Albert van der Horst wrote:
Einstein introduced the summation convention for indices that are used twice. Leaving out summation signs is absolutely hideous, but it has saved generations of physicists of loosing track (and their minds.)
There is a joke among mathematicians that if Einstein hadn't been remembered for a couple of other fairly contributions things in physics :-), he would have been remembered in mathematics for that convention, since it has saved everyone -- mathematicians included -- a lot of time and anguish. When using tensor calculus, there's even very easy ways to verify you have a valid tensor equation using it.
-- Erik Max Francis && m...@alcyone.com && http://www.alcyone.com/max/ San Jose, CA, USA && 37 18 N 121 57 W && AIM/Y!M/Skype erikmaxfrancis If the sky should fall, hold up your hands. -- (a Spanish proverb) -- http://mail.python.org/mailman/listinfo/python-list
