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Author | Topic: A science question | |||||||||||||||||||||||||||||||
TheLiteralist Inactive Member |
Holmes,
I think (I could be wrong) that all heat is IR, which is one form of EMR (light); therefore, heat is light and can be "lost to space" according to your criteria. A quick google seems to confirm my hazy notion about all heat being IR. AbE:I'm not saying you're wrong about this...it's just that I've never heard that a vacuum is an insulator...where did you get that information from? Perhaps it is only an insulator of electricity? --TheLit This message has been edited by TheLiteralist, 03-06-2005 05:57 AM
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TheLiteralist Inactive Member |
TheLit tries to remember how physics works...
The problem would seem to work out like this: (Assumptions)
S = Joules per second received from the sunE = Joules per second generated by earth (whatever the process) L = Joules per second lost to space from the earth Jmax = Maximum joules that could be contained by a completely molten earth Jcurrent = Joules contained by earth currently (Variables) t = time the earth has been cooling (The initial equation) Jmax + (S t) + (E t) - (L t) = JcurrentThe initial energy of the molten earth plus the total energy ever recieved from the sun plus the total energy ever generated by the earth minus the total heat ever lost by the earth equals how much energy the earth has now. (Solve for t) Jmax + t(S + E - L) = Jcurrentt (S + E - L) = (Jcurrent - Jmax) (The final equation) t = (Jcurrent - Jmax) / (S + E - L)The time period required for the earth to go from a completely molten body to its present partially solid state equals the change in the earth's total energy from its molten to its current state divided by the overall rate by which energy is lost from (or gained by) the earth. S, E, L, and Jcurrent can all be measured, can't they? I would think that Jmax could be figured out to a close approximation. This would give the "worst-case scenario" or oldest age possible (starting from the time that the earth was molten)--given the assumptions are all true. It seems doable to me...though I certainly don't have the resources to get the numbers to replace the varibles. But I certainly could have made some stupid error...it's been a long time since I took level I physics. Just foolin' around...--TheLit This message has been edited by TheLiteralist, 03-06-2005 05:39 AM This message has been edited by TheLiteralist, 03-06-2005 08:18 AM
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TheLiteralist Inactive Member |
Percy,
I agree that heat can be transferred by conduction and convection as well as by radiation (I mean the act of radiating, in this case). However, Holmes appears to think (and no one except me appears to correct his thought) that there are different kinds of heat, only one of which is infrared light. In fact, unless I am mistaken, ALL heat is infrared radiation (invisible light with long wave lengths). Holmes IS correct in that heat can move around within the earth system via conduction or convection as well as radiation (the act of radiating) but that the ONLY way it can be lost to space is via radiation (the act of radiating). However, he is INCORRECT if he thinks there are two or three different forms of heat energy. Either that or *I* am wrong in asserting that ALL heat is light, a point about which I would readily accept correction--myself not being an expert in the science of heat or light. --TheLit
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TheLiteralist Inactive Member |
Okay guys,
I am actually confused, now. I thought all heat was IR (which I thought was part of the light spectrum). From this online dictionary heat is defined as:
A form of energy associated with the motion of atoms or molecules and capable of being transmitted through solid and fluid media by conduction, through fluid media by convection, and through empty space by radiation. While this seems to be what Percy said (in much abbreviated format), this definition doesn't UNCONFUSE me at all. I would think that IF heat can be "transmitted...through empty space by radiation," then heat is, in fact, radiation (light)--regardless of whether it can be transmitted other ways or what different radiation wavelengths occur as the temperature (amount of heat?) increases. I likely have some fundamental misunderstanding of "heat." My last technical dealings with "heat" was in level I physics, in which case it was usually regarded as energy lost from a system due to friction. --TheLit This message has been edited by TheLiteralist, 03-07-2005 00:15 AM
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TheLiteralist Inactive Member |
Percy,
Are you saying that kinetic energy IS heat energy? I thought heat was merely a by product of kinetic energy.
