This is known as the "Problem of Time." In General Relativity, time is not a rigid background clock but a dynamic component of space-time geometry. If the universe is a closed system containing all of space-time, there is no "outside" clock to measure its evolution. The wave function, therefore, is timeless. It simply is .
If you have downloaded a and feel overwhelmed, here are the prerequisites you need to understand the core equations: wave function of the universe pdf
The mathematical backbone of this concept is the Wheeler-DeWitt equation. In 1967, Bryce DeWitt published a seminal paper that laid the groundwork for quantum gravity. The equation is famously written as: This is known as the "Problem of Time
