> new physics had been learned, and it had not been in his physics book.
Again, there is a difference between learning new techniques and phenomena running on top of known physical law, and learning new fundamental laws. When engineers say "new physics", they refer to the former, but when physicists say "new physics", they refer to the latter. And there hasn't been any new physics, more or less, since the 60's.
The computational limits are thought to be encoded in the fundamental laws, in a way very analogous to the limiting speed c.