Agnoiology is the study of ignorance. More specifically :
The doctrine of things of which we are necessarily ignorant" ref.[ paywalled ]
In other words. the opposite of epistemology which is the study of knowledge.
Given that human intelligence has limits, and that we have not explored the entire universe, it's a given that the extent of human ignorance is currently unknown.
There are a plethora of reasons why ignorance occurs and persists. Some examples (in no particular order) :
Note that Agnoiology also covers subjects which are by their nature unknowableplugin-autotooltip__plain plugin-autotooltip_big#Unknowable
Pages with this tag are about concepts or entities which, by their nature, can never be accurately described.
See :. An example would be trying to definitively classify a growing sequence of numbers as randomplugin-autotooltip__plain plugin-autotooltip_bigRandom numbers
unknowable
"We can never decide for sure that a number is random, but what we can do is apply an increasing number of tests and treat our sequence of numbers as innocent until proved guilty."
Source : Prof. Colva Roney-Dougal, senior lecturer in Pure Mathematics at the University of St Andrews, speaking in - given that the next digits may start repeating.