A science question

We're moving off topic here. I don't think we need to correct every instance of slightly improper usage when we see it; but I don't see a need to use it incorrectly ourselves. I'll prefer to say "hot", not "having heat"; and to let other usage slide in informal conversation. But when science or thermodynamics is the actual topic of discussion, then it is worth getting more pedantic.As for my background; nothing formal. I used to be outstanding in physics at high school, and I did one year of physics in a BSc, before being sucked into the dark side of computers. Sometimes I regret that switch; in any case I still read widely.Cheers -- SylasAdded in edit: I've just looked over the thread again; and I am not sure if you have a clear answer to your questions. The answer is that the nearly all energy entering and leaving the Earth is by EMR. Most of the input is from the Sun, with a hot blackbody spectrum. About 31% of this is reflected; and the rest is absorbed. The amount absorbed is balanced by the amount leaving as infrared radiation. There is slightly more radiation leaving the Earth than is ariving, by a factor of about 1.00003; the excess is due to heat from the Earth's own core. Percy is correct in pointing out that the center of the Earth being hotter means that the Earth is cooling, with a net flow of heat from from the center to the surface. But since the surface remains at roughly a constant temperature, there is a mean energy balance between what is radiated from the Earth and what is received from the Sun, and received from the Earth's core. This energy flow does indeed continue out into space by infrared radiation.Cheers -- SylasThis message has been edited by Sylas, 03-08-2005 07:01 AM

I agree.My main argument was just that a person coming on here and talking about the earth losing heat, would be using a colloquial term of heat which is related to kinetics (internal energy), and so it would make sense to stick with that for argument. It certainly is not wholly off the wall or unconnected to an understanding of what is going on in the system.But yes, if we are addressing the scientific understanding of the phenomenon called heat, then it would be useful to be accurate and explain that it is a quantitative measurement of change (or transfer) in internal energy.I guess this thread's topic straddles both realms. Oh that happened to me too, but from a chem/geochem angle (though I reached grad level chem). I have regretted it and have spent years reversing it. I am now almost functionally illiterate in computers (as I showed recently). I am now making some moves toward a full return to science.

---

holmes
"...what a fool believes he sees, no wise man has the power to reason away.."(D. Bros)"...don't believe I'm taken in by stories I have heard, I just read the Daily News and swear by every word.."(Steely Dan)

Hi Sylas,I think Holmes and I are trying to make the same point, however unsuccessfully. If it were just you and me trying to have a discussion about heat, I'd switch to the formal definition in an instant. But we're trying to have discussions about heat with people with little background in science, and the more formal definitions you're pulling out of physics textbooks like An Introduction to Thermal Physics and Elementary General Thermodynamics are not accessible to this type of layperson. He has nothing in his experience upon which to base his understanding of these principles expressed at this level. The confusion is most evident where light is now being confused with heat.Sorry to be emphatic again, mostly it's just lack of time, didn't say everything I wanted, but gotta go.--Percy

I understand this; but I don't believe it matches what happens in this thread. It was not me, but TheLiteralist who first said in Message 61 "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."MY point, which I ALSO insist upon, is that when someone actually introduces into discussion a correct point, we should ACKNOWLEDGE IT.OK? He was RIGHT. He scores a point. Given that he had been making a lot of other errors, which I was correcting, I also felt it was important to speak up and give credit where due for what bits of his posts were correct.Then you guys started jumping all over me, as if it was somehow vitally important to keep protecting the sloppy usage. What gives? It sure as eggs looks to me that TheLiteralist was correct on this point, and you chaps couldn't see it.Sure, when helping a student we don't want to get overly pedantic. But when THEY introduce a correct point, recognize it for heaven sake.Sheesh.SylasThis message has been edited by Sylas, 03-08-2005 09:30 AM

