The *Einstein Franchise* hit the big time after World War II when Einstein’s portrait appeared on the cover of *Time* magazine in July 1946.

The background imagery of the magazine cover has the equation *E = mc ^{2}* embossed on a

*mushroom cloud*that rises above an inferno.

After the very public demonstration of huge energies released from nuclear fission after the atomic bombings of Hiroshima and Nagasaki in 1945, the equation E = mc

^{2}became directly linked in the public eye with the power and peril of nuclear weapons.The equation was featured as early as page 2 of the Smyth Report, the official 1945 release by the US government on the development of the atomic bomb, and by 1946 the equation was linked closely enough with Einstein’s work that the cover of Time magazine prominently featured a picture of Einstein next to an image of a mushroom cloud emblazoned with the equation.

http://en.wikipedia.org/wiki/Mass%E2%80%93energy_equivalence

The *Einstein Franchise* promoted by *Time* magazine was very strange because Einstein’s scientific contribution to the Manhattan Project was “inconsequential”.

Einstein himself had only a minor role in the Manhattan Project: he had cosigned a letter to the U.S. President in 1939 urging funding for research into atomic energy, warning that an atomic bomb was theoretically possible.

The letter persuaded Roosevelt to devote a significant portion of the wartime budget to atomic research.

Without a security clearance, Einstein’s only scientific contribution was an analysis of an isotope separation method in theoretical terms.

It was inconsequential, on account of Einstein not being given sufficient information (for security reasons) to fully work on the problem.http://en.wikipedia.org/wiki/Mass%E2%80%93energy_equivalence

Furthermore, the *Einstein Franchise* promoted by *Time* magazine was “in no way an explanation of the large energies released in radioactive decay” and “is not required in discussing fission”.

Einstein’s equation is in no way an explanation of the large energies released in radioactive decay(this comes from the powerful nuclear forces involved; forces that were still unknown in 1905).In any case, the enormous energy released from radioactive decay (which had been measured by Rutherford) was much more easily measured than the (still small) change in the gross mass of materials, as a result.

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As the physicist and Manhattan Project participant Robert Serber put it:Somehow the popular notion took hold long ago that Einstein’s theory of relativity, in particular his famous equation E = mc2, plays some essential role in the theory of fission.

Albert Einstein had a part in alerting the United States government to the possibility of building an atomic bomb, but

his theory of relativity is not required in discussing fission.The theory of fission is what physicists call a non-relativistic theory, meaning that relativistic effects are too small to affect the dynamics of the fission process significantly.

http://en.wikipedia.org/wiki/Mass%E2%80%93energy_equivalence

And, just to confuse matters even further, the *Einstein Franchise* equation promoted by *Time* magazine was **not** the equation Einstein published in 1905.

Albert Einstein did not formulate exactly the formula E = mc“Does the Inertia of an object Depend Upon Its Energy Content?”; rather, the paper states that if a body gives off the energy L in the form of radiation, its mass diminishes by L/c2.^{2}in his 1905 Annus Mirabilis paperhttp://en.wikipedia.org/wiki/Mass%E2%80%93energy_equivalence

Does the inertia of a body depend upon its energy content? – A. Einstein – 27 Sept 1905

http://www.fourmilab.ch/etexts/einstein/E_mc2/e_mc2.pdf

Wikipedia explains away the rebranding of the *Einstein Franchise* in the 1940s as a “simple expression of the ideas of Albert Einstein”.

However the association between E = mc

^{2}and nuclear energy has since stuck, and because of this association, and its simple expression of the ideas of Albert Einstein himself, it has become “the world’s most famous equation”.http://en.wikipedia.org/wiki/Mass%E2%80%93energy_equivalence

Wikipedia [also] cleverly glosses over any misunderstanding the reader may have regarding “the origin of energy in nuclear processes” by stating that “such processes” can be understood “without the need to invoke mass–energy equivalence”.

E = mc

^{2}has frequently been used as an explanation for the origin of energy in nuclear processes, but such processes can be understood as simply converting nuclear potential energy, without the need to invoke mass–energy equivalence.http://en.wikipedia.org/wiki/Mass%E2%80%93energy_equivalence

Therefore, for anyone who is confused by this rebranding it is helpful to remember that Einstein’s original 1905 equation:

1) Does **not** define an absolute relationship between *mass* and *energy*.

2) Only defines a relationship between *changes in mass* and *changes in energy* when the *energy* is electromagnetic.

(Here, “radiation” means electromagnetic radiation, or light, and mass means the ordinary Newtonian mass of a slow-moving object.)

This formulation relates only a change Δm in mass to a change L in energy without requiring the absolute relationship.

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Einstein’s equation, by theory, can give these energies by measuring mass differences before and after reactions, but in practice, these mass differences in 1905 were still too small to be measured in bulk.http://en.wikipedia.org/wiki/Mass%E2%80%93energy_equivalence

Additionally, it is only Einstein’s original 1905 equation that has been experimentally tested.

In 1933, the energy released from the reaction of lithium-7 plus protons giving rise to 2 alpha particles (as noted above by Rutherford), allowed Einstein’s equation to be tested to an error of ± 0.5%.

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Instead, mass–energy equivalence merely indicates that the large amounts of energy released in such reactions may exhibit enough mass that the mass loss may be measured, when the released energy (and its mass) have been removed from the system.For example, the loss of mass to an atom and a neutron, as a result of the capture of the neutron and the production of a gamma ray, has been used to test mass–energy equivalence to high precision, as the energy of the gamma ray may be compared with the mass defect after capture.

In 2005, these were found to agree to 0.0004%, the most precise test of the equivalence of mass and energy to date. This test was performed in the World Year of Physics 2005, a centennial celebration of Albert Einstein’s achievements in 1905.

http://en.wikipedia.org/wiki/Mass%E2%80%93energy_equivalence

Finally, because Einstein plucked **c ^{2}** out of thin air it is probably worthwhile to remember Max Planck’s observation that Einstein’s 1905 derivation “is only valid to first approximation”.

The correctness of Einstein’s 1905 derivation of E = mc

^{2}was criticized by Max Planck (1907), who argued that it is only valid to first approximation.http://en.wikipedia.org/wiki/Mass%E2%80%93energy_equivalence

Yeah, the mainstream press popularity of E = mc2 as some sort of magical equation for everything – which did indeed seem to really catch hold with the simplistic “gee whiz” enthusiasm for new advances in science in the first hald of the 1900s, with the need for catchy personality-based propaganda during WW2 and the post-war period – is hilarious. And Einstein, through no fault of his own, did have a very media friendly face, compared with the rest of the crowd. (Of the ‘serious contributing scientists’, probably Richard Feynmann has approached this level since.)

Nothing wrong with E=mc2 itself, ‘cos it’s very handy – as you point out, it has a particular context (special relativity) and relates to conservation under transformation:

– Encyclopedia Brittanica

Now, we can’t necessarily expect the general press to understand special relativity and so on, but this sort of lazy reporting still continues to this day, and misinforms the passing reader when it doesn’t need to.

http://geosciencebigpicture.com/2012/06/30/what-is-it-with-squares-in-nature-anyway/

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