[idi banashapan]

Correct, there is no certainty it exists. It is just the best explanation (that dark matter does not interact with light, but does have mass, as something is holding things together) that fits the driven theories used in physics (Newton’s laws of motion and Einstein’s theory of relativity). Keep in mind dark matter has not been show horned into the theories, more the observations in relation to the theories show that something is missing. It’s the most logical answer to what is being seen.

The other option is that physics needs a new theory, such as Modified Newtonian Dynamics.