The principles of physics are like lighthouses. If you want to work on theoretical physics, you should never lose them from your sight. Each provides some kind of guidance in your logical conclusions and thought experiments. The principles are a discipline; self-control over your thoughts. They prevent you from drifting away to wrong places, into the depths of fallacies. They have emerged as a result of our knowledge of physics and of our vast experience.

The most important feature of the principles of physics is that they receive wide acceptance in the world of science. A written principle of physics, even if it is true, can never become a true principle unless it is accepted by the majority of the world of science; it just becomes the personal opinion of someone or some people. Principles of physics should not be confused with the laws of physics. Laws of physics are unchangeable and always have absolute mathematics. The principles are, on the other hand, not as sharp and absolutely unchanging as the laws of physics; instead, they are just for guidance. Occasions when a principle turns into a mathematical equality are quite rare. In this case, principles lose their characteristics and become laws. Principles of physics are logical in their essence and they can be expressed using words.

I would like to give some examples of some principles of physics related to our topic.

Galilean Relativity: Two observers who are moving at a constant speed and direction relative to each other will get the same results from all the mechanical experiments they do.

Galilean Relativity suggests that there is no physical difference between being motionless and being in motion at a constant speed for an object. Obviously, an object can notice that it moves relative to another object, but it cannot determine who is moving and who is not. The laws of physics are identical for a system that moves at a constant speed relative to another system, so the object cannot reveal if it is in motion or not by any physical experiment.

Albert Einstein's Special Relativity Principles:

The Principle of Relativity: The laws of physics are invariant (i.e. identical) in all inertial systems (non-accelerating frames of reference). 

The Principle of The Speed of Light Constant: .... Light is always propagated in empty space with a definite velocity [speed] c which is independent of the state of motion of the emitting body. 
This principle is interpreted this way: "The speed of light in a vacuum is the same for all observers, regardless of the motion of the light source." 

I wanted to spare a part at the beginning of the book for principles. These principles have played a vital role in the developmental phase of Alice Law. Here we will see how Alice Law fits with these principles with utmost loyalty and how it is based entirely upon them at each and every stage. Of course, you may think that (c+v) (c-v) mathematics violates Albert Einstein's "Principle of The Speed of Light Constant", but it is not that simple. This principle defines the speed of light constant, the "c" constant, and at the same time emphasizes that the speed of light is independent of the speed of the source that emits it. Without these descriptions, it is not possible to show that the light moves relative to the rules of (c+v) (c-v) mathematics. For Alice Law, this principle is of vital importance.