“What that’s trying to codify,” Walker said, “is the fact that some things have so many steps to produce them that it requires a memory.” That memory can be genetic or neurological or something we can’t imagine, but the result takes too many steps to arise otherwise.

Isaac Newton and Albert Einstein both produced successful theories of motion, which are technically time-reversible.2 They explain the motion of cannonballs, planets, and satellites without a clear distinction between where an object is and where it is going. This symmetry, which is true for simple systems, fails to explain why lions eat and digest