Editing Thomas Gold (section)

===Steady-state theory===
{{Main|Steady-state theory}}
Gold began discussing problems in physics with Hoyle and Bondi again, centering on the issues over [[redshift]] and [[Hubble's law]]. This led the three to all start questioning the [[Big Bang]] theory originally proposed by [[Georges Lemaître]] in 1931 and later advanced by [[George Gamow]], which suggested that the [[universe]] expanded from an extremely dense and hot state and continues to expand today. As recounted in a 1978 interview with physicist and historian [[Spencer R. Weart]], Gold believed that there was reason to think that the creation of matter was "done all the time and then none of the problems about fleeting moments arise. It can be just in a steady state with the expansion taking things apart as fast as new matter comes into being and condenses into new galaxies".<ref name="Burbidge6">{{Harvnb|Burbidge|Burbidge|2006|p=6}}.</ref>

Two papers were published in 1948 discussing the "[[steady-state theory]]" as an [[non-standard cosmology|alternative]] to the Big Bang: one by [[Hermann Bondi]] and Gold,<ref name=steady-bondi>{{cite journal |last1=Bondi |first1=Hermann |last2=Gold |first2=Thomas |title=The Steady-State Theory of the Expanding Universe |journal=Monthly Notices of the Royal Astronomical Society |volume=108 |date=1948 |issue=3 |page=252 |doi=10.1093/mnras/108.3.252 |bibcode=1948MNRAS.108..252B|doi-access=free }}</ref> the other by [[Fred Hoyle]].<ref name=steady-hoyle>{{cite journal |last=Hoyle |first=Fred |title=A New Model for the Expanding Universe |journal=Monthly Notices of the Royal Astronomical Society |volume=108 |date=1948 |issue=5 |page=372 |doi=10.1093/mnras/108.5.372 |bibcode=1948MNRAS.108..372H|doi-access=free }}</ref> In their seminal paper, Bondi and Gold asserted that although the universe is expanding, it nevertheless does not change its look over time; it has no beginning and no end.<ref name="Burbidge6"/><ref name="Silk">{{citation|last=Silk|first=Joseph|author-link=Joseph Silk|title=Fundamental Issues in Cosmology|url=http://cosmology.berkeley.edu/Education/Essays/cosprinc.html|publisher=[[University of California, Berkeley]]|date=September 5, 1994|access-date=June 17, 2009}}.</ref> They proposed the [[perfect cosmological principle]] as the underpinning of their theory, which held that the [[universe]] is [[homogeneity (physics)|homogeneous]] and [[isotropy|isotropic]] in space and time. On the large scale, they argued that there "is nothing outstanding about any place in the universe, and that those differences which do exist are only of local significance; that seen on a large scale the universe is homogeneous."<ref>{{Harvnb|Bondi|Gold|1948|pp=253–254}}.</ref> However, since the universe was not characterized by a lack of evolution, distinguishing features or recognizable direction of time, they postulated that there had to be large-scale motions in the universe. They highlighted two possible types of motion: large-scale expansion and its reverse, large-scale contraction.<ref>{{Harvnb|Bondi|Gold|1948|p=255}}.</ref> They estimated that within the expanding universe, [[hydrogen]] atoms were being created out of a [[vacuum]] at a rate of one atom per [[cubic meter]] per 10<sup>9</sup> years.<ref>{{Harvnb|Bondi|Gold|1948|p=256}}.</ref> This creation of matter would keep the density of the universe constant as it expanded. Gold and Bondi also stated that the issues with [[Age of the universe|time scale]] that had plagued other cosmological theories – such as the discrepancy between the age of the universe as calculated by Hubble and dating of radioactive decay in terrestrial rocks – were absent for the steady-state theory.<ref>{{Harvnb|Bondi|Gold|1948|p=262}}.</ref>

It was not until the 1960s that major problems with the steady-state theory began to emerge, when observations apparently supported the idea that the universe was in fact changing: [[quasar]]s and [[radio galaxy|radio galaxies]] were found only at large distances (therefore existing only in the distant past), not in closer galaxies. Whereas the Big Bang theory predicted as much, steady state predicted that such objects would be found everywhere, including close to our own galaxy, since evolution would be more evenly distributed, not observed only at great distances.<ref name="Silk"/> In addition, proponents of the theory predicted that in addition to hydrogen atoms, [[antimatter]] would also be produced, as with cosmic [[gamma rays|gamma ray background]] from the annihilation of [[proton]]s and [[antiproton]]s and [[X-ray]] emitting gas from the creation of [[neutron]]s.<ref name="Silk"/>

For most cosmologists, the refutation of the steady-state theory came with the discovery of the [[cosmic microwave background radiation]] in 1965, which was predicted by the Big Bang theory.<ref name="Burbidge7">{{Harvnb|Burbidge|Burbidge|2006|p=7}}.</ref> [[Stephen Hawking]] said that the fact that microwave radiation had been found, and that it was thought to be left over from the Big Bang, was "the final nail in the coffin of the steady-state theory."<ref>{{citation|last=Hawking|first=Stephen|author1-link=Stephen Hawking|contribution=Sixty years in a nutshell|title=The future of theoretical physics and cosmology|editor1-last=Gibbons|editor1-first=G. W. |editor2-last=Shellard|editor2-first=E. Paul S.|editor3-last=Rankin|editor3-first=Stuart J.|date=2003|publisher=[[Cambridge University Press]]|location=Cambridge|isbn=978-0-521-82081-3|page=109}}.</ref> Bondi conceded that the theory had been disproved, but Hoyle and Gold remained unconvinced for a number of years. Gold even supported Hoyle's modified steady-state theory; however, by 1998 he started to express some doubts about the theory, but maintained that despite its faults, the theory helped improve understanding regarding the origin of the universe.<ref name="Telegraph"/>