An electron helical path has two velocity components, perpendicular to each other. One responsible for circular motion the other translation along the direction of the spiral. Since there is no reason that they experience different drag in uniform space, they are equal, \(c\). And so their resultant is \(\sqrt{2}c\).
When an electron is at simple circular motion around a nucleus, its terminal velocity is \(\sqrt{2}c\).
A photon is in a helical path, light speed so measured is the translation velocity along the direction of the helix. Light speed is \(c\), not the resultant \(\sqrt{2}c\). Light speed is not the true terminal velocity given that space is a thin fluid. The true terminal velocity of space is \(\sqrt{2}c\)...here's the bomber...at a given gravity, ie. a given space density!
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