## 1. Online Resources

### 1.1 Rindler’s Scholarpedia Resource

Key Quotes:

- “Later it was found (Ignatowski 1910 and, e.g., Rindler 1979) that Einstein’s light postulate is, in fact, an almost inevitable consequence of the relativity principle. The latter, by itself, has the interesting mathematical implication of leaving exactly one velocity invariant among inertial frames, which can be chosen at will.”
- “Newton’s theory is at the limiting edge of possible relativistic theories; in it, the invariant velocity is infinity. In it, therefore, a particle (or just an ideal point) moving with infinite velocity in one inertial frame moves with infinite velocity in all other inertial frames. Let us stand back for a moment to see what this implies. A particle moving along a line with infinite velocity is everywhere at once. It thus passes all the clocks along the way at the same reading, say at noon. And in Newton’s theory it then does the same thing in every other inertial frame as well. So when the clocks of one inertial frame all read noon, those of another such frame will also all read the same time, which might as well be noon. This leads to Newton’s ‘absolute’ (or universal) time. Not so in special relativity. For various reasons — mainly because of Maxwell’s theory — the invariant speed is here chosen to be c . The infinite speed is no longer invariant. Time is no longer absolute.”