Charge is considered relativistically invariant because it is a fundamental property of particles that remains unchanged regardless of the observer's frame of reference. This concept is rooted in the principles of special relativity, developed by Albert Einstein.
According to special relativity, the laws of physics should be the same for all observers in inertial reference frames moving at a constant velocity relative to each other. In other words, the fundamental laws governing the behavior of particles and fields should remain consistent across different frames of reference.
Charge is one of the fundamental properties of particles, such as electrons and protons. It determines the strength of the electromagnetic interactions between particles. The principle of charge conservation states that the total electric charge in an isolated system remains constant over time.
In special relativity, the concept of relativistic invariance implies that certain physical quantities, including charge, should remain the same when transforming from one inertial reference frame to another through Lorentz transformations. These transformations involve a combination of spatial and temporal coordinate changes that account for the effects of relative motion and time dilation.
Experimental observations have consistently shown that charge is indeed conserved and invariant under Lorentz transformations. This invariance is a fundamental property of charge that allows for the consistent application of electromagnetic theory in the framework of special relativity.