Editing Scientific theory (section)

===Example: Relativity===

In 1905, [[Albert Einstein]] published the theory of [[special relativity]].<ref>[[Albert Einstein]] (1905) "[http://www.pro-physik.de/Phy/pdfs/ger_890_921.pdf ''Zur Elektrodynamik bewegter Körper''] {{webarchive|url=https://web.archive.org/web/20091229162203/http://www.pro-physik.de/Phy/pdfs/ger_890_921.pdf |date=2009-12-29 }}", ''Annalen der Physik'' 17: 891; English translation [http://www.fourmilab.ch/etexts/einstein/specrel/www/ On the Electrodynamics of Moving Bodies] by [[George Barker Jeffery]] and Wilfrid Perrett (1923); Another English translation [[s:On the Electrodynamics of Moving Bodies|On the Electrodynamics of Moving Bodies]] by [[Megh Nad Saha]] (1920).</ref>
He started with a principle known for three hundred years, since the time of [[Galileo Galilei]]: the principle of relativity and a prediction from a well established theory for electromagnetism known as [[Maxwell's equations]], the prediction that the speed of light in a vacuum does not depend on relative motion of the source and receiver. Einstein proposed, or hypothesized, that the concept of [[Galilean relativity]] should be modified to align mechanical physics with electromagnetism.<ref name=Weinberg-1972>{{cite book |last=Weinberg |first=Steven |url=https://archive.org/details/gravitationcosmo00stev_0 |title=Gravitation and cosmology |date=1972 |publisher=John Wiley & Sons |isbn=9780471925675 |author-link=Steven Weinberg |url-access=registration}}.</ref>{{rp|17}} In addition to unifying two branches of physics, this modification lead to specific consequences such as  [[time dilation]] and [[length contraction]]. Careful, repeated experiments have both confirmed Einstein's postulates are valid and that the predictions of the special theory of relativity match experiement.<ref>Will, C. M. (2005). Special relativity: a centenary perspective. In Einstein, 1905–2005: Poincaré Seminar 2005 (pp. 33-58). Basel: Birkhäuser Basel.</ref> 

Einstein next sought to generalize the invariance principle to all reference frames, whether inertial or accelerating.<ref name=Torrettipp289-90/> Rejecting Newtonian gravitation—a [[central force]] [[action at a distance|acting instantly at a distance]]—Einstein presumed a gravitational field. In 1907, Einstein's [[equivalence principle]] implied that a free fall within a uniform gravitational field is equivalent to [[inertial]] motion.<ref name=Torrettipp289-90>Roberto Torretti, ''The Philosophy of Physics'' (Cambridge: Cambridge University Press, 1999), [https://books.google.com/books?id=vg_wxiLRvvYC&pg=PA289&dq=Newtownian+Relativity+Equivalence#v=twopage pp. 289–90].</ref> By extending special relativity's effects into three dimensions, [[general relativity]] extended length contraction into [[space contraction]], conceiving of 4D space-time as the gravitational field that alters geometrically and sets all local objects' pathways.  Even massless energy exerts gravitational motion on local objects by "curving" the geometrical "surface" of 4D space-time. Yet unless the energy is vast, its relativistic effects of contracting space and slowing time are negligible when merely predicting motion. Although general relativity is embraced as the more explanatory theory via ''[[scientific realism]]'', Newton's theory remains successful as merely a predictive theory via ''[[instrumentalism]]''. To calculate trajectories, engineers and NASA still use Newton's equations, which are simpler to operate.<ref name=Project2061/>