On the axis away from the observer in opposite directions, lets call it the vector a and b, energy cant escape in a direction from an energy quantum, or energy packet already travel with the speed of light, in the same direction.

From the moment of the existence of any observe, a mirror horizon is created expanding outward with the speed of light. As more energy resources this mirror horizon passes as more energy has to be reflected inward. The energy has to be reflected, cause the energy cant under any circumstances pass this horizon, and energy has to be contained. (thermodynamic)

This doenst represent an problem because the energy can escape with the expanding horizon outward into space. But as soon as the observer (like earth which rotates around the sun) is in motion to any object with in this horizon, the horizon gets contracted in the direction of the movement.

This is where the reflection starts, all energy stored at the mirror horizon, gets now reflected back to the relative position of the observer.