The atom, which is considered to be the building block of physical reality, is itself an unknown entity because it can be either a particle or a wave. And this wave or particle is only there by virtue of probability (according to Heisenberg’s Theory of Uncertainty). Furthermore, these particles and waves abide in relatively enormous empty space—comparable to the distance between the stars and celestial bodies of the universe.
When the scientist scans the atom and interacts with it by altering its form, the observer influences the observed. It then becomes subjective. This is why we cannot prove “reality.”
What we call reality is also a combination of our waking state and our physical senses. A cat or a bee sees reality in a completely different way. They may not see the colors we see but can see others in the infrared or ultraviolet range. They may not see the same shapes we see either, because all this is dependent on our human systems of perception and the structure of our eyes and optic nerve.
Yet, I can tell you that the chair I just stubbed my toe on is real. The pain is real. The blood is real. The anger and upset I feel is real. But where is all the pain and upset when I am asleep? It is only to my waking consciousness that the pain exists.
These are just a few reasons why we cannot objectively prove reality.