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TheLiteralist Inactive Member |
Hi Sylas,
I'm still convinced that IR is heat (I will readily concede if I can be made to understand...this ISN'T about theology after all).
A body gives off radiation depending on its temperature. The hotter the object, the more its emitted radiation shifts from infrared into higher frequencies. A sufficiently hot object will radiate primarily in the ultraviolet. But the IR must continue to be radiated, also, I think--or else there would be no heat radiated from the object, right? I think that both temperature and the wavelengths emitted depend on the amount of kinetic energy present in the system; however, only the IR radiated is the heat of the object. (I could be wrong, I readily admit).
This link seems to disagree with you guys (or I'm reading it wrong...entirely possible).
Far infrared waves are thermal. In other words, we experience this type of infrared radiation every day in the form of heat!...Shorter, near infrared waves are not hot at all - in fact you cannot even feel them. These shorter wavelengths are the ones used by your TV's remote control. While I agree that ALL wavelengths are energy...it appears to me that only (far) infrared wavelengths are HEAT energy (which I have always understood to be a type of energy all its own and different from, say, potential, kinetic, mechanical, or chemical energy). Apparently not even all of the infrared spectrum is considered to be "heat."
I can't makes sense of "all heat is light". No one wavelength of light stands out as have any special association with heat in general. Light is just a form of energy. Heat is also "just a form of energy." If all heat is actually IR, then all heat is light; however, not all light would be heat, if that makes sense. Now, if there are different kinds of heat (I don't believe this, yet), then not all heat is light...but no one has yet demonstrated that all heat isn't IR. I really don't think that kinetic energy (of molecules) IS heat; rather, molecular kinetic energy GENERATES heat (IR). I may be wrong, but if the amount of molecular kinetic energy increases (for whatever reason), IR will increase in amount radiated (temperature increases) and also the molecules will begin radiating in other wavelengths (including visible and beyond). However, the IR must continue to be generated or else there would be no heat felt from the object in question (the sun, for example, generates nearly the complete, if not the complete, light spectrum--including IR--and it VERY hot). Feel free to point out my ignorance...I'm truly curious why several very knowledgeable people are disagreeing with me...I can only surmise that I misunderstand the concept of "heat" fundamentally, in some way. --TheLit
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TheLiteralist Inactive Member |
CF,
I could be wrong, but I am not convinced, yet.
...all heat is the kinetic energy of atoms. Sometimes this energy is transmitted via IR radiation; other times it is transmitted via the direct collision of atoms. Right now, I see it this way:
Either I'm wrong or you guys are confusing kinetic energy with heat energy. Since the heat energy of a system is directly dependant upon kinetic energy of the system, this would be completely understandable. The two forms of energy, while extremely interrelated and interdependant, are completely different forms of energy...I thought. Temperature is a measurement of kinetic energy only because heat energy is always generated by kinetic energy (and always in dependable proportion to the kinetic energy). OTOH, several knowledgeable people are agreeing with you and finding my assertions problematic; for this reason only, I permit a shadow of doubt in my mind about my position on this matter. It's just that, so far, I haven't seen anything to change my mind. --TheLit This message has been edited by TheLiteralist, 03-07-2005 00:13 AM
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TheLiteralist Inactive Member |
Hi JonF,
...[TheLit's] equations don't include the rates at which energy is conducted/convected from the interior of the Earth to the surface... Well, I was hoping that my constant "L" (the rate at which the earth loses energy to space) would make knowing the complex movements of heat energy within the earth unnecessary. I wonder if understanding the complexities of heat movement within the earth system is necessary for estimating the current energy contained by the earth system or the rate at which the earth generates energy. I was hoping not and thought that a mean earth temperature plus some calculations based on the rotational/revolving motions of the earth might do the trick. Oh well...whether it can be done or not...I certainly can't do it! So, it's pointless anyways, I guess. --TheLit
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TheLiteralist Inactive Member |
NosyNed,
So a wide range of different wavelengths will allow an energy transfer. That will raise the kenetic energy of the skin and be experienced as heat. Some wavelengths will be inefficient some not. There is no "heat" energy. Heat is a manifestation of the kenetic energy of the atoms of materials. It is colloquially called "heat energy" for that reason. Okay. I guess that could be batted around for a bit. To prevent that, I will concede (not only due to your post but also due to Sylas's post)--for now, for argument's sake--that no particular light wavelength can be classified as heat. This actually would make the discussion clearer perhaps (for me, anyways)...thanks.--TheLit
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TheLiteralist Inactive Member |
Ha ha.
