Deep underground, the survivors' offspring convened for their first day of apocalypse history class.

"Teacher?"

"Yes, Susan?"

"My mom said a scientist warned it would happen, but everyone called them a quack."

"Yes, that's true." The teacher chuckled.

"Why?"

"The scientist tried to warn the world that while the SSLTF (Solar Satellite-Laser Terrestrial Fusion) array was remarkable, the designers hadn't considered the complex interwoven ecology that formed life and helped it to evolve."

"And?"

"Well, a mishap rapidly cascaded into a global climatic disaster."

"How?"

"They miscalibrated the lasers and cranked up the power too high. It was that simple."