by Daniel Ranard
Math works pretty well. We can count apples and oranges; we can scribble equations and then launch a rocket that lands gently upright. When an argument is indisputable, we colloquially say “do the math,” and we speak of events that will happen with “mathematical certainty.” Math works so well that you're forced to wonder: why, and what does it mean about our world? I won't fully answer these questions, but I'll offer a few perspectives.
You don't need to know much math to see it works. Say you go apple-picking with a friend; you count 12 as you pick them, and your friend counts 19 of her own. How many apples are in the basket? Maybe you crunch the numbers on a scrap of paper, just to be sure. You manipulate symbols on a page, and afterward you make a claim about reality: you know how many apples you would count if you pulled them out.
But was that math or just common sense? If you're not impressed by addition, let's try multiplication. I suspect many of us encounter our first real mathematical “theorem” when we learn that A times B is B times A. As Euclid wrote circa 300 BC, “If two numbers multiplied by one another [in different orders] make certain numbers, then the numbers so produced equal one another.” This fact may be so familiar you forget its meaning: 4 x 6 = 6 x 4, or rather 6 + 6 + 6 + 6 = 4 + 4 + 4 + 4 + 4 + 4. It may be obvious, but a curious child would still ask, why? The equation demands proof, much like the Pythagorean Theorem. Euclid gave a proof in Book VII, Proposition 16 of the Elements. And though he proved an abstract fact using abstract symbols, the world seems to obey this arithmetic rule: if you have four groups of six apples, Euclid predicts you can always rearrange them into six groups of four.
Maybe it's no surprise we can use arithmetic to make these predictions. But what about the success of more sophisticated math and physics?