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. The standard method of proving this set is countable is to consider (10[1])an infinite square grid and to cross out repeated elements when considering successive diagonals. For (10[1])showing a number did not belong to this (-5[1])set, (-5[2])Hippasus was supposedly drowned by the Pythagoreans. The decimal expansions (10[1])of elements of this set either terminate or have a repeating sequence. For 10 points, name this set (-5[1])denoted by (-5[1])a blackboard (10[1])Q which is contrasted with the irrational numbers. ■END■ (10[3]0[1])