I went on to test the program in every way I could devise. I strained
it to expose its weaknesses. I ran it for high-mass stars and low-mass
stars, for stars born exceedingly hot and those born relatively cold.
I ran it assuming the superfluid currents beneath the crust to be
absent -- not because I wanted to know the answer, but because I had
developed an intuitive feel for the answer in this particular case.
Finally I got a run in which the computer showed the pulsar's
temperature to be less than absolute zero. I had found an error. I
chased down the error and fixed it. Now I had improved the program to
the point where it would not run at all.
-- George Greenstein, "Frozen Star: Of Pulsars, Black
Holes and the Fate of Stars"