The Earth and Neptune and Sirius are all affected by gravity, why don't they simply clump up? Dark matter is quite accurately simulated in this endeavour, though we are unsure of the direct significance of the results. The dark matter reacts to semi-traditional gravitational forces, but only with other dark matter. Dark matter does not, in any way, react with the normal matter we are familiar with; this is because dark matter is simply the type of unusual matter that a black hole spits out once it absorbs regular matter.
The only possible interaction we could have with dark matter is when you turn on a walkie-talkie and hear static -- that static is deemed unpredictable simply because we can't model the dark matter creating it precisely enough. One of the reasons dark matter doesn't directly interact with light matter is because it can actually have nine electrons in its valence shell, hence making it unable to "fit" into the aether that we have access to. That being said, it is nearly impossible to accurately simulate its behavior and the scientists who took on this endeavour are to be praised for effort but ignored for their 'precision'.
