In a thoughtful contribution to the ongoing discussion on the foundations of relativity, Mr. André Michaud offers an important historical and linguistic clarification regarding Einstein’s original 1905 postulates in Zur Elektrodynamik bewegter Körper (On the Electrodynamics of Moving Bodies). His insights help distinguish between Einstein's precise statements and how they have evolved—perhaps even been oversimplified—over more than a century of scientific interpretation.

Common Modern Formulation of the Postulates:

While these are widely accepted as the foundational postulates of special relativity, Michaud points out that Einstein's original phrasing in 1905 was more nuanced and contextually specific.

Einstein’s Actual 1905 Statements:

First Postulate (1905 German Original):

"Sich das Licht im leeren Raume stets mit einer bestimmten, vom Bewegungszustande des emittierenden Körpers unabhängigen Geschwindigkeit V fortplanze."

Translation: "Light always propagates in empty space at a certain speed V independent of the state of motion of the emitting body."

This clarification emphasizes that Einstein did not initially frame the postulate as being observer-invariant (as it is commonly presented today), but rather focused on the emission independence—that the speed of light does not depend on the motion of its source. This reflects a more physical description rooted in wave behaviour, not yet tied to a geometric interpretation of spacetime or to transformations between reference frames.

Second Postulate (1905 German Original):

"für alle Koordinatensysteme, für welche die mechanischen Gleichungen gelten, auch die gleichen elektrodynamischen und optischen Gesetze gelten."

Translation: "For all coordinate systems for which the mechanical equations apply, the same electrodynamic and optical laws also apply."

Here again, Einstein's original intent appears to align electrodynamic and optical laws with Newtonian mechanics in the specific class of inertial frames, without invoking full symmetry between all physical laws across frames as implied by today’s more abstract formulations.

Historical Context and Overshadowed Work

Mr. Michaud also reminds us of a critical moment in early 20th-century physics history. In 1907, the scientific community broadly adopted Special Relativity, but in doing so, it abandoned Wilhelm Wien’s project—an effort aimed at synchronizing classical kinetic mechanics with Maxwellian electromagnetic theory. According to Michaud, this was a premature closure that left open the deeper unification of dynamical principles, a task that some researchers, including Michaud himself, have since attempted to complete.

His referenced work, “Electromagnetic and Kinematic Mechanics Synchronized in Their Common Frame of Reference,” claims to fulfil that long-standing objective. It reopens the possibility of reconciling inertial dynamics with wave-based electromagnetic behaviour under a shared theoretical structure—an endeavour deeply aligned with the spirit of Einstein’s original goal: a unified understanding of motion and radiation.

Implications

Michaud’s clarification is not merely a linguistic correction; it has conceptual significance. It invites renewed scrutiny of how we define invariance, how postulates shape theoretical development, and whether alternative formulations—like Extended Classical Mechanics (ECM) or wave-based cosmologies—might offer more physically grounded pathways to foundational constants like the speed of light.

By drawing our attention back to the source, Mr. Michaud encourages a return to first principles, rather than reliance on inherited interpretations. This kind of rigorous re-examination is essential for advancing theoretical physics in a post-relativistic landscape.