A few months ago, Stephen Wolfram (of Mathematica
and A New Kind Of Science
fame) announced a $25,000 reward
for proving or disproving that a certain small Turing machine was universal
. The Turing machine has 2 states and uses 3 tape symbols. If universal, it would necessarily be the smallest possible universal Turing machine.
The prize has now been claimed by 20-year old Alex Smith, who proved that the machine was in fact universal. His long proof can be found here if you're interested. Perl enthusiasts will be glad to know that it appears he used a lot of Perl simulations to help decipher the behavior of this machine. His code is included in the PDF proof document.