I bet him $1,000 that "By 2020, no one will have won a Nobel Prize for work on superstring theory, membrane theory, or some other unified theory describing all the forces of nature." This year's Nobel Prize in Physics, which recognized solid work in cosmology and astronomy, was Kaku's last chance to win before 2020.
Physicist Lee Smolin, a proponent of a rival to string theory called loop-space theory, was supposed to bet against me, but after fussing over the wording of the wager, he backed out.
Physicists have yet to produce any empirical evidence for either string theory, which was invented more than 40 years ago, loop-space theory or any other unified theory.
A theory of everything is also a theory of everyday energies, where we find familiar electrons, protons, and atoms.
If the results disagree with known data, then string theory will be shown to be a "theory of nothing.
Because string theory has near-miraculous breakthroughs every 8 to 10 years, we can expect 2 more breakthroughs in the theory before 2020, and hence might be able to solve this theory by then.
In 1994 I bet physicist Michael Riordan a case of California wine that his Stanford colleague Andrei Linde would not win a Nobel Prize by the end of the century for his work on inflation, a theory of cosmic creation.