> Presumably, if Maxwell's equations are solved in empty space, in the absence of charged particles, the E and B fields will be identically zero.
> If the same problem is solved in Quantum EM theory, won't we also get the same classical result,
> but then won't the HUP fail to be satisfied?
>>> but then won't the HUP fail to be satisfied?>> I don't know about that but HUP fails to satisfy me because IHA.> Never heard of the HUP, the Heisenberg Uncertainty Principle?
> As for the Casimir Effect, it can be predicted classically,
> so it proves nothing about virtual particles.
On Mon, Apr 28, 2025 at 9:21 PM Alan Grayson <agrays...@gmail.com> wrote:
> Presumably, if Maxwell's equations are solved in empty space, in the absence of charged particles, the E and B fields will be identically zero.
Yes.> If the same problem is solved in Quantum EM theory, won't we also get the same classical result,
No. If the electric, magnetic, gravitational, or any other type of field was precisely zero then you would know exactly what the energy density was in any arbitrarily short amount of time, zero. And quantum mechanics says that is impossible.
So the amount of energy must be greater than zero for short amounts of time, the shorter the time the greater the energy. This is why there are virtual particles, they can't be detected directly but they produce effects that can be detected, the simplest and most dramatic is the Casimir Effect.
> but then won't the HUP fail to be satisfied?
I don't know about that but HUP fails to satisfy me because IHA.
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>> If the electric, magnetic, gravitational, or any other type of field was precisely zero then you would know exactly what the energy density was in any arbitrarily short amount of time, zero. And quantum mechanics says that is impossible.
> No, QM says that if you measure the field there is an uncertainty relation between the energy and duration measured values. Measure also refers to interactions that imply values.
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>> If you place two macroscopic conductive plates close to each other the Casimir Effect will cause the two plates to attract each other; this occurs regardless of if you make any measurements or not. It happens because there are fewer virtual particles between the two plates than there are outside the plates. And virtual particles exist because it's impossible for the energy in the electromagnetic field to be exactly zero for any arbitrary length of time; and the shorter the time the greater the deviation from zero it's likely to be.
>That's why the qualification about measure like interactions. The two conductive plates exclude longer wavelengths.
> I don't recall that the effect depended on duration.
John K Clark See what's on my new list at Extropolis
> The Casimir Effect can be predicted classically, as Van der Waals forces. BTW,
On Tue, Apr 29, 2025 at 8:09 PM Brent Meeker <meeke...@gmail.com> wrote:
>> If you place two macroscopic conductive plates close to each other the Casimir Effect will cause the two plates to attract each other; this occurs regardless of if you make any measurements or not. It happens because there are fewer virtual particles between the two plates than there are outside the plates. And virtual particles exist because it's impossible for the energy in the electromagnetic field to be exactly zero for any arbitrary length of time; and the shorter the time the greater the deviation from zero it's likely to be.
>That's why the qualification about measure like interactions. The two conductive plates exclude longer wavelengths.
Yes.
> I don't recall that the effect depended on duration.Heisenberg's uncertainty principle is not just about the relationship between momentum and position, it also insists there is a similar relationship between energy and time; the shorter amount of time the greater the random variation from a zero value there is.
And without that there wouldn't be any wavelengths (or virtual particles) inside or outside those plates and the Casimir Effect would not exist.
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On 4/30/2025 4:29 AM, John Clark wrote:
On Tue, Apr 29, 2025 at 8:09 PM Brent Meeker <meeke...@gmail.com> wrote:
>> If you place two macroscopic conductive plates close to each other the Casimir Effect will cause the two plates to attract each other; this occurs regardless of if you make any measurements or not. It happens because there are fewer virtual particles between the two plates than there are outside the plates. And virtual particles exist because it's impossible for the energy in the electromagnetic field to be exactly zero for any arbitrary length of time; and the shorter the time the greater the deviation from zero it's likely to be.
>That's why the qualification about measure like interactions. The two conductive plates exclude longer wavelengths.
Yes.
