Two observers \( O \) and \( O' \) observe two events \( P \) and \( Q \). The observers have a constant relative speed of 0.5c. In the units, where the speed of light, \( c \), is taken as unity, the observer \( O \) obtained the following coordinates:
\text{Event P: } x = 5, y = 3, z = 5, t = 3
\text{Event Q: } x = 5, y = 1, z = 3, t = 5
\text{The length of the space-time interval between these two events, as measured by \( O' \), is \( L \). The value of \( |L| \) (in integer) is \(\underline{\hspace{2cm}}\).}
\text{Event P: } x = 5, y = 3, z = 5, t = 3
\text{Event Q: } x = 5, y = 1, z = 3, t = 5
\text{The length of the space-time interval between these two events, as measured by \( O' \), is \( L \). The value of \( |L| \) (in integer) is \(\underline{\hspace{2cm}}\).}
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Correct Answer: 2
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