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Path: ...!news.misty.com!weretis.net!feeder9.news.weretis.net!i2pn.org!i2pn2.org!.POSTED!not-for-mail From: tomyee3@gmail.com (ProkaryoticCaspaseHomolog) Newsgroups: sci.physics.relativity Subject: Re: Want to prove =?UTF-8?B?RT1tY8KyPyBVbml2ZXJzaXR5IGxhYnMgc2hvdWxkIHRy?= =?UTF-8?B?eSB0aGlzIQ==?= Date: Thu, 21 Nov 2024 04:12:04 +0000 Organization: novaBBS Message-ID: <8f76ec6246444b6ea169426a7421934f@www.novabbs.com> References: <b00a0cb305a96b0e83d493ad2d2e03e8@www.novabbs.com> <cfcd6e742c4f3c2f8a5f69d4db75206f@www.novabbs.com> <d793169808c9c1e887527df5f967c216@www.novabbs.com> <98a0a1fbdc93a5fcc108882d99718764@www.novabbs.com> <fd4937f7b180bac934eb677cca8f5c55@www.novabbs.com> <ebcad35958736e6602cf803fddfdb0fd@www.novabbs.com> <141e19a1c6acd54116739058391ca9f8@www.novabbs.com> <a4f98fa5d026bfbf5127fcbc6a585772@www.novabbs.com> <b859adf3e138697712b038bd1d73902e@www.novabbs.com> <3da6cb303f9998fa49034c557d5c314b@www.novabbs.com> <6bdb52ff942fd2465d8344d6c61488dc@www.novabbs.com> <a3c12890fdabb69ea3891b0cb506b158@www.novabbs.com> <c0b264e21841e8646f5a6d9ab1a06ccc@www.novabbs.com> <7e1b61de8c10dfacab84e6219ff3c2e6@www.novabbs.com> <ee05718ea12f5d38e4bffa92989f732d@www.novabbs.com> <071baf0a7783e388db0a3d6d2255613f@www.novabbs.com> <33ce7ff1379e934f323bb5d92d03254b@www.novabbs.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Injection-Info: i2pn2.org; logging-data="3439920"; mail-complaints-to="usenet@i2pn2.org"; posting-account="Ooch2ht+q3xfrepY75FKkEEx2SPWDQTvfft66HacveI"; User-Agent: Rocksolid Light X-Spam-Checker-Version: SpamAssassin 4.0.0 X-Rslight-Site: $2y$10$pNBrNDHoxL5/SLolbNez7eRQIYu5z8TnSh3v85W4v1nJ5w/AaCIma X-Rslight-Posting-User: 504a4e36a1e6a0679da537f565a179f60d7acbd8 Bytes: 6149 Lines: 90 On Wed, 20 Nov 2024 22:04:22 +0000, rhertz wrote: > On Wed, 20 Nov 2024 19:57:18 +0000, ProkaryoticCaspaseHomolog wrote: > >> On Wed, 20 Nov 2024 18:37:40 +0000, rhertz wrote: >>> Do you see any error in my interpretation? I just reversed the entry of >>> power, taking it as power emitted by the reflecting surface. Maybe I'm >>> wrong, but I don't think so. >> >> 1) You multiplied to get 0.03927 Wm² (funky units!) instead of >> dividing to get 637 W/m². >> 2) I was using a cube geometry, not a sphere. So our numbers are going >> to differ by a substantial amount. >> 3) You should not be starting from absolute zero, but from room >> temperature. >> 4) Look at my original calculation, where part of my calculation is >> T_f^4 - T_i^4 since I am not starting from absolute zero. > > I told you that it was the unit area (effective). You can't use 637 W/m² > because a surface of 1 m² doesn't exist. Only a surface 127 times > smaller exist, which is the inner area of the cavity. A driver can be issued a speeding ticket for driving 80 miles/hour despite not having driven for an hour. Why should it be impossible to do the calculation because "a surface of 1 m² doesn't exist"? > Stefan used his formula first to calculate the temperature of the Sun, > with a HUGE effective area. He calculated the "radiant power" by > estimating it in terms of the Sun's luminosity, decades before Planck. > > In that case (even when I disagree about using Kirchoff's black body > radiation), he obtained a surface temperature that SEEMED TO LET HAPPY > most astronomer of his epoch (and even today). Even IF it's FALSE. > > But, as in many other things in science, if you had NOTHING, something > seemed to be useful and was adopted by 1870. Using such law, stars > temperatures were calculated using their relative luminosity. But NOBODY > was accountable for the errors, if such equation was/is FALSE. > > Go close to a star or the Sun and MEASURE its temperature. You can't, > can you? It's THE SAME CRAP as using Planck's equation to measure the > CBR by the COBE/WMAP satellites and (curiously) getting a perfect match. > > > I think that it's incorrect to use Stefan's formula in this case. How do > you spread 5 Watts over 0.00785 m²? Using 637 W/m², the formula gives > 325.6 K = 52.45 "C. This is not reasonable, because scaling down, it > would represent a STEADY STATE of 41,350 K for such small surface. > > The Stefan formula is empirical, and doesn't scale down well. It was > developed for big surfaces. > > Better to use calories, converting the loss of energy in Joules. Then > using an approximation of 1 calorie --> 1"C rise/gram of water, you > could have a better result. > > > Now, how do you propose to use Stefan with a surface of 0.00785 m² that > radiates 5 Watts of power? I shouldn't have trusted *ANY* of your numbers. Where did you get 0.00785 m² as the surface area of your sphere? A 5 cm radius sphere has a surface area of 0.031 m², so 5 W divided by the surface area gives 159 W/m². The question is now, what temperature T_f will result in 159 W/m² GREATER radiant emittance (radiant flux per unit area) than the radiant emittance of a room temperature ball? I'll let you do the calculation. (I have a tendency to key things wrong in my Windows calculator, as Paul has undoubtedly noticed and has been kind enough not to point out.) The important thing is that despite silly computational errors on _both_ our parts, we can agree that your statement of Wed, 20 Nov 2024 08:46 is false, where you wrote: | "The stored energy increases constantly until the temperature of the | cavity walls (not cancelled by any means) destroy the material that | form the cavity (either coatings or places on the cavity surface, | making holes)." Since once it reaches steady state, the ball radiates as much power as is being pumped in, there is no danger of the ball being destroyed, as you claimed in earlier posts. I have absolutely no idea what this scaling crap is to which you refer. The Stefan-Boltzmann law is applicable to small surfaces as well as large. It _DOES_ need to be modified for bodies that are not black, by application of an empirical emmisivity term.