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Conducted in April 1932 at the [[University of Cambridge]]'s [[Cavendish Laboratory]] in England,  the physicists Cockroft and Walton successfully split [[lithium]] atom [[nucleus|nuclei]] by colliding them with artificially accelerated protons. This experiment is general hailed as being the first [[transmutation]] of an element using artificially accelerated particles, for which they were honored with the [[Nobel Prize]] in 1951.<ref>[http://www.nobelprize.org/nobel_prizes/physics/laureates/1951/  ''The Nobel Prize in Physics 1951''], Nobelprize.org, 23 Jan 2013</ref>

Conducted in April 1932 at the [[University of Cambridge]]'s [[Cavendish Laboratory]] in England,  the physicists Cockroft and Walton successfully split [[lithium]] atom [[nucleus|nuclei]] by colliding them with artificially accelerated protons. This experiment is general hailed as being the first [[transmutation]] of an element using artificially accelerated particles, for which they were honored with the [[Nobel Prize]] in 1951.<ref>[http://www.nobelprize.org/nobel_prizes/physics/laureates/1951/  ''The Nobel Prize in Physics 1951''], Nobelprize.org, 23 Jan 2013</ref>

Cockcroft and Walton "''did not see their experiments as a ''test'' of Einstein's mass-energy relationship; rather, they simply used that relationship in their analysis, assuming it to be valid ''"<ref>Roger H. Stuewer: ''Mass-Energy'' in ''Einstein in Context'', Cambridge University Press</ref> The E=mc&sup2; equation had in fact been known, and [[Quantitative_Analysis_of_Alpha_Decay|verified for nuclear decays]], more than 20 years earlier.  But this experiment appears to be the first to verify the equation for artificially accelerated particles.  The first to stress this aspect of the experiment was the eminent physicist Kenneth Bainbridge in 1933:

 

Cockcroft and Walton "''did not see their experiments as a ''test'' of Einstein's mass-energy relationship; rather, they simply used that relationship in their analysis, assuming it to be valid ''"<ref>Roger H. Stuewer: ''Mass-Energy'' in ''Einstein in Context'', Cambridge University Press</ref> The first to stress this aspect of the experiment was the eminent physicist Kenneth Bainbridge in 1933:

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The gain in energy in the reaction is 16.97&times;10⁶ e-volts, an energy equivalent to 0.0182 mass units on the O¹⁶ scale if &Delta;E =C²&Delta;m. Taking Aston's values for the mass of helium and hydrogen and the author's value, 7.0146&#0177;0.0006 for Li⁷, the mass change is 0.0181 &#0177; 0.0006 in the reaction which may be represented as Li⁷ + p &rarr; 2&alpha;. Within the probable error of the measurements the equivalence of mass and energy is satisfied.'' --Kenneth Bainbridge

The gain in energy in the reaction is 16.97&times;10⁶ e-volts, an energy equivalent to 0.0182 mass units on the O¹⁶ scale if &Delta;E =C²&Delta;m. Taking Aston's values for the mass of helium and hydrogen and the author's value, 7.0146&#0177;0.0006 for Li⁷, the mass change is 0.0181 &#0177; 0.0006 in the reaction which may be represented as Li⁷ + p &rarr; 2&alpha;. Within the probable error of the measurements the equivalence of mass and energy is satisfied.'' --Kenneth Bainbridge