Mordred Posted April 7, 2015 Posted April 7, 2015 If your dealing with the surface exclusively granite and basalt are the two primary minerals. http://www.omega.ca/literature/transactions/volume1/emissivityb.html
swansont Posted April 7, 2015 Posted April 7, 2015 Based on my calculation : ε = 0.0013 You claim that it is 0.7. Can you please explain how did you get this value? Based on some other numbers I saw, and that fact that it doesn't matter very much to the final answer. Anything based on your calculation is not to be trusted.
swansont Posted April 7, 2015 Posted April 7, 2015 Thanks Mordred Somehow, I'm not sure that I get a consistent feedback with regards to Stefan Boltzmann law. It one had you claim that Stefan Boltzmann law works well in the correct applications: Also, in the article which you have pointed it is stated: " The cooling time from an initial temperatureTi to a final temperature Tf is given approximately by t = (1/T 3− 1/T 3 )mc/3σA where Ti is the temperature at time t , Tf the ambient temperature (both expressed in kelvins), m is the mass, c the specific heat capacity and A the area of the object (see Block A2). Applying this formula to the small iron sphere, we find that the cooling time is about 47 minutes. For the time of cooling of a globe of the size of the Earth that is made entirely of iron, we obtain about 45 000 years (see Block A2)." Hence, the science is using Stefan Boltzmann law to calculate the cooling time of the Earth. However, in the other hand you claim: The only difference between my calculation and the above one is the emissivity. They assume that the emissivity is 1 and I tried to find the real value. As you can see they do not care about - "continous heat source such as radiation, convection and conduction" They do not care about - "Surface area, convection rates as the crust develops greater depth, this influences emmisivity rates, your also dealing with different materials with different conductivity values" The position you have been given is consistent. S-B works for radiative cooling. But there are other mechanisms in play other than that. As I recall you claimed a background in electrical engineering. Let me use an electrics analogy. You have a circuit and are trying to assume all components are resistors, even though in reality you also have inductors and capacitors. You can't fudge the response of the circuit by pretending these other components are resistors and have work as a general solution. Thermodynamics has radiation, conduction and convection as methods. S-B only applies to radiation. And what you want to use is a power balance equation, of which one term will be the S-B equation. Any analysis you use that only has the S-B equation in it is flawed from the start.
David Levy Posted April 7, 2015 Author Posted April 7, 2015 If your dealing with the surface exclusively granite and basalt are the two primary minerals. http://www.omega.ca/literature/transactions/volume1/emissivityb.html It seems that you prefer to avoid a direct answer to my question. O.K. - no problem. With regards to emissivity I would expect the emissivity of the Earth should be quite different from any object or matter on the planet. What is your advice?
swansont Posted April 7, 2015 Posted April 7, 2015 Hence, if we can find the correct values of the emissivity, there is no need to calculate the green house effect, the radiation, the curst of Iron/silicon conductivity or solar radiation. All included in one small sign - emissivity – ε. It wasn't true when you said this before and saying it again isn't going to change things. With regards to emissivity I would expect the emissivity of the Earth should be quite different from any object or matter on the planet. What is your advice? Why would the emissivity of a molten earth be very different from that of lava?
Mordred Posted April 7, 2015 Posted April 7, 2015 It seems that you prefer to avoid a direct answer to my question. O.K. - no problem. With regards to emissivity I would expect the emissivity of the Earth should be quite different from any object or matter on the planet. What is your advice? I provided direct answers. I told you directly Stefan Boltzmann law isn't useful or accurate in this application due to convection, conduction and radiation. I then provided the link for emmissivity for granite and basalt which will be your two primary ingredients of the crust. Heavier metals will sink towards the Earths center. However you don't want to include convection flows.
