Riddle: The distance from the Earth to the Sun is about 100 million miles. The speed of light is 186,000 miles per second, and light takes eight minutes to reach the Earth from the Sun. Let's say the Sun rose at 6am this morning, and that by some freak of physics the speed of light is suddenly doubled to 372,000 miles a second.
What time will the Sun rise tomorrow?
Answer: 6am again. After all, what diffrence does the speed of light make to the answer? It's irrelevant- only the speed of the roation of the Earth matters here.