A particle for Heat?

[JohnSSM]

Convection and conduction are easy enough to understand, but when it comes to radiation of heat, im wondering why there isnt a particle for heat in QFT.

It seems that radiated heat is carried in infrared waves, which are light or at least, EMR.

Light and heat are not the same thing (are they?), but it does seem they are both commonly radiated together.

Does heat just become a factor of light like "brightness" or "color"? Was there ever a consideration to create a particle for heat or does the photon cover it?

Ive done a good bit of research, but these questions have not been answered.

[andrewcellini]

this might be a good place to start - https://en.wikipedia.org/wiki/Phonon

[studiot]

 

Convection and conduction are easy enough to understand

 

I'm glad you find this easy, because understanding what 'heat' actually is is key to answering your question.

And yes certain types of photons carry (transport or transfer) radiative energy called heat.

[JohnSSM]

this might be a good place to start - https://en.wikipedia.org/wiki/Phonon

I am embarrased to say that in all my reading I have never come across the term phonon. And through all those Feyman youtube lectures...maybe I mistook it for photon or maybe he never said it. Wow...thanks for the lead on that one.

 

 

 

I'm glad you find this easy, because understanding what 'heat' actually is is key to answering your question.

And yes certain types of photons carry (transport or transfer) radiative energy called heat.

Convection and conduction both seem to need "physical" interactions through materials. I guess I dont understand how heat would travel through a vacuum, but if heat is just another form of light, thats not an issue,

 

I come across the term "frequency" a lot when it comes to heat within a material. They describe the equilibrium of heat like it is the equilibrium of a frequency. What dictates the frequency within a material that would "tell" it where to find equilibrium?

 

Im still reading, but made my way through the wiki article on phonons and had that question.

[Strange]

It seems that radiated heat is carried in infrared waves, which are light or at least, EMR.

 

Light and heat are not the same thing (are they?), but it does seem they are both commonly radiated together.

 

They are not the same thing; they are different forms of energy. Heat is a measure of the kinetic energy of the particles (atoms) in a material. Light is electromagnetic radiation. A hot object can cool down by radiating electromagnetic radiation (or photons, if you want the quantum view). Or it gain heat by absorbing radiation (photons).

[studiot]

 

Heat is a measure of the kinetic energy of the particles (atoms) in a material

 

Another view is that heat is a measure of motion transferred from onle lot of of particles to another lot of particles.

[Strange]

 

Another view is that heat is a measure of motion transferred from onle lot of of particles to another lot of particles.

 

That is a better definition (I was thinking of temperature).

[swansont]

 

Another view is that heat is a measure of motion transferred from onle lot of of particles to another lot of particles.

 

It's the energy transferred owing to a temperature difference. Thus EM radiation can be heat, but only in the case of radiating because the object is at some temperature, i.e. blackbody radiation.

 

I come across the term "frequency" a lot when it comes to heat within a material. They describe the equilibrium of heat like it is the equilibrium of a frequency. What dictates the frequency within a material that would "tell" it where to find equilibrium?

 

I'm not sure what you are reading to see that; equilibrium occurs when the incoming amount of heat equals the outgoing amount.

[Klaynos]

I think there is an important distinction to make here:

 

Temperature is a measure of the average kinetic energy of an ensemble.

 

Heat is an energy transfer due to a temperature difference. It is not a type of energy itself.

[studiot]

Picking up some points made in the previous posts,

 

I agree that conduction and convection are easier to understand than radiation, but remember phonon theory only applies to crystalline solids.

It is easy to see how agitation of particles can be mechanically transferred to other particles in direct contact.

 

EM Radiation is not, of itself, heat or even composed of material particles that can jostle others.

 

Nevertheless when radiation of any wavelength (frequency) falls onto material objects heating (raising of its temperature) of that object is possible and often occurs.You only have to stand in the sunlight to appreciate that.

The Sun is at a very much higher temperature than you are so when the energy in the sunlight warms you (transfers energy to you) we say that heat is transferred by radiation.

This is in accord with the comment by Klaynos, but is not the whole story.

 

If you attend radiation therapy then the temperature of your cancer will rise in response to absorbing the radiation, although the temperature of both the source and yourself are pretty much the same. Further the frequencies of these Xrays are much higher than infra red.

Energy can even be transferred from a colder to a hotter body by this means, although this does not contravene the laws of thermodynamics.

 

What this shows is that EM radiation can be generated by several different means.

EM radiation that is generated by virtue of the temperature of a material body is called thermal radiation and governed by the laws of Stephan and Wien.

