In 1965, computer scientist Chris Strachey published a letter in Computer Journal proving, with a language called CPL, that you can't solve the halting problem. I wanted to blog his elegant proof, but I also wanted to link to background about Strachey (who led an interesting life) and CPL (which had interesting ideas). I found a good paper, Christopher Strachey and the Cambridge CPL Compiler, by Martin Richards. But it's in a Springer journal. And it costs 34 dollars online. There is no free version on Richards's web site or in arXiv. Other good articles also cost. So I haven't blogged Strachey's proof. And if you read, write, or buy research papers, I'd like to point you at the advice in John Baez's essay What We Can Do About Science Journals. Why, John asks, enrich the former soap salesman who is now CEO of Reed Elsevier?