D O C . 3 1 6 F E B R U A R Y 1 9 2 0 2 6 3 From this last relation it necessarily follows that t and are different measures of one and the same timespan, as I demonstrated clearly in my first letter [6] t, or , or their increments dt or , never can be regarded as periods.[7] Hence, when such a relation is valid, , one must necessarily set so . But now, look at this! What is being observed? Wouldn’t it just perhaps be ? Then one would have:[8] . In my notation, then, we should set 2π⎛ Θ t lx my nz⎞ + + c ------------------------------⎠ – sin------⎝ x ctl = y ctm = z ctn = x′ ct′l′ = x β( x′ αct′) + = y′ ct′m′ = z′ ct′n′ = l 1 αl′ + ----------------α+′l -= l l′ α + 1 αl′ + ---------------- -= ct β( ct′ αx′) + = 2π⎛ Θ′⎝ ------ t′ l′x′ m′y′ n′z + + c ----------------------------------------′⎞ - – ⎠ sin m m′ β( 1 αl′) + ------------------------ - = m β(1 αl′) + -------------------------′m = y y′ = z z′ = Θ t ⋅ Θ′ t ′⋅ = n n′ β(1 αl′) + ------------------------- = Θ Θ′ β(1 αl′) + ------------------------- = n n′ β(1 αl′) + ------------------------- = t t′β( 1 αl′) + = t′ t′ dt′ ds g44dx4 = g44Θs Θ4 = ds Θs ⋅ dx4 Θ4 ⋅ = Θs Θs Θ4 g44 ----------- Θ4 = dx4 c0dt = ds cdt =