It is this type that takes part in radiative cooling or heating and energy transferred by this type of radiation is called heat transfer by radiation.

EM radiation generated by other means such as a microwave oven or Xrays as above also cause heating in the recipient, but there is no 'loss of heat' by the source so is not called heat transfer.

Again this is in accordance with the laws of thermodynamics since they allow other forms of energy input to a system to appear as heat within a system.

[swansont]

Picking up some points made in the previous posts,

 

I agree that conduction and convection are easier to understand than radiation, but remember phonon theory only applies to crystalline solids.

It is easy to see how agitation of particles can be mechanically transferred to other particles in direct contact.

 

EM Radiation is not, of itself, heat or even composed of material particles that can jostle others.

 

Nevertheless when radiation of any wavelength (frequency) falls onto material objects heating (raising of its temperature) of that object is possible and often occurs.You only have to stand in the sunlight to appreciate that.

The Sun is at a very much higher temperature than you are so when the energy in the sunlight warms you (transfers energy to you) we say that heat is transferred by radiation.

This is in accord with the comment by Klaynos, but is not the whole story.

 

If you attend radiation therapy then the temperature of your cancer will rise in response to absorbing the radiation, although the temperature of both the source and yourself are pretty much the same. Further the frequencies of these Xrays are much higher than infra red.

Energy can even be transferred from a colder to a hotter body by this means, although this does not contravene the laws of thermodynamics.

 

What this shows is that EM radiation can be generated by several different means.

EM radiation that is generated by virtue of the temperature of a material body is called thermal radiation and governed by the laws of Stephan and Wien.

It is this type that takes part in radiative cooling or heating and energy transferred by this type of radiation is called heat transfer by radiation.

EM radiation generated by other means such as a microwave oven or Xrays as above also cause heating in the recipient, but there is no 'loss of heat' by the source so is not called heat transfer.

Again this is in accordance with the laws of thermodynamics since they allow other forms of energy input to a system to appear as heat within a system.

 

Exactly. Radiation from a non-thermal source is considered work in thermodynamic terms.

 

One of the confounding issues here is that "heat" and heating" are used in a sloppy manner at times, and some of the terminology is confusing. One might be led to believe that heat is a substance, e.g. with the term "heat capacity". But that really refers to thermal energy.

[studiot]

A further source of possible confusion occurs when chemical reactions take place without any work being done.

Some reactions vigourously raise the temperature (heat) of the system, and flashes of light may also be emitted.

The energy for this is coming from the TdS term in the Heat Content (also called Enthalpy) of the system.

 

Once the system temperature rises, heat may then be transferred to the surroundings by the three conventional mechanisms.

[JohnSSM]

 

It's the energy transferred owing to a temperature difference. Thus EM radiation can be heat, but only in the case of radiating because the object is at some temperature, i.e. blackbody radiation.

 

I'm not sure what you are reading to see that; equilibrium occurs when the incoming amount of heat equals the outgoing amount.

Its from the wiki on phonons..."A phonon is a quantum mechanical description of an elementary vibrational motion in which a lattice of atoms or molecules uniformly oscillates at a single frequency"

Picking up some points made in the previous posts,

 

I agree that conduction and convection are easier to understand than radiation, but remember phonon theory only applies to crystalline solids.

It is easy to see how agitation of particles can be mechanically transferred to other particles in direct contact.

 

EM Radiation is not, of itself, heat or even composed of material particles that can jostle others.

 

Nevertheless when radiation of any wavelength (frequency) falls onto material objects heating (raising of its temperature) of that object is possible and often occurs.You only have to stand in the sunlight to appreciate that.

The Sun is at a very much higher temperature than you are so when the energy in the sunlight warms you (transfers energy to you) we say that heat is transferred by radiation.

This is in accord with the comment by Klaynos, but is not the whole story.

 

If you attend radiation therapy then the temperature of your cancer will rise in response to absorbing the radiation, although the temperature of both the source and yourself are pretty much the same. Further the frequencies of these Xrays are much higher than infra red.

Energy can even be transferred from a colder to a hotter body by this means, although this does not contravene the laws of thermodynamics.

 

What this shows is that EM radiation can be generated by several different means.

EM radiation that is generated by virtue of the temperature of a material body is called thermal radiation and governed by the laws of Stephan and Wien.

It is this type that takes part in radiative cooling or heating and energy transferred by this type of radiation is called heat transfer by radiation.

EM radiation generated by other means such as a microwave oven or Xrays as above also cause heating in the recipient, but there is no 'loss of heat' by the source so is not called heat transfer.

Again this is in accordance with the laws of thermodynamics since they allow other forms of energy input to a system to appear as heat within a system.

