Consider a ballistics computer, that accepts inputs for the most relevant data, to precise-enough measurements, runs it through known physics equations, and produces a result that tells you exactly where a bullet will impact/be at any point in flight. If you wanted more precision, you’d have to start considering peripheral/less influential factors, use measurements of ever greater precision to more significant digits, etc. eventually you’d use the entire closed system for maximum precision.. but the physics is known and so an accurate prediction will be the result
Now do the same thing, except the machine is a physics engine and inputs are the positions and forces acting upon every single particle in a closed system, in one splice of time. The closed system for maximum accuracy is the entire observable universe. If the laws of physics are indeed constant and if we have discovered and quantified them to exact precision (which isn’t important actually, all that matters is that there is no random number generator in the universe, thus everything CAN be known with perfect certainty to infinite accuracy), you could hit fast forward, run the physics simulation, skip to next year, observe what’s happening on earth and you would be seeing the future, The only possible future, the only possible way events can unfold.
It’s an elaborate explanation, I’m sure there is a better one, but yeah this proves fate (kinda. Freewill can exist if there are any naturally occuring “random number generators”).
I guess just saying “cause and effect” would have sufficed. Oh well.