[alancalverd]

And thermal energy is the internal energy of an atom.

No. It is the kinetic energy of all the atoms in a body.

You could go on forever and still not be sure what you are measuring in a photon.

On the contrary, the energy of every photon I have measured was its ability to do work, usually releasing electrons from a photocathode, heating a block of graphite, causing a current to flow in a circuit, ionising air, or initiating a chemical reaction.

Where I part company with philosophers is over their insistence on asking what something "is", because that can lead to a sterile reductio ad nauseam. In the case of energy or elephants, it is a lot more productive to define its characteristics. Energy eats shoots and leaves, elephants are conserved. I know because a friend works in elephant conservation - much more reliable than Google.

[yor_on]

Don't get stuck on words MXP
There is a lot we don't know.

But we can still measure the 'coin of exchange'.
Temperature is one.

[mxplxxx (OP)]

Don't get stuck on words MXP
There is a lot we don't know.

But we can still measure the 'coin of exchange'.
Temperature is one.

It seem to me what is being measured is the effects of something we call energy and we are not too sure exactly what energy is but the science of it is very useful anyway.

ps1 I think energy, like the speed of light, is absolute, not relative as I have previously stated (and not been challenged). If a particle absorbs a photon, it likely changes its momentum (and other?) relationship to ALL other particles. This makes sense given that a photon is not a relational entity. In fact, it seems to me that measuring the momentum of a particle before and after it has absorbed photon should give the  energy of the photon.

ps2 talking about the energy of a photon is meaningless anyway without the time to transfer the energy being involved. i.e. we should be measuring power, not energy.

[alancalverd]

ps2 talking about the energy of a photon is meaningless anyway with the time to transfer the energy being involved. i.e. we should be measuring power, not energy.

However you measure the energy of Co-60 gamma photons, you get the same result, though the initial interactions are very different. The constants (energy) tell us something about the source of the photons and are predictive of their other interactions. The power, though measurable (depending on how you define it) is not constant, explanatory or usefully predictive.

[mxplxxx (OP)]

ps2 talking about the energy of a photon is meaningless anyway with the time to transfer the energy being involved. i.e. we should be measuring power, not energy.

However you measure the energy of Co-60 gamma photons, you get the same result, though the initial interactions are very different. The constants (energy) tell us something about the source of the photons and are predictive of their other interactions. The power, though measurable (depending on how you define it) is not constant, explanatory or usefully predictive.

I guess with all photons "containing" a quantum of action, once we know the energy of a particular photon we know the power and vice versa. Let me try some maths:

E = hf
P = E/t
t = 1/f
P = Ef

QED?

[alancalverd]

The quantum of action is h, a universal constant. The energy of photons spans an enormous spectrum.

t≠1/f

Your handling of mathematical symbols is impeccable, but has nothing to do with photon physics.

[mxplxxx (OP)]

Your handling of mathematical symbols is impeccable, but has nothing to do with photon physics.

Can you tell me more? I would have thought it had everything to do with photon physics given e=hf is the basic equation of quantum physics and a photon "contains" one quantum of energy (h).

A better way of imagining how a quantum of action behaves, is to use the formula E=h/t applied to photons where t is the time of one oscillation of a photon. This formula is the equivalent of E=hf. As the time does down (i.e. the faster the oscillation/cycle or the higher the frequency), the energy goes up and vice versa and, of course, all the while h stays the same.  Of course where the frequency is increasing, the power is really taking off as energy is increasing and time is decreasing.

[Bored chemist]

we are not too sure exactly what energy is

Speak for yourself.

[Bored chemist]

E = hf
P = E/t
t = 1/f
P = Ef

QED?

No
Because you are using  "t" for two different things.
One is the time period over which energy is transferred, and the other is the time between successive peaks in the em field of the photon.

It's like muddling up the reciprocal of the frequency of a car radio  and time take to get from one town to the next.

[mxplxxx (OP)]

E = hf
P = E/t
t = 1/f
P = Ef

QED?

No
Because you are using  "t" for two different things.
One is the time period over which energy is transferred, and the other is the time between successive peaks in the em field of the photon.

It's like muddling up the reciprocal of the frequency of a car radio  and time take to get from one town to the next.

I am pretty sure, because of wave/particle duality, that a photon and an EM wave are nearly equivalent (see http://galileo.phys.virginia.edu/classes/531.cas8m.fall05/l26.pdf). Can you supply me a good reference to back up your statement that t in E=h/t has two different meanings? I certainly can't after a fairly long search.

[mxplxxx (OP)]

E = hf
P = E/t
t = 1/f
P = Ef

QED?

No
Because you are using  "t" for two different things.
One is the time period over which energy is transferred, and the other is the time between successive peaks in the em field of the photon.

It's like muddling up the reciprocal of the frequency of a car radio  and time take to get from one town to the next.

