Imagine that we'd like to measure the length of Sulaco as it coasts with speed v past Nostromo.
Here are two ways that come to mind:
Method 1:
Using a single
clock, time how long it takes (call this interval
Dt) for Sulaco to coast past
the location of the clock. At
the end of the time interval, disable the clock so that its reading is
frozen at Dt. Sulaco's length is
vDt.
Method 2:
Using a large number
of synchronized
clocks (labeled 1 - 13 in the illustration), determine which clocks are
closest to Sulaco's nose
and tail
at the instant at which
each clock reads zero. The length of Sulaco is the same as
the separation
between these two clocks. Inscribe the result in Nostromo's
ship's log. In the drawing,
Sulaco's length is the same as the separation between clocks 11
and 3.
Methods 1 and 2 will always
yield
the same answer.
