(January 29, 2022 at 10:50 pm)Jehanne Wrote:

(January 29, 2022 at 10:38 pm)Neo-Scholastic Wrote: Substance is not a concept of physics. It comes from Scholasticism. So IMO at least some of the mind-body problem stems from mixing the nomenclature of two very different conceptual frameworks.

Like the so-called Eucharist?  It's not really bread after the Consecration, but, it only appears to be bread, and the bread is just the "accident" that remains after the true "substance" has become the Body & Blood of Jesus Christ?

Yeah, the blessing changes of the final cause even though the material cause remains unchanged.

And sometimes a cigar is just a cigar.

(January 30, 2022 at 2:20 pm)Neo-Scholastic Wrote:

(January 29, 2022 at 10:50 pm)Jehanne Wrote: Like the so-called Eucharist?  It's not really bread after the Consecration, but, it only appears to be bread, and the bread is just the "accident" that remains after the true "substance" has become the Body & Blood of Jesus Christ?

Yeah, the blessing changes of the final cause even though the material cause remains unchanged.

And to think that some human beings got burned alive at the stake for the "desecration" of a consecrated host.  A sign of progress, perhaps?

(January 29, 2022 at 10:38 pm)Neo-Scholastic Wrote: Substance is not a concept of physics. It comes from Scholasticism. So IMO at least some of the mind-body problem stems from mixing the nomenclature of two very different conceptual frameworks.

I think it goes back at least to Aristotle. it certainly wasn't invented in the middle ages since many ancient Christian controversies were about the 'substance' of Christ.

PS: I was right. Aristotle talked about substances in his Categories.

https://plato.stanford.edu/entries/substance/

(January 29, 2022 at 10:08 pm)polymath257 Wrote: A LOT of care is required here.  Several statements are either wrong or seriously misleading.

First, all particles are associated with a field and vice versa.

So, there are electron fields. And the electromagnetic field is associated with photons.

This means that each of the forces is described by an exchange of some particle.

When two charged particles interact electromagnetically, they do so by the exchange of a photons. So, you were wrong when you said that photons do not interacts with electrons via the electromagnetic force. In fact, the electromgnetic force is *precisely* charged particles interacting with photons.

You were also factually wrong when you said that neutrons do not interact electromagnetically. While they are not charged, they *do* have a magnetic field.

The weak force is the exchange of W and Z particles. So, leptons and quarks interact via W and Z particles and that interaction is the weak force. Neutrinos are one type of lepton. Here, the W particles are charged and the Z particles are electrically neutral.

The particles associated with the strong force are called gluons. There are 8 types of gluons.

Now, there *is* a difference between the 'matter' particles and the 'force' particles. The 'matter' particles are all fermions (electrons, quarks, neutrinos), while the 'force particles (photons, W, Z, and gluons) are all bosons.

BTW, the particle for gravity is called the graviton and is spin 2. We can *also* consider gravity as the curvature of spacetime: the two descriptions are mathematically equivalent.

For each basic interaction, there is a diagram detailing that interaction. So, the diagram for an electron and a photon just has the photon, an incoming electron, and an outgoing electron. Because of symmetries, this same diagram describes the interaction of positrons and photons and describes both a single incoming photon or a single outgoing photon. For any given observed interaction, we have to write down all of the diagrams with those incoming particles and those outgoing particles and 'add them up' to get the probability of that interaction and its properties.

Interactions with W and Z particles can change leptons to quarks and vice versa. Interactions with gluons can change the type of quarks.

Quote:When two charged particles interact electromagnetically, they do so by the exchange of a photons. So, you were wrong when you said that photons do not interacts with electrons via the electromagnetic force. In fact, the electromagnetic force is *precisely* charged particles interacting with photons.

Thanks. About this line of mine:
“A neutrino, a neutron, a photon does not interact with an electron via the electric force/magnetic force.”

I’m not an expert on this but I think it depends on the conditions.

Case 1:
For example, if you send a beam of photons right between 2 charged plates and the distance between the photon beam and the electrons in the plates is 1 cm, there is no interaction at all.
The photons go in a straight line as if the electric field is not even there.
The same goes for a magnetic field.
If this was not the case, the beam would bend. It would be easy to observe a lens effect around a piece of magnet.

