- The act of preserving the state of something that can be used in the present so that it can still be used in the future.
- In galactic economics, it was defined as the postponement of consumption.
- After the extinction, the term came to mean the question of what, among what had already been lost, could still be left to the future.
Because energy does not earn interest, confining one unit of light for a thousand years does not turn it into two units. Even if a photon were reflected forever between perfect mirrors, the number of photons would not increase. Real mirrors absorb part of the light and return the absorbed energy as heat of a longer wavelength. Stored light loses its usefulness before it loses its quantity. Yet in the storage space of the late galaxy, energy did earn interest. The energy inside did not increase by itself. Rather, while the energy outside the storage space continued to age, the energy inside remained almost unchanged. The energy outside lost value, much as late Roman coins had lost value as their gold content declined. The difference between starlight stored yesterday and the waste heat remaining in the universe today grew larger with time. The amount of stored energy remained the same, but the possibilities it could create for the future increased. The interest earned by the storage space was the entropy that accumulated outside it.
The first photon-storage device consisted of two reflective membranes. A photon traveled back and forth between them, and a small portion was lost with each reflection and measurement. Later, superconducting cavities, gravitational lenses, and stopped-light technologies were used, but perfect preservation remained impossible. A device for trapping light was still made of matter, and matter was never a perfect reflector. Every time a photon was reflected, measured, or controlled, it lost a minute amount of energy, most of which remained as heat. Civilization did not extend storage time so much as continually replace stored energy with fresh energy. It resupplied from the stars as much light as had been lost and released the accumulated heat outside. Permanent storage did not mean storage without loss. It meant that the facilities compensating for those losses operated permanently.
The last scientist left the object being stored unchanged and altered the rate at which time passed during storage. In a place where time had stopped, energy could neither enter nor leave, so the entrance had to function and states had to be classified, which required an order of events. He reduced the rate until a single moment inside corresponded to billions of years outside. From the outside, photons appeared to stop after crossing the boundary. From the inside, countless photons poured in almost simultaneously. Light from stars whose emissions were separated by millions of years formed a single flash inside the storage space. Light did not travel backward through time. Time folded before the light. If that flash were concentrated in one place, it could turn into heat before storage had even begun. The storage space therefore had to separate incoming energy according to its state. Short-wavelength light was sent to radiation zones, rotational motion to kinetic zones, and chemical potential energy to matter zones. Each zone had a different rate of time and a different boundary. Behind an entrance that appeared smaller than a cat’s collar from the outside, countless interiors were layered together. The last scientist completed the boundary of the storage space using rotational energy from black holes in the future. Only then did the escaping energy gain a place in which to gather. The photon deficit had not been recognized as a single phenomenon until Galactic Standard Time was completed. Long before the storage space was created, accumulated time differences in the wormhole network crossed a threshold and opened a new path of outflow, and as the number of wormholes, the magnitude of their time differences, and the number of energy conversions increased, the deficit rate also rose. The last scientist was never able to fully explain that relationship. The only certainty was that the first recorded deficit predated the storage space. But what mattered to him was not the past but the future. He did not preserve the life of the past. He preserved only the differences that might allow life to begin again. Even human genes and memories were excluded.