Clever, with nice ideas, but impossible for me because some ideas weren't carried through logically. For example Euler is a scientist - the constant is known as 'Euler's number', never just Euler, so oiler doesn't work in a group of homophones of mathematical/scientific constants. Was looking for a group of homophones for scientists and homophones of constants or just letters. Would be an excellent grid if things like that were edited to make sense.