Small-speed length contraction estimate
= Small-speed length contraction estimate
At <speed> $v\ll c$, an endpoint separation $L$ measured simultaneously in its own <rest frame> becomes $L\sqrt{1-v^2/c^2}$ in the moving frame, shorter by approximately $Lv^2/(2c^2)$. The stable evaluation $L\beta^2/[1+\sqrt{1-\beta^2}]$ avoids subtracting nearly equal floating-point numbers.