In high-school chemistry, you learn that the ideal gas law is

P·V = n·R·T

These letters are drilled into my head, but I realised yesterday that I am losing my intuitive understanding of the relation. The physics version of it is

P·V = N·kT

where N is now a dimensionless number and k is comes from the definition of T. Let ρ be our number density and the relation simplifies to

P = ρ·kT

Pressure is density times temperature.

In the heterogeneous CS Unix environment, I may be executing emacs from a console as “emacs -nw” or from an icon on the desktop. Some computers will have the emacs-color-theme package installed, others won't. So in my .emacs file, I put the following lines:

;; from .emacs ...
(setq emacs-style-file "~/.emacs-style")
    (and window-system
         (require 'color-theme nil t)
         (file-readable-p emacs-style-file))
    (load emacs-style-file)