I hope this wasn't serious. If you felt like I was jumping on you then I apologize. I was really trying to back you up regarding the specific scientific property called heat (admitting that some of my own terminology uses had to change), while backing up the practical argument Percy was making.I saw benefits of both sides, and wholly recognized that while much of my conceptual commentary/description regarding heat was valid, your semantic definitions were in line with official scientific use.As far as theLit goes, I supported him when he seemed to take on the definition you used. It was not as early as message 61. I believe I had already (if not shortly afterward) seperated kinetics from heat when discussing what science really conceived of it (Lit noted this as well). I certainly said it is related to kinetic energy, which means Lit's assessment and mine agreed on that account.However, although one could congratulate him for that one correct assessment the rest (the majority) of what he wrote was so filled with errors it seems odd to say he was on the right track. I focused on the errors he still needed to correct.Maybe that makes me too negative? I dunno.In any case, I apologize if it seemed I was trying to beat down anyone or be critical just to be critical. I really thought I was just being helpful. I do agree that theLit is correct in running with the current def which is the one you presented. That is even if I back up Percy's practical argument for those not totally in the know who might appear in the future.

---

holmes
"...what a fool believes he sees, no wise man has the power to reason away.."(D. Bros)"...don't believe I'm taken in by stories I have heard, I just read the Daily News and swear by every word.."(Steely Dan)

Look at what else TheLiteralist said in Message 61:

• Heat is light--always.
• Kinetic energy produces light--always.
• I think (emphasize: THINK) it is only an illusion that heat is conducted.

Placed in context, the statement you quoted doesn't seem to reflect understanding. He made lots of statements about heat, and to me it seems that it is only by happenstance that one of them is reminiscent of the formal definition which draws a distinction between internal energy and molecular motion. But since internal energy of an object "is related to the random motion of their atoms or molecules" (Wikipedia's entry on Heat), the additional level of abstraction seems an impediment to clarity. Granted. Were I more familiar with the formal definition of heat I might have recognized his definition myself and acknowledged it. Certainly I have acknowledged TheLiteralist's success at making good progress despite our best efforts to confuse him. But I would probably have added that a discussion concerning whether the Earth is a net gainer or loser of heat doesn't need overly formal definitions of heat. Sorry it seemed that way. I tried to balance my posts. At one point I mentioned the high regard in which you're held here, at another point I likened my objections to being akin to Buzsaw in style, and at another acknowledging my potential for making a botch of it, all this trying to indicate that if my style seemed overly emphatic that I still understand my definition is "wrong" in a formal sense, but still strongly feel it more appropriate for this discussion.--PercyThis message has been edited by Percy, 03-08-2005 11:10 AM

Attempting to make the case for my simpler definition based upon web-available references...At Answers.com (http://www.answers.com/heat#Encyclopedia): At Wikipedia (Heat - Wikipedia): These sources are also unequivocal in defining heat as a "transfer of thermal energy" or as "nonmechanical energy in transit", and they are careful to distinguish between heat and internal energy, so you are correct, and I never meant to imply otherwise. When the discussion reaches the point where these distinctions are important then I'll advocate for the formal definitions right along side you.While the distinction between heat and internal energy is important to you, the distinction between moving molecules (heat, in my misbegotten terminology) and photons is important to me.At the level of detail of the discussion about whether the Earth is gaining or losing heat, it really only boils down to whether the Earth is getting hotter or colder, and temperature is a measure of the average kinetic energy of molecules. To make this point about the Earth I don't see the necessity, and see a lot of downside in the area of clarity, to saying that temperature is really only indirectly related to internal energy which is related to the motion of molecules and isn't really heat because heat is actually a flow. Sorry, now I'm tending toward sarcasm, but I'm just trying to be realistic. I can't say if I have an above or below average memory, but I guarantee that if I come back to this post next month and read what I just wrote that I will have little recollection of what I was talking about, and will have to follow the links to refresh my memory. But heat as kinetic energy of molecules seems like a reasonable and simple definition not only less likely to be forgotten, but also very easy for anyone to understand.--Percy

