Star Trek: Everything We NOW Know About The Burn

As the Burn rendered all of the Dilithium in the Milky Way Galaxy inert, propulsion, as it had been, was over, at least in terms of space flight. Dilithium, as a substance, controlled the reaction between matter and antimatter. Without it, they would annihilate each other, resulting in a warp core breach. 

With the shockwave moving outward from Su'Kal's reaction, thousands of starships exploded as their cores breached. In that moment, warp drive, the time-honoured means of travel, became lethal. Though seemingly instantaneous, the shockwave had a small delay, allowing some ships to see their demise coming, including the one carrying Chancellor Nahla Ahke's son.

For over a century, the true cause of the Burn remained unknown, thus leaving those ships relying on warp drive in a precarious position. Other means of transport were possible, though one required a rare source of fuel, benamite, to use quantum slipstream. The Gorn attempted to create artificial wormholes, though they ended up destroying subspace in a two-light year diametre. 

The galaxy became a much larger place, having enjoyed a period of interstellar co-operation beginning in the late 24th century and early 25th. When Michael Burnham arrived in 3188 via the red angel suit, she discovered a darker, more hostile environment than she was used to. Starfleet had become a much smaller organisation, spread now over vast distances.