111–120 of 124 posts
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Kelvin is not measured in degrees however, so is excluded by implication
Wait, so it's just "five Kelvin", not "five degrees Kelvin"? TIL. Now that I think about, what's the etymological reason we use "degrees" to talk about temperature? We don't measure force in "degrees Newton" or electric current in "degrees Ampère". Why do we do it for Celsius and Fahrenheit?
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Most of my use of degrees is either in cooking or weather. Having a larger scale means more accuracy, seeing as we don't use decimals in either. I'm not saying it makes a ton of sense, but my only real defense of it. That said, I find negative units rather silly in most measurements, so we should really be using K I think.
> we don't use decimals in either Measuring body temperature with precision of 0.1°C is very common. In fact, I never saw an integer in this context.
I always want to ask “degrees what?" I once worked on a system that ran at -40 degrees. I loved leaving off the scale when giving tours and telling about it, because someone would invariably ask if I meant Celsius or Fahrenheit and then everyone got to learn where the crossing point of the two scales is.
LEELA: Fry, night lasts two weeks on the moon.
MOON FARMER: Yup. Drops down to -173.
FRY: Fahrenheit or Celsius?
MOON FARMER: First one, then the other.
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Lasers often have negative temperatures. It's not that weird
Okay, can we use it for cooling like in Sundiver by David Brin[0], where people (IIRC) used lasers to keep themselves cool while, as per title, diving their ship into the Sun? -- [0] - https://en.wikipedia.org/wiki/Sundiver
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Compare https://en.wikipedia.org/wiki/Negative_temperature
Interesting I wasn't aware of this definition but I would consider that moving the goal posts (not by you to be clear). Since that's using a different definition of temperature, the original poster was referring to the more common definition of temperature where at 0K nothing moves anymore.
That's a common simplification, but not really the definition. At the minimum, quantum mechanical effects make this complicated.
But you are right in a sense. From Wikipedia:
> The absolute temperature (Kelvin) scale can be understood loosely as a measure of average kinetic energy. Usually, system temperatures are positive. However, in particular isolated systems, the temperature defined in terms of Boltzmann's entropy can become negative.
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Negative temperature is a perfectly normal and well-studied phenomenon with lots of common examples. Temperature is defined as the rate of change of entropy wrt internal energy, usually more energy means more entropy, but it's not a given. https://en.wikipedia.org/wiki/Negative_temperature
> A system with a truly negative temperature on the Kelvin scale is hotter than any system with a positive temperature. If a negative-temperature system and a positive-temperature system come in contact, heat will flow from the negative- to the positive-temperature system Wait what?!! That feeds my daily “oh oooh” moment.
Basically, coldness is 1/temperature but makes more theoretical sense:
> Though completely equivalent in conceptual content to temperature, β is generally considered a more fundamental quantity than temperature owing to the phenomenon of negative temperature, in which β is continuous as it crosses zero whereas T has a singularity.[6]
> In addition, β has the advantage of being easier to understand causally: If a small amount of heat is added to a system, β is the increase in entropy divided by the increase in heat. Temperature is difficult to interpret in the same sense, as it is not possible to "Add entropy" to a system except indirectly, by modifying other quantities such as temperature, volume, or number of particles.