Especially carefully designed to the highest sphere of cosmology of Mahayana, which is divided into tiers nebesa- and home to a subject karmic law of the gods, and freed him Bodhisattva. All the worlds in general do not last forever - they exist only for mahakalpy, which is divided into four Kalpa (each lasts for millions of years). Mahakalpy and Kalpa alternate worlds die and reappear. Not every Kalpa marked by the appearance of the Buddhas - there are those where the Buddhas are not born at all; Kalpa is empty. The current Kalpa buddonosnaya and considered to be very successful: during its existence in the world to appear in 1000 (actually 1008) Buddhas, about one for every five thousand years.. A special force of the law (dharma) of each buddha is only about 500 years, after which this power is gradually disappearing, and the world plunged into the darkness of avidya - until the next Buddha. A similar pattern in all the worlds.