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This '''experiment''' by John Cockcroft and Ernest Walton is championed by [[liberals]] as being confirmation  of [[Albert Einstein]]'s famous formula ''[[E=mc&sup2;]]'',<ref>[http://cerncourier.com/cws/article/cern/31864 Mike Poole ''Cockcroft's subatomic legacy: splitting the atom''], Cern Courier, Nov 20, 2007</ref> even though no such claim was made by the experimenters at the time and experimental error was too large for it confirm the formula.  Moreover, an isolated experiment such as this could not demonstrate the sweeping claim made by the formula.

This '''experiment''' by John Cockcroft and Ernest Walton is championed by [[liberals]] as being confirmation  of [[Albert Einstein]]'s famous formula ''[[E=mc&sup2;]]'',<ref>[http://cerncourier.com/cws/article/cern/31864 Mike Poole ''Cockcroft's subatomic legacy: splitting the atom''], Cern Courier, Nov 20, 2007</ref> even though no such claim was made by the experimenters at the time and experimental error was too large for it confirm the formula.  Moreover, an isolated experiment such as this could not demonstrate the sweeping claim made by the formula.

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 proposed, and [[Quantitative_Analysis_of_Alpha_Decay|considered for nuclear decays]], more than 20 years earlier.  The experimental error was too large -- and the scope of the experiment to narrow -- to purport to verify the equation for all 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 E=mc&sup2; equation had in fact been proposed, and [[Quantitative_Analysis_of_Alpha_Decay|considered for nuclear decays]], more than 20 years earlier.  The experimental error was too large -- and the scope of the experiment to narrow -- to purport to verify the equation for all artificially accelerated particles.   

 

{{cquote|As Stuewer (1993) has suggested, Cockcroft and Walton '''''use''''' mass-energy equivalence to confirm their hypothesis about what happens when 7Li is bombarded by protons.  Hence, it does not seem we ought to regard this experiment as a confirmation of E<nowiki>=</nowiki>mc&sup2; }}

 

Others have asserted that Cockcroft and Walton did discovery some kind of confirmation of the E=mc&sup2; equation, such as 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