Earth's location in the universe

Knowledge of Earth's location in the universe has been shaped by 400 years of telescopic observations, and has expanded radically in the last century. Initially, Earth was believed to be the center of the universe, which consisted only of those planets visible with the naked eye and an outlying sphere of fixed stars.[1] After the acceptance of the heliocentric model in the 17th century, observations by William Herschel and others showed that the Sun lay within a vast, disc-shaped galaxy of stars.[2] By the 20th century, observations of spiral nebulae by Edwin Hubble revealed that our galaxy was one of billions in an expanding universe,[3][4] grouped into clusters and superclusters. By the end of the 20th century, the overall structure of the visible universe was becoming clearer, with superclusters forming into a vast web of filaments and voids.[5] Superclusters, filaments and voids are the largest coherent structures in the Universe that we can observe.[6] At still larger scales (over 1000 megaparsecs)[b] the Universe becomes homogeneous meaning that all its parts have on average the same density, composition and structure.[7]

Since there is believed to be no "center" or "edge" of the universe, there is no particular reference point with which to plot the overall location of the Earth in the universe.[8] Because the observable universe is defined as that region of the universe visible to terrestrial observers, Earth is, by definition, the center of the observable universe.[9] Reference can be made to the Earth's position with respect to specific structures, which exist at various scales. It is still undetermined whether the universe is infinite. There have been numerous hypotheses that our universe may be only one such example within a higher multiverse; however, no direct evidence of any sort of multiverse has ever been observed, and some have argued that the hypothesis is not falsifiable.[10][11]

Earth's location in the universe

A diagram of our location in the observable universe.
Feature Diameter Notes Sources
Earth 12,756.2 km
(equatorial) 		Measurement comprises just the solid part of the Earth; there is no agreed upper boundary for Earth's atmosphere.
Atmospheric hydrogen atoms have been detected as far as 100,000 km from Earth's surface.
The Kármán line, defined as the boundary of space for astronautics, lies at 100 km. 		[12][13][14][15]
Geospace 6,363,000–12,663,000 km
(110-210 Earth radii) 		The space dominated by Earth's magnetic field. Like a comet, its shape is pulled into a tail by the solar wind. [16]
Orbit of the Moon 768,210 km[a] The average diameter of the orbit of the Moon relative to the Earth. [17]
Earth's orbit 299.2 million km[a]
2 AU[b]		 The average diameter of the orbit of the Earth relative to the Sun.
Encompasses the Sun, Mercury and Venus. 		[18]
Inner Solar System ~6.54 AU Encompasses the Sun, the inner planets (Mercury, Venus, Earth, Mars) and the asteroid belt.
Cited distance is the 2:1 resonance with Jupiter, which marks the outer limit of the asteroid belt. 		[19][20][21]
Outer Solar System 60.14 AU[a] Includes the outer planets (Jupiter, Saturn, Uranus, Neptune).
Cited distance is the orbital diameter of Neptune. 		[22]
Kuiper belt ~96 AU Belt of icy objects surrounding the outer solar system. Encompasses the dwarf planets Pluto, Haumea and Makemake.
Cited distance is the 2:1 resonance with Neptune, generally regarded as the edge of the main Kuiper belt. 		[23]
Heliosphere 160 AU Maximum extent of the solar wind and the interplanetary medium. [24][25]
