Principles of Classical Physics - Reality

Let's examine the first principle (from previous post) of Classical Physics, Reality.  What is meant by reality?  It refers to the concept that the physical world is real, and exists independently of the observer.  The old philosophical question about whether the tree falling in a forest makes a sound if no-one is present to hear it, is answered as definite 'yes' in Classical Physics.  The moon is still there whether we look at it or not.  The laws of gravity affect the apple falling from the tree in the same way whether or not we see it falling.  It all makes sense to us in our everyday world, and the calculations based on these assumptions are practical and very useful.

However, this all changed when quantum physics came along.  The first glaring outness with this assumption came with the famous double slit experiment.  It was determined  (Double Slit Experiment) that one got different results in the experiment if the particle is observed and when it is not. This phenomena can be seen easily at an atomic level, with electrons, photons, and other small particles.  This just opened the door.  Since then it has been confirmed in a multitude of experiments and conditions.  The upshot is the observer is intimately involved with what we observe as reality and is not separate at all.  Quantum Theory is able to show that Classical Physics, and the assumption of a separate physical world reality, is just a special case of a much broader view of the universe, and it works only as an approximation of the real world.

This is called the Measurement Problem, and there are many interpretations of why it exists (which shows there are no definite answers), but none can avoid the fact that the observer influences what is being observed.