IF dark matter is intangible, but reacts to gravity, shouldn;t it be sinking down and accumulating in the aarths core? And wouldn’t that add to the planet’s mass and gravity over time? Anybody know?
You make a good point, why wouldn’t dark matter form it’s own stars and solar systems? There is certainly a tendency for normal matter to clump up and form huge clumps.
However, as to your first question. If dark matter only interacts gravitationally, then, if was not originally graviationally bound to the earth, it would gain enough kinetic energy as it fell towards (or even through!) the earth to have escape velocity from the earth as it passes through it and out the other side! The interaction of the two bodies (earth and dark matter) might deflect them, but there would be not net exchange of energy.
Not quite. If the current concept of dark matter is correct than it would be able to pass clean through regular matter (for the most part). In which case a particle of dark matter on a collision course with the earth would start out (before impact) traveling at some speed greater than the planet’s escape velocity. The dark matter would be influenced by earth’s gravity, likely being deflected into a new trajectory. But it won’t crash onto the surface like regular matter would and so will not lose its energy, so it just keeps going, traveling though the earth’s interior and emerging from the other side still traveling faster than escape velocity.
I hope that was clear.