@aviationdoctor.eth
Trusting the math is a bit like trusting your instruments while flying in poor visibility: they don’t lie, even when your gut feels otherwise (sometimes literally — you could be flying upside down and, with the right acceleration, not know it).
The quintessential example is Dirac’s equation. Around 1927, he set off to find a quantum equation for the electron that was fully relativistic and linear in time, unlike the Schrödinger equation.
Problem was, his equation had two roots, one positive and one negative. Because a negative energy solution seemed nonsensical, it was ignored by most physicists, except Dirac, who stood by his result.
He was vindicated in 1932 when the first positron was observed: same mass as the electron, just with an opposite charge. The negative energy solution pointed to the existence of antimatter. We “just” had to trust the math, even as they felt unintuitive.
The thing is… this works until it doesn’t. In fact, Dirac’s equation is more exception than rule. We can’t have negative length or probabilities, or violate causality or energy conservation, and yet plenty of math results give exactly that.
So what’s the difference? Dirac’s negative results met three conditions: they were unavoidable, they solved the system’s instability, and they mapped cleanly to a (at least predictably) observable particle with definite charge and mass. Most other negative solutions fail at least one of these.
TL;DR: shit’s complicated, yo