[ARCHIVED THREAD] - How cold is COLD! (Page 1 of 2)
Posted: 12/7/2009 6:45:43 PM EDT
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My freezer is warmer than my back yard,
24 degrees and falling @ 7:45pm in Tacoma. How cold is it where you are tonight? |
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It was 8 when I took the kids to school this morning. Currently, it is 4 degrees. |
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It was 8 when I took the kids to school this morning. Currently, it is 4 degrees. nobody cares about you guys up on the hill 
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Al gore doesn't like 72 in the house! (unless it's his house) That fucking Douche Canoe isn't paying the bill, nor is he keeping my infant healthy and warm. 
In all honesty, I have the thermostat at 70, but once we are all home and moving around and I have the stove and oven on cooking dinner, the temp in the house goes up. |
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-459* is cold (absolute zero). -273 degrees Kelvin? I think................ Cold as shit here, central Pierce County. 'Bout 28 last time I looked. Hovered around 30-32 today while I worked. YeeeeHaaaawwww! There is no negative scale in Kelvin scale, 0 K is absolute zero same with 0 R (Rankine scale)
[edit] Thermodynamics near absolute zero At temperatures near 0 K, nearly all molecular motion ceases and ΔS = 0 for any adiabatic process. Pure substances can (ideally) form perfect crystals as T → 0. Max Planck's strong form of the third law of thermodynamics states the entropy of a perfect crystal vanishes at absolute zero. The original Nernst heat theorem makes the weaker and less controversial claim that the entropy change for any isothermal process approaches zero as T → 0: The implication is that the entropy of a perfect crystal simply approaches a constant value. The Nernst postulate identifies the isotherm T = 0 as coincident with the adiabat S = 0, although other isotherms and adiabats are distinct. As no two adiabats intersect, no other adiabat can intersect the T = 0 isotherm. Consequently no adiabatic process initiated at nonzero temperature can lead to zero temperature. (≈ Callen, pp. 189–190) An even stronger assertion is that It is impossible by any procedure to reduce the temperature of a system to zero in a finite number of operations. (≈ Guggenheim, p. 157) A perfect crystal is one in which the internal lattice structure extends uninterrupted in all directions. The perfect order can be represented by translational symmetry along three (not usually orthogonal) axes. Every lattice element of the structure is in its proper place, whether it is a single atom or a molecular grouping. For substances which have two (or more) stable crystalline forms, such as diamond and graphite for carbon, there is a kind of "chemical degeneracy". The question remains whether both can have zero entropy at T = 0 even though each is perfectly ordered. Perfect crystals never occur in practice; imperfections, and even entire amorphous materials, simply get "frozen in" at low temperatures, so transitions to more stable states do not occur. Using the Debye model, the specific heat and entropy of a pure crystal are proportional to T 3, while the enthalpy and chemical potential are proportional to T 4. (Guggenheim, p. 111) These quantities drop toward their T = 0 limiting values and approach with zero slopes. For the specific heats at least, the limiting value itself is definitely zero, as borne out by experiments to below 10 K. Even the less detailed Einstein model shows this curious drop in specific heats. In fact, all specific heats vanish at absolute zero, not just those of crystals. Likewise for the coefficient of thermal expansion. Maxwell's relations show that various other quantities also vanish. These phenomena were unanticipated. Since the relation between changes in the Gibbs energy, the enthalpy and the entropy is thus, as T decreases, ΔG and ΔH approach each other (so long as ΔS is bounded). Experimentally, it is found that all spontaneous processes (including chemical reactions) result in a decrease in G as they proceed toward equilbrium. If ΔS and/or T are small, the condition ΔG < 0 may imply that ΔH < 0, which would indicate an exothermic reaction that releases heat. However, this is not required; endothermic reactions can proceed spontaneously if the TΔS term is large enough. More than that, the slopes of the temperature derivatives of ΔG and ΔH converge and are equal to zero at T = 0, which ensures that ΔG and ΔH are nearly the same over a considerable range of temperatures, justifying