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Special Rel. Doubt


mathematic
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11 minutes ago, mathematic said:

In the latest issue of American Scientist there is an article by Tony Rothman questioning E=mc^2. Are the assertions made in the article valid?  Are there comments by other physicists available?

A link to the article could be good.

edit: Is this the articlehttps://www.americanscientist.org/article/the-curse-of-emc2

(Can't read it, requires a login)

Edited by Ghideon
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1 hour ago, mathematic said:

In the latest issue of American Scientist there is an article by Tony Rothman questioning E=mc^2. Are the assertions made in the article valid?  Are there comments by other physicists available?

Can you summarize the objections?

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I'm pretty sure Albert knew he was standing on the shoulders of giants of the past and of his own time, he was generally seen as a humble man. 

the article here concludes thus.....https://www.scientificamerican.com/article/was-einstein-the-first-to-invent-e-mc2/

 

"One naturally wonders whether Einstein knew of Hasenöhrl’s work. It is difficult to believe that he did not, given that the bulk of the prize-winning trilogy appeared in the most prominent journal of the day. Certainly at some point he learned of Hasenöhrl: a famous photo of the first Solvay Conference in 1911 shows both men gathered around the table with the other illustrious attendees. 

And so, although Einstein achieved a definite conceptual advance in equating the mass of an object with its total energy content—whether or not it is moving, whether or not it has an electromagnetic field—we can also credit Hasenöhrl for unambiguously recognizing that heat itself possess an equivalent mass, and physicists before him for providing a chain of shoulders on which to stand. E = mc2 is the short punch line to a long and winding scientific story".

 

And I'm sure he wouldn't object to anything above.

Tony of course was/is also selling books.

 

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2 hours ago, Ghideon said:

A link to the article could be good.

edit: Is this the articlehttps://www.americanscientist.org/article/the-curse-of-emc2

(Can't read it, requires a login)

The part that is available to be read includes this:

"

  • In extended systems, one often gets the equation as E = 3/4 mc2, and debate continues even to this day on the best way to interpret or fix this strange result."

I don't recall ever hearing that...

Anyone have knowledge or thoughts on that?

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1 hour ago, J.C.MacSwell said:

The part that is available to be read includes this:

"

  • In extended systems, one often gets the equation as E = 3/4 mc2, and debate continues even to this day on the best way to interpret or fix this strange result."

I don't recall ever hearing that...

Anyone have knowledge or thoughts on that?

in the this link...https://www.scientificamerican.com/article/was-einstein-the-first-to-invent-e-mc2/ it says...."Thomson’s slightly complicated result depended on the object’s charge, radius and magnetic permeability, but in 1889 English physicist Oliver Heaviside simplified his work to show that the effective mass should be m = (43) E / c2, where E is the energy of the sphere’s electric field. German physicists Wilhelm Wien, famous for his investigations into blackbody radiation, and Max Abraham got the same result, which became known as the “electromagnetic mass” of the classical electron (which was nothing more than a tiny, charged sphere). Although electromagnetic mass required that the object be charged and moving, and so clearly does not apply to all matter, it was nonetheless the first serious attempt to connect mass with energy"...

then on to say....

"Hasenöhrl, though, next asked what the system looks like as it moves at a fixed velocity with respect to an observer sitting in a laboratory. Basic physics tells us that light emitted from a source moving toward you becomes bluer, and gets redder from a source moving away from you—the famous Doppler shift. Photons from one end disk will therefore appear Doppler blue-shifted to the laboratory observer and those from the other end will be red-shifted. Blue photons carry more momentum than red photons and hence, in order to keep the cavity moving at constant velocity the two external forces must now be different. A simple application of the “work–energy theorem,” which equates the difference in work produced by the forces to the cavity’s kinetic energy, allowed Hasenöhrl to conclude that blackbody radiation has mass m = (83) E / c2. In his second paper Hasenöhrl considered a slowly accelerating cavity already filled with radiation and got the same answer. After a communication from Abraham, however, he uncovered an algebraic error and in his third paper corrected both results to m = (43) E / c2."   

But we are now way beyond my pay grade!!!! help!!! Can't be too much of any disagreement though, considering the article concludes thus...

"And so, although Einstein achieved a definite conceptual advance in equating the mass of an object with its total energy content—whether or not it is moving, whether or not it has an electromagnetic field—we can also credit Hasenöhrl for unambiguously recognizing that heat itself possess an equivalent mass, and physicists before him for providing a chain of shoulders on which to stand. E = mc2 is the short punch line to a long and winding scientific story."

Edited by beecee
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2 hours ago, J.C.MacSwell said:

In extended systems, one often gets the equation as E = 3/4 mc2

and 

1 hour ago, beecee said:

Oliver Heaviside simplified his work to show that the effective mass should be m = (43) E / c2

are equivalent if an 'extended' system has an 'effective' mass.
The effective mass usually means the mass that the system seems to have, and acts like it has.

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I think the author is taking some liberties in demonstrating his thesis.

"The main error in Hasenöhrl’s first thought experiment is that he did not realize that if the end caps are emitting heat, they must be losing mass—an ironic oversight given that it is exactly the equivalence of mass and energy he was attempting to establish."

From the description, it sounds like Hasenöhrl was arguing that radiation has mass, not that mass and energy are equivalent. Conceptually these are different. 

The other arguments were for the equivalent mass of particles moving through some field which impedes their motion. Again, not an investigation of mass-energy equivalence.

Somewhat unrelated, we have "If we think of c, the speed of light, as one light year per year, the conversion factor c2 equals 1" which is just a wretched abuse of unit analysis IMO, but in line with the use of "natural units" (which essentially means "ignoring units to make the math easier")

 

 

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