The study of light and its speed is a complex undertaking that physicists have not even nearly completed. Does light travel at different fixed speeds in either direction of a round trip? Has its speed always been what it appears to be today? Can anything material travel faster than it?
No physicist alive seems to know the answers to these questions for certain.
But God does.
Numerous hypotheses have been presented to resolve the apparent tussling-twin difficulties of the observation of distant starlight and its doppelganger the "horizon problem", both of which arouse many of the same frustrations. A few proposed solutions include inflationary epoch models (Job 9:8; Isaiah 40:22, 42:5; Jeremiah 10:12; Zechariah 12:1), VSL theories, the Anisotropic Synchrony Convention (Genesis 1:14-19), and an earth-centered universe.
The short answer is, I myself have no idea. But I'm not losing any sleep over it.