A stream is a line of identical objects (usually spaceships), each of which is moving in a direction parallel to the line, generally on the same lane. In many uses the stream is periodic. For example, the new gun produces a period 46 glider stream. Here, the period of a moving stream is often defined as either the number of generations it takes for an arbitrary region to repeat. In this case, the period of the stream is always equal to the least common multiple of the gun that generates it and the period of the spaceships in the stream. The stream produced by a pseudo-random glider generator can have a very high period.