A Texan once said: "If you can't beat 'em with facts, baffle 'em with bullsh.....".
Conflating quantum mechanics and special relativity?
Very few understand physics, so it is used by those who don't understand it to prove their points, and very few can argue. Those who can argue are not understood by the masses.
Special relativity concerns non-accelerating reference frames (accelerating frames are covered in general relativity). Those non-accelerating frames are called inertial reference frames.
Quantum mechanics, on the other hand, concerns wave functions (also called state functions because they describe the state), and are used with the Schroedinger equation to find probabilities of location and energy. The Schroedinger equation is based on Hamilton's energy equation, and contains the Hamiltonian operator (converted to a composite eigenvalue to avoid complicated calculations). Dirac notation is used to describe the probability density (which is imaginary for electrons), and the wave function's magnitude squared is probability.
In calculating the age of the universe, using Friedman's equation (which comes from General Relativity), co-moving observers are used. Those are parts of the universe that were not blown off course by explosions of stars since the big bang, so they remain where they started. Those are identified by the homogeneous and isotropic background radiation, as measured from earth. In other words, comoving observers are supposed to have the same amount of cosmic background radiation from all directions.
Observers can be part of nature.
Feedback systems also use observers (to observe how part of the system is doing, and make changes based on those changes).
God is an observer. God observes the world, and based on what he sees, makes corrections (occasionally). The Noah flood, destruction of Sodom, parting the Red Sea, and expulsion from Eden are examples of God's interventions.