Ernest Rutherford: Difference between revisions - Wikipedia

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In 1903, Rutherford considered a type of radiation discovered (but not named) by French chemist [[Paul Villard]] in 1900, as an emission from [[radium]], and realised that this observation must represent something different from his own alpha and beta rays, due to its very much greater penetrating power. Rutherford therefore gave this third type of radiation the name of [[gamma ray]]. All three of Rutherford's terms are in standard use today – other types of [[radioactive decay]] have since been discovered, but Rutherford's three types are among the most common.

In 1904, Rutherford suggested that radioactivity provides a source of energy sufficient to explain the existence of the Sun for the many millions of years required for the slow biological evolution on Earth proposed by biologists such as [[Charles Darwin]]. The physicist Lord Kelvin had argued earlier for a much younger Earth (see also [[William Thomson, 1st Baron Kelvin#Age of the Earth: |geology]]) based on the insufficiency of known energy sources, but Rutherford pointed out at a lecture attended by Kelvin that radioactivity could solve this problem.<ref name="England et al 2007">{{cite journal |author1=England, P. |author2=Molnar, P. |author3=Righter, F. | title=John Perry's neglected critique of Kelvin's age for the Earth: A missed opportunity in geodynamics |journal=GSA Today |date=January 2007 |volume=17 |issue=1 |pages=4–9 |doi=10.1130/GSAT01701A.1 |doi-access= free}}</ref>

In Manchester, he continued to work with alpha radiation. In conjunction with [[Hans Geiger]], he developed zinc sulfide [[zinc sulfide|scintillation screens]] and [[ionisation chamber]]s to count alphas. By dividing the total charge they produced by the number counted, Rutherford decided that the charge on the alpha was two. In late 1907, Ernest Rutherford and [[Thomas Royds]] allowed alphas to penetrate a very thin window into an evacuated tube. As they [[atomic emission spectroscopy|sparked the tube into discharge]], the spectrum obtained from it changed, as the alphas accumulated in the tube. Eventually, the clear spectrum of helium gas appeared, proving that alphas were at least ionised helium atoms, and probably helium nuclei.