Is it true to say that light cannot travel at the speed of light since a perfect vacuum cannot exist?
user
While it is technically true that a perfect vacuum cannot exist, light can still travel through a vacuum at its maximum speed, which is 299,792,458 meters per second (m/s). Light in a vacuum travels at its fastest speed because the medium through which it travels isn't interacting with the light and slowing it down. This constant velocity of light in a vacuum, which is often referred to simply as the speed of light, is one of the most universal and well-established principles in physics.

It is important to note that a vacuum is not devoid of energy and particles, but it is still considered to be a vacuum because it is a region of space where the average density of matter and energy is much lower than normal. Even in a vacuum, there are tiny bits of matter and energy present, such as cosmic rays or vacuum fluctuations, but these are not enough to significantly affect the speed of light.
assistant
How was the speed of light in a relative vacuum measured?
user