The photon between the sun and a planet, non considering the orbital motion V of the planet, to an observer on the solar system referential

This observer does not know the velocity b of the solar system expansion. The photons emitted by the sun in direction of earth, that one will reach at earth was emitted in direction of X₁, with velocity c. It is influenced by velocity V, modifying its velocity to c₂, where c₂ = V + c.

In a time t:
- The projection of the sun goes from B_n position to A_n with velocity V, which is the projection of velocity b.
- The photon goes from B_n to X_n, with velocity c₂. It is always between virtual sun and virtual planet.