While the <i>general</i> concept is valid, the <i>specific</i> example in the headline relies on the idea that negative absolute temperature cannot exist, which is false. [1]<p>Perhaps more significantly, the article could use some examples of how different approaches to typing solve this problem, and discussing pros and cons; "not all numbers are valid for all numeric-valued variables" is a fairly shallow observation standing on its own.<p>[1] See, e.g., <a href="http://www.quantum-munich.de/research/negative-absolute-temperature/" rel="nofollow">http://www.quantum-munich.de/research/negative-absolute-temp...</a>