This story need part two. The Universe is all of time and space. This includes planets, holes, stars, galaxies, the contents of intergalactic space, the smallest subatomic particles, and all matter and energy, the majority of which are most likely in the form of dark matter and dark energy. The part of the Universe that we can see, referred to as the observable universe, is about 28 billion parsecs (91 billion lightyears) in diameter at the present time. The size of the whole universe is not known and may be infinite. Scientific observation of the Universe has led to inferences about its evolution. These observations suggest that the Universe has been governed by the same physical laws and constants throughout most of its extent and for all time. The Big Bang theory is the prevailing cosmological model that describes the development of the Universe. Assuming that the prevailing model is correct, the age of the Universe is measured to be 13.798 s´ 0.037 billion years. Space in the Universe is expanding, and the rate of its expansion is increasing.