Editing Black body (section)

== Definition ==
[[Isaac Newton]] introduced the notion of a black body in his 1704 book ''[[Opticks]]'', with query 6 of the book stating:<ref>{{Cite book |last=Bochner |first=Salomon |url=https://books.google.com/books?id=naH_AwAAQBAJ&pg=PA221 |title=Role of Mathematics in the Rise of Science |date=1981 |publisher=Princeton Univ. Pr |isbn=978-0-691-08028-4 |edition= |location=Princeton, NJ |pages=221, 347 |language=en}}</ref><ref>{{Cite book |last=Rowlands |first=Peter |url=https://books.google.com/books?id=u0NBDwAAQBAJ&pg=PA69 |title=Newton - Innovation And Controversy |publisher=[[World Scientific Publishing]] |year=2017 |isbn=9781786344045 |pages=69 |language=en}}</ref>{{blockquote|Do not black Bodies conceive heat more easily from Light than those of other Colours do, by reason that the Light falling on them is not reflected outwards, but enters into the Bodies, and is often reflected and refracted within them, until it be stifled and lost?}}The idea of a black body originally was introduced by [[Gustav Kirchhoff]] in 1860 as follows:
{{blockquote|...the supposition that bodies can be imagined which, for infinitely small thicknesses, completely absorb all incident rays, and neither reflect nor transmit any. I shall call such bodies ''perfectly black'', or, more briefly, ''black bodies''.<ref name=Kirchhoff/>}}

A more modern definition drops the reference to "infinitely small thicknesses":<ref name=infinitesimal/>
{{blockquote|An ideal body is now defined, called a ''blackbody''. A ''blackbody'' allows ''all'' incident radiation to pass into it (no reflected energy) and internally absorbs ''all'' the incident radiation (no energy transmitted through the body). This is true for radiation of all wavelengths and for all angles of incidence. Hence the blackbody is ''a perfect absorber for all incident radiation.''<ref name=Siegel/>}}