The "universe" is defined as everything that physically exists: the entirety of space and time, all forms of matter, energy, and momentum, and the physical laws and constants that govern them. The term universe may also be used in slightly different contextual senses, denoting such concepts as the cosmos, the world, or Nature.
Sunrise at Second 24, Earth from low-orbit space (ESA/Hubble).
Astronomical observations indicate that the universe is 13.73 ± 0.12 billion years old. Its diameter is at least 93 billion light years, or 880 ×1024 (i.e., 880 followed by twenty-four zeroes) metres. According to the prevailing scientific theory, the universe has expanded from a gravitational singularity known as the Big Bang, a point in space and time at which all the matter and energy of the observable universe were concentrated. Since the Big Bang, the universe has expanded to its present form, possibly with a brief period of cosmic inflation.... (Buddhism, as well as Hinduism and Jainism, teach that such cosmic expansions and contractions happen cyclically, terming each such event a "world cycle" or maha-kalpa, "great aeon").
The word "universe" is usually defined as encompassing everything. However, using an alternate definition, some have speculated that this "universe" is one of many disconnected "universes," which are collectively denoted as the multiverse in addition to additional dimensions within a single universe. For example, in bubble universe theory, there are an infinite variety of "universes," each with different physical constants. Similarly, in the many-worlds hypothesis, new "universes" are spawned with every quantum measurement.
Throughout recorded history, several cosmologies and cosmogonies have been proposed to account for observations of the universe. The earliest quantitative models were developed by the ancient Greeks [borrowed from India], who proposed that the universe possesses infinite space and has existed eternally, but contains a single set of concentric spheres of finite size corresponding to the fixed stars, the Sun and various planets rotating about a spherical but unmoving Earth.
- (Source: Wikipedia). "Buddhist cosmology" and "Buddhist cosmography" may be searched at Wisdom Quarterly for extensive coverage of space, this "world system," and the universe from Buddhist, Jain, Hindu, and pre-Greek perspectives.