April 02, 2016 at 02:05AM

Today I Learned: 1) ...a bit more about the evolution of trophallaxis, or sharing of food by regurgitation, in ants. The most evolutionarily-basal ant clades (ponerine and one I forget) don't regurgitate food -- they can only carry droplets back to the nest and offer them to other nestmates. They can't perform trophallaxis, in fact, because they lack a specialized trophallaxic gut (not the real name) that holds food without digesting it. Fun trophallaxis fact -- some species of ants will regurgitate and offer food during combat with ants from other colonies, particularly when they take submissive stances. This is thought to be a kind of surrender gesture, though it may just be accidental firing of the trophallaxis behavior reflex, which is triggered by a friendly ant tapping the offerer's antannae. 2) There is no solid evidence that ants communicate with each other through any kind of visual means, and not for lack of trying. Ants just don't communicate by visual signals. 3) Ok, so I still don't understand why temperature does what it does in the Boltzmann equation, but I've at least found a more concrete nugget of not-understanding to try to hack apart. In statistical mechanics, where Boltzmann's equation reigns supreme, it seems that temperature has a really funny definition. Specifically, the temperature T of a system is defined as 1/T = dS/dE, where S is the entropy of the system (the log of the number of microstates possible in that system) and E is the energy of the system. That is, temperature is a measure of the change in the number of states accessible by the system as the energy of the system is raised. Actually, it's 1 over that rate of change. I find this really frustrating, because this is where every text I can find on statistical mechanics starts, when it comes to temperature, but this gives me no intuition of how temperature is related to either the thermodynamic definition (average kinetic energy of the molecules) or the everyday experience of temeperature. Chris Lennox, I know you've worked with definition before -- why the hell is that what temperature is?!