My guess is that somewhere TheLiteralist has read descriptions of heat as being different from internal energy, and that heat was only properly used for a transfer of this energy. His actual errors were failing to recognize conductive transfer, and limiting heat to a certain frequency range of EMR. But his association of heat with transfer rather than kinetic energy itself was correct.TheLiteralist... apologies for talking about you so much in the third person here. Making you the topic of discussion may be a bit off putting.So I had not seen this as being correct by happenstance; but more likely as something he did learn, while drawing some invalid implications. I felt it good pedagogy to acknowledge and build on what was correct; and to explicitly affirm that he got this right; especially when I spent so much more time on the bits that were wrong.I disagree that correct usage is an impediment to clarity, and I disagree that the level of discussion in this case was such that we should avoid being accurate. It was actually at quite a high level, and explicitly dealing with terms and definitions which deserved to be treated carefully.I agree that there are some cases in which the distinction between heat and internal energy can be glossed over; though I still believe it is possible even then for our input to use terms carefully (for example, by saying "hot" rather than "has heat").But once this distinction has been introduced, then the proper thing is to explain it accurately. This is actually fundamental; it shows up right at the start of the texts I was using, which were themselves at an introductory level.You've both picked up on "jumping all over me". That came across badly; no offense is taken. I do find it weird that when the distinction had been introduced you still wanted to maintain technically incorrect usage, even to the point of being so emphatic about heat "very definitely the kinetic energy of molecules". An explcit statement like that, in the context where definitions of heat and internal energy were starting to be used, can only be called wrong; just as "heat is light--always" is wrong.Cheers -- Sylas

There's no necessity that we agree on the best way to explain heat. Your ability at explaining complex topics is better than most (certainly the best I've seen outside published books) and perhaps justifies your confidence that it can be explained sensibly to non-science types.--Percy

Sylas, I imagine many people might have a hard time being talked about in third person on a public forum; however, I find it amusing (in this case, at least). I'm glad you did pick up on the (one?) part that was right; I'm even more glad you have taken time to correct the horrible misunderstandings I had about the concept of heat. I took physics in high school and level I physics in college (my major was Accounting, though--I never finished the degree). I also took both Chem I and college level chem (level I chem) in high school. So between two Physics courses (well, the book in both was extrememly similar...its just that in college we covered more of the book in less time...whew!) and two Chemistry courses, heat was discussed in formal terms somewhere along the way (but more than a decade ago--so it was not fresh in my mind).You had earlier added one more restriction on the definition of heat: that the transiting energy from the hotter to the colder object not do work (I have some fuzzy recollection of "work" from physics class)...thanks for the clarification--as I had not considered that further limitation. It is perhaps the most important restriction: I remember in physics frequently seeing the phrase "the energy is lost as heat due to friction."For the benefit of all, I confess to a multitude of horrendous erroneous assertions regarding the definition of heat...both before and after reading the definition from hyperphysics--but particularly before.Heat appears to be a chameleon energy--i.e., it can be any or a combination of any of the other kinds of energy (kinetic, mechanical, light, chemical, etc.) as long as it is energy in transit from a hotter to a colder object and not being used to accomplish work.AbE: Okay, I see heat must be a non-mechanical form of energy, too (info gotten from one of Percy's links, answers.com or something).I'm sure I still have some incorrect concepts regarding heat, but I did want to thank you for taking the time (to the point that you'd look up material in textbooks) to correct the more horrendous errors I made--and even some of the less horrendous (if some were not so horrendous).--TheLitThis message has been edited by TheLiteralist, 03-09-2005 02:59 AMThis message has been edited by TheLiteralist, 03-09-2005 04:26 AM

Sylas, Thank you Sylas. Doesn't this seem to override any need to know the complexities of how energy (maybe using the general term "energy" will avoid the need to discuss heat?) moves about within the earth? This information seems to answer my earlier question in Message 38.However, JonF indicated that my question could not be answered unless we measured escaping energy from the earth system over say 100,000 years (at least) in his Message 75.OTOH, I've got contracycle telling me in Message 67: Is it possible we can make such determiniations about JUPITER but have to wait 100,000 years to figure it out about our own earth?I am not saying JonF is wrong. I am wondering what I am missing, though. Based on your assertion that the earth is experiencing an overall net energy loss of a factor of about 1.00003...it would seem possible to make at least a rough estimate of how long it would take the earth to cool to its present state from a completely molten one.--TheLitThis message has been edited by TheLiteralist, 03-09-2005 03:53 AM

quote:

---

Is it possible we can make such determiniations about JUPITER but have to wait 100,000 years to figure it out about our own earth?

