(Spacetime phenomena beyond direct perception)
The principle that defines science for Isaac Newton is the repeatability of experiments illustrating observations and with the same results exactly.
He arrived at this by saying that if one develops a theory or idea that formulates how to calculate or predict an effect resulting from actions or a cause, and the experiment repeating this action or cause then repeatedly be carried out and each and every time proves the prediction correct, then the premises upon which the predictions are made are correct, and the theory itself can be regarded as a law of the physical world. This demonstration or experiment can be carried out any number of times and the predicted results will be seen every time.
This among other things establishes fact and reality, as opposed to imagined, illusory, or opinionated.
Physics as a branch of science is about the physical world and physics, being concerned with the physical world, is about reality and space such that the physical laws must be true for all observers.
If a physical law is found not to be true for all observers, then that physical law cannot be a physical law.
The importance and efficacy of the physical law being true for all observers is such a fundamental aspect, especially in observations of the universe that, without this principle where laws of physics have to be true for all observers if they are to remain laws of physics, we cannot ever understand fully space and time, or the universe.
(To be extended & continued ..... )
It could be that the first reason for my interest in physics is that physics does not involve and is not subject to human opinion. Essentially, nature does not care what we think. Physics is physics, nature is nature, and opinions are not reality.
Furthermore, laws of physics are true for all observers. This is one of the profound tenets of physics.