The same is true of scientific facts. New tools and techniques have resulted in new observations, sometimes forcing revision of what had been taken as fact in the past. The world is real. The physical universe exists, whether we can sense it or not. In other words, it is not just our imagination.
Humans can accurately perceive and understand the physical universe.
In other words, such understanding is possible. Nature operates the same way everywhere in the universe, and at all times, except where we have contrary evidence. Observations are confined to the biological limits of our senses, even with technological enhancement. The mental processing of our sensory information is unconciously influenced by previous experiences, which may result in inaccurate or biased perceptions of the world. It is impossible to know if we have observed every possible aspect of a phenomenon, have thought of every possible alternative explanation, or controlled for every possible variable.