I am thinking about this problem :
suppose the world is deterministic and there exist an entity "D" able to predict the future based on the knowledge of the state of the world at a given time T (like Laplace deamon).
then suppose we engineer an object "A" to shine some light or no light based on some input, and the experiment would go that way :
At time T, we ask D to predict "the state of the world at time T+2" and to present its prediction to A at time T+1, and we engineer A such that it shines a light at time T+2 if the prediction presented by D at time T+1 was "no light" and reversely, no light if the prediction was light. Then by construction D was wrong in its prediction.
It seems completely paradoxical to me and I don't know what to conclude or what to do with that. Has it been already solved somewhere ?
thanks