## It is believed that nothing is faster than the speed of light. And if a light source emits two photons simultaneously in different directions, what will be the speed of each photon compared to the other photon?

That is, you can answer as follows: It is generally impossible to measure the speed of anything, even other photons, compared to photons. The object from which motion is measured (such as the Earth or a ship in space) is called a reference object. To understand where something is relative to a reference object at a particular point in time, we need a coordinate grid. And the clock counts down the exact moment. These three pillars (reference body, coordinates, and clock) form the reference system. The theory that “forbids” faster-than-light acceleration (confirmed by countless experiments!) is called Special Theory of Relativity (STR). SRT considers only inertial reference frames. It is so called because it obeys the law of inertia. This law states: If no force acts on an object, the object is either at rest or in uniform motion in a straight line. One of the STR hypotheses states: In all inertial frames of reference, the speed of light is the same everywhere, regardless of how fast or fast the light source is moving.

One of the STR hypotheses states: In all inertial frames of reference, the speed of light is the same everywhere, regardless of how fast or fast the light source is moving. Let’s ask a simple question here. What is the relative speed of the photon? Obviously, it should be equal to zero. After all, the reference frame is “fixed to the photon.” But this contradicts the postulate. In an inertial frame, the speed of light cannot be zero. The only possible conclusion is that photons cannot be assigned to an inert (actually arbitrary) coordinate system. In other words, it is impossible to measure the speed of itself, another photon, or a car compared to a photon; it has no speed at all. This prohibition seems strange, but that’s because we don’t deal with the speed of light in everyday life. The universe has no need to correspond to the physical intuitions of intelligent primates, which are shaped by questions such as “How do I throw a stone so that it hits its target?”