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this is the crux of the problem. wirebender does not understand the difference between radiation and heat flow. radiation is a function of the temperature of the radiating object (in very simple terms) and heat flow is the measurement of the size and direction of net radiation.
wirebender- this is what you posted
Re: Vacuum Chamber with plates.
First, identify the ONLY energy source in the Vacuum Chamber with an electric heater.
The ONLY energy source is the ELECTRIC HEATER that heats a plate with electricity to a temperature of 150 deg F or 338.56 K.
Asuume an emissivity = 1 and a surface Area for the plate = 1 m^2
Using the Stefan-Boltzmann Law, the Watts provided by the Electric Heater is:
P = e*BC*A*T^4
Where P = net radiated power (Watts), e = emissivity, BC = Stefans constant 5.67 X 10^-8, A = area and T = temperature of radiator in K
P = (5.67X10^-8) X 1m^2 X (338.56 K)^4 = 744.95 Watts
(***Thats ALL the Energy Available and cannot be exceeded without CREATING ENERGY***)
The EM field produced by the plate is 744.95 Watts/ 1 m^2 = 744.95 w/m^2
If another identical non-heated and colder plate is inserted into the Vacuum Chamber next to the heated Plate then:
The 2nd Plate also has an emissivity = 1 and a surface Area for the 2nd plate = 1 m^2
We can easily determine the equilibrium temperature of both plates by using the Stefan-Boltzmann Law and The Law of Conservation of Energy.
The TOTAL amount of energy available is 744.95 Watts and both plates will have the same temperature at equilibrium, so they can be considered to be a single radiating body with double the radiating surface area.
The area of both plates = 2 m^2 so the Radiation emitted by both plates at equilibrium = 744.95 Watts / 2 m^2 = 372.48 w/m^2
And the equilibrium temperature for both plates will be 284.69 K or 53 deg F.
is it a different experiment by [Gord] or just his description of Spencer's example? you didnt specify.
it doesnt really matter because Spencer's description is correct and your copied description is incorrect.
you still havent described the mechanism by which you think both plates (or bars) will come to equilibrium at the same temperature even though one is heated and the other is not.
you still havent explained why you think the heat loss in the direction of the second bar is the same as the heat loss in the direction of the cooled vacuum, even though there is an obvious difference in temperatures.
the math in your example is not only wrong but farfetched. no wonder you refuse to bump your post where you 'proved that photons disappear in space, and did the math'. obviously it was just as infintile and incorrect as your 'proof' that Spencer was wrong.
I just want to address a few things directly...
"you still havent described the mechanism by which you think both plates (or bars) will come to equilibrium at the same temperature even though one is heated and the other is not."
Its due to the laws of thermodynamics Ian... Particularly the last one I mentioned in a previous post.. The zeroth law... I suggest you read it again..
here is a better explanation than I gave I believe...
Zeroth Law, Thermal Equilibrium and Temperature
Zeroth Law
The zeroth law is a consequence of thermal equilibrium and allows us to conclude that temperature is a well-defined physical quantity. The zeroth law of thermodynamics states:
If a body A and a body B are both in equilibrium with each other; then a body C which is in thermal equilibrium with body B will also be in equilibrium with body Aand the temperature of body C is equal to the temperature of body A.
It is the zeroth law, because it preceeds the first and second laws of thermodynamics and is also a tacit assumption in both laws.
We use the zeroth law when we wish to compare the temperatures of two objects, A and B. We can do this by using a thermometer, C and placing it again object A it reaches thermal equilibrium with object A and measure the temperature of A. Placing the thermometer against object B until thermal equilibrium is reached we measure the temperature of object B. If they are the same temperature then they will be in thermal equilibrium with each other.
Now if you are somehow changing the distance of the plates from one another that would be effected by that new distance. I was under the assumption the plates were placed on top of one another. This was implied throughout the experiment I believe. if they are indeed in contact with one another the outside temps only effect the outside surface areas of the plates. Of course the closer to the heat source the warmer it will be no one made any claim to the contrary. however, the assumed term "all things being equal" will apply here.
The entire experiment is a thought experiment. The physical reality is its not even a good example of how a real physical experiment would be. First there is always a difference in the temperature of any heated surface the farther it gets from its point of contact with the heat source. Second standing plates are not a moving atmosphere with all the variables it entails. Third, the vacuum is only applicable to the relation of the Sun to the atmospheric surface. Once it hits that atmosphere the vacuum is no longer a factor. The earth sits in a vacuum, but the atmosphere is not a vacuum, and that is the part that is in contention in greenhouse effect theory. That would make the entire premise of the experiment pointless.