Case 2:
If you have a beam of electrons and a beam of photons and you cross the beams, they will not interact, no matter what the wavelength of the electrons and photons is.
I might be wrong about that. Perhaps if their wavelengths are the same, there would be an interaction.

Case 3:
Electrons around atoms. If the compound is in a gaseous state, and you send a photon, if the wavelength matches the wavelength of the orbit (?), the photon might get absorbed by the electron.

Case 4:
If you have 2 beams of photons. If you cross the beams, no matter what the wavelength of the photons is, there is no interaction between the photons.

Quote:You were also factually wrong when you said that neutrons do not interact electromagnetically. While they are not charged, they *do* have a magnetic field.

Thanks. That is interesting.
I looked at the wikipedia page. I think there is something I do not understand. There is a difference between having a magnetic field and a magnetic moment?
The wikipedia says that it is hard to guide a neutron beam. A heterogenous field needs to be used which has an impact on a neutron because a neutron has magnetic moment.
Apparently, a parallel magnetic field has no effect?

I have heard of W, Z, gluons, fermions, bosons, but mostly, I do not know those details.

Apparently, a team might have discovered a dineutron and another team might have discovered a tetraneutron.
It looks like there is a lot of exotic stuff to be discovered.

(January 30, 2022 at 6:46 pm)Ferrocyanide Wrote:

(January 29, 2022 at 10:08 pm)polymath257 Wrote: A LOT of care is required here.  Several statements are either wrong or seriously misleading.

First, all particles are associated with a field and vice versa.

So, there are electron fields. And the electromagnetic field is associated with photons.

This means that each of the forces is described by an exchange of some particle.

When two charged particles interact electromagnetically, they do so by the exchange of a photons. So, you were wrong when you said that photons do not interacts with electrons via the electromagnetic force. In fact, the electromgnetic force is *precisely* charged particles interacting with photons.

You were also factually wrong when you said that neutrons do not interact electromagnetically. While they are not charged, they *do* have a magnetic field.

The weak force is the exchange of W and Z particles. So, leptons and quarks interact via W and Z particles and that interaction is the weak force. Neutrinos are one type of lepton. Here, the W particles are charged and the Z particles are electrically neutral.

The particles associated with the strong force are called gluons. There are 8 types of gluons.

Now, there *is* a difference between the 'matter' particles and the 'force' particles. The 'matter' particles are all fermions (electrons, quarks, neutrinos), while the 'force particles (photons, W, Z, and gluons) are all bosons.

BTW, the particle for gravity is called the graviton and is spin 2. We can *also* consider gravity as the curvature of spacetime: the two descriptions are mathematically equivalent.

For each basic interaction, there is a diagram detailing that interaction. So, the diagram for an electron and a photon just has the photon, an incoming electron, and an outgoing electron. Because of symmetries, this same diagram describes the interaction of positrons and photons and describes both a single incoming photon or a single outgoing photon. For any given observed interaction, we have to write down all of the diagrams with those incoming particles and those outgoing particles and 'add them up' to get the probability of that interaction and its properties.

Interactions with W and Z particles can change leptons to quarks and vice versa. Interactions with gluons can change the type of quarks.

Quote:When two charged particles interact electromagnetically, they do so by the exchange of a photons. So, you were wrong when you said that photons do not interacts with electrons via the electromagnetic force. In fact, the electromagnetic force is *precisely* charged particles interacting with photons.

Thanks. About this line of mine:
“A neutrino, a neutron, a photon does not interact with an electron via the electric force/magnetic force.”

I’m not an expert on this but I think it depends on the conditions.

Case 1:
For example, if you send a beam of photons right between 2 charged plates and the distance between the photon beam and the electrons in the plates is 1 cm, there is no interaction at all.
The photons go in a straight line as if the electric field is not even there.
The same goes for a magnetic field.
If this was not the case, the beam would bend. It would be easy to observe a lens effect around a piece of magnet.

This is not correct. A magnetic field that varies can affect the polarization of light going through it. it doesn't change the direction, but it does change the characteristics of the light.

