The current theoretical model for the composition of the universe is that it's made of normal matter, dark energy and dark matter. A new University of Ottawa study challenges this.
Dark matter does interact with matter, though: it interacts gravitationally. It just does not interact in other ways (that we know of yet). All you would have to do to disprove the existence of dark matter is to show that some things interact with it gravitationally but others don’t. However, this is not what we see; what we actually see is a whole bunch of separate things that all experience the effect of the existence of dark matter in the same way. It’s effectiveness as an explanation in this regard is exactly what makes it so difficult to dethrone.
Dark matter does interact with matter, though: it interacts gravitationally. It just does not interact in other ways (that we know of yet). All you would have to do to disprove the existence of dark matter is to show that some things interact with it gravitationally but others don’t. However, this is not what we see; what we actually see is a whole bunch of separate things that all experience the effect of the existence of dark matter in the same way. It’s effectiveness as an explanation in this regard is exactly what makes it so difficult to dethrone.
Dark matter is exactly like adding a constant to your equation so that it fits the numbers.
If by “constant” you mean “3D distribution that explains not just one equation but lots of separate observations”, then sure, it’s just like that.