However you brought this experiment into the discussion and professed its accuracy. So we tried to show how it was not an accurate example of how the "greenhouse effect" works. You vehemently defended it and still do so now. This experiment forces many of the natural finer points and details to be ignored.
Now if you want us to ignore the finer points and details and allow this experiment to go through to its claimed result, you cannot very well fall back on those finer points to defend it when it falls flat.. The experiment assumes "all things being equal" from the start, that is the only way it can work even in a thought experiment. So either all things are indeed equal in it or all things are as they would be in the real world, either way it falls flat. But you must stick to one or the other, switching between them only confounds the thing and makes it impossible..
I see your test had the same result...
EDIT: Maybe next time you should test it BEFORE neg repping me and making the false claim...
However you brought this experiment into the discussion and professed its accuracy. So we tried to show how it was not an accurate example of how the "greenhouse effect" works. You vehemently defended it and still do so now. This experiment forces many of the natural finer points and details to be ignored.
I agree with the zeroith law but it does not apply to one object that is being heated and another one that is only absorbing the radiation from the first. the two objects are not the same temperature even if they are in an equilibrium of sorts.
he was specifically dealing with the radiation properties of objects. and he successfully showed that adding an object between the source of heat and the cold outside would raise the temperature of the radiating source.
an analogy is a water source (electricity) going to a connection with multiple hoses and sprinklers (the heated bar). if you put a crimp into one of the hoses (second bar which hampers the ability to radiate to the cold outside) then the water pressure backs up and the remaining sprinklers are more forceful (the heated bar is warmer). the whole thought experiment is logical and easy to understand if you just think about it.
Spencer's experiment is not an explanation of the greenhouse effect. it is an explanation of why the greenhouse effect is not in violation of thermodynamic laws, specifically 'a cooler body cant warm a warmer body'.
I agree with the zeroith law but it does not apply to one object that is being heated and another one that is only absorbing the radiation from the first. the two objects are not the same temperature even if they are in an equilibrium of sorts.
Mighty caucasian of you even though you clearly don't grasp its inplications.
he was specifically dealing with the radiation properties of objects. and he successfully showed that adding an object between the source of heat and the cold outside would raise the temperature of the radiating source.
The only thing spencer showed is that he doesn't recognize a heat sink when he imagines it.
an analogy is a water source (electricity) going to a connection with multiple hoses and sprinklers (the heated bar). if you put a crimp into one of the hoses (second bar which hampers the ability to radiate to the cold outside) then the water pressure backs up and the remaining sprinklers are more forceful (the heated bar is warmer). the whole thought experiment is logical and easy to understand if you just think about it.
The math is logical and easy to understand, your interpretation of the experiment and end result is twisted in tangled up knots.
The heat transfer from the heatsink is mediated by two effects: convection via the coolant, and thermal radiation.
Heat transfer by radiation is a function of both the heat sink temperature, and the temperature of the surroundings that the heat sink is optically coupled with. When both of these temperatures are on the order of 0 °C to 100 °C, the contribution of radiation compared to convection is generally small, and this factor is often neglected. In this case, finned heat sinks operating in either natural-convection or forced-flow will not be effected significantly by surface emissivity.
In situations where convection is low, such as a flat non-finned panel with low airflow, radiative cooling can be a significant factor. Here the surface properties may be an important design factor. Matte-black surfaces will radiate much more efficiently than shiny bare metal.[10] A shiny metal surface has low emissivity, so it absorbs and radiates only a small amount of radiant heat, while matte-black has high emissivity so it absorbs and radiates radiant heat highly. The emissivity in the visible spectrum is closely related to color. For most materials, the emissivity in the visible spectrum is similar to the emissivity in the infrared spectrum; however there are exceptions, notably certain metal oxides that are used as "selective surfaces".
