It's interesting, but at thirty pages kind of long; Tegmark has also written a three-page article on the same topics called Shut Up and Calculate!.
I am led to wonder if Tegmark is deliberately referring to the Flying Spaghetti Monster here, in his discussion of Newtonian gravitation. (The "frog" sees only the universe as it exists right now; the "bird" sees the universe "as a whole" and in particular sees all time at once.)
If the frog sees a particle moving with constant velocity, the bird sees a straight strand of uncooked spaghetti. If the frog sees a pair of orbiting particles, the bird sees two spaghetti strands intertwined like a double helix. To the frog, the world is described by Newton’s laws of motion and gravitation. To the bird, it is described by the geometry of the pasta, obeying the mathematical relations corresponding to minimizing the Newtonian action.Also of interest is the claim that the Mathematical Universe Hypothesis "banishes... the classical notion of randomness", essentially because all probability can be recast as measure theory. The randomness of quantum mechanics, according to Tegmark, is essentially "epistemological" -- we perceive what looks like randomness because we do not have perfect knowledge. This, of course, is not believed by all physicists; the Copenhagen interpretation of quantum physics does fundamentally include randomness.
And why aren't there other interpretations of quantum mechanics named after cities?