoherence...a point I made but which you elided to aid your rhetoric.  If observations were quantum they could exist in superpositions; and it's not that we'd disagree on the observation, we'd agree that it had no definite value.

 

> His position was that the Heisenberg cut has to exist. 

He believed it must exist because otherwise things would be odd, not paradoxical, just odd.  But quantum mechanics is odd! 

He observed that the instruments and records that science, even the science of quantum mechanics, relies on were not "odd".  He also recognized the quantum mechanics was odd.  Something he could not have done if there were not observations and records he could rely on.

> surprisingly small things, like many biological molecules behave classically.

Yes if you're only interested in approximate behavior, but as the years go by and our experimental techniques become more and more sensitive those "small things" keep getting larger and larger. And now it's up to 60 million atoms. 

But only if you're interest in collective behavior of Bose-Einstein condensates.  By the measure of collective behavior, superconducting circuits exhibit quantum behavior of 1e17 atoms or more.  

Citing the fact that we can detect quantum attributes of bigger and bigger things is beside the point of my statement that even molecular level things can behave classically.  Some biological molecules need to behave deterministically in order that life function consistently.  

Brent