"The most perfect philosophy of the natural kind only staves off our ignorance a little longer, as perhaps the most perfect philosophy of the moral or metaphysical kind serves only to discover larger portions of it. Thus the observation of human blindness and weakness is the result of all philosophy, and meets us at every turn, in spite of our endeavours to elude or avoid it." David Hume (An Enquiry Concerning Human Understanding, 1772)
Even though the scope of this page is not philosophical, it is interesting to realize that deep philosophical questions are behind the fact that most of our universe is invisible and that we are confined to a very limited sensorial realm.
Such questions arise when one considers the existence of objects external to us, the objects of 'human enquiry' and how one can be certain about their existence. We know that science has developed its own procedures in order to explain natural phenomena. Today we known that there are many invisible things in our Universe, things that do not interact with our sensory organs. How do we know that they exist ?
Non-observed and invisible phenomena are understood in terms of theories that first explain how the intermediary devices or methods, used to make such facts visible, can work. In order to build or develop such equipments or methods, we need to understand the theory and strongly believe the existence of the things they are design to show.
In this sense, we must broaden our view, considering not only what is 'observable' and 'visible' as part of the Universe. We must be guided by procedures and tacit considerations in order not to neglect what is not directly observable, for these things might possess a rich ontological content (they may exist independent of us and represent a new reality) and they may be identified as the cause of many phenomena yet unexplained.
Science has unveil the existence of unobservable things along its history, and this is hardly a finished process.