Our Universe

The universe consists of all matter, light, and other forms of radiation and energy that have been discovered by man. The universe also consists of everything that man believes to be present in space / time as a result of his theories. This includes the Earth, solar system, stars which includes our sun. Most people believe that the universe is expanding.

In the first half of the 20th century, the name Universe was used to mean the whole spacetime continuum in which we exist, together with all the energy and matter within it. Attempts to understand the Universe in this sense, on the largest possible scales, are made in cosmology, a science that has grown from physics and astronomy. During the second half of the 20th century, the development of observational cosmology, also called physical cosmology, led to a split in the meaning of the word Universe, between observational cosmologists and theoretical cosmologists; where the former (usually) abandon the hope of observing the whole spacetime continuum, the latter retain this hope, attempting to find the most reasonable speculations for modelling the whole of spacetime, despite the extreme difficulty in imagining any empirical constraints on these speculations and the risk of declining into metaphysics.