David Levy Posted April 7, 2015 Author Posted April 7, 2015 Based on some other numbers I saw, and that fact that it doesn't matter very much to the final answer. Anything based on your calculation is not to be trusted. Is it? Please see the following: http://jennifermarohasy.com/2011/03/total-emissivity-of-the-earth-and-atmospheric-carbon-dioxide/ "Introducing 7700 meters as the average altitude of the troposphere and the real partial pressure of the atmospheric carbon dioxide (0.00038 atm-m), the resulting total emissivity of the carbon dioxide is 0.0017 (0.002, rounding up the number). Evidently, the carbon dioxide is not a blackbody, but a very inefficient emitter (a gray-body). In this note I have calculated the real total emissivity of the atmospheric carbon dioxide at its current partial pressure and instantaneous temperature to be 0.002." It is quite close to my calculation.
Strange Posted April 7, 2015 Posted April 7, 2015 I would expect the emissivity of the Earth should be quite different from any object or matter on the planet. Why? Googling for emissivity of lava brings up results with values between 0.83 and 0.9. Why would a molten not be similar to that?
swansont Posted April 7, 2015 Posted April 7, 2015 Is it? Please see the following: http://jennifermarohasy.com/2011/03/total-emissivity-of-the-earth-and-atmospheric-carbon-dioxide/ "Introducing 7700 meters as the average altitude of the troposphere and the real partial pressure of the atmospheric carbon dioxide (0.00038 atm-m), the resulting total emissivity of the carbon dioxide is 0.0017 (0.002, rounding up the number). Evidently, the carbon dioxide is not a blackbody, but a very inefficient emitter (a gray-body). In this note I have calculated the real total emissivity of the atmospheric carbon dioxide at its current partial pressure and instantaneous temperature to be 0.002." It is quite close to my calculation. Are you claiming that the earth is a gas ball, comprised of carbon dioxide? edit: also, you might consider the wisdom of quoting from a global warming denier. A quick scan of the article leads me to conclude that he's calculating the "total emissivity" which would include a whole range of wavelengths where the gas is transparent, thus would have an emissivity of zero. That's why it has a low value in the calculation. Picking and choosing articles based on short phrases that you've found is not a good way to find support for your ideas.
Mordred Posted April 7, 2015 Posted April 7, 2015 (edited) (One rule of thumb with me I always try to supply links to study and learn from. Those links contain the answers) One of those papers gave the emissivity, it's first formula is Stefan Boltzmann. Then it covered the problems and corrections. Edited April 7, 2015 by Mordred
David Levy Posted April 7, 2015 Author Posted April 7, 2015 Are you claiming that the earth is a gas ball, comprised of carbon dioxide? It's not me. I just expect to get some basic appreciation.
Strange Posted April 7, 2015 Posted April 7, 2015 Please see the following http://jennifermarohasy.com/2011/03/total-emissivity-of-the-earth-and-atmospheric-carbon-dioxide/ Citing a crank as a source doesn't really help your case.
Greg H. Posted April 7, 2015 Posted April 7, 2015 How did you come up with this value? Are there any materials which have emissivity this low? Some materials which resemble parts of the Earth's surface: Asphalt: 0.88 Concrete: 0.91 Ice: 0.97 Snow: 0.8 to 0.9 Water: 0.96 http://en.wikipedia.org/wiki/Emissivity#Emissivities_of_common_surfaces The lowest value there is polished silver (0.02). So you are saying that the Earth's average emissivity is 10 times less than that. Sounds implausble. I looked at this list(pdf), and the lowest values they list are also .02, for polished silver, polished gold, cadmium, and unoxidized aluminum.
swansont Posted April 7, 2015 Posted April 7, 2015 It's not me. I just expect to get some basic appreciation. By citing an irrelevant number from a questionable source? How do you think that's going to work? And it is you. You provided the info.
