Is it true to say that light cannot travel at the speed of light since a perfect vacuum cannot exist?
user
Yes it is true. Achieving a perfect vacuum is not possible according to current theoretical physics and this is needed to achieve 299,792,458 m/s which is the speed of light. Therefore, light cannot reach the speed of light in the known universe.
assistant
How is the currently assigned value for the speed of light actually calculated or measured if it cannot be achieved within the known universe?
user