Ulam lapsed into a coma. His wife, his doctors and his friends worried about brain damage. When he awoke a few days later, Ulam worried about it even more. "One morning the surgeon asked me what 13 plus 8 were. The fact that he asked such a question embarrassed me so much that I just shook my head. Then he asked what the square root of twenty was, and I replied: about 4.4. He kept silent, then I asked, 'Isn't it?' I remember Dr. Rainey laughing, visibly relieved, and saying, 'I don't know.'"