I want to write down my thoughts about what is physical reality. I do not assume that my ideas on this is something novel, but want to share it anyway. If somebody knows a philosopher with similar ideas, please notify me.
Physical reality may be roughly described (by definition!) as the reality which we can feel (see, hear, etc.) and measure. The below is dedicated to elaborate this rough definition in more details.
First, we take as granted that physical reality is some mathematical object (in wide sense of this word).
Physical reality conforms to some mathematical “restrictions” (called “laws of physics”). In the hope to understand reality people assume that these restrictions are simple enough mathematical formulas.
Physical reality is assumed to be experimentally verifiable, what means simply that all kinds of projections of physical reality somehow influence our feelings (well, experimental verifiability also requires that they influence our feelings in a predictable way, but I skip this topic). Invisible things like God or a some vector field which cannot be measured in any way do not belong to physical reality. Speaking about “kinds” of projections, I keep in mind that some particular projections of physical reality may be immeasurable accordingly known laws of physics. (For example, we cannot measure the part of the metagalaxy which is outside Hubble sphere because they move away from us at above light speed.)
The next natural question to ask is what it means “to feel” or “to measure”. There is no strict distinction between to feel and to measure: To measure is to feel using some means of increased reliability and exactness (often using some sophisticated device between the measured object and our sensory organs).
We “feel” something when our brain is influenced by something in physical reality. The brain (or taking wider, our body together with some measuring devices) is itself a physical object (that is a part of physical reality).
I will skip the question that we cannot define the word brain with technical precision, but we know what is and what isn’t a brain with a great number of details.
We can define “measuring” in a very general way: It is when the state of a physical object (for example, a brain) is influenced with some another (or maybe even the same, as when we see ourselves in a mirror) physical object. This is indeed very general: For example, every object measures the force applied to it, as the force influences its another part of physical state, the acceleration.
However usually the words feeling and measuring are applied only when they are interpreted by some mind (or a computer or another cybernetic device).
The laws of physics must be such that their description of being measured by a man (or a computer) as interacting between the measuring agent and the rest of physical reality produce the same description of measurement as what we actually measure.
Notice circularity in definitions of laws of physics and measurement: the physical reality the reality which describes the measurement and the measurement is defined based on laws of physics as in the previous paragraph.
So we cannot define physical reality and measurement exactly (it is a circular definition), well unless we actually define them. I mean that we should consider the possibility of laws of physics to be exactly defined as a well-defined part of the platonic reality (what means that physical reality is a mathematical object).
I believe that Christ is electromagnetic radiation of the universe: (Jn. 8:12) “Again, therefore, Jesus spoke to them, saying, “I am the light of the world””. So Christ is a physical object, but Christ is also a mathematical object (truth, wisdom, word). So a part (electromagnetic radiation) of our universe is also a part of platonic reality.
Actually, it seems that the entire world cannot be a well-defined object in platonic reality, because the world seems to be non-deterministic and we thus have no way to finitely describe mathematically the actual random state which is our physical reality.
What is a “physicist” (or more generally a “scientist”)? When a child grows he initially does not know the laws of physics but has some feelings. As he grows and study his conception of reality may become more exact during time. This can be described as an iterated process of attempting to define the laws of physics based on feelings and then explaining feelings by the laws of physics and then doing it again and again. Laws of physics are a fixed point of this process (that is when both laws of physics explain actual feelings and the reasons why feelings are such (under the condition that the child reaches scientific maturity) are explained by laws of physics.
By the way, understanding nature by a brain (or computer) is just a very complex case of measurement, when the state of the brain as a measuring device depends on the outside world in a very sophisticated (and complex) way.
I am myself not a physicist, but I have some hope that this my little philosophy may possibly help for example quantum scientists to define what is and what isn’t a part of physical reality, for example whether both wave function and measured states of particles belong to physical reality.