Thanks for the added descriptive...its often in those bits where I find new info...and new questions.

 

Can we consider that there is an electric heated cooking element in a vacuum and we turn up the current and the element begins to glow. But it begins to emit photons for what reason? We sent enough EM current through a material to a point where it "can no longer handle" it. What does that really mean? We added enough current so that the material is pushed to some limit where it begins to emit photons and glow. Or does it emit photons as soon as we pass current through it, and we must turn up the current to get enough to see as a glow?

 

Watching a movie about Edison as a kid, I remember him trying to find a material that could take enough current to glow brightly, but also not burn apart in that process. Heat was killing his light element...

 

So then we take that same electric heated cooking element in a vacuum and we turn up the current and it begins to emit heat, or a change in temperature...its already getting fuzzy for me...In a vacuum, without something to transfer the heat from that element to my hand, or another heat detecting element, how would any transfer of kinetic/heat/temperature energy occur if heat were not in it's own particle? And it makes me wonder about dissipation of heat in a vacuum. To me, heat seems to dissipate much faster than light or nuclear radiation. And the reason I didnt want to use the sun was so as not to confuse any heat energy being emitted from the fusion reactions in the sun. So i used the electric plate as the example instead.

 

I have a few things to google in order to answer my own new questions, but any leads and info would be great.

I think there is an important distinction to make here:

 

Temperature is a measure of the average kinetic energy of an ensemble.

 

Heat is an energy transfer due to a temperature difference. It is not a type of energy itself.

With two objects that are millions of miles apart, and if heat is only due to a temperature difference, how does one object "know" that the other object has less temperature? IT seems a silly thing to ask, but then, heat would be emitted without the need for a temperature difference.,..and those objects with less temperature "absorb" it...I suppose there would be no heat transferred between two objects of the exact same temperature, this is not to say that both objects are not emitting heat energy...If that isnt the case, then it seems that we are implying that the heating element becomes aware of my less-heated hand coming close to it, and then emits some heat energy to bring my hand to equilibrium ...isnt the heat being emitted either way? ie, With or without my hand near it...

[swansont]

Its from the wiki on phonons..."A phonon is a quantum mechanical description of an elementary vibrational motion in which a lattice of atoms or molecules uniformly oscillates at a single frequency"

 

That's not heat. Vibrational motion of a lattice is represented by temperature.

 

Can we consider that there is an electric heated cooking element in a vacuum and we turn up the current and the element begins to glow. But it begins to emit photons for what reason? We sent enough EM current through a material to a point where it "can no longer handle" it. What does that really mean? We added enough current so that the material is pushed to some limit where it begins to emit photons and glow. Or does it emit photons as soon as we pass current through it, and we must turn up the current to get enough to see as a glow?

 

It's emitting photons even before you pass current through it. All objects radiate according to their temperature. The ideal body that does this is a blackbody — a perfect absorber and emitter (no reflections). The amount of power per unit area it radiates is proportional to T^4.

 

At room temperature, the radiation is mostly in the IR, near 10 microns. As the temperature goes up, the peak shifts to smaller wavelengths. So you start to see the red part of that spectrum, and as it gets hotter, it more closely matches the visible spectrum.

[JohnSSM]

 

 

 

It's emitting photons even before you pass current through it. All objects radiate according to their temperature. The ideal body that does this is a blackbody — a perfect absorber and emitter (no reflections). The amount of power per unit area it radiates is proportional to T^4.

 

At room temperature, the radiation is mostly in the IR, near 10 microns. As the temperature goes up, the peak shifts to smaller wavelengths. So you start to see the red part of that spectrum, and as it gets hotter, it more closely matches the visible spectrum.

Aha...good stuff...just did the reading at wiki about blackbody radiation, thermal radiation and Plank's law. I'm floored by what I still don't understand. Ill continue working it out but i do have one big question.

 

IS this EM radiation enabled by the weak force? Or does the weak force dictate a different form of radiation?

 

It seems the bottom line is that anything above absolute zero has kinetic energy which really just seems to equate to "atomic movements" ...Do these atomic movements create "interactions" and those interactions end up radiating subatomic particles due to the weak force? Isnt the weak force with it's W and Z bosons which dictate what gets radiated and why?

[Klaynos]

With two objects that are millions of miles apart, and if heat is only due to a temperature difference, how does one object "know" that the other object has less temperature? IT seems a silly thing to ask, but then, heat would be emitted without the need for a temperature difference.,..and those objects with less temperature "absorb" it...I suppose there would be no heat transferred between two objects of the exact same temperature, this is not to say that both objects are not emitting heat energy...If that isnt the case, then it seems that we are implying that the heating element becomes aware of my less-heated hand coming close to it, and then emits some heat energy to bring my hand to equilibrium ...isnt the heat being emitted either way? ie, With or without my hand near it...

