Its spin produced light and darkness. Depending on its position, it would be able to determine whether we would be able to see. We never knew the cause until we uncovered their tomb.

Deep in the jungle, a long dead civilizaiton buried in vegetation had left a massive city of ancient stone. Exploring their buildings uncovered an intricate maze of interconnected streets and rooms underground.

One led to an expansive hallway where we found the source of day and night, a spinning disk, light on one side, dark on the other, balanced to produce equal parts daylight and nighttime.

That wasn't the only thing we found. In countless adjoining rooms, other objects were found, each spinning at their own speeds. Our archaeologists were still working on determining what they all did. Another disk spun much more slowly. Heat on one side, none on the other. We were eventually able to match the period of its spin with the cycle of the seasons.

Each room contained a single spinning object, each different from the others. The rooms themselves were different as well, carved with symbols and shapes we could not decipher.

The rooms stretched in all directions. We did not have an accurate count of them all. Nobody wanted to carry out such a mindless task when so many more amazing things were available for us to examine. The vast majority of the objects remained a mystery, but based on what we did figure out, we guessed they all affected the physical world in some way. Or they merely reflected physical reality, we couldn't be sure.

Discovery of the rooms changed our understanding of the universe. Increasingly we began to model our theories based on cycles and the interactions of different periodic influences. One object spun so fast that we were barely able to measure it using our most advanced technology. It seemed no matter how we tried to measure it, we could only capture its state at one specific moment of its spin. It was as if everything that happened during the rest of its spin could not be observed, stretches of time that were out of phase with the known universe. What lay behind the other phases, we could never know.

Other objects spun at rates that were much easier to handle, but some revealed a facet only for the briefest parts of their cycles, as if to say the world could be the same for the vast majority of time, but on a regular basis, for just the briefest instant of a moment, everything could be different in some unknown way, and then everything would return to normal once again.

Something else was coming though, perhaps something important. In one room we found a cylinder spinning so slowly that it appeared to be stationary, but careful examination by some of our most sensitive instruments revealed that it did indeed turn. We determined that its period was longer than the estimated age of the universe, meaning that as far as we could tell, it had never made one complete revolution around its axis.

What would happen if it did? We could not tell how soon it would complete its rotation because we could not tell when it started, but we did know that if it represented a change in the state of the known universe, it would be a change perhaps no civilzation had ever experienced, at any point in time.

It made the future entirely unpredictable. We did not know whether to view that with hope or with dread, but it was likely there would be nothing we could do about it when the time came.