I am a 16 year old and i have been asking myself the same question for a very long time but only recently was able to finally word the question.. Isnt it true that there can not be a certainty of anything outside a person's current observed world?  It still sounds very wierd but if i am sitting in a room in a building that i walked into myself, i saw all of my surrounding as i entered the building and the room. The door is closed and there is no way for me to observe anything on the outside of the room.   I can say that i know exactly what is outside that door because i saw it as i came in the room, but in reality i have zero way of being competely certain of anything i cant see or hear outside the room. I could, potentially, be in a room floating in space and have no way of knowing, givin there isnt any ovservable evidence of my location.  It may sound strange, but i believe it could be related to particle physics, etc.  The fact is that i have no certainty of anything outside my personal observed "picture": the surroundings in my field of vision and what i can hear around me.