In a vacuum or in outer space, there is no convective heat transfer, thus in these environments, radiation is the only factor governing heat flow between the heat sink and the environment. For a satellite in space, a 100 °C (473 Kelvin) surface facing the sun will absorb a lot of radiant heat, since the sun's surface temperature is nearly 6000 Kelvin, whereas the same surface facing deep-space will radiate a lot of heat, since deep-space has an effective temperature of only a few Kelvin.
wirebender- this is what you posted
is it a different experiment by [Gord] or just his description of Spencer's example? you didnt specify.
it doesnt really matter because Spencer's description is correct and your copied description is incorrect.
you still havent described the mechanism by which you think both plates (or bars) will come to equilibrium at the same temperature even though one is heated and the other is not.
you still havent explained why you think the heat loss in the direction of the second bar is the same as the heat loss in the direction of the cooled vacuum, even though there is an obvious difference in temperatures.
the math in your example is not only wrong but farfetched. no wonder you refuse to bump your post where you 'proved that photons disappear in space, and did the math'. obviously it was just as infintile and incorrect as your 'proof' that Spencer was wrong.
I just want to address a few things directly...
"you still havent described the mechanism by which you think both plates (or bars) will come to equilibrium at the same temperature even though one is heated and the other is not."
Its due to the laws of thermodynamics Ian... Particularly the last one I mentioned in a previous post.. The zeroth law... I suggest you read it again..
here is a better explanation than I gave I believe...
Zeroth Law, Thermal Equilibrium and Temperature
Zeroth Law
The zeroth law is a consequence of thermal equilibrium and allows us to conclude that temperature is a well-defined physical quantity. The zeroth law of thermodynamics states:
If a body A and a body B are both in equilibrium with each other; then a body C which is in thermal equilibrium with body B will also be in equilibrium with body Aand the temperature of body C is equal to the temperature of body A.
It is the zeroth law, because it preceeds the first and second laws of thermodynamics and is also a tacit assumption in both laws.
We use the zeroth law when we wish to compare the temperatures of two objects, A and B. We can do this by using a thermometer, C and placing it again object A it reaches thermal equilibrium with object A and measure the temperature of A. Placing the thermometer against object B until thermal equilibrium is reached we measure the temperature of object B. If they are the same temperature then they will be in thermal equilibrium with each other.
Now if you are somehow changing the distance of the plates from one another that would be effected by that new distance. I was under the assumption the plates were placed on top of one another. This was implied throughout the experiment I believe. if they are indeed in contact with one another the outside temps only effect the outside surface areas of the plates. Of course the closer to the heat source the warmer it will be no one made any claim to the contrary. however, the assumed term "all things being equal" will apply here.
The entire experiment is a thought experiment. The physical reality is its not even a good example of how a real physical experiment would be. First there is always a difference in the temperature of any heated surface the farther it gets from its point of contact with the heat source. Second standing plates are not a moving atmosphere with all the variables it entails. Third, the vacuum is only applicable to the relation of the Sun to the atmospheric surface. Once it hits that atmosphere the vacuum is no longer a factor. The earth sits in a vacuum, but the atmosphere is not a vacuum, and that is the part that is in contention in greenhouse effect theory. That would make the entire premise of the experiment pointless.
However you brought this experiment into the discussion and professed its accuracy. So we tried to show how it was not an accurate example of how the "greenhouse effect" works. You vehemently defended it and still do so now. This experiment forces many of the natural finer points and details to be ignored.
Now if you want us to ignore the finer points and details and allow this experiment to go through to its claimed result, you cannot very well fall back on those finer points to defend it when it falls flat.. The experiment assumes "all things being equal" from the start, that is the only way it can work even in a thought experiment. So either all things are indeed equal in it or all things are as they would be in the real world, either way it falls flat. But you must stick to one or the other, switching between them only confounds the thing and makes it impossible..
I agree with the zeroith law but it does not apply to one object that is being heated and another one that is only absorbing the radiation from the first. the two objects are not the same temperature even if they are in an equilibrium of sorts.
if you are talking about Spencer's experiment the diagram specifically shows separation between the two bars, to stop conduction. and states a vacuum, to stop convection. he was specifically dealing with the radiation properties of objects. and he successfully showed that adding an object between the source of heat and the cold outside would raise the temperature of the radiating source.
an analogy is a water source (electricity) going to a connection with multiple hoses and sprinklers (the heated bar). if you put a crimp into one of the hoses (second bar which hampers the ability to radiate to the cold outside) then the water pressure backs up and the remaining sprinklers are more forceful (the heated bar is warmer). the whole thought experiment is logical and easy to understand if you just think about it.
please explain to me how you think the two bars will equilibrate to the same temperature in Spencer's experiment even though one is heated and the other is not.
you have said many foolish things in the past but that is right up there with saying that a blanket make you colder.
