Vacuum Energy: Gravitational Attraction or Repulsion?

[tenchotomic]

I initially thought of posting this thread in cosmology section but then I realized it's much more general in scope,so Iam posting it here.

Massive bodies attract gravitationally and mass-energy equivalence implies that energy contributes to gravitational attraction.

Then what's so peculiar about vacuum energy that it gives rise to gravitational repulsion instead of attraction?
Is this because of some kind of internal structure it has,which is somehow producing repulsion at the microscopic scale.
Or is it a mere fact that has been observed experimentally(expanding universe etc.) and no theoretical justification yet.

Isn't the term vacuum energy itself a misnomer?

 

[Bloodthunder]

It is not a misnomer. Vacuum (not vacuum =) ) energy is the background energy that exists in space even when there is nothing else in that space (basically a vacuum).

You could read http://en.wikipedia.org/wiki/Vacuum_energy to know more.

 

[tenchotomic]

It is not a misnomer. Vacuum (not vacuum =) ) energy is the background energy