Sida Liu

Einstein believed that the apparent “randomness” in quantum mechanics was due to incomplete knowledge of underlying factors. His famous quote, “God does not play dice”, rejected the idea of true randomness. After Einstein, the mainstream Copenhagen interpretation prevailed, accepting the randomness and uncertainty as fundamental features.

Wolfram’s Physics Project was launched in 2020, aiming to develop a fundamental theory of physics that can derive relativity, quantum mechanics, the second law of thermodynamics, and more. Naturally, this fundamental theory provides an explanation for the phenomenon of “randomness”.

Wolfram’s Physics conjectures that step-by-step computation is the foundation of everything. There are all possible sets of rules and all possible initial conditions, and the computations are carried out to form everything. This system, the largest possible, is called the Ruliad. If the Ruliad were simple, anyone could perform all the necessary computations and compute the entire Ruliad. However, the Ruliad is full of computational irreducibility, meaning these computations must be carried out step by step to reach each state; one cannot simply jump ahead.

In the Ruliad, different sets of rules give rise to different multiway causal graphs. Those graphs are causal because every node is caused by other nodes, according to the rules. They are called multiway because the rules can be applied to the nodes in different orders, creating different paths or threads.

Each node in the multiway causal graph is a hypergraph of space in itself. A hypergraph is similar to a graph, but its edges can connect more than two nodes at once. A node in the hypergraph of space is an “atom of space”. The computation of a set of rules applies to these “atoms of space”, taking their neighbors as input to compute the current states. Each computational action can be thought of as an “atom of time”.

We exist within a multiway causal graph, which is part of the Ruliad, where the set of rules correspond to our physical laws. Because we exist within it, we are computationally bounded by the system. We occupy multiple threads that are close to each other, but we experience being in a single thread because those threads are so similar, and we aggregate them into one. This is analogous to the situation when we facing a ball: although many quantum-level activities occur underneath the appearance, we aggregately consider it a single ball.

This underlying structure can describe phenomena previously explained by quantum mechanics. When small differences inevitably lead to significant ones, for example, when a quantum measurement is made, the aggregated multiple threads split into multiple aggregated branches. Since we are within the system, we split as well. In each branch, the “us” in that branch experience one possible outcome, with probabilities calculated by Schordinger’s equation and Born’s rule.

The structure can also describe phenomena previously explained by relativity. If an object moves quickly from a place to another, more computation is required to rewrite the states (the object) into their neighbors (another place), leaving less computation available for the object’s intrinsic evolution, causing time to slow down for that object. Similarly, when an object is in a strong gravitational field (i.e., where there is more energy-momentum), more computation is required to rewrite for gravity, causing time to slow down for that object as well.

This is my current understanding of Wolfram’s Physics Project. His theory is still in the phase of exploring possible scenarios and constructing a consistent framework. I hope it will mature and lead to some testable experiments. I look forward to a moment, like the eclipse for relativity, that will establish this theory as mainstream.