I am pretty sure, because of wave/particle duality, that a photon and an EM wave are nearly equivalent (see http://galileo.phys.virginia.edu/classes/531.cas8m.fall05/l26.pdf). Can you supply me a good reference to back up your statement that t in E=h/t has two different meanings? I certainly can't after a fairly long search.

Actually I did find something at https://www.quora.com/Does-it-take-any-time-for-photons-to-be-released-or-absorbed-or-does-it-happen-instantaneously:

However, the creation and annihilation of photons are random processes, whose statistics are governed by quantum mechanics. This means that the probability of creating or annihilating a photon is time-dependent. Typically, the frequency of the photon sets the timescale for the absorption/emission probability. So, for example, if a photon of wavelength λ= 500 nm (corresponding to green light) and frequency f=c/λ=6×1014 Hz encounters an atom with the appropriate resonance frequency, the maximum probability for absorption is 1 / (6×10−14 Hz) = 1.67×10−15 seconds after the interaction begins. So, the photon is most likely to be absorbed after 1.67 femtoseconds. But, the photon can really be absorbed at any instant before or after (with varying probability).

I am a great fan of the probability nature of a photon. The author of the reference also states that the absorption is instantaneous. So what you are saying makes a lot of sense. Pity physics makes this distinction so hard to come by:)
. What then does the time (t) variable in E=h/t mean?. How do we calculate the power of a photon?

[mxplxxx (OP)]

The author of the reference also states that the absorption is instantaneous.

But how can it be instantaneous? Is it possible the photon has attributes that are immediately transferred to the receiving particle, much like an event in a computer program immediately updates the status of an affected object. 

[alancalverd]

The quantum of action is not a quantum of energy. They are dimensionally distinct.

"Wave-particle duality" is outdated superstition. There are two mathematical models of a photon, neither of which "is" a photon.

We know exactly what energy is, because we (i.e. physicists) have defined it as a conserved scalar. Just as farmers have defined a cow as a quadruped that moos, poos and makes milk. Only philosophers pretend that we don't know what anything "is", which is why they are not put in charge of dangerous machines.

The problem with suggesting that a photon takes around 10^-15 seconds to interact with an atom is that in that time it will have travelled about 3 x 10^-7 meters, several thousand atom radii past its supposed target.

[mxplxxx (OP)]

The quantum of action is not a quantum of energy. They are dimensionally distinct.

E=hf. E is a quantum of energy, h is a quantum of action. E is "real", h is mathematical.

[mxplxxx (OP)]

The problem with suggesting that a photon takes around 10-15 seconds to interact with an atom is that in that time it will have travelled about 3 x 10-7 meters, several thousand atom radii past its supposed target.

Unless the photon is coming from the future (which is not out of the realms of possibility given the probability aspects of a photon) and the fact that the transverse waves of an EM wave are travelling faster than SOL.

If not what, then, is the mechanism for transferring the energy of a photon to a recipient particle? It would seem this must happen in a certain time to satisfy the power/conservation of energy aspects of the transfer. e.g. a gamma ray should transfer faster than a visible light ray.

The problem with a transfer of  energy in 0 seconds is that the energy will have traveled 0 meters in that time:) But,  totally unsatisfactorily, according to quantum physics that is what happens. Quantum physics is forcing us to speculate that our concept of reality is out of step with the actuality of reality. Is this really the case or do we need to advance our theories?

[mxplxxx (OP)]

We know exactly what energy is, because we (i.e. physicists) have defined it as a conserved scalar.

From https://www.quora.com/Why-is-energy-a-scalar-quantity

A “scalar” quantity is defined as one that does not change under a transformation. Making this meaningful requires specifying which quantity and which transformation: so for instance energy is a scalar under spatial rotations, or under spatial translations, but it is the time component of a four-vector under Lorentz boosts. Under the Poincare group composed of of all those operations, energy is not a scalar.

That means that facing another direction, or changing position, doesn’t change the measurement of some object’s energy; but changing your velocity does.

[mxplxxx (OP)]

There are two mathematical models of a photon, neither of which "is" a photon.

Pardon? Tell me more.

[mxplxxx (OP)]

The problem with suggesting that a photon takes around 10-15 seconds to interact with an atom is that in that time it will have travelled about 3 x 10-7 meters, several thousand atom radii past its supposed target.

But, presumably, the photon has been stopped in its tracks by the atom:) so no question of it travelling past the atom.

[mxplxxx (OP)]

"Wave-particle duality" is outdated superstition.

Can you give me a good reference for this? I do not see it personally. In my computer model of reality system objects travel through time, much like waves in physics. Each system object (e.g. a galaxy) consists of a central object  and peripheral system objects (e.g. in the case of a galaxy, a black hole and surrounding solar systems). The central object contains the state of the system and would be considered the particle in the wave/particle duality paradigm. This works fine for me and I cannot see why it would not also work for reality.

basically, System = structure, Wave = position, Particle = state

[alancalverd]

The problem with all computer models is GI(G+)O. Why +? because the response is not instantaneous or even related directly to reality, but is a function of the model and the system it runs on. Physics is different.