David Levy Posted April 7, 2015 Author Posted April 7, 2015 (edited) By citing an irrelevant number from a questionable source? How do you think that's going to work? And it is you. You provided the info. Sorry It seems that you have no real information about the emissivity of the Earth/atmosphere. Do you really believe that the emissivity of the Atmosphere should be the same as silver, iron or silicon? How can you use those elements on the surface of the Earth as a represented objects for the emissivity of the Earth itself? There is something between the surface of the Earth and the space. This something is called atmosphere. I have got similar results to that article by using different approach of calculation. They have calculated the effect of the atmosphere and the influence of carbon dioxide, while I extract it directly from Stefan Boltzmann law. You didn't provide any article which try to set the calculation of the emissivity of the atmosphere. It's easy to claim that you don't agree with that article. However, it is expected that you should offer other alternative for measuring the real effect of the atmosphere. Please, if you reject that article, you should offer other real alternative for the emissivity of the atmosphere. Edited April 7, 2015 by David Levy -1
swansont Posted April 7, 2015 Posted April 7, 2015 Sorry It seems that you have no real information about the emissivity of the Earth/atmosphere. I posted a link. Do you really believe that the emissivity of the Atmosphere should be the same as silver, iron or silicon? How can you use those elements on the surface of the Earth as a represented objects for the emissivity of the Earth itself? There is something between the surface of the Earth and the space. This something is called atmosphere. In case you haven't noticed, the atmosphere of the earth is fairly transparent. Under significantly warmer conditions (i.e. the conditions relevant to the discussion) it would be even more so — there would be no clouds. The only issue would be some radiation in the IR, where it absorbs. And the emissivity at those wavelengths (i.e. not the total) is probably large. It doesn't matter if the constituents of the atmosphere are blackbodies or not if they transmit the radiation rather than absorbing it. I have got similar results to that article by using different approach of calculation. They have calculated the effect of the atmosphere and the influence of carbon dioxide, while I extract it directly from Stefan Boltzmann law. But that's not what you said. You said it was the emissivity of the earth. The earth is not a ball of CO2 You didn't provide any article which try to set the calculation of the emissivity of the atmosphere. It's easy to claim that you don't agree with that article. However, it is expected that you should offer other alternative for measuring the real effect of the atmosphere. Please, if you reject that article, you should offer other real alternative for the emissivity of the atmosphere. The emissivity of the atmosphere is irrelevant. Its heat content is tiny compared to that of the earth (it has ~ one one-millionth of the mass of the earth), and it's essentially transparent. It has a negligible effect in this analysis.
John Cuthber Posted April 7, 2015 Posted April 7, 2015 Sorry It seems that you have no real information about the emissivity of the Earth/atmosphere. Do you really believe that the emissivity of the Atmosphere should be the same as silver, iron or silicon? How can you use those elements on the surface of the Earth as a represented objects for the emissivity of the Earth itself? There is something between the surface of the Earth and the space. This something is called atmosphere. I have got similar results to that article by using different approach of calculation. They have calculated the effect of the atmosphere and the influence of carbon dioxide, while I extract it directly from Stefan Boltzmann law. You didn't provide any article which try to set the calculation of the emissivity of the atmosphere. It's easy to claim that you don't agree with that article. However, it is expected that you should offer other alternative for measuring the real effect of the atmosphere. Please, if you reject that article, you should offer other real alternative for the emissivity of the atmosphere. Actually, I already told you (roughly) what the emissivity of the earth is (about 61%). I even cited the source However, you seem not to understand that the Earth doesn't have "an emissivity" any more than it has "a colour".
