Three amazing facts and what they imply
Physics gives us, among many amazing facts, these three facts:
(1) Sensitive dependence: In any deterministic, nonlinear system such as our universe, the slightest change at one time produces huge differences later. Meteorologist Edward Lorenz called this phenomenon the butterfly effect, arguing that the flap of the wings of a single butterfly can (eventually) bring about a distant tornado that wouldn’t have occurred otherwise. In one simple run of the Lorenz equations, a minuscule initial change is amplified 40 million times in just 30 seconds.
(2) Time-symmetry: The laws of motion for atoms and molecules work the same way in both the earlier-to-later and the later-to-earlier directions. For example, nothing about the motions of the molecules of a gas in a closed container tells us whether time is running in one direction or the opposite direction.
(3) Entropy increases: The total entropy of the universe (a measure of its disorder) always increases ‒ just as surely as an ice cube at room temperature always melts. The probability that total entropy doesn’t increase is literally negligible, i.e., zero to as many finite decimal places as you like. Contrary to popular opinion, the conjectured “heat death” of the universe doesn’t challenge this result.
Given (1)-(3), it follows that changing anything about the present implies a remote past that differs radically from the actual past, with (again) a literally negligible chance that it doesn’t differ radically. Biologists tell us that the actual evolution of the human species depended very sensitively on prior conditions. Given a radically different remote past, then, humans never come to exist at all. If you hadn’t read this post, then neither you nor I nor the rest of humanity would have existed. How’s that for an implication!
You can find the full argument for this conclusion in Chapter 5 of my book.
