Changes

Perhaps the most precise direct empirical verification of E=mc² was done in 2005 by Simon Rainville ''et. al.''<ref>[http://www.nature.com/nature/journal/v438/n7071/full/4381096a.html Nature 438, 1096-1097 (22 December 2005)] doi:10.1038/4381096a; Published online 21 December 2005</ref> The article states that &quot;Einstein's relationship is separately confirmed in two tests, which yield a combined result of 1−&Delta;mc²/E=(−1.4±4.4)×10⁻⁷, indicating that it holds to a level of at least 0.00004%. To our knowledge, this is the most precise direct test of the famous equation yet described.&quot;

Perhaps the most precise direct empirical verification of E=mc² was done in 2005 by Simon Rainville ''et. al.''<ref>[http://www.nature.com/nature/journal/v438/n7071/full/4381096a.html Nature 438, 1096-1097 (22 December 2005)] doi:10.1038/4381096a; Published online 21 December 2005</ref> The article states that &quot;Einstein's relationship is separately confirmed in two tests, which yield a combined result of 1−&Delta;mc²/E=(−1.4±4.4)×10⁻⁷, indicating that it holds to a level of at least 0.00004%. To our knowledge, this is the most precise direct test of the famous equation yet described.&quot;

==Alleged Experimental verification--the Cockcroft-Walton experiment==

==Experimental verification--the Cockcroft-Walton experiment==

In 1932 English physicist John Cockcroft and Irish physicist Ernest Walton performed the first artificial nuclear transmutation of nuclei, for which they were awarded the 1951 [[Nobel Prize]] in physics -- '''''but not for any verification of E=mc²'''''.<ref>[http://www.nobelprize.org/nobel_prizes/physics/laureates/1951/cockcroft-lecture.pdf John D. Cockroft ''Experiments on the interaction of high-speed nucleons with atomic nuclei''], Nobel Lecture, Dec 11, 1951</ref>  The award was for ''&quot;their pioneer work on the transmutation of atomic nuclei by artificially accelerated atomic particles.&quot;''<ref>[http://www.nobelprize.org/nobel_prizes/physics/laureates/1951/# Nobel Prize Organization]</ref>  

In 1932 English physicist John Cockcroft and Irish physicist Ernest Walton performed the first artificial nuclear transmutation of nuclei, for which they were awarded the 1951 [[Nobel Prize]] in physics.<ref>[http://www.nobelprize.org/nobel_prizes/physics/laureates/1951/cockcroft-lecture.pdf John D. Cockroft ''Experiments on the interaction of high-speed nucleons with atomic nuclei''], Nobel Lecture, Dec 11, 1951</ref>  The award was for ''&quot;their pioneer work on the transmutation of atomic nuclei by artificially accelerated atomic particles.&quot;''<ref>[http://www.nobelprize.org/nobel_prizes/physics/laureates/1951/# Nobel Prize Organization]</ref>  

Verifying E=mc² was not the goal of the experiment, and the Nobel prize was awarded for the transmutation itself, not any verification of the equation.  But analysis of the experiment does in fact verify the equation for the transmutation involved.

Verifying E=mc² was not the goal of the experiment, and the Nobel prize was awarded for the transmutation itself, not any verification of the equation.  But analysis of the experiment does in fact verify the equation for the transmutation involved.

::::<math>\approx \,17.3\,\mathrm{MeV}</math>

::::<math>\approx \,17.3\,\mathrm{MeV}</math>

Accurate measurements and detailed calculations allowed for verifying the theoretical values with an accuracy of ±0.5%. This was the first time a nucleus was artificially split, and thereby the first transmutation of elements using accelerated particles:

Accurate measurements and detailed calculations allowed for verifying the theoretical values with an accuracy of ±0.5%. This was the first time a nucleus was artificially split, and thereby the first transmutation of elements using accelerated particles.

 

With the invention of the mass spectrometer in 1919 by Francis W. Aston]]<ref>{{cite journal | last1 = Downard | first1 = KM | year = 2009 | title = Francis William Aston - The Man Behind the Mass Spectrograph | url = | journal = Eur. Mass Spectrom | volume = 13 | issue = | pages = 177–190 | doi= 10.1255/ejms.878}}</ref> in 1919, it became possible to measure atomic masses accurately.  This made it possible to demonstrate multiple isotopes for various element (e.g. Neon) and to measure the various isotopes' [https://www.thebigger.com/chemistry/nuclear-and-radiation-chemistry/what-is-packing-fraction/ packing fraction].  This, in turn, made it possible to validate the equation for radioactive decays with some precision, well before the Cockcroft/Walton experiment.  Modern measurements [[Quantitative Analysis of Alpha Decay|verify it with exquisite accuracy]].

 

 

 

==A Famous Example -- Nuclear Fission of Uranium==

==A Famous Example -- Nuclear Fission of Uranium==