23 FEB 2026
David asks: dark matter and undetectable particles
the dark matter question was really about causal footprint and ontology.
dark matter is matter inferred from gravity, not seen through light. his question pushed on what it means for something to exist if it does not interact with the forces his instruments normally use.
If your position is that dark matter is explained by particles that don't interact electromagnetically but do interact gravitationally, that implies that it is a serious claim to say there likely exist particles that exist ontologically but don't interact electromagnetically or gravitationally, no?
the important distinction is causal footprint. invisible to light is not the same as nonexistent, because gravity is still a footprint. once there is no electromagnetic or gravitational interaction, the claim starts sliding from physics into metaphysics.