Scattered disk 200 AU Region of sparsely scattered icy objects surrounding the Kuiper belt. Encompasses the dwarf planet Eris. [26]
Oort cloud 100,000–200,000 AU
0.613–1.23 parsecs[c]		 Spherical shell of over a trillion (1012) comets. Existence is currently hypothetical, but inferred from the orbits of long-period comets. [27]
Solar System 1.23 parsecs The Sun and its planetary system. Cited diameter is that of the Sun's Hill sphere; the region of its gravitational influence. [28]
Local Interstellar Cloud 9.2 parsecs Interstellar cloud of gas through which the Sun and a number of other stars are currently travelling. [29]
Local Bubble 2.82–250 parsecs Cavity in the interstellar medium in which the Sun and a number of other stars are currently travelling.
Caused by a past supernova. 		[30][31]
Gould Belt 1,000 parsecs Ring of young stars through which the Sun is currently travelling. [32]
Orion Arm 3000 parsecs
(length)		The spiral arm of the Milky Way Galaxy through which the Sun is currently travelling.
 [33]
Orbit of the Solar System 17,200 parsecs The average diameter of the orbit of the Solar System relative to the Galactic Center.
The Sun's orbital radius is roughly 8,600 parsecs, or slightly over half way to the galactic edge.
One orbital period of the Solar System lasts between 225 and 250 million years. 		[34][35]
Milky Way Galaxy 30,000 parsecs Our home galaxy, composed of 200 billion to 400 billion stars and filled with the interstellar medium. [36][37]
Milky Way subgroup 840,500 parsecs The Milky Way and those satellite dwarf galaxies gravitationally bound to it.
Examples include the Sagittarius Dwarf, the Ursa Minor Dwarf and the Canis Major Dwarf.
Cited distance is the orbital diameter of the Leo T Dwarf galaxy, the most distant galaxy in the Milky Way subgroup. 		[38]
Local Group 3 megaparsecs[c] Group of at least 47 galaxies of which the Milky Way is a part.
Dominated by Andromeda (the largest), the Milky Way and Triangulum; the remainder are dwarf galaxies.		 [39]
Local Sheet 7 megaparsecs Group of galaxies including the Local Group moving at the same relative velocity towards the Virgo Cluster and away from the Local Void. [40][41]
Virgo Supercluster 30 megaparsecs The supercluster of which our Local Group is a part.
It comprises roughly 100 galaxy groups and clusters, centred on the Virgo Cluster.
Our Local Group is located on the outer edge of the Virgo Supercluster. 		[42][43]
Laniakea 160 megaparsecs A group connected with the superclusters of which our Local Group is a part.
Comprises roughly 300 to 500 galaxy groups and clusters, centred on the Great Attractor in the Hydra-Centaurus Supercluster. 		[44][45][46][47]
Observable universe 28,000 megaparsecs More than 100 billion galaxies, arranged in millions of superclusters, galactic filaments, and voids, creating a foam-like superstructure. [48][49]
Universe Minimum of 28,000 megaparsecs Beyond the observable universe lie the unobservable regions from which no light has reached the Earth yet.
No information is available, as light is the fastest travelling medium of information.
However, uniformitarianism argues that the universe is likely to contain more galaxies in the same foam-like superstructure. 		[50]
a Semi-major and semi-minor axes
b 1 AU or astronomical unit is the distance between the Earth and the Sun, or 150 million km. Earth's orbital diameter is twice its orbital radius, or 2 AU.
c A parsec is the distance at which a star's parallax as viewed from Earth is equal to one second of arc, equal to roughly 206,000 AU or 308,570,000 km.
One megaparsec is equivalent to one million parsecs.