Well I am glad you agree with the zeroth law.. With it being a natural law you really little choice in the matter it simply is regardless of your agreement with it....
please explain to me how you think the two bars will equilibrate to the same temperature in Spencer's experiment even though one is heated and the other is not.
Because they are in a vacuum Ian where conduction and convection into the atmosphere are eliminated. Radiation is the only means of bleeding off heat and the bars (plates;same thing) are in close proximity. They will achieve equilibrium or very close to it.
As I have already told you, volumes have been written about the issue of heat within vacuum tubes from the old days when everything used them. In a vacuum, materials heated and passive reach an equilibrium temperature very quickly. Great pains had to be taken in the design of vacuum tube components using materials of widely varied absorptivity and emissivity, and wild heat sink designs were fabricated precisely to keep the internal components of the vacuum tube from reaching thermal equilibrium. It doesn't happen in the open atmosphere because convection and conduction are in operation to carry energy away from the heat sink. Not so in a vacuum.
Face it Ian, math and the laws of physics are stronger than your faith in a mythical greenhouse effect.
The math is correct and is a correct useage of the Stefan-Boltzman law dealing with blackbody radiation. You are accepting your intuition over hard mathematical evidence that has been proven reliable for over a hundred years.
What else need be said?
you have said many foolish things in the past but that is right up there with saying that a blanket make you colder.
Funny you should mention that Ian, and state it with your usual confidence as if it were a statement of fact. Sorry Ian, the second law of thermodynamics defeats you again. The fact is, that a blanket does reduce your surface temeprature. Once again, your intuition, belief, faith, or whatever intermal system your intellect runs on, has lead you off in the wrong direction. The fact is, Ian, that putting a blanket over your body does make you colder just as the second law of thermodynamics predicts.
Your problem Ian, is that you believe you are smarter than the laws of physics and the math that proves those laws. You aren't.
"Human Body Emission
As all matter, the human body radiates some of a person's energy away as infrared light.
The net power radiated is the difference between the power emitted and the power absorbed:
Applying the Stefan Boltzman Law
The total surface area of an adult is about 2 m², and the mid- and far-infrared emissivity of skin and most clothing is near unity, as it is for most nonmetallic surfaces.[ Skin temperature is about 33 °C, but clothing reduces the surface temperature to about 28 °C when the ambient temperature is 20 °C. Hence, the net radiative heat loss is about
"
If you put a 20C blanket (which is colder) on a warmer 33C body, the surface temperature is going to reduce to about 28C. Heat flowed from the warmer body to the cooler blanket just as the 2nd law of thermodynamics predicts.
It is true that the blanket will trap warm air between the body and itself, but that heat will not increase the temperature of the body.
This buisness is a matter of the laws of physics and the mathematics that prove them Ian. Not, as you seem to believe, a matter of faith. You pit yourself against the laws of nature and you will lose every time.
wirebender- your link supports my position! skin radiates more when it is exposed. when an insulator is put between skin and a colder ambient temperature there is less heat loss. surely you didnt think that the skin underneath the clothing has cooled? are you really that stupid?
again. please explain how a heated object and an unheated object will equilibrate at the same temperature when the heated object is the only source of heat in an open system. just describe the heat flow from one to the other so we can understand this amazingly counterintuative feat of physics.
... my bet is that the math I just gave him regarding the fact that a blanket does in fact cool you down will remain unchallenged by anything more than a verbal objection and perhaps an ad hominim delivered in frustration;
IanC said:surely you didnt think that the skin underneath the clothing has cooled? are you really that stupid?
Ian, the skin is the radiator, the clothing or blanket if it is colder than the skin at the time it is placed in contact with it will indeed make the skin overall cooler for a time. Once the the inside of the blanket reaches equilibrium with the skin its in contact with, then the situation will change of course. But at the point a cooler body (blanket) first makes contact with a warmer body (skin) the skin will get cooler until equilibrium is reached.
I think Wirebender is referring to that, and you are most likely referring to after equilibrium is reached. When broken down fully you will find they are two different situations both mathematically and naturally...
A good example, is a cold pillow.. I like to turn my pillow over at night so I have a cooler side on my face until I fall asleep. I can feel it making my skin cooler at first, then once equilibrium is established, it of course causes my skin to get warmer on the side touching that same pillow. I turn that same pillow over and its cold on that side, and again it cools my skin for a time...