Well, you two are agreeing this time--for what it's worth.
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TheLiteralist Inactive Member |
Everybody,
Due to the most recent posts by Ned and Sylas, I concede (for argument’s sake) that the wavelength is irrelevant to defining heat. The problem then becomes even simpler. Heat is light--always. All the laws that apply to light apply to heat. Heat can be radiated, reflected, refracted, or absorbed. Therefore, heat, regardless of it’s source, is a candidate for being lost to space via radiation. Kinetic energy produces light--always. Usually this light is invisible and is felt as heat. Heat (or light) is NOT kinetic energy, but heat is very, very closely related to kinetic energy. Kinetic energy produces heat. Heat produces kinetic energy. I think (emphasize: THINK) it is only an illusion that heat is conducted. I believe the kinetic energy is conducted, and the heat results from the increased kinetic energy. Similarly, irradiation increases the kinetic energy--not the light energy--of the absorbing system. However, increased heat results from the increased kinetic energy. (Am I arguing apples and oranges? I feel like I'm making much ado about nothing, in a way--OTOH, it seems fundamental to the discussion--plus I'm having fun blathering on about it, I suppose.) --TheLit
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TheLiteralist Inactive Member |
Sylas,
Just in case you're curious... From this link:
More than half the Sun's power output is in the form of infrared light, though much of it is absorbed by the Earth's atmosphere. Of course, being absorbed by the earth's atmosphere is still being absorbed by the earth system (it's mighty convenient for us, too, I imagine...I'm only too happy to have a bit of the IR for myself, but I am just as happy to let the atmosphere have the rest...I believe in sharing!). --TheLit
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TheLiteralist Inactive Member |
Sylas,
Thanks for the link. Thanks for the replies, too.
The one quibble I have with your description is where you say heat is always light; there are other ways in which energy flows from hot objects to cooler ones, and they are heat as well. Uh oh. Maybe I'm completely wrong, then. What are the other ways in which energy flows from hot objects to cooler ones? If it's conduction and convection, I'm dead wrong! See, I've been considering heat transfer via conduction to be a sort of illusion. What I mean is that there is actually a transfer of kinetic energy (molecular collisions). This transfer of kinetic energy results in increased heat, of course, which I considered to ALWAYS be light. Oh well...,--TheLit
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TheLiteralist Inactive Member |
Holmes,
You are wrong. See my post #65 and hopefully it will seem clearer. If I have understood Sylas correctly, then ALL light is heat, but not all heat is light. If this is the case, then we are BOTH wrong, right? I say this because you seem to separate heat utterly from light and kinetic energy per phrases like...
However, it is true that as energy increases in a system one will have increases in both kinetic and electromagnetic manifestations of that energy. Thus heat can be determined indirectly from EM radiation (they vary proportionally). That is after all why IR goggles will help pick out a hot body from colder surroundings. ... Light is not a loss of heat Perhaps we will both be enlightened? But just think of how much more typing than you I had to do in order to be enlightened! I can be awfully stubborn, sometimes. --TheLit
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TheLiteralist Inactive Member |
JonF,
Okay. But couldn't the rate of energy being lost to space from the outer atmosphere be directly measured? Perhaps measured over time just in case it is cyclical or is on a curve (not a constant rate). Wouldn't this negate the need to find out all the complex mechanisms of HOW the heat got to and through the upper atmosphere? I mean maybe it wouldn't...but I thought maybe it could. Thanks for the reply and discussion of it, at any rate. --TheLit This message has been edited by TheLiteralist, 03-07-2005 10:09 AM
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