In the theory of relativity, specifically in the framework of special relativity, the concept of a frame of reference refers to a coordinate system that is used to measure the position, time, and other physical quantities of objects and events. Frames of reference are typically defined by observers who are at rest or in motion relative to each other.
Photons, as particles of light, are special because they travel at the speed of light in a vacuum. According to the principles of special relativity, an object with mass cannot reach or exceed the speed of light. Consequently, photons cannot have a rest frame or be at rest relative to any observer.
Since photons travel at the speed of light, time dilation and length contraction occur from their perspective. Time dilation means that time appears to pass more slowly for an object moving relative to an observer at rest. However, for a photon, time dilation is extreme, and from its frame of reference, time does not appear to pass at all. This means that from the perspective of a photon, it is emitted and absorbed instantaneously, and there is no meaningful notion of the time or distance traveled.
Additionally, as photons travel at the speed of light, they have a constant velocity in all inertial reference frames. In other words, regardless of the observer's motion, the speed of light remains the same. This is one of the fundamental postulates of special relativity.
So, in summary, photons cannot have a frame of reference in the traditional sense because they travel at the speed of light and experience extreme time dilation. They are not at rest relative to any observer, and from their perspective, they are emitted and absorbed instantaneously, without a notion of time or distance traveled.