Location of Earth explained

Knowledge of the location of Earth has been shaped by 400 years of telescopic observations, and has expanded radically since the start of the 20th 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 revealed that the Milky Way 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) 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, because of the constancy of the speed of light, the center of Earth's observable universe. 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 the known universe may be only one such example within a higher multiverse; however, no direct evidence of any sort of multiverse has been observed, and some have argued that the hypothesis is not falsifiable.[9] [10]

Details

Earth is the third planet from the Sun with an approximate distance of 149.6e6km, and is traveling nearly 1.3abbr=offNaNabbr=off through outer space.[11]

Table

Feature Diameter Notes Sources
(most suitable unit)(km, with scientific notation) (km, as a power of 10, Logarithmic scale)
Earth12,756.2 km
(equatorial)
1.28×1044.11Measurement comprises just the solid part of the Earth; there is no agreed upper boundary for Earth's atmosphere.
The geocorona, a layer of UV-luminescent hydrogen atoms, lies at 100,000 km.
The Kármán line, defined as the boundary of space for astronautics, lies at 100 km.
[12] [13] [14] [15]
Orbit of the Moon768,210 km7.68×1055.89The average diameter of the orbit of the Moon relative to the Earth. [16]
Geospace6,363,000–12,663,000 km
(110–210 Earth radii)
6.36×106–1.27×1076.80–7.10The space dominated by Earth's magnetic field and its magnetotail, shaped by the solar wind.
Earth's orbit299.2 million km
AU
2.99×1088.48The average diameter of the orbit of the Earth relative to the Sun.
Encompasses the Sun, Mercury and Venus.
[17]
Inner Solar System~6.54 AU 9.78×1088.99Encompasses 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.
[18] [19] [20]
Outer Solar System60.14 AU 9.00×1099.95Includes the outer planets (Jupiter, Saturn, Uranus, Neptune).
Cited distance is the orbital diameter of Neptune.
[21]
Kuiper belt~96 AU 1.44×101010.16Belt 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 outer edge of the main Kuiper belt.
[22]
Heliosphere160 AU2.39×101010.38Maximum extent of the solar wind and the interplanetary medium. [23] [24]
Scattered disc195.3 AU2.92×101010.47Region of sparsely scattered icy objects surrounding the Kuiper belt. Encompasses the dwarf planet Eris.
Cited distance is derived by doubling the aphelion of Eris, the farthest known scattered disc object.
As of now, Eris's aphelion marks the farthest known point in the scattered disc.
[25]
Oort cloud100,000–200,000 AU
0.613–1.23 pc
1.89×1013–3.80×101313.28–13.58Spherical shell of over a trillion (1012) comets. Existence is currently hypothetical, but inferred from the orbits of long-period comets. [26]
Solar System1.23 pc 3.80×101313.58The Sun and its planetary system. Cited diameter is that of the Sun's Hill sphere; the region of its gravitational influence. [27]
Local Interstellar Cloud9.2 pc 2.84×101414.45Interstellar cloud of gas through which the Sun and a number of other stars are currently travelling. [28]
Local Bubble2.82–250 pc 8.70×1013–7.71×101513.94–15.89Cavity in the interstellar medium in which the Sun and a number of other stars are currently travelling.
Caused by a past supernova.
[29] [30]
Gould Belt1,000 pc 3.09×101616.49Projection effect of the Radcliffe wave and Split linear structures (Gould Belt),[31] between which the Sun is currently travelling.[32]
Orion Arm3000 pc
(length)
9.26×101616.97The spiral arm of the Milky Way Galaxy through which the Sun is currently travelling.
Orbit of the Solar System17,200 pc5.31×101717.72The 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 halfway to the galactic edge.
One orbital period of the Solar System lasts between 225 and 250 million years.
[33] [34]
Milky Way Galaxy30,000 pc 9.26×101717.97Our home galaxy, composed of 200 billion to 400 billion stars and filled with the interstellar medium. [35] [36]
Milky Way subgroup840,500 pc 2.59×101919.41The 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. Currently 59 satellite galaxies are part of the subgroup.
[37]
Local Group3 Mpc9.26×101919.97Group of at least 80 galaxies of which the Milky Way is a part.
Dominated by Andromeda (the largest), the Milky Way and Triangulum; the remainder are dwarf galaxies.
[38]
Local Sheet7 Mpc2.16×102020.33Group of galaxies including the Local Group moving at the same relative velocity towards the Virgo Cluster and away from the Local Void. [39] [40]
Virgo Supercluster30 Mpc 9.26×102020.97The supercluster of which the Local Group is a part.
It comprises roughly 100 galaxy groups and clusters, centred on the Virgo Cluster.
The Local Group is located on the outer edge of the Virgo Supercluster.
[41] [42]
Laniakea Supercluster160 Mpc 4.94×102121.69A group connected with the superclusters of which the Local Group is a part.
Comprises roughly 300 to 500 galaxy groups and clusters, centred on the Great Attractor in the Hydra–Centaurus Supercluster.
[43] [44] [45] [46]
Pisces–Cetus Supercluster Complex 330 Mpc1×102221.98Galaxy filament that includes the Pisces-Cetus Superclusters, Perseus–Pisces Supercluster, Sculptor Supercluster and associated smaller filamentary chains. [47] [48]
Observable Universe28,500 Mpc 8.79×102323.94At least 2 trillion galaxies in the observable universe, arranged in millions of superclusters, galactic filaments, and voids, creating a foam-like superstructure. [49] [50] [51] [52]
Universe Minimum 28,500 Mpc
(possibly infinite)
Minimum 8.79×1023Minimum 23.94Beyond the observable universe lie the unobservable regions from which no light has yet reached the Earth.
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.
[53]

Gallery

See also

Notes and References

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    NOTE: Estimated velocity of the Earth traveling through outer space may be between NaNabbr=offNaNabbr=off – see discussion at ""
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