An article by Ian O’Neill summarizes the results of a new study of dark matter.
By observing collisions between galaxies they found that when dark matter passes close by other dark matter the dark matter does not exert any observable force or drag on each other.
Where does that leave us?
Not much has changed. Currently the only way we can detect dark matter is by its gravitational effects on matter. I suspect we will need to keep our minds wide open if we are ever to solve this problem. The answer may be something we cannot imagine.
We have to hope that chance, serendipity,or an insight from an unusual mind, will reveal the secrets of dark matter. In the meantime legions of brilliant and hard-working physicists will continue to bash particles together while others concoct audacious theories from their calculations.