Derive the geodesic equation for this metric.
$$\frac{d^2t}{d\lambda^2} = 0, \quad \frac{d^2x^i}{d\lambda^2} = 0$$ moore general relativity workbook solutions
which describes a straight line in flat spacetime. Derive the geodesic equation for this metric
$$ds^2 = -dt^2 + dx^2 + dy^2 + dz^2$$