“The causal nexus divided when Nyssa changed history... causing the universe to exist in two quantum states and releasing blinovitch energy.” Tardis | Fandom
Elias stood in the ruins of the Great Library, clutching a charred leather notebook. He was a "Time-Sensitive," capable of feeling the hum of a —a point where time tracks diverged and collided. Causal Nexus
“Wally learns the hard way that good intentions don't off set the consequence of time travel... Wally's actions have already set off a chain of events that can't be stopped.” Fanfiction.net “The causal nexus divided when Nyssa changed history
He emerged decades in the past, in the same Library, before the rot had set in. There, he saw a young version of himself reading by a window. Elias looked down at his hands—they were aged, his hair now a shock of silver. He walked toward the boy, the charred notebook heavy in his hand. “Wally learns the hard way that good intentions
The concept is widely explored in fiction and philosophy as a way to understand our interconnected reality.
In a panic, Elias realized the "fire" the man spoke of was the very act of building the machine. He grabbed the notebook and stepped through the shimmering portal.