<s>[INST] Is it true to say that light cannot travel at the speed of light since a perfect vacuum cannot exist? [/INST] 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.</s>\ <s>[INST] How would someone be able to prove that light goes at the speed of light in outer space? [/INST] 