The Emperor's New Mind: Concerning Computers, Minds, and the Laws of Physics

1 card

1. 01

   Time's direction exists because the universe began with extremely low entropy, and this rare initial state makes the past distinct from the future.

   The Emperor's New Mind: Concerning Computers, Minds, and the Laws of Physics · 1989

   The arrow of time stems not from physical laws, but from the universe's extremely special initial condition: the low entropy of the Big Bang.

   Penrose argues that the second law of thermodynamics — entropy increases over time — does not explain time's direction. The key is that the universe started in a state of incredibly low entropy, far lower than a black hole of the same mass. For instance, at the Big Bang, the universe's entropy was about 10^10 times smaller than the maximum possible. This extremely special initial condition creates the arrow of time: things evolve from order to disorder. Without it, processes would be reversible, and memory and causality would vanish. Penrose calls this the initial entropy problem, which he considers unsolved by current physics.

   “The arrow of time is a consequence of the extremely special initial conditions of the universe, particularly the low entropy of the Big Bang. Without this condition, time would be symmetric, and past and future would be indistinguishable.”

   Open the card →