- #36
DrGreg
Science Advisor
Gold Member
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The Lorentz transformation is$$\begin{align}
x' &= \gamma (x - vt) \\
t' &= \gamma ( t - vx/c^2),
\end{align}$$ and the inverse transformation is$$\begin{align}
x &= \gamma (x' + vt') \\
t &= \gamma ( t' + vx'/c^2).
\end{align}$$So, from (1), ##x' = \gamma x## is true only when ##t = 0##, and, from (3), ##x' = x / \gamma## is true only when ##t' = 0##.
So you need to look through the argument to see whether there is an implicit or explicit assumption that either ##t = 0## or ##t' = 0##.
x' &= \gamma (x - vt) \\
t' &= \gamma ( t - vx/c^2),
\end{align}$$ and the inverse transformation is$$\begin{align}
x &= \gamma (x' + vt') \\
t &= \gamma ( t' + vx'/c^2).
\end{align}$$So, from (1), ##x' = \gamma x## is true only when ##t = 0##, and, from (3), ##x' = x / \gamma## is true only when ##t' = 0##.
So you need to look through the argument to see whether there is an implicit or explicit assumption that either ##t = 0## or ##t' = 0##.