the approximate empirical Principle of Thomsen and Berthelot, which says that the equilibrium state to which a system proceeds is the one which evolves the greatest amount of heat, i.e., an actual process is the most exothermic one. (Callen, pp. 186–187) One model that estimates the properties of an electron gas at the absolute zero of temperature is the fermi gas. What is interesting is that the fermi temperature of electrons, where the lattice temperature is zero, is non-zero. In fact, the electrons have very high velocities. For an isolated system, this is probably a violation of conservation of momentum, since - if the electrons are interacting with the lattice, and the total momentum is zero, then the lattice cannot be at zero velocity. Also, if the lattice were precisely at zero temperature, its nuclei would have infinite de Broglie wavelength. (If the momementum goes to zero, the wavelength becomes infinite). [edit] Relation with Bose–Einstein condensates Main article: Bose–Einstein condensate A Bose-Einstein Condensate is an unusual state of matter that only exists at extremely low temperatures, maybe a few billionths of a degree above absolute zero. [edit] Absolute temperature scales Absolute or thermodynamic temperature is conventionally measured in kelvins (Celsius-scaled increments), and increasingly rarely in the Rankine scale (Fahrenheit-scaled increments). Absolute temperature is uniquely determined up to a multiplicative constant which specifies the size of the "degree", so the ratios of two absolute temperatures, T2/T1, are the same in all scales. The most transparent definition comes from the classical Maxwell-Boltzmann distribution over energies, or from the quantum analogs: Fermi-Dirac statistics (particles of half-integer spin) and Bose-Einstein statistics (particles of integer spin), all of which give the relative numbers of particles as (decreasing) exponential functions of energy over kT. On a macroscopic level, a definition can be given in terms of the efficiencies of "reversible" heat engines operating between hotter and colder thermal reservoirs. [edit] Lowest observed temperatures The average background temperature of the Universe today is 2.73 Kelvin, but it has spatial fluctuations. For example, the Boomerang Nebula has been spraying out gas at a speed of 500,000 km/h (over 300,000 mph) for the last 1,500 years. That has cooled it down to 1 K, as deduced by astronomical observation. This might be the lowest natural temperature recorded.[13] Much lower temperatures, however, can be achieved in the laboratory. The current (May 2009) world record was set in 1999 at 100 picokelvin by cooling a piece of rhodium metal.[14] |
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-459* is cold (absolute zero). 0.0 degrees Kelvin -273.15* C -459.67* F But the wind chill at those temps is not as bad as you would think,................................................cause there is no wind. Thank you good sir! I obviously got the 273 mixed up, didn't I......................glad Phil didn't see that.........he's good at catching my pseudo-science and rippin' me a new one.
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My freezer is warmer than my back yard, 24 degrees and falling @ 7:45pm in Tacoma. How cold is it where you are tonight? 
Freaking cold! ETA: Lest you think I'm roasting –– the pellet stove is in the basement. It is having a hard time keeping the upstairs (where we actually live) at 70F so I'm having to supplement with electrons. December is not going to be a good power month, so much for trying to save by using the stove 
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According to Weather Underground, it is currently 24.4 F in Kent. Somewhere during my second or third Korea tour––maybe during that tent fire on the DMZ––I decided that below a certain point, "how cold is it?" is an academic question. Maybe not when you are sprawled on the couch, full of spaghetti and syrah, with a cat curled up snoozing in your lap while posting on ARFCOM and watching Top Gear, but, trust me, the degree of misery at 0 F is not significantly greater than it is at 20F. (Less other contributing factors, i.e., wet, cold, hungry, stuck in Korea, some asshole shooting at you, your tent burned down...)
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Maybe not when you are sprawled on the couch, full of spaghetti and syrah steak & potatoes, with a cat curled up snoozing in your lap while posting on ARFCOM and watching Top Gear, but, trust me,
How did you know? Wait... Are you looking in my windows? and its 20.3 |
. Just need it to SNOW a ton!!!!!!
