Re: Travelling Salesman
Yes, well, as Mephistopheles says in Goethe's
Faust,
My worthy friend, gray are all theories,
And green alone Life's golden tree.
(Though it's taken a bit out of context.) People may conceive and develop beautiful theories, like those about complexity or encryption, but there are thousands of circumstances that are impossible to take into account and that can override all efforts put into those theories. For example, ten years ago a
paper (PDF) was published about vulnerabilities in the Java virtual machine where memory faults were induced by
heat (!) and then exploited in order to execute arbitrary code. You can prove that Java is type-safe until you are blue in the face, and then someone comes along and does something you never imagined.
Here is another example from the movie
Under Siege 2 with Steven Seagal (scroll to 24s).