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huh - lambda represents energy?

So, 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).

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( 8 comments — Leave a comment )
flamingnerd
Jun. 4th, 2009 04:16 am (UTC)
hm. that's annoying. I don't think it's energy in chemistry. I never studied chem at the grad level, but my undergrad was in biochem. It's just nonscientific blather. *shrug*
easwaran
Jun. 4th, 2009 06:38 am (UTC)
I thought the queer lambda had something to do with the labrys, or double-headed axe, wielded by Artemis, or something like that. (A quick check on Wikipedia confirms that I mostly remembered that correctly from reading up about this sort of thing while I was an undergrad - except that the lambda has nothing to do with the labrys, and in fact they had been associated with different genders. As I guess you saw on the same page I just saw it.)
spoonless
Jun. 5th, 2009 02:28 am (UTC)
When I saw it, my first thought was that it was just a Greek L for "lesbian", and that it had been invented first for lesbians and moved on to encompass the broader LGBT movement.

But apparently, the only L word it stands for is Liberation.
luxvalence
Jun. 5th, 2009 02:09 am (UTC)
Wavelength is a length, specifically, the length of a wave...

Even knowing nothing on the subject, I must say, this struck me as VERY funny. :)
bob_the_normal
Jun. 5th, 2009 03:51 am (UTC)
Probably just someone who didn't pay attention properly in chemistry and is confusing the fact that there is an equation that tells you the energy of light as a function of lambda. Obviously it's not because lambda is energy, but wavelength.

Plus it's a Greek letter, much like using Latin... quidquid latine dictum sit, altum videtur.

Later.
vaelynphi
Jun. 8th, 2009 02:59 am (UTC)
Perhaps they were thinking of latent heat, or of eigenvalues? (Either of which would have plenty of coming-of-age style connotations appropriate enough, eh?)
spoonless
Jun. 8th, 2009 10:14 pm (UTC)
Eigenvalues, that's a good point... I hadn't thought of that. Of course, they would usually just be used temporarily to solve the linear algebra problem and then switch back to the usual notation. Latent heat, isn't that an L?
vaelynphi
Jun. 9th, 2009 09:43 pm (UTC)
Dunno; in most of my fields of research, notation is sketchy at best. I've seen one book write the gradient in five different ways, none of which were correct (except, arguably, the del notation, which I think of as incorrect no matter what--can't stand anything without indices!)...
( 8 comments — Leave a comment )

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