David Levy Posted April 8, 2015 Author Posted April 8, 2015 (edited) In case you haven't noticed, the atmosphere of the earth is fairly transparent. Under significantly warmer conditions (i.e. the conditions relevant to the discussion) it would be even more so — there would be no clouds. The only issue would be some radiation in the IR, where it absorbs. And the emissivity at those wavelengths (i.e. not the total) is probably large. It doesn't matter if the constituents of the atmosphere are blackbodies or not if they transmit the radiation rather than absorbing it. But that's not what you said. You said it was the emissivity of the earth. The earth is not a ball of CO2 The emissivity of the atmosphere is irrelevant. Its heat content is tiny compared to that of the earth (it has ~ one one-millionth of the mass of the earth), and it's essentially transparent. It has a negligible effect in this analysis. The atmosphere set the green house effect and keeps the heat of the Earth. Why the Earth is considered as Habitable Planet for more than 3.5 By? Don't you think that it is due to the atmosphere? Hence, the emissivity of the atmosphere is the most relevant issue. Without the atmosphere - the Earth will be considered as a black body. Without the atmosphere – there is no possibility to set any form of life on Earth. (So, instead of black body it is a dead body). Stefan Boltzmann law uses specifically the ambient temperature. This temperature is outside the atmosphere. So, how can we ignore the atmosphere? Therefore, if the atmosphere "has a negligible effect" let's verify what might be the impact without it. We don't have to go far away. Just look at the Moon. Day temperature - about 250K, Night temperature – less than 100K. The moon represents a black body. The earth should be considered as gray body. It also seems that the Earth is considered as black body or gray body just in order meet the current theories. As we all know, the science assume that in the Earth had been cool down to 300K in just 30My. Please see again that calculation: http://hyperphysics.phy-astr.gsu.edu/hbase/thermo/cootime2.html#c1 The assumption is that the emissivity of the Earth is one, therefore, it is a black body. During this period of time, the science didn't calculate the effect of the Sun radiation. Why? It just used as to proof that in a very short time the Earth had lost significant amount of temperature (from over 6000K to about 300K). However, in our days: -Suddenly there is an impact of the sun radiation -Suddenly "The Stefan Boltzmann law works well in the correct applications." -Suddenly we need to take in account the "Surface area, convection rates as the crust develops greater depth, this influences emissivity rates" -Suddenly "your also dealing with different materials with different conductivity values" Where were all of those impacts and factors during the first 30 My? Therefore, Stefan Boltzmann law was perfectly O.K. for the first 30My, but unfortunately, it is not applicable for our days Hence, when ever is convenient to the science – The emissivity of the atmosphere is irrelevant. Its value could be 1 or 0.61. The Earth can be considered as black body or gray body with or without atmospher . Edited April 8, 2015 by David Levy
Mordred Posted April 8, 2015 Posted April 8, 2015 (edited) The first 30 mly the Earth probably didn't have an atmosphere with a distinquishable temperature from the surface. This is also a period of heavy bombardment. Tons of dust, rocks were thrown into the atmosphere. You also need to keep in mind the atmosphere itself evolves. Originally it is mainly hydrogen and helium. (With that debris mixed in) http://www.ecology.com/2011/09/10/earths-beginnings-origins-life/ Now not all atmospheric components are greenhouse gases. (Hydrogen and Helium are not) http://en.m.wikipedia.org/wiki/IPCC_list_of_greenhouse_gases http://en.m.wikipedia.org/wiki/Greenhouse_gas Although water quickly formed once the crust started forming, in the first 30 Mly much of the lighter gases including water vapor was escaping the atmosphere due to extreme temperatures. (Though this is highly debatable, might be safer to consider its presence) Your starting to see the difficulties in modelling the Earths history via thermodynamic processes. In point of fact doing so is highly complex and convoluted. (Also extremely unreliable). The radiation levels of materials are also generating heat. The Earths magnetic field is unlikely to have formed at this time period, the atmosphere itself would offer little protection from the Suns rays, heavy bombardment also produces radiation. With all the complexities mentioned during this thread, can you now understand why we use meteors, moon samples, and radioactive dating? With your last post. It should be apparent as a more reliable methodology. If you want good details on the first 30mly Google Hadean won. Each stage has a specific eon, Google the conditions seperately in each. http://en.m.wikipedia.org/wiki/History_of_Earth Hint type pdf after each Google search it will lead to better quality and possibly peer reviewed papers. Edited April 8, 2015 by Mordred
