Draw a spacetime diagram to include a worldline for
- a photon moving in the positive x direction; label this P+ .
- a photon moving in the negative x direction; label this P− .
- an object moving in the positive x direction with a speed of v=0.3c (and show the angle, θ+ , that this worldline makes with the ct axis); label this Q+ .
- an object moving in the negative x direction with a speed of 0.8c (and show the angle, θ− , that this worldline makes with the ct axis); label this Q− .