> I don't recall that the effect depended on duration.Heisenberg's uncertainty principle is not just about the relationship between momentum and position, it also insists there is a similar relationship between energy and time; the shorter amount of time the greater the random variation from a zero value there is.
In quantum mechanics energy and the time per unit change of a variable are conjugate variables. So they satisfy an Heisenberg uncertainty relation, often written $\Delta E \Delta t \geq \hbar$ . This is sloppy though and not quite right. What is right is given any operator $A$ and the Hamiltonian $H$ defining the time evolution of $A$, then $\Delta A \Delta H \geq \frac{1}{2} \hbar [d<A>/dt]$ . In this case I don't see what is the time per unit change in the expected value of the energy density between the plates? The plates are assumed stationary.
Brent
And without that there wouldn't be any wavelengths (or virtual particles) inside or outside those plates and the Casimir Effect would not exist.
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On 4/30/2025 5:54 PM, Alan Grayson wrote:
On Wednesday, April 30, 2025 at 2:41:43 PM UTC-6 Brent Meeker wrote:
On 4/30/2025 4:29 AM, John Clark wrote:
On Tue, Apr 29, 2025 at 8:09 PM Brent Meeker <meeke...@gmail.com> wrote:
>> If you place two macroscopic conductive plates close to each other the Casimir Effect will cause the two plates to attract each other; this occurs regardless of if you make any measurements or not. It happens because there are fewer virtual particles between the two plates than there are outside the plates. And virtual particles exist because it's impossible for the energy in the electromagnetic field to be exactly zero for any arbitrary length of time; and the shorter the time the greater the deviation from zero it's likely to be.
>That's why the qualification about measure like interactions. The two conductive plates exclude longer wavelengths.
Yes.
> I don't recall that the effect depended on duration.Heisenberg's uncertainty principle is not just about the relationship between momentum and position, it also insists there is a similar relationship between energy and time; the shorter amount of time the greater the random variation from a zero value there is.
In quantum mechanics energy and the time per unit change of a variable are conjugate variables. So they satisfy an Heisenberg uncertainty relation, often written $\Delta E \Delta t \geq \hbar$ . This is sloppy though and not quite right. What is right is given any operator $A$ and the Hamiltonian $H$ defining the time evolution of $A$, then $\Delta A \Delta H \geq \frac{1}{2} \hbar [d<A>/dt]$ . In this case I don't see what is the time per unit change in the expected value of the energy density between the plates? The plates are assumed stationary.
Brent
In the time-energy form of the HUP, what is the role of time as an operator? What does time per unit change of a variable mean? Which variable is referenced? About virtual particles; aren't they elements of a perturbation expansion and thus not to be considered real since those terms violate conservation of energy? TY, AGThat's why I include the equations (although I see they didn't get converted to display). It can be any variable whose change is encoded by the Hamiltonian, A and H respectively in the equation. It doesn't have anything to do with how you might solve the equations; which is where perturbation expansions and virtual particles enter.
Brent
If your claim is correct, ISTM that Clark cannot apply the Time-Enegy form of the HUP to make his claim about the Casmir Effect. Do you agree?
TY, AG
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On 5/1/2025 7:25 AM, Alan Grayson wrote:
On Wednesday, April 30, 2025 at 11:06:07 PM UTC-6 Brent Meeker wrote:
On 4/30/2025 5:54 PM, Alan Grayson wrote:
On Wednesday, April 30, 2025 at 2:41:43 PM UTC-6 Brent Meeker wrote:
On 4/30/2025 4:29 AM, John Clark wrote:
On Tue, Apr 29, 2025 at 8:09 PM Brent Meeker <meeke...@gmail.com> wrote:
>That's why the qualification about measure like interactions. The two conductive plates exclude longer wavelengths.
Yes.
> I don't recall that the effect depended on duration.Heisenberg's uncertainty principle is not just about the relationship between momentum and position, it also insists there is a similar relationship between energy and time; the shorter amount of time the greater the random variation from a zero value there is.