---

I am sure I have seen figures for the net rate of the earths energy budget. Here is a link on the topic, showing the calucaltions used:7(i) Net Radiation and the Planetary Energy BalanceThis message has been edited by contracycle, 03-09-2005 04:44 AM

I think we can perhaps avoid the terminology issue by referring to temperature instead of heat. As the temperature of an object rises its molecules move faster and faster. It's really that simple.The requirements of a consistent conceptual framework for thermodynamics make impossible the equating of any formal definition of heat with the kinetic energy of molecules. The digression into the definition of heat was primarily about the importance of maintaining formal terminology at a lay level. I don't think there is any disagreement at all about what actually happens to molecules as they are heated.My concern throughout this discussion has been that you might only learn the proper words to recite without understanding what is actually happening to molecules of matter when they're heated. Without that understanding it is only too easy to confuse light and heat, something which in my view the formal thermodynamic definition actually encourages for people without a formal background.--Percy

I was making the implicit assumption that we were talking about suficient precision to predict average global temperatures within a few degrees. Sure sounds wrong to me. The Earth is generating a significant amount of its own heat by radioactive decay. If it weren't, we'd be a lot colder, and the core of the Earth would no longer be warm. Lord Kelvin showed that in the late 1800's. I know I've posted stuff about this before, but here's a good link again: No webpage found at provided URL: http://thermo.gg.utk.edu/courses/Ge475/Dalrymple.htmlCHAPTER TWO, Age of the Earth by G. Brent Dalrymple, the "Cooling of the Earth and Sun" heading. I question the precision of that number, I doubt that we know the Earth's energy balance to one part in 100,000. If you want to assume that number is correct and extrapolate that it will stay the same for millions of years (or that it has stayed the same for millions of years) yes, you could do a calculation ... but it would take some fancy dancin' to convince me, for one, that such extrapolation is justified!

Percy, Temperature is NOT heat nor even a measure of heat. Temperature is a measure of object's internal energy--the energy associated with the movement of an object's molecules. Even though an object can be hot (it's temperature is relatively high); that object cannot be properly said to "have heat," because heat is energy IN TRANSIT. Whatever energy an object POSSESSES is NOT in transit and, therefore, cannot be heat. An object POSSESSES the energy associated with the movement of its molecules (internal energy); therefore, THAT energy is NOT heat--since heat is limited to "energy in transit." I'm not 100% sure, but I think heat can indeed be kinetic energy--I am thinking of conduction. If a cooler object contacts a hotter object, the hotter object's molecules will collide with the molecules of the cooler object. This appears to be kinetic energy in transit from a hotter object to a cooler object, which is heat. However, until a cooler object contacts the hotter object the kinetic energy of the molecules of the hotter object cannot ever be heat.If something's molecules move around more than before, then it is hotter than it was before (it has a greater internal energy, but it doesn't have any heat). The sun has a very high temperature, but it has no heat. The sun radiates a great amount of energy (light), but if there were no cooler objects around for that energy to contact, then the sun would not radiate any heat, either. Not even all energy in transit is heat...it has to be in transit from a hotter to a cooler object in order to qualify as heat.Earlier in the thread, I incorrectly limited heat to IR, and now you are trying to redefine the term entirely by giving it the exact same definition that "internal energy" has. Why? It makes no sense to me. Heat is energy in transit. Internal energy is not in transit and, therefore, is not heat--even though it is what causes the phenomena we call temperature. Why do you keep insisting that light is not heat? Some light IS heat. Heat is energy in transit from a hotter object to a cooler object. Light is energy in transit. If that light is going from a hotter object to a cooler object, then that light is energy in transit from a hotter object to a cooler object and, therefore, heat. This is a good concern. I've seen people act like they understand something when they don't (I've done it myself). However, I think I've got a fair grip on the basics of the concepts...I am worried about you, though...When molecules are heated they move around more (but do not gain "heat"). Also, energy can be added to an object in other ways than by heat to make the molecules move around more without being heated (to be heated an object must specifically have received energy from a hotter object). I'm not sure, but I think that an exothermic chemical reaction will increase the internal energy of the chemicals involved (and, therefore, their temperature)...but this is not heating (even though the chemicals got hotter). However, the increased kinetic energy of the chemicals will increase the kinetic energy of the molecules of the glass of the beaker (by conduction)...this is heating.This message has been edited by TheLiteralist, 03-09-2005 11:08 AM