I will give my personal check of one thousand dollars to the person, or persons, who will submit to me the lowest, credible argued, upper limit on the number of excess electrons within our visible universe.
Professor Robert Hellwarth, USC
That means: how many more electrons are there than e.g. protons, if any? The lowest obvious answer would be 0 (in which case the universe is symmetric and neutral), but how can you prove it?