What's YOUR explanation for The Scream? Post your "something else entirely" in comments!
Sudden awareness of a layer of reality hidden from most, where humanity's dreams (but mostly nightmares) dog our steps.
The popularity of extra-dimensional beings makes me think there's great potential for a Silent Legions crossover.
Election night, November 2016.
"We're also out of coffee." (/Airplane)
Tampering with psionics too deeply OR someone stepped on the Kwisatz Haderach's foot.
I thought I was clever with the Munch background, but a lot of the comments seem to explain the painted scene more than the event in SWN. Hmm...allowed!
Someone tried to improve the Spike Drive too much and got... noticed. By... something. Cue DooM, Event Horizon, and the Androsynth in Star Control II.
But seriously: the Scream was an entirely natural event that ample study and care might have predicted and ameliorated in the same way that earthquakes, rogue waves, and solar flares might be. (It is also a periodic event, albeit on a long, slow, deep time cycle.) Thus, the first problem is living long enough to be able to figure out where to begin studying it...
I'm going with a natural event.
I've come to entertain two options:
A) In the final years before the Scream, humanity was at its peak of technological development, with cutting-edge research approaching magic-like effects. Like such were also maltech experiments, and I find it feasible that the event could've been caused by either some experiment gone catastrophically awry, or a deliberate action, the ultimate terrorist attack.
B) The explanation of the Fermi Paradox. Either a recurring natural event which has the side effect of wiping out advanced civilizations which end up relying on their psychics too much, or a control mechanism devised by a godlike master race with the desire to remain unchallenged in its reign over the galaxy (or galaxies).