totality o planets, starns, galaxies, intergalactic space, an aw matter an energy

The Universe is commonly defined as the totality o existence,[1][2][3][4] includin planets, starns, galaxies, the contents o intergalactic space, the smawest subatomic pairticles, an aw matter an energy.[5][6] Similar terms include the cosmos, the warld, reality, an naitur.

The earliest scienteefic models o the Universe war developit bi auncient Greek an Indie filosofers an war geocentric, placin Yird at the centre o the Universe.[7][8] Ower the centuries, mair precise astronomical observations led Nicolaus Copernicus (1473–1543) tae develop the heliocentric model wi the Sun at the centre o the Solar Seestem. In developin the law o universal gravitation, Sir Isaac Newton (NS: 1643–1727) biggit upon Copernicus's wark as well as observations bi Tycho Brahe (1546–1601) an Johannes Kepler's (1571–1630) laws o planetary motion.

Faur observational impruivements led tae the realisation that oor Solar Seestem is locatit in the Milky Way galaxy, which is ane o mony galaxies in the Universe. It is assumed that galaxies are distributit uniformly an the same in aw directions, meaningthat the Universe haes neither an edge nor a centre. Discoveries in the early 20t century hae suggestit that the Universe haed a beginnin an that it is expandin[9] at an increasin rate.[10] The majority o mass in the Universe appears tae exeest in an unkent form cried dark matter.

The Big Bang theory is the prevailin cosmological description o the development o the Universe. Unner this theory, space an time emerged thegither 13.799±0.021 billion years ago[11] wi a fixed amoont o energy an matter that haes acome less dense as the Universe haes expandit. Efter the ineetial expansion, the Universe cuiled, allaein the first subatomic particles tae form an then semple atoms. Giant cloods later merged throu gravity tae form galaxies, starns, an everything ense seen the day.

Thare are mony competin hypotheses aboot the ultimate fate o the Universe an aboot what, if onything, precedit the Big Bang, while ither pheesicists an filosofers refuise tae speculate, doubtin that information aboot prior states will ever be accessible. Some pheesicists hae suggestit various multiverse hypotheses, in which the Universe micht be ane amang mony universes that likwise exeest.[12][13]


  1. Universe. Webster's New World College Dictionary, Wiley Publishing, Inc. 2010.
  2. "Universe". Encyclopedia Britannica. the whole cosmic system of matter and energy of which Earth, and therefore the human race, is a part
  3. "Universe". Dictionary.com. Retrieved 21 September 2012.
  4. "Universe". Merriam-Webster Dictionary. Retrieved 21 September 2012.
  5. The American Heritage Dictionary of the English Language (4th ed.). Houghton Mifflin Harcourt Publishing Company. 2010.
  6. Cambridge Advanced Learner's Dictionary.
  7. Dold-Samplonius, Yvonne (2002). From China to Paris: 2000 Years Transmission of Mathematical Ideas. Franz Steiner Verlag.
  8. Thomas F. Glick; Steven Livesey; Faith Wallis. Medieval Science Technology and Medicine: An Encyclopedia. Routledge.
  9. Hawking, Stephen (1988). A Brief History of Time. Bantam Books. p. 125. ISBN 0-553-05340-X.
  10. "The Nobel Prize in Physics 2011". Retrieved 16 Apryle 2015.
  11. Planck Collaboration (2015). "Planck 2015 results. XIII. Cosmological parameters (See Table 4 on page 31 of pfd)". Astronomy & Astrophysics. 594: A13. arXiv:1502.01589. Bibcode:2016A&A...594A..13P. doi:10.1051/0004-6361/201525830.
  12. Ellis, George F.R.; U. Kirchner; W.R. Stoeger (2004). "Multiverses and physical cosmology". Monthly Notices of the Royal Astronomical Society. 347 (3): 921–936. arXiv:astro-ph/0305292. Bibcode:2004MNRAS.347..921E. doi:10.1111/j.1365-2966.2004.07261.x.
  13. Palmer, Jason. (2011-08-03) BBC News – 'Multiverse' theory suggested by microwave background. Retrieved 2011-11-28.