The two objects would be separated by some medium, even space counts, what is the relative temp of that medium?

 

The objects would always emit their blackbody spectrum. If the system is in equilibrium then energy out equals energy in.

 

You're still using the term "heat energy". Heat is energy transfer not a type of energy.

[Robittybob1]

....

You're still using the term "heat energy". Heat is energy transfer not a type of energy.

Wouldn't it be a transfer of a photon?

[Strange]

Wouldn't it be a transfer of a photon?

 

Only if it is radiated.

[Robittybob1]

 

Only if it is radiated.

So in heat transfer by conduction how do you think the energy is transferred from one molecule to another? Could it be virtual photons in that case?

Edited July 28, 2015 by Robittybob1

[Klaynos]

So in heat transfer by conduction how do you think the energy is transferred from one molecule to another? Could it be virtual photons in that case?

Phonons are quite likely. They of course do interact using the EM force. But that's probably just going to confuse the discussion somewhat.

[swansont]

Aha...good stuff...just did the reading at wiki about blackbody radiation, thermal radiation and Plank's law. I'm floored by what I still don't understand. Ill continue working it out but i do have one big question.

 

IS this EM radiation enabled by the weak force? Or does the weak force dictate a different form of radiation?

 

It seems the bottom line is that anything above absolute zero has kinetic energy which really just seems to equate to "atomic movements" ...Do these atomic movements create "interactions" and those interactions end up radiating subatomic particles due to the weak force? Isnt the weak force with it's W and Z bosons which dictate what gets radiated and why?

 

Nothing to do with the weak force. It's all electromagnetic.

[JohnSSM]

 

Nothing to do with the weak force. It's all electromagnetic.

I suppose the reason I asked is because Im associating radiation with entropy. I think im still confused about both.

 

Im confused about light's purpose as a gauge boson for electromagnetism, and Im confused about the transfer of heat...is it separate from light? Is heat a type of light or a trait of light?

 

Its the smallest things that seem to have totally lost their meanings...or maybe I just never really thought about heat and temperature until recently...

[swansont]

I suppose the reason I asked is because Im associating radiation with entropy. I think im still confused about both.

Im confused about light's purpose as a gauge boson for electromagnetism, and Im confused about the transfer of heat...is it separate from light? Is heat a type of light or a trait of light?

Its the smallest things that seem to have totally lost their meanings...or maybe I just never really thought about heat and temperature until recently...

 

Radiation because of an object's temperature - blackbody radiation, e.g. from an incandescent light bulb - is one manifestation of heat. Any other radiation, e.g. from a laser, is not heat.

[Sensei]

I suppose the reason I asked is because Im associating radiation with entropy. I think im still confused about both.

 

Im confused about light's purpose as a gauge boson for electromagnetism, and Im confused about the transfer of heat...is it separate from light? Is heat a type of light or a trait of light?

 

Its the smallest things that seem to have totally lost their meanings...or maybe I just never really thought about heat and temperature until recently...

 

Imagine body with temperature. It's emitting photons in the all directions, using inverse square law

https://en.wikipedia.org/wiki/Inverse-square_law

The higher temperature, the more energy have emitted photons.

Bodies with low temperature are emitting photons in infrared, or microwave spectrum.

Hot bodies such as stars are emitting photons in visible spectrum.

These photons are absorbed by neighbourhood particles of gas, liquids, solids, and heating them.

These gases, liquids and solids also emits their own photons to environment (otherwise their temperature and energy would be going to infinity, and they would be changing state, melting, vaporizing, ionizing. Radiation is a way to release too much energy in them).

If emission meets absorption there is subtle equilibrium.

 

Bodies heated in day (from Sun), will release accumulated energy at night time.

If next day is not sunny, they'll receive little energy, and won't emit more than they have.

 

We can use infra red cameras (expensive), or infra red thermometers (cheap), to learn body temperature from distance.

They analyze spectrum of photons emitted by body to calculate temperature (typically invisible spectrum) to show on display (or make array of them width x height in camera case).

Edited August 15, 2015 by Sensei

[singhsippi]

When heat is added to a substance, the molecules and atoms vibrate faster. As atoms vibrate faster, the space between atoms increases. The motion and spacing of the particles determines the state of matter of the substance. The end result of increased molecular motion is that the object expands and takes up more space.

Edited August 26, 2015 by singhsippi