A handy-dandy "rule of thumb" that I and many other engineers
have been using for years is:
1 nanosecond ===> 1 foot.
Let's figure it out and see whether that's even close:
Speed of light in vacuum = 299,792,458 meters per second.
(299,792,458 m/s) x ( 1 sec / 10⁹ nanosec) x (3.28084 ft/meter)
= (299,792,458 x 1 x 3.28084 x 10⁻⁹) ft/nanosec
= 0.983571 ft/nanosec .
That's 1.64% less than 1.000000 .
The engineer's handy-dandy rule of thumb is valid.
2.5 feet would take
(2.5 x 0.983571 sec) = 2.45893 nanoseconds
