Editing History of physics (section)

===Radiation experiments===
[[File:J.J Thomson.jpg|thumb|upright|[[J.J. Thomson]] (1856–1940), discoverer of [[electron]] and [[Isotope|isotopy]], and inventor of [[mass spectrometer]], received 1906 [[Nobel Prize in Physics]].]]
In the 19th century, experimenters began to detect unexpected forms of radiation: [[Wilhelm Röntgen]] caused a sensation with his discovery of [[X-ray]]s in 1895; in 1896 [[Henri Becquerel]] discovered that certain kinds of matter emit radiation on their own accord. In 1897, [[J. J. Thomson]] discovered the [[electron]], and new radioactive elements found by [[Marie Curie|Marie]] and [[Pierre Curie]] raised questions about the supposedly indestructible atom and the nature of matter. Marie and Pierre coined the term "[[radioactive decay|radioactivity]]" to describe this property of matter, and isolated the radioactive elements [[radium]] and [[polonium]]. [[Ernest Rutherford]] and [[Frederick Soddy]] identified two of Becquerel's forms of radiation with electrons and the element [[helium]]. Rutherford identified and named two types of radioactivity and in 1911 interpreted experimental evidence as showing that the atom consists of a dense, positively charged nucleus surrounded by negatively charged electrons. Classical theory, however, predicted that this structure should be unstable. Classical theory had also failed to explain successfully two other experimental results that appeared in the late 19th century. One of these was the demonstration by [[Albert A. Michelson]] and [[Edward W. Morley]]&nbsp;– known as the [[Michelson–Morley experiment]]&nbsp;– which showed there did not seem to be a [[preferred frame]] of reference, at rest with respect to the hypothetical [[luminiferous ether]], for describing electromagnetic phenomena. Studies of radiation and radioactive decay continued to be a preeminent focus for physical and chemical research through the 1930s, when the [[discovery of nuclear fission]] by [[Lise Meitner]] and [[Otto Frisch]] opened the way to the practical exploitation of what came to be called [[Nuclear power|"atomic" energy]].