Edit: This is my first question. If I don't conform to community guidelines please comment and I will happily update the question to meet the requests of the community I am asking for help. I am trying to understand notation in the following exposition relating to the Schrödinger equation. I am a...

In GR, we are working with Lorentzian metrics, which are examples of a pseudo-Riemannian metrics. That is, we are trying to find pseudo-Riemannian $g_{\mu\nu}$ that are solutions to the field equation $$R_{\mu\nu} - \frac{1}{2}Rg_{\mu\nu} + \Lambda g_{\mu\nu} \propto T_{\mu\nu}.$$ Does the form o...

Say there is a spaceship really far away from Earth moving at 80% the speed of light (away from Earth-edited), at some point a radio signal is sent by observers on Earth. I need to be able to calculate how long it would take for the signal to reach the spaceship. Would calculating the time requir...