1. The problem statement, all variables and given/known data Hello, I have a question about length contraction transformation. In my textbook it looks like this: [tex]x_1=γ(x_1'+ut'), x_2=γ(x_2'+ut')[/tex] If the coordinates of the two events are [tex](x_1,t_1), (x_2, t_2) [/tex], why is t used instead of t_1and t_2? The second problem I have is with the length contraction transformation. If we use the formula in my textbook: [tex]x_1=γ(x_1'+ut'), x_2=γ(x_2+ut')[/tex] then indeed [tex]Δx=γΔx'[/tex] and [tex]Δx'=Δx/γ[/tex] so we do get length contraction. But what about starting with: [tex]x_1'=γ(x_1-ut) x_2'=γ(x_2-ut)[/tex] Then [tex]Δx'=γΔx[/tex] and it looks like we obtain length expansion rather than contraction. What's wrong with my reasoning? 2. Relevant equations 1.Why is the time of two events equal to t not [tex]t_1[/tex]and [tex]t_2[/tex] 2. What's wrong with the second transformation for length contraction?