In many Star Trek, we have heard references to weapons ranges. For example, a Nebula class starship has a weapons range of roughly 300,000 kilometers.
We can reliably predict that a projectile weapon (like a photon torpedo) could possibly almost continue on forever, unless, miraculously (or unfortunately), it hits an object in space.
Certain types of energy/particle weapons might dissipate or steadily disperse at a certain point--but would all types of particle weapons do so? There hasn't been on-screen evidence that a phaser will dissipate at some point (unless physics says otherwise). Ships, however, are never seen firing at each other at a certain distance--not even launching torpedoes. What limits the range of starships' weapons in Star Trek?