I understand that. But in astronomy, there are so many vastly different scales to work with, that in practice, at any particular scale, there is usually only o

I understand that. But in astronomy, there are so many vastly different scales to work with, that in practice, at any particular scale, there is usually only one physical process that dominates. It is extremely unlikely for two independent physical processes to operate at nearly the same scale! So it's hard to get processes that are the sum of enough random variables to make a distribution approximately Gaussian. The situation is probably different in a field like biology because there are many factors that, say, affect a person's height. The closest that I've ever encountered in astronomy was the distribution of the powers of a class of radio galaxies I studied that exhibited an approximately log-normal distribution. (See figure 7 of [1].) [1]: http://adsabs.harvard.edu/abs/2012ApJ...756..116A http://adsabs.harvard.edu/abs/2012ApJ...756..116A