The Enigma of Time

The Enigma of Time is the term used by temporal researchers to describe the strange, seemingly natural limitations on their tools: the only "epoch" a temporal researcher can observe or visit is between June 3, 3512 BC (the Early Boundary) and July 29, 3512 AD (the Late Boundary), regardless of the researcher's temporal origin within that epoch. No researchers sent to July 29, 3512 AD to "wait it out" have returned.

Discovery and Research
When Dur Ot Onl first invented the Spatio-Temporal Visualizer on Earth in 2309 AD, he attempted to view several points in time prior to the Early Boundary, but was unable to. He tended to consider this a failure of his equipment rather than what later researchers proved it to be: a barrier in time, inexplicable by the learning of that era, and only partly understood today.

Ot Onl never attempted to probe the future, though his devices were capable of it. The first such "Future Scans" were not performed until 2622, by Pel & Rhame zuVhydjy of the Pan-Republican Institute for Education, Science and Technology (PRIEST), who both discovered the Late Boundary and demonstrated that the two Boundaries of the epoch were fixed, regardless of origin within the epoch.

Prevailing Theories
Many theories have been put forth to explain this phenomenon since its discovery, with varying degrees of plausibility. The latest is that there are many such "epochs", each isolated from the others by temporal mountains which can only be crossed naturally, though the crossing itself is speculated to be most disruptive to normal minds, regressing them to a primitive state and erasing all memories. This last neatly explains why no writings predating our epoch have been unearthed, and why all the ancient cultures of the galaxies seem to have arisen after June 3, 3512 BC.