The last 2 days Physorg.com has had articles about repulsive gravity being a possible candidate to replace Dark Energy.
Repulsive gravity as an alternative to dark energy (Part 1: In voids)Repulsive gravity as an alternative to dark energy (Part 2: In the quantum vacuum)In Part 1 the idea is that antimatter is concentrated in the cosmic voids where we don't see any stars. The thought is that the repulsion of the antimatter is what keeps the visible stars and galaxies out of the voids and causes the accelerated expansion of the universe. My first problem with this is: what is the antimatter? if it is just matter that is made up of antiparticles then I should think that the voids would be full of stars and galaxies, because the antimatter would work the same as regular matter.
In part 2 the idea is that the quantum vacuum is full of virtual particles and antiparticles that would produce enough repulsion to account for the accelerated expansion of the universe. The problem with this one and in a way with the first one is that nobody knows that antiparticles have the opposite gravitational sign from normal particles. There are currently tests going to to see if the repulsion can be detected.
Both of the ideas do have consequences on the expansion of the universe. With these ideas the acceleration may be tapering off and so the end of the universe will be quite different from what current theory says.
Bill Gill