swansont Posted April 8, 2015 Posted April 8, 2015 The atmosphere set the green house effect and keeps the heat of the Earth. Why the Earth is considered as Habitable Planet for more than 3.5 By? Don't you think that it is due to the atmosphere? Hence, the emissivity of the atmosphere is the most relevant issue. Without the atmosphere - the Earth will be considered as a black body. Without the atmosphere – there is no possibility to set any form of life on Earth. (So, instead of black body it is a dead body). We're talking about the initial cooling of the earth, not the earth after it reached steady-state. Stefan Boltzmann law uses specifically the ambient temperature. This temperature is outside the atmosphere. So, how can we ignore the atmosphere? Because the atmosphere is largely transparent. It has an effect on the final temperature, but not much on the cooling to where water could exist on the earth. Therefore, if the atmosphere "has a negligible effect" let's verify what might be the impact without it. We don't have to go far away. Just look at the Moon. Day temperature - about 250K, Night temperature – less than 100K. The moon represents a black body. The earth should be considered as gray body. And how does this relate to cooling to ~350K from 6000K? It also seems that the Earth is considered as black body or gray body just in order meet the current theories. As we all know, the science assume that in the Earth had been cool down to 300K in just 30My. Please see again that calculation: http://hyperphysics.phy-astr.gsu.edu/hbase/thermo/cootime2.html#c1 No. It. Doesn't. Please see all of the commentary that Kelvin was wrong because he ignored heating from radioactive decay, among other things. Also look carefully at the results of the calculation. It says 30,000 years. But no matter, it's wrong. The assumption is that the emissivity of the Earth is one, therefore, it is a black body. During this period of time, the science didn't calculate the effect of the Sun radiation. Why? We've been through this. You refused to do the exceedingly simple calculation, so I did it for you. The Power radiated by the earth when hot is 100x or more larger than the power it gets from the sun. The sun has minimal effect until the earth has cooled significantly. It just used as to proof that in a very short time the Earth had lost significant amount of temperature (from over 6000K to about 300K). However, in our days: -Suddenly there is an impact of the sun radiation -Suddenly "The Stefan Boltzmann law works well in the correct applications." -Suddenly we need to take in account the "Surface area, convection rates as the crust develops greater depth, this influences emissivity rates" -Suddenly "your also dealing with different materials with different conductivity values" Where were all of those impacts and factors during the first 30 My? ONE PERSON famously ignored them. That person's model was WRONG. EVERYBODY ACKNOWLEDGES THIS. And it's not like people are saying Kelvin was a buffoon, or anything. He was making an estimate, and almost assuredly knew this was a lower bound because of his assumptions, and was no better than an order-of-magnitude estimate. But I fear that subtlety is lost in this conversation. Therefore, Stefan Boltzmann law was perfectly O.K. for the first 30My, but unfortunately, it is not applicable for our days No, that's a complete bungling of the information you have been given. Hence, when ever is convenient to the science – The emissivity of the atmosphere is irrelevant. Its value could be 1 or 0.61. The Earth can be considered as black body or gray body with or without atmospher . More bungling of the information.
Greg H. Posted April 8, 2015 Posted April 8, 2015 (edited) However, you seem not to understand that the Earth doesn't have "an emissivity" any more than it has "a colour". Tch. It's so obvious. The Earth is blue (except where it isn't). Edited April 8, 2015 by Greg H. 1
Phi for All Posted April 8, 2015 Posted April 8, 2015 ! Moderator Note David Levy, you've been given 12 pages to make your case, and it's clear you aren't able to overcome preconceptions that are blocking you from understanding the rest of the members in this conversation. I'm seeing the same arguments being refuted over and over, and you're repeating things you were corrected on pages ago. I'm going to close this because you haven't supported your arguments per the Speculations rules, and it seems like you never were interested in discussing this idea so much as you were preaching about it. Don't bring this subject up again unless you find more support. 1
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