Missing Matter

One of the purposes of the new LHC at Cern is to search for dark matter. My understanding is that this has been so elusive thus far, because it has been completely undetectable by current technology. 'Normal' matter is completey oblivious to it and unaffected by it.I understand that we are only aware of it's existence because the observed motion of galaxies cannot be explained just by the mass of the matter which we know about.So how can it be that dark matter affects the motion of galaxies when 'normal' matter is not affected by dark matter? Because the we know the motion of observable matter in galaxies is affected by dark matter, am I not correct to suggest that it should be possible to detect dark matter?I'm sure there's a simple explanation to this.Edited by Hoof Hearted, : No reason given.Edited by Hoof Hearted, : No reason given.

If normal matter is affected by the gravity of dark matter, then I would assume that dark matter is similarly affected by the gravity of normal matter.Our earth is held together by the force of gravity. So if dark matter is affected by the gravitational forces of normal matter, I would expect dark matter to be attracted towards our earth.So I wonder therefore, if there is a sphere of dark matter occupying the same region of space as our earth.

Of course that probably would be dependent on dark matter having similar physical properties as normal matter. What I mean is that normal matter can form planets because it is capable of becoming complex molecules which can have a solid state.

So am I to assume that particles such as WIMPs cannot practically be detected, because we don't have a means of detecting their gravitional forces amongst the gravity of conventional matter which surrounds us?