See also

References

  1. ↑ Kuhn, Thomas S. (1957). The Copernican Revolution. Harvard University Press. pp. 5–20. ISBN 0-674-17103-9.
  2. ↑ "1781: William Herschel Reveals the Shape of our Galaxy". Carnegie Institution for Science. Retrieved 19 March 2014.
  3. ↑ "The Spiral Nebulae and the Great Debate". Eberly College of Science. Retrieved 22 April 2015.
  4. ↑ "1929: Edwin Hubble Discovers the Universe is Expanding". Carnegie Institution for Science. Retrieved 22 April 2015.
  5. ↑ "1989: Margaret Geller and John Huchra Map the Universe". Carnegie Institution for Science. Retrieved 22 April 2015.
  6. ↑ John Carl Villanueva (2009). "Structure of the Universe". Universe Today. Retrieved 22 April 2015.
  7. ↑ Robert P Kirshner (2002). The Extravagant Universe: Exploding Stars, Dark Energy and the Accelerating Cosmos. Princeton University Press. p. 71. ISBN 0-691-05862-8.
  8. ↑ Klaus Mainzer and J Eisinger (2002). The Little Book of Time. Springer. ISBN 0-387-95288-8.. P. 55.
  9. ↑ Andrew R. Liddle; David Hilary Lyth (13 April 2000). Cosmological inflation and large-scale structure. Cambridge University Press. pp. 24–. ISBN 978-0-521-57598-0. Retrieved 1 May 2011.
  10. ↑ Clara Moskowitz (2012). "5 Reasons We May Live in a Multiverse". space.com. Retrieved 29 April 2015.
  11. ↑ Kragh, H. (2009). "Contemporary History of Cosmology and the Controversy over the Multiverse". Annals of Science 66 (4): 529. doi:10.1080/00033790903047725.
  12. ↑ "Selected Astronomical Constants, 2011". The Astronomical Almanac. Archived from the original on 26 August 2013. Retrieved 25 February 2011.
  13. ↑ World Geodetic System (WGS-84). Available online from National Geospatial-Intelligence Agency Retrieved 27 April 2015.
  14. ↑ "Exosphere — overview". University Corporation for Atmospheric Research. 2011. Retrieved 28 April 2015.
  15. ↑ Dr. S. Sanz Fernández de Córdoba (2004-06-24). "The 100 km Boundary for Astronautics". Fédération Aéronautique Internationale. Retrieved 2014-05-07.
  16. ↑ Koskinen, Hannu (2010), Physics of Space Storms: From the Surface of the Sun to the Earth, Environmental Sciences Series, Springer, ISBN 3-642-00310-9
  17. ↑ NASA Moon Factsheet and NASA Solar System Exploration Moon Factsheet NASA Retrieved on 17 November 2008
  18. ↑ NASA Earth factsheet and NASA Solar System Exploration Earth Factsheet NASA Retrieved on 17 November 2008
  19. ↑ Petit, J.-M.; Morbidelli, A.; Chambers, J. (2001). "The Primordial Excitation and Clearing of the Asteroid Belt" (PDF). Icarus 153 (2): 338–347. Bibcode:2001Icar..153..338P. doi:10.1006/icar.2001.6702. Retrieved 22 March 2007.
  20. ↑ Roig, F., Nesvorný, D., & Ferraz-Mello, S. (2002). "Asteroids in the 2 : 1 resonance with Jupiter: dynamics and size distribution". Monthly Notices of the Royal Astronomical Society 335 (2): 417-431.
  21. ↑ M. Broˇz, D. Vokrouhlick´y, F. Roig, D. Nesvorn´y, W. F. Bottke and A. Morbidelli (2005). "Yarkovsky origin of the unstable asteroids in the 2/1 mean motionresonance with Jupiter". Monthly Notices Royal Astronomical Society 359: 1437–1455.
  22. ↑ NASA Neptune factsheet and NASA Solar System Exploration Neptune Factsheet NASA Retrieved on 17 November 2008
  23. ↑ M. C. De Sanctis, M. T. Capria, and A. Coradini (2001). "Thermal Evolution and Differentiation of Edgeworth–Kuiper Belt Objects". The Astronomical Journal 121 (5): 2792–2799. Bibcode:2001AJ....121.2792D. doi:10.1086/320385. Retrieved 28 August 2008.
  24. ↑ NASA/JPL (2009). "Cassini's Big Sky: The View from the Center of Our Solar System". Retrieved 20 December 2009.
  25. ↑ Fahr, H. J.; Kausch, T.; Scherer, H.; Kausch; Scherer (2000). "A 5-fluid hydrodynamic approach to model the Solar System-interstellar medium interaction" (PDF). Astronomy & Astrophysics 357: 268. Bibcode:2000A&A...357..268F. See Figures 1 and 2.
  26. ↑ "JPL Small-Body Database Browser: 136199 Eris (2003 UB313)" (2008-10-04 last obs). Retrieved 21 January 2009. (Aphelion of Eris, the farthest known scattered disk object)
