“If a body gives off the energy L in the form of radiation, its mass diminishes by L/c2. The fact that the energy withdrawn from the body becomes energy of radiation evidently makes no difference, so that we are led to the more general conclusion that the mass of a body is a measure of its energy-content; if the energy changes by L, the mass changes in the same sense by L/9 × 1020, the energy being measured in ergs, and the mass in grammes. It is not impossible that with bodies whose energy content is variable to a high degree (e.g. with radium salts) the theory may be successfully put to the test.”
Albert Einstein —“Ist die Trägheit eines Körpers von seinem Energieinhalt abhängig?”
(Manuscript received on September 27 1905)
November 21 2020 — On this day in 1905, the physics journal Annalen der Physik published Albert Einstein’s paper “Does the Inertia of a Body Depend Upon Its Energy Content?” Contrary to popular belief, the equation E = m c² does not appear in this paper. Follow us on Twitter: @INTEL_TODAY
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Today (November 21 2020), the website of the prestigious Physics Today magazine posted a very short story about Einstein best known equation.
E=mc2 — On this day in 1905, the journal Annalen der Physik published Albert Einstein’s paper “Ist die Trägheit eines Körpers von seinem Energieinhalt abhängig?” (“Does the inertia of an object depend upon its energy content?”)
The term mc² had already made an appearance in his paper of 26 September, which introduced special relativity. The paper of 21 November showed that E = m c² applies to bodies at rest. [Physics Today]
I would like to make two quick comments. Firstly, Einstein’s first manuscript was received on September 27 1905. Secondly, the equation E = m c² does not appear in that paper!
As a matter of fact….
Einstein’s 1905 paper on mass-energy equivalence does not say “E=mc²”. Roughly, the article states: “m=L/c²”.
Change just one letter, and you will find out that this equation had been written many years before.
Of course, Einstein did write the equation as “E=mc²” in the first issue of “Science Illustrated” in 1946 in the article “E=mc²: The Most Urgent Problem of Our Time”.
This edition of Einstein’s Does the Inertia of a Body Depend upon its Energy Content is based on the English translation of his original 1905 German language paper — published as “Ist die Tragheit eines Korpers von seinem Energiegehalt abhangig?”, in Annalen der Physik.18:639, 1905 — which appeared in the book The Principle of Relativity, published in 1923 by Methuen and Company, Ltd. of London.
Most of the papers in that collection are English translations by W. Perrett and G.B. Jeffery from the German Das Relativats prinzip, 4th ed., published by in 1922 by Tuebner. All of these sources are now in the public domain; this document, derived from them, remains in the public domain and may be reproduced in any manner or medium without permission, restriction, attribution, or compensation.
The footnote is as it appeared in the 1923 edition. The 1923 English translation modified the notation used in Einstein’s 1905 paper to conform to that in use by the 1920’s; for example, c denotes the speed of light, as opposed the V used by Einstein in 1905. In this paper Einstein uses L to denote energy; the italicised sentence in the conclusion may be written as the equation “m=L/c2” which, using the more modern E instead of L to denote energy, may be trivially rewritten as “E=mc2”.
And just in case you did not know, the theory was successfully put to the test in Hiroshima on August 6 1945.
PS — By the way, the reader may be surprised to learn that Einstein was not the first to equate forms of mass to energy, nor did he definitively prove the relationship. [see: Scientific American : Was Einstein the First to Invent E = m c2?]
A great joke about “E=m c2”
One of my best memories is an evening with Lev Okun, a true genius who may well be the real father of the Russian thermonuclear weapons.
Lev told me the very best joke about this equation. Every teacher should be ashamed!
The Night Before — This was a splendid evening on the coastal city of a beautiful country that no longer exists.
The war was coming, but people were still trying to pretend that everything was ok. I found myself alone with Lev Okun, the legendary Russian physicist.
We ordered a bottle of wine and we talked, and talked. Little talk. Things like: “Could quark masses asymmetry generates a second-class induced tensor current in semi-leptonic interactions?”
And a few other light topics. CP violation and neutrino oscillations. I told Lev why I believe that the neutrinos are Majorana particles. We still do not know about that 30 years later.
Despite being one of the greatest physicists alive, Lev impressed me most by his humility.
Today, I believe that it is quite logical. Bright minds are always honest minds. And honesty always brings humility. Only imbeciles are pretentious.
Next Day, Lev is on Fire! — So, here we are having lunch! One of the top dogs at the table is John Ellis, the then CERN Theory Division Leader.
Lev asked him: “Hey John, what are the best 3 papers you ever published anyway?”
You could see on the face of the British man that he was seriously offended.
Then, Lev added: “Relax. I was kidding you. Name just ONE!”
Boy, I can tell you that one never forget a moment of truth like that one.
And Now, the ‘Joke’
Lev asked the people seated at the table to answer 2 simple questions. Which of the following four equations was actually written by Einstein? And which one should we use to teach our students?
E = m c2
E0 = m c2
E = m0 c2
E0 = m0 c2
Most people answered: E = m0 c2
This of course is completely absurd even if this equation is printed in all modern textbooks.
Of course, the mass is a property of a particle at rest! There is no need for the zero in subscript!
That one knocked down half the people at the table. Then came the second punch.
Many of them had answered differently the two questions!
And Lev simply pointed out the obvious.
“So, you think Einstein wrote that equation, but we should use a different one to teach our students? Surely, you are an imbecile!”
We all had a good laugh.
Please, take this joke seriously…
What I just wrote about Einstein is of course true for many other famous papers that journalists are happy to discuss despite the fact that they never read them!
Here is an example that recently caught my attention. On April 29 2019, the Brussels Times wrote:
“As early as in 1896, a scientist was warning against the potential negative effects of CO2 emissions, the Nobel Committee mentioned on Twitter on Monday. Svante Arrhenius was the first person to quantify the responsibility of CO2 in the greenhouse effect, in an article published in the Philosophical Magazine and Journal of Science.“
Nothing could be further from the truth. Arrhenius believed that human emission of CO2 would be strong enough to prevent the world from entering a new ice age, and that a warmer earth would be needed to feed the rapidly increasing population.
“We may find a kind of consolation in the consideration that here, as in every other case, there is good mixed with the evil.
By the influence of the increasing percentage of carbonic acid in the atmosphere, we may hope to enjoy ages with more equable and better climates, especially as regards the colder regions of the earth, ages when the earth will bring forth much more abundant crops than at present, for the benefit of rapidly propagating mankind.”
REFERENCES
Does the Inertia of a Body Depend upon its Energy Content by A. EINSTEIN (September 27, 1905)
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On This Day — Einstein writes : ” E = m0 c2″ (Fake News)
On This Day — Annalen der Physik publishes Albert Einstein’s Famous Equation [November 21 1905]
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