I have claimed that the fundamental insight of Einstein’s 1905 paper is that the relativity principle can be taken as an explanans rather than an explanandum. However, I do not mean to assert that Einstein ever saw the matter in this light; indeed, I am inclined to favour the view that he did not.Wikipedia defines:
An explanandum is a phenomenon that needs to be explained and its explanans is the explanation of that phenomenon. For example, one person may pose an explanandum by asking "Why is there smoke?", and another may provide an explanans by responding "Because there is a fire". In this example, "smoke" is the explanandum, and "fire" is the explanans.So Einstein explained relativity without realizing that he was doing so. She argues that the relativity principle should be taken as a postulate instead of being explained, as she acknowledges that Lorentz complained "Einstein simply postulates what we have deduced". (She cites a 1916 publication for this remark, but Lorentz said it much earlier.) A similar argument was made in a Einstein book by a NY Times science editor:
In a way the message of relativity theory was that physics was not about real objects; rather, it concerned the measurements of real objects. ... No such declarations of grandeur, of course, intruded on the flat and somewhat brisk tone of the [1905 Einstein relativity] paper.The bizarre thing about this argument is that it adopts a subtle philosophical interpretation of relativity; it admits that Einstein did not have that interpretation; it has strange complaints about Poincare's philosophy that are not rooted in anything he actually said; it points to some technical differences between Poincare's and Einstein's papers; and it end up insisting on credit for Einstein.
The foolishness of this argument should be obvious. If it is so important to give credit for relativity, then the credit ought to be for the essence of what is great about the theory. Einstein should not be credited for an interpretation that he rejected. Adlam argues:
Since 1905, the issue of explanation in special relativity has been made more complex by the emergence of Minkowski spacetime. ... Thus the introduction of Minkowski spacetime is no reason to abandon the successful explanatory strategy introduced by Einstein’s 1905 paper: spacetime structure is merely a convenient mathematical representation of the original theory, not a new element which must be separately incorporated into our explanations.But Adlam does not mention the fact that Minkowski spacetime geometry was introduced by Poincare in 1905. She admits that the spacetime geometry was a convenient mathematical representation of the relativity explanation that escaped Einstein's awareness.
The easiest way to understand the credit for relativity is to look at the enormous effort that Einstein scholars have been making to credit him over the last century, and to see how contrived and silly their arguments are. Usually a priority argument simply points to the ideas that someone had first. But no one has ever been able to find an idea that Einstein had first. This is all detailed in my book.