SCIENCE: What measurement misses

Science measures everything, and tonight's writers are interested in what's left over. Whitman walks out of an astronomy lecture and looks up at the actual stars. Sacks examines a man whose brain can identify nothing by sight and discovers that neurology alone can't account for a person. Levi follows a single carbon atom through geological time and into his own hand as he writes. Each piece asks where knowledge ends and something else begins.