Editing Cosmic microwave background (section)

===Early speculations===
In 1931, [[Georges Lemaître]] speculated that remnants of the early universe may be observable as radiation, but his candidate was [[cosmic rays]].<ref name=PeeblesPrinciples/>{{rp|140}} [[Richard C. Tolman]] showed in 1934 that expansion of the universe would cool blackbody radiation while maintaining a thermal spectrum.
The cosmic microwave background was first predicted in 1948 by [[Ralph Alpher]] and [[Robert Herman]], in a correction<ref>
{{cite journal|last1=Alpher|first1=R. A.|last2=Herman|first2=R. C.|s2cid=4113488|date=1948|title=Evolution of the Universe|journal=[[Nature (journal)|Nature]]|volume=162|issue=4124|pages=774–775|doi=10.1038/162774b0|bibcode=1948Natur.162..774A}}</ref> they prepared for a paper by Alpher's PhD advisor [[George Gamow]].<ref>
{{cite journal|last=Gamow|first=G.|s2cid=4793163|date=1948|title=The evolution of the universe|journal=[[Nature (journal)|Nature]]|volume=162|pages=680–682|doi=10.1038/162680a0|pmid=18893719|bibcode = 1948Natur.162..680G|issue=4122}}</ref> Alpher and Herman were able to estimate the temperature of the cosmic microwave background to be 5&nbsp;K.<ref>
{{cite journal|last1=Assis|first1=A. K. T.|last2=Neves|first2=M. C. D.|date=1995|title=History of the 2.7&nbsp;K Temperature Prior to Penzias and Wilson|url=http://www.ifi.unicamp.br/~assis/Apeiron-V2-p79-84(1995).pdf|issue=3|pages=79–87 |periodical=Apeiron }}</ref>