Redshift: Difference between revisions

The history of the subject began with the development in the 19th century, with the development of classical [[wave]] mechanics and the exploration of phenomena which are associated with the [[Doppler effect]]. The effect is named after the [[Austria|Austrian]] mathematician, [[Christian Doppler]], who offered the first known physical explanation for the phenomenon in 1842.<ref>

}}</ref> TheIn 1845, the hypothesis was tested and confirmed for [[sound wave]]s by the [[Netherlands|Dutch]] scientist [[C. H. D. Buys Ballot|Christophorus Buys Ballot]] in 1845.<ref>

}}</ref> Doppler correctly predicted that the phenomenon shouldwould apply to all waves, and, in particular, suggested that the varying [[color]]s of [[star]]s could be attributed to their motion with respect to the Earth.<ref>

The first Doppler redshift was first described by French physicist [[Hippolyte Fizeau]] in 1848, who pointed tonoted the shift in [[spectral line]]s seen in stars as being due to the Doppler effect. The effect is sometimes called the "Doppler–Fizeau effect". In 1868, British astronomer [[William Huggins]] was the first to determine the velocity of a star moving away from the Earth by thisthe method.<ref name=Huggins>

}}</ref> In 1871, optical redshift was confirmed when the phenomenon was observed in [[Fraunhofer lines]], using solar rotation, about 0.1 Å in the red.<ref>

}}</ref> In 1887, Vogel and Scheiner discovered the ''"annual Doppler effect''", the yearly change in the Doppler shift of stars located near the ecliptic, due to the orbital velocity of the Earth.<ref>{{cite book|last=Pannekoek|first=A.|title=A History of Astronomy |date=1961|publisher=Dover|page=451|isbn=978-0-486-65994-7}}</ref> In 1901, [[Aristarkh Belopolsky]] verified optical redshift in the laboratory using a system of rotating mirrors.<ref>

[[Arthur Eddington]] used the term ''"red -shift''" as early as 1923.,<ref>{{Cite book |last=Eddington |first=Arthur Stanley |url=https://books.google.com/books?id=errkj2WXGzIC&pg=PA164 |title=The Mathematical Theory of Relativity |date=1923 |publisher=The University Press |page=164 |language=en |author-link=Arthur Eddington}}</ref><ref>{{Cite OED|term=redshift|id=160477|access-date=2023-03-17}}</ref> Thealthough the word does not appear unhyphenated until about 1934, bywhen [[Willem de Sitter]] used it.<ref>

Beginning with observations in 1912, [[Vesto Slipher]] discovered that most [[Spiralspiral galaxy|spiral galaxies]], then mostly thought to be [[Spiral galaxy#Spiral nebula|spiral nebulae]], had considerable redshifts. Slipher first reportsreported on his measurement in the inaugural volume of the ''[[Lowell Observatory]] Bulletin''.<ref>

}}</ref> In it he statesstated that "the early discovery that the great Andromeda spiral had the quite exceptional velocity of –300 km(/s) showed the means then available, capable of investigating not only the spectra of the spirals but their velocities as well."<ref>

Slipher reported the velocities for 15 spiral nebulae spread across the entire [[celestial sphere]], all but three having observable "positive" (that is recessional) velocities. Subsequently, [[Edwin Hubble]] discovered an approximate relationship between the redshifts of such "nebulae", and the [[distance]]s to them, with the formulation of his eponymous [[Hubble's law]].<ref>

}}</ref> [[Milton Humason]] worked on thesethose observations with Hubble.<ref>{{Cite web|url=https://imagine.gsfc.nasa.gov/educators/programs/cosmictimes/online_edition/1929/expanding.html|title=Universe is Expanding|date=2017-12-08|access-date=2023-09-06}}</ref> These observations corroborated [[Alexander Friedmann]]'s 1922 work, in which he derived the [[Friedmann equations|Friedmann–Lemaître equations]].<ref>{{cite journal

}} English translation in {{cite journal |title=On the Curvature of Space|doi=10.1023/A:1026751225741 |last=Friedman |first=A. |date=1999 |journal=[[General Relativity and Gravitation]] |volume=31 |issue=12 |pages=1991–2000 |bibcode=1999GReGr..31.1991F|s2cid=122950995 }})</ref> InThey theare presentnow dayconsidered theyto are consideredbe strong evidence for an [[expanding universe]] and the [[Big Bang]] theory.<ref name=Eddington>This was recognized early on by physicists and astronomers working in cosmology in the 1930s. The earliest layman publication describing the details of this correspondence is {{cite book