Space Situational Awareness Venn Diagram

Please see (and widely share) the attached Venn Diagram:

1. We have the set of all things (events and processes) that occur in the space domain. It is impossible for us to actually, completely, know this set for a variety of reasons. For one, we do not know all things about life, the universe, nature, etc. For another, our sensors don’t measure everything and beyond that, all sensors have finite resolution, accuracy, and precision. 
2. From (1) we have a subset comprising those things we model or believe is happening. You will notice how this sub-set extends outside of the total events and processes. Why? Because there are hypotheses we have and model which are actually not true and physically impossible and/or inaccurate. You will also notice that any given time, our measurements do not fully inform us of our total set of beliefs. One would hope to mitigate or minimize this by gathering as much data from as many sources as possible…in other words, ideally what we hypothesize and what we measure, coincide. 
3. From (1) we have a subset comprising those thing we measure. You will notice how this sub-set extends outside of the total events and processes. Why? Because sensors are corrupted by noise and are biased and report apparent events or processes that never really occurred. You will also notice how there are things we measure that we do not hypothesize or model. Why? See (2). There are things that we observe that we cannot explain and for which we have no model or hypothesis. This is the job of scientific research, to extend our body of knowledge (our beliefs). 

There you have it…where (2) AND (3) overlap, these are the things we know that we know. There is another subset of things in (2) that we believe but we know we have not measured and thus comprise things that we know we do not know (or known unknowns). Then there is a subset in (3) that we have measured but we have not hypothesized and therefore things we do not know that we actually know (or unknown knows).