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-459* is cold (absolute zero). -273 degrees Kelvin? I think................ Cold as shit here, central Pierce County. 'Bout 28 last time I looked. Hovered around 30-32 today while I worked. YeeeeHaaaawwww! There is no negative scale in Kelvin scale, 0 K is absolute zero same with 0 R (Rankine scale)
[edit] Thermodynamics near absolute zero At temperatures near 0 K, nearly all molecular motion ceases and ΔS = 0 for any adiabatic process. Pure substances can (ideally) form perfect crystals as T → 0. Max Planck's strong form of the third law of thermodynamics states the entropy of a perfect crystal vanishes at absolute zero. The original Nernst heat theorem makes the weaker and less controversial claim that the entropy change for any isothermal process approaches zero as T → 0: The implication is that the entropy of a perfect crystal simply approaches a constant value. The Nernst postulate identifies the isotherm T = 0 as coincident with the adiabat S = 0, although other isotherms and adiabats are distinct. As no two adiabats intersect, no other adiabat can intersect the T = 0 isotherm. Consequently no adiabatic process initiated at nonzero temperature can lead to zero temperature. (≈ Callen, pp. 189–190) An even stronger assertion is that It is impossible by any procedure to reduce the temperature of a system to zero in a finite number of operations. (≈ Guggenheim, p. 157) A perfect crystal is one in which the internal lattice structure extends uninterrupted in all directions. The perfect order can be represented by translational symmetry along three (not usually orthogonal) axes. Every lattice element of the structure is in its proper place, whether it is a single atom or a molecular grouping. For substances which have two (or more) stable crystalline forms, such as diamond and graphite for carbon, there is a kind of "chemical degeneracy". The question remains whether both can have zero entropy at T = 0 even though each is perfectly ordered. Perfect crystals never occur in practice; imperfections, and even entire amorphous materials, simply get "frozen in" at low temperatures, so transitions to more stable states do not occur. Using the Debye model, the specific heat and entropy of a pure crystal are proportional to T 3, while the enthalpy and chemical potential are proportional to T 4. (Guggenheim, p. 111) These quantities drop toward their T = 0 limiting values and approach with zero slopes. For the specific heats at least, the limiting value itself is definitely zero, as borne out by experiments to below 10 K. Even the less detailed Einstein model shows this curious drop in specific heats. In fact, all specific heats vanish at absolute zero, not just those of crystals. Likewise for the coefficient of thermal expansion. Maxwell's relations show that various other quantities also vanish. These phenomena were unanticipated. Since the relation between changes in the Gibbs energy, the enthalpy and the entropy is thus, as T decreases, ΔG and ΔH approach each other (so long as ΔS is bounded). Experimentally, it is found that all spontaneous processes (including chemical reactions) result in a decrease in G as they proceed toward equilbrium. If ΔS and/or T are small, the condition ΔG < 0 may imply that ΔH < 0, which would indicate an exothermic reaction that releases heat. However, this is not required; endothermic reactions can proceed spontaneously if the TΔS term is large enough. More than that, the slopes of the temperature derivatives of ΔG and ΔH converge and are equal to zero at T = 0, which ensures that ΔG and ΔH are nearly the same over a considerable range of temperatures, justifying the approximate empirical Principle of Thomsen and Berthelot, which says that the equilibrium state to which a system proceeds is the one which evolves the greatest amount of heat, i.e., an actual process is the most exothermic one. (Callen, pp. 186–187) One model that estimates the properties of an electron gas at the absolute zero of temperature is the fermi gas. What is interesting is that the fermi temperature of electrons, where the lattice temperature is zero, is non-zero. In fact, the electrons have very high velocities. For an isolated system, this is probably a violation of conservation of momentum, since - if the electrons are interacting with the lattice, and the total momentum is zero, then the lattice cannot be at zero velocity. Also, if the lattice were precisely at zero temperature, its nuclei would have infinite de Broglie wavelength. (If the momementum goes to zero, the wavelength becomes infinite). [edit] Relation with Bose–Einstein condensates Main article: Bose–Einstein condensate A Bose-Einstein Condensate is an unusual state of matter that only exists at extremely low temperatures, maybe a few billionths of a degree above absolute zero. [edit] Absolute temperature scales Absolute or thermodynamic temperature is conventionally measured in kelvins (Celsius-scaled increments), and increasingly rarely in the Rankine scale (Fahrenheit-scaled increments). Absolute temperature is uniquely determined up to a multiplicative constant which specifies the size of the "degree", so the ratios of two absolute temperatures, T2/T1, are the same in all scales. The most transparent definition comes from the classical Maxwell-Boltzmann distribution over energies, or from the quantum analogs: Fermi-Dirac statistics (particles of half-integer spin) and Bose-Einstein statistics (particles of integer spin), all of which give the relative numbers of particles as (decreasing) exponential functions of energy over kT. On a macroscopic level, a definition can be given in terms of the efficiencies of "reversible" heat engines operating between hotter and colder thermal reservoirs. [edit] Lowest observed temperatures The average background temperature of the Universe today is 2.73 Kelvin, but it has spatial fluctuations. For example, the Boomerang Nebula has been spraying out gas at a speed of 500,000 km/h (over 300,000 mph) for the last 1,500 years. That has cooled it down to 1 K, as deduced by astronomical observation. This might be the lowest natural temperature recorded.[13] Much lower temperatures, however, can be achieved in the laboratory. The current (May 2009) world record was set in 1999 at 100 picokelvin by cooling a piece of rhodium metal.[14] 
Truly cool! |
