Watsisname wrote:Hornblower, The origin of the highest energy cosmic rays, and why we observe as many as we do despite the expectation that the CMB would apply an important breaking effect to them, is a significant unresolved problem in astrophysics. Dark energy is also pretty darn mysterious, but I'm doubtful that there is any important connection between the two.
When modeled as a cosmological constant, dark energy is a type of gravitational field (more generally, a correction to the metric of space-time) and so it affects all particles equivalently.
Dark energy also can't accelerate particles in a particular direction. Intuitively one would think dark energy would expand the universe by "pushing out" on things, but that's actually not how it works -- in cosmology it can't work that way because there is no preferred direction to push from and no walls to push against. The dark energy is uniform and so it does not apply a net force on anything. Instead, it affects the expansion of space itself because of its energy density, which changes the metric of space-time.
Didn't we observe some off-the-charts cosmic ray particle a few years ago that had the energy of a fast ball (pretty amazing for a subatomic particle.) It had extragalactic origins.