  27. ↑ Alessandro Morbidelli (2005). "Origin and dynamical evolution of comets and their reservoir". arXiv:astro-ph/0512256 [astro-ph].
  28. ↑ Littmann, Mark (2004). Planets Beyond: Discovering the Outer Solar System. Courier Dover Publications. pp. 162–163. ISBN 978-0-486-43602-9.
  29. ↑ Mark Anderson, "Don't stop till you get to the Fluff", New Scientist no. 2585, 6 January 2007, pp. 26–30
  30. ↑ DM Seifr; Lallement; Crifo; Welsh et al. (1999). "Mapping the Countours of the Local Bubble". Astronomy and Astrophysics 346: 785–797. Bibcode:1999A&A...346..785S.
  31. ↑ Dr. Tony Phillips (2014). "Evidence for Supernovas Near Earth". NASA. Retrieved 2015-04-30.
  32. ↑ S. B. Popov, M. Colpi, M. E. Prokhorov, A. Treves and R. Turolla (2003). "Young isolated neutron stars from the Gould Belt". Astronomy and Astrophysics 406 (1): 111–117. arXiv:astro-ph/0304141. Bibcode:2003A&A...406..111P. doi:10.1051/0004-6361:20030680. Retrieved 2 October 2009.
  33. ↑ Harold Spencer Jones, T. H. Huxley, Proceedings of the Royal Institution of Great Britain, Royal Institution of Great Britain, v. 38–39
  34. ↑ Eisenhauer, F.; Schoedel, R.; Genzel, R.; Ott, T.; Tecza, M.; Abuter, R.; Eckart, A.; Alexander, T. (2003). "A Geometric Determination of the Distance to the Galactic Center". Astrophysical Journal 597 (2): L121–L124. arXiv:astro-ph/0306220. Bibcode:2003ApJ...597L.121E. doi:10.1086/380188.
  35. ↑ Leong, Stacy (2002). "Period of the Sun's Orbit around the Galaxy (Cosmic Year)". The Physics Factbook.
  36. ↑ Christian, Eric; Samar, Safi-Harb. "How large is the Milky Way?". Retrieved 28 November 2007.
  37. ↑ Frommert, H.; Kronberg, C. (25 August 2005). "The Milky Way Galaxy". SEDS. Retrieved 9 May 2007.
  38. ↑ Irwin, V.; Belokurov, V.; Evans, N. W. et al. (2007). "Discovery of an Unusual Dwarf Galaxy in the Outskirts of the Milky Way". The Astrophysical Journal 656 (1): L13–L16. arXiv:astro-ph/0701154. Bibcode:2007ApJ...656L..13I. doi:10.1086/512183.
  39. ↑ "The Local Group of Galaxies". University of Arizona. Students for the Exploration and Development of Space. Retrieved 2 October 2009.
  40. ↑ Tully, R. Brent; Shaya, Edward J.; Karachentsev, Igor D.; Courtois, Hélène M.; Kocevski, Dale D.; Rizzi, Luca; Peel, Alan (March 2008). "Our Peculiar Motion Away from the Local Void". The Astrophysical Journal 676 (1): 184–205. arXiv:0705.4139. Bibcode:2008ApJ...676..184T. doi:10.1086/527428.
  41. ↑ Tully, R. Brent (May 2008), "The Local Void is Really Empty", Dark Galaxies and Lost Baryons, Proceedings of the International Astronomical Union, IAU Symposium 244, pp. 146–151, arXiv:0708.0864, Bibcode:2008IAUS..244..146T, doi:10.1017/S1743921307013932
  42. ↑ R. Brent Tully (1982). "The Local Supercluster" (PDF). The Astrophysical Journal 257: 389–422. Retrieved 27 April 2015.
  43. ↑ "Galaxies, Clusters, and Superclusters". NOVA Online. Retrieved 27 April 2015.
  44. ↑ "Newly identified galactic supercluster is home to the Milky Way". National Radio Astronomy Observatory (ScienceDaily). 3 September 2014.
  45. ↑ Irene Klotz (3 September 2014). "New map shows Milky Way lives in Laniakea galaxy complex". Reuters. ScienceDaily.
  46. ↑ Elizabeth Gibney (3 September 2014). "Earth's new address: 'Solar System, Milky Way, Laniakea'". Nature. doi:10.1038/nature.2014.15819.
  47. ↑ Camille M. Carlisle (3 September 2014). "Laniakea: Our Home Supercluster". Sky and Telescope.
  48. ↑ Mackie, Glen (1 February 2002). "To see the Universe in a Grain of Taranaki Sand". Swinburne University. Retrieved 20 December 2006.
  49. ↑ Lineweaver, Charles; Tamara M. Davis (2005). "Misconceptions about the Big Bang". Scientific American. Retrieved 6 November 2008.
  50. ↑ Margalef-Bentabol, Berta; Margalef-Bentabol, Juan; Cepa, Jordi (8 February 2013). "Evolution of the cosmological horizons in a universe with countably infinitely many state equations". Journal of Cosmology and Astroparticle Physics. 015 2013 (02). arXiv:1302.2186. Bibcode:2013JCAP...02..015M. doi:10.1088/1475-7516/2013/02/015.