Every non-trivial norm on this set is either the standard absolute value or a p-adic norm according to Ostrowski's theorem. This set is the smallest field with characteristic zero. (10[1])The standard method of proving this set is countable is to consider an infinite square grid and to cross out (10[1])repeated (10[1])elements when considering successive (10[1])diagonals. (-5[1])For showing a number did not belong to this set, (-5[1])Hippasus was supposedly drowned by the Pythagoreans. (10[1]-5[1])The decimal expansions of elements of this set either terminate or have a repeating sequence. For 10 points, name this set denoted by a blackboard Q which is contrasted with the irrational numbers. ■END■ (10[3])