I'm slowly trying to understand sp relativity. I admit I got lost in the last thread I posted . But thanks to all who replied! I have a question about the Lorentz transformations formulas. This is more of a mathematical question about how the formulas are derived. If you have the two formulas, x'= γ( x- vt) and x= γ(x' + vt') which represent the x components for two reference frames S and S', and where γ is the Lorentz factor, and you combine them to solve for t: x'= γ[γ(x' + vt') - vt] how do you arrive at the formula t= γ(t' + vx'/c^2) ? I know that you simply solve for t from the other formula, but I really cannot figure out how. Sorry, I realize this is more of a math-related problem, but I'm wondering if anybody can give me some tips?