This occurs because the strong gravitational effect of the sun curves space in such a way that the shortest distance for light to travel is the geodesic path curved around the edge of the sun. An earth-based analogy is that aeroplane flight paths follow geodesic paths instead of straight lines around the curved earth surface to save both time and fuel. This geometry is a fundamental part of Einstein's general theory of relativity. An earth rotation day is the varying time it takes for the earth to rotate once relative to the sun. The speed of light in a vacuum is exactly 299,792,458 metres per second.
Light reaches all objects from all directions at the same speed, regardless of their motion.
So, regardless of the speed of light sources and receivers, light always travels at the same speed. It was this thinking which led Einstein to his theories of relativity. No physical object can travel at or faster than the speed of light. The speed of light is generally considered to be a physical speed barrier. The age of the universe is widely believed to be 12 to 13 billion years old, and still expanding as a result of the 'big bang'.