Quote:Case 2:
If you have a beam of electrons and a beam of photons and you cross the beams, they will not interact, no matter what the wavelength of the electrons and photons is.
I might be wrong about that. Perhaps if their wavelengths are the same, there would be an interaction.

This is not correct. The electrons *will* interact with the photons. One way is via Compton scattering. Another is simply from the changing electric field of the light beam.

Quote:Case 3:
Electrons around atoms. If the compound is in a gaseous state, and you send a photon, if the wavelength matches the wavelength of the orbit (?), the photon might get absorbed by the electron.

close, but not quite right. The photons have to be tuned to the *difference* in energy between two available orbitals. This does NOT require the sample to be a gas. it is also possible for the photon to interact with the electron and ionize the atom.

Quote:Case 4:
If you have 2 beams of photons. If you cross the beams, no matter what the wavelength of the photons is, there is no interaction between the photons.

This is correct to a very high degree of accuracy, but not absolutely so. A photon can produce a positron/electron pair, which interacts with another photon before the pair collapses back into a photon. The effect is small, but it exists.

Quote:

Quote:You were also factually wrong when you said that neutrons do not interact electromagnetically. While they are not charged, they *do* have a magnetic field.

Thanks. That is interesting.
I looked at the wikipedia page. I think there is something I do not understand. There is a difference between having a magnetic field and a magnetic moment?

The magnetic moment gives the strength of the dipole part of the magnetic field.

Quote:The wikipedia says that it is hard to guide a neutron beam. A heterogenous field needs to be used which has an impact on a neutron because a neutron has magnetic moment.
Apparently, a parallel magnetic field has no effect?

Yes. More precisely, the magnetic field cannot be uniform. It needs to vary with position to produce a force on the neutron.

Quote:I have heard of W, Z, gluons, fermions, bosons, but mostly, I do not know those details.

Apparently, a team might have discovered a dineutron and another team might have discovered a tetraneutron.
It looks like there is a lot of exotic stuff to be discovered.

Most definitely. It gets even stranger when you allow quarks other than just up and down to come into play. (protons are two ups and a down, neutrons are two downs and an up).

(January 29, 2022 at 7:57 pm)Ferrocyanide Wrote: Interact is the keyword.
How does matter interact with matter?
An electron interacts with another electron or any other charged particle via its electric field/magnetic field.

A neutrino, a neutron, a photon does not interact with an electron via the electric force/magnetic force.

I think its already been mentioned, but photons absolutely do interact with electrons.  

A photon is literally a quanta of electro-magnetic energy.  While it does not interact with static electric or magnetic fields, it interacts with electrons by causing them to accelerate.  If there is no scattering or absorption, this interaction instead delays the photon.

(January 30, 2022 at 8:30 pm)HappySkeptic Wrote:

(January 29, 2022 at 7:57 pm)Ferrocyanide Wrote: Interact is the keyword.
How does matter interact with matter?
An electron interacts with another electron or any other charged particle via its electric field/magnetic field.

A neutrino, a neutron, a photon does not interact with an electron via the electric force/magnetic force.

I think its already been mentioned, but photons absolutely do interact with electrons.  

A photon is literally a quanta of electro-magnetic energy.  While it does not interact with static electric or magnetic fields, it interacts with electrons by causing them to accelerate.  If there is no scattering or absorption, this interaction instead delays the photon.

These interactions being the basis of lasers.

(January 30, 2022 at 1:45 pm)The Grand Nudger Wrote: A hard problem of matter?  That sounds interesting.  Something like...if we discovered everything there was to discover about material interaction, everything that causes it, everything it can do - the universe will still be fundamentally or at least partially inexplicable?  An open question sort of issue?

Correct.

Glad I got that right, there were two ways to go with it, either that - or, learn everything there is about the universe..and matter is still fundamentally unexplained. Either way, it's the suggestion that something or everything is fundamentally unknowable. Not just unknown or difficult. Unknowable.

Like the hard problem of chocolate chip cookies. Everything that a baker knows or can know about them, but, ultimately... chocolate chip cookies are inexplicable.