Variables influencing speeds of light, cr, relative to a body or reference frame.      The two figures below show two spaceships (red rectangles) moving through the qm with absolute velocities of va=.2 ca and va=.6 ca. The black arrows represent the magnitudes and directions of these absolute velocities of the ships. The ships emit light in all directions and the blue arrows represent the magnitudes and directions of the light through the qm in several directions. These blue arrows show light that has been emitted from the ships in the forward, rearward, and transverse directions, the forward direction being the direction of the ship's absolute velocity. The black and blue arrows show velocities and directions relative to the quantum medium, and the gray arrows show the directions and speeds of light relative to the ships. In the forward direction the speed of the light relative to the ship, cr, is the difference between the speed of light through the medium, ca, and the absolute velocity of the ship, va, as shown by the velocity arrows. In the rearward direction the relative speed of light is the sum of ca and va, as the arrows show. When va=.6 ca, the speed of light relative to the ship ranges from .4 ca to 1.6 ca, as you can see. Inside the ship, cr(forward)=.4 ca and cr(rearward)=1.6 ca, so it takes photons four times as long to move from the rear of the ship to the front as from front to rear.
 In directions transverse to the direction of va, the relative speed of light is cr=.98 ca when va=.2 ca and cr=.8 ca when va=.6 ca. The vectors show that for light to move in a transverse direction relative to a ship the light must have a forward component of its 1 ca velocity equal to the absolute velocity of the ship. The figures show that when the absolute velocity of a ship is low it has little effect on cr. But when va=.6 ca the speed of light in a transverse direction is reduced to .8 ca, so photons take longer to move from one side of the ship to the other. Throughout the ship and its atomic structure the rate of energy exchange in transverse directions is decreased to .8 times the rate when va=0. This is also true for the rate of round-trip energy exchange in all other directions, as explained later.      The above figures involve photons emitted from the spaceships, and an analysis involving photons arriving from various directions would be similar. Whether photons are emitted or absorbed at the ships, Doppler shifts are involved when va≠0. This is an important further consequence of motion through the medium that is discussed later.