The Lorentz transformation makes it possible to know what will happen if
we observe a phenomenon moving relative to the object, the carrier of the
phenomenon, at a speed v, or if the object moves relative to us at a speed v,
provided that we know how the phenomenon occurs when the object is stationary. Therefore, the following statement of the question will often be used
in the future. In a stationary system, the phenomenon is described. How
will this phenomenon occur if the object that carries the phenomenon is moving at speed v? The answer assumes a description of this phenomenon in the
system a reference point that moves at a speed of −v relative to the system
in which the phenomenon is described. This is equivalent to describing this
phenomenon in the case of the movement of an object, the carrier of the phenomenon, with a velocity v relative to a stationary observer. The second option
is interesting because it can be extended to several isolated objects moving at
different speeds. Use this to solve the following problem. The observation station recorded light signals from two rockets moving in a straight line towards
the station. The frequencies of signals registered by the station are v₁ and v₂.
The signal frequency of stationary rockets is equal to v₀. How fast do rockets
approach each other?