In what class of 4-dimensional spacetimes does there exist a real, non-constant scalar field ? with the following properties:
It obeys the wave equation: ??=0
Its gradient is everywhere null: ??.??=0
(I would like the answer to be: “almost none”, but don't let that influence you.)
I read somewhere (I think it was in the works of George Mikes) that in the early months of World War 2, one of the London newspapers staged the following stunt: they got someone to dress in the uniform of a Nazi storm trooper and march up and down Whitehall all day, and no one paid any attention. Did that happen, and if so, where can I find out about it?
Churchill once quoted Disraeli as saying “The Lord deals with the nations as the nations deal with the Jews”. Is this merely a paraphrase of Disraeli quoting Genesis 12:3, or is it literally a quote from Disraeli? Either way, where did Disraeli say it?
http://www.qubit.org/people/david/index ... =Questions