the inability of current science to square relativity and its predictions of space-time with quantum mechanics is exactly the reason why we aren't sure, and one of the biggest open questions in physics.
I mean it could all be strings, or quantum gravity, or Wolfram's crazy graph theory automatons, or maybe something else entirely.
note that the Higgs is not responsible for all mass as is understood by a layperson. The Higgs field gives mass to subatomic particles but it doesn't translate directly into the mass of objects as we know them.
The mass of the three quarks (one up quark and two down quarks) making up a neutron is only about 1% of the mass of a neutron. The rest of the mass comes from strong nuclear force interactions via gluons which are themselves massless.
Doesn't this simply follow from the mass-energy equivalence (the energy being that of interaction with the Higgs in this case)? Not to say that said equivalence is intuitively obvious, of course.
No. The higgs is a field that gives some elementary particles themselves (the W and Z bosons) mass, but doesn't necessarily say anything about gravity or how gravitic 'force' is transferred.
There was a lot of media hype about 'the god particle' that doesn't really translate into reality. I've said this in another comment, but if you add up the mass of the constituent quarks of a neutron, you get approximately 1% of a neutron's mass. The majority of the mass comes from interactions with strong nuclear force which are mediated by gluons, which are themselves massless.
There is no current agreed upon understanding of quantum gravity or if gravitons exist. I think the big contenders right now are String Theory (which seems to be having issues progressing in a way that is useful) and loop quantum gravity, but there are a lot more theories than that.
