huh - lambda represents energy?
Jun. 3rd, 2009 08:22 pm![[personal profile]](https://www.dreamwidth.org/img/silk/identity/user.png){kind=small}
spoonlessSo, recently I was reading the Wikipedia entry on LGBT symbols and I ran across the "pink lambda". They list a lot of different reasons why the pink lambda was chosen, but one of them says "The charged energy of the gay movement. This stems from the lambda's use in chemistry and physics to denote energy in equations." You would think, after studying physics for 4 years (stretched out over 7 physical years) at the college level, and then another 6 years at the masters and doctorate level, so a total of a decade, I'd have some clue of what the heck they are talking about. But no, I can't think of any instance in all my years of study where I've run across a lowercase λ being used to represent energy--is it something from chemistry then?
After seeing that, I also found this website that also associates lambda with energy, although I don't know if it is a gay rights thing... click on the image to see the text surrounding it, it says "The Lambda Energy" followed by "And From the Infinite God Created Humankind". So wherever this idea came from, it appears widespread.
In physics, "E" is the symbol most commonly used to represent energy. lowercase λ is pretty much always used to represent wavelength, never energy. Wavelength is a length, specifically, the length of a wave... with massless particles like photons, there is a simple inverse relationship between energy and wavelength: as you increase the wavelength you decrease energy, but that's the only relationship I can think of where lambda might have anything to do with energy. But of course then lambda would be more appropriately the symbol for a lack of energy, not energy. If you allow for uppercase Λ, then there are a few instances I can think of where it represents an energy, but they are pretty obscure and it's very unlikely whoever made up the symbol for the LGBT movement was aware of them. One is the cosmological constant, aka "Dark Energy", although technically &Lambda there represents an energy density, that is... energy per unit volume... not energy itself. The other is the cutoff scale for a quantum field theory. Because quantum field theory is only an approximation to quantum gravity, there is a shortest distance scale where the theory gets "cut off"... it's kind of like making spacetime into a discretum instead of a continuum... but then you always end up computing quantities that don't depend on Λ, and after everything is said and done, you can just take &Lambda -> ∞. And probably the only reason that &Lambda is an energy is because *everything* in quantum field theory is measured in units of energy, or some power of energy... so you can express the shortest distance scale equivalently as a "highest energy" (again, because of the inverse relationship between length and energy). Another use, which is arguably the same use as the second, is Λ as in ΛQCD to represent an energy scale associated with an asymptotically free quantum field theory, ie one that is generated through dimensional transmutation. (I've actually been planning on making a whole post on dimensional transmutation and quantum anomalies soon... so stay tuned!)
After E, the most commonly used symbols in physics that represent energy are U or V (for potential energy), and T (for kinetic energy). Then there are also several kinds of energies you can define in thermodynamics, F (Helmholtz free energy), H (enthalpy), G (Gibbs free energy), or Ω (Landau potential). And of course, you can also use M to represent energy, because of mass-energy equivalence, as long as you are working in units where the speed of light is equal to 1. Any of these would have made more sense than λ if you wanted to represent energy. But again, it's probably something from chemistry? Even racking my brain back to the chemistry classes I've taken, I still can't recall any use of λ for energy there, but I wouldn't be surprised if I am just forgetting (or if I didn't take an advanced enough chemistry course).
After seeing that, I also found this website that also associates lambda with energy, although I don't know if it is a gay rights thing... click on the image to see the text surrounding it, it says "The Lambda Energy" followed by "And From the Infinite God Created Humankind". So wherever this idea came from, it appears widespread.
In physics, "E" is the symbol most commonly used to represent energy. lowercase λ is pretty much always used to represent wavelength, never energy. Wavelength is a length, specifically, the length of a wave... with massless particles like photons, there is a simple inverse relationship between energy and wavelength: as you increase the wavelength you decrease energy, but that's the only relationship I can think of where lambda might have anything to do with energy. But of course then lambda would be more appropriately the symbol for a lack of energy, not energy. If you allow for uppercase Λ, then there are a few instances I can think of where it represents an energy, but they are pretty obscure and it's very unlikely whoever made up the symbol for the LGBT movement was aware of them. One is the cosmological constant, aka "Dark Energy", although technically &Lambda there represents an energy density, that is... energy per unit volume... not energy itself. The other is the cutoff scale for a quantum field theory. Because quantum field theory is only an approximation to quantum gravity, there is a shortest distance scale where the theory gets "cut off"... it's kind of like making spacetime into a discretum instead of a continuum... but then you always end up computing quantities that don't depend on Λ, and after everything is said and done, you can just take &Lambda -> ∞. And probably the only reason that &Lambda is an energy is because *everything* in quantum field theory is measured in units of energy, or some power of energy... so you can express the shortest distance scale equivalently as a "highest energy" (again, because of the inverse relationship between length and energy). Another use, which is arguably the same use as the second, is Λ as in ΛQCD to represent an energy scale associated with an asymptotically free quantum field theory, ie one that is generated through dimensional transmutation. (I've actually been planning on making a whole post on dimensional transmutation and quantum anomalies soon... so stay tuned!)
After E, the most commonly used symbols in physics that represent energy are U or V (for potential energy), and T (for kinetic energy). Then there are also several kinds of energies you can define in thermodynamics, F (Helmholtz free energy), H (enthalpy), G (Gibbs free energy), or Ω (Landau potential). And of course, you can also use M to represent energy, because of mass-energy equivalence, as long as you are working in units where the speed of light is equal to 1. Any of these would have made more sense than λ if you wanted to represent energy. But again, it's probably something from chemistry? Even racking my brain back to the chemistry classes I've taken, I still can't recall any use of λ for energy there, but I wouldn't be surprised if I am just forgetting (or if I didn't take an advanced enough chemistry course).