In quantum mechanics energy and the time per unit change of a variable are conjugate variables. So they satisfy an Heisenberg uncertainty relation, often written $\Delta E \Delta t \geq \hbar$ . This is sloppy though and not quite right. What is right is given any operator $A$ and the Hamiltonian $H$ defining the time evolution of $A$, then $\Delta A \Delta H \geq \frac{1}{2} \hbar [d<A>/dt]$ . In this case I don't see what is the time per unit change in the expected value of the energy density between the plates? The plates are assumed stationary.
Brent
In the time-energy form of the HUP, what is the role of time as an operator? What does time per unit change of a variable mean? Which variable is referenced? About virtual particles; aren't they elements of a perturbation expansion and thus not to be considered real since those terms violate conservation of energy? TY, AGThat's why I include the equations (although I see they didn't get converted to display). It can be any variable whose change is encoded by the Hamiltonian, A and H respectively in the equation. It doesn't have anything to do with how you might solve the equations; which is where perturbation expansions and virtual particles enter.
Brent
Can you give some examples of what A could be, and mustn't A be an operator, not a variable, that commutes with H?Yes, A is an operator, but it doesn't commute with H. That would imply the variable measured by A is constant in time. The time per unit change in the expected value of the variable is the inverse of [d<A>/dt].
I don't know. I don't understand the proposed role of time.
Brent
On Thursday, May 1, 2025 at 8:42:45 PM UTC-6 Brent Meeker wrote:On 5/1/2025 7:25 AM, Alan Grayson wrote:On Wednesday, April 30, 2025 at 11:06:07 PM UTC-6 Brent Meeker wrote:On 4/30/2025 5:54 PM, Alan Grayson wrote:On Wednesday, April 30, 2025 at 2:41:43 PM UTC-6 Brent Meeker wrote:On 4/30/2025 4:29 AM, John Clark wrote:On Tue, Apr 29, 2025 at 8:09 PM Brent Meeker <meeke...@gmail.com> wrote:>> If you place two macroscopic conductive plates close to each other the Casimir Effect will cause the two plates to attract each other; this occurs regardless of if you make any measurements or not. It happens because there are fewer virtual particles between the two plates than there are outside the plates. And virtual particles exist because it's impossible for the energy in the electromagnetic field to be exactly zero for any arbitrary length of time; and the shorter the time the greater the deviation from zero it's likely to be. JC
>That's why the qualification about measure like interactions. The two conductive plates exclude longer wavelengths.
Yes.
> I don't recall that the effect depended on duration.Heisenberg's uncertainty principle is not just about the relationship between momentum and position, it also insists there is a similar relationship between energy and time; the shorter amount of time the greater the random variation from a zero value there is.
In quantum mechanics energy and the time per unit change of a variable are conjugate variables. So they satisfy an Heisenberg uncertainty relation, often written $\Delta E \Delta t \geq \hbar$ . This is sloppy though and not quite right. What is right is given any operator $A$ and the Hamiltonian $H$ defining the time evolution of $A$, then $\Delta A \Delta H \geq \frac{1}{2} \hbar [d<A>/dt]$ . In this case I don't see what is the time per unit change in the expected value of the energy density between the plates? The plates are assumed stationary.
Brent
In the time-energy form of the HUP, what is the role of time as an operator? What does time per unit change of a variable mean? Which variable is referenced? About virtual particles; aren't they elements of a perturbation expansion and thus not to be considered real since those terms violate conservation of energy? TY, AGThat's why I include the equations (although I see they didn't get converted to display). It can be any variable whose change is encoded by the Hamiltonian, A and H respectively in the equation. It doesn't have anything to do with how you might solve the equations; which is where perturbation expansions and virtual particles enter.
Brent
Can you give some examples of what A could be, and mustn't A be an operator, not a variable, that commutes with H?
Respect my religious belief in operators!
How about the epicycles ?!!!
What is d?
Can you give one or two specific examples of A? I thought the HUP is applicable only for non-computing operators. Am I mistaken? AG