There was one thing that always bothered me about “the science of stargate”. No, it’s not about the stargate’s FTL movement means that causality is violated — that’s a problem common to any FTL travel, and can be dealt with in a number of ways.
The bigger problem is something that was obviously invented for plot device purposes: “when you open a wormhole, matter can only move in the direction it was opened, but energy can move both ways”. How can it make sense? After all, matter and energy are interchangeable. Here is a possible solution: it pertains to the difference between fermions and bosons. In quantum mechanics, fermions are particles with spin of the form “n 1/2”. Bosons are particles with spin of the form “n”. There are many deep differences between them: for example, the Pauli exclusion principle, responsible for the structure of atoms, applies only to fermions.
Normal matter is made of atoms. Atoms are made of electrons, protons and neutrons. Electrons are fermions. Protons and neutrons are made of quarks, which are also fermions. In other words, atoms are made of fermions. Radio waves, the most common communication in the Stargate series across stargates, are made of photons. Photons are bosons.
It makes sense, of course, that Capt. Carter would simplify (“dumb down”) the science. Instead of saying “fermions” and “bosons”, the O’Neill would respond better to matter and energy. So there we have it: bosons can travel both ways, fermions can only travel one way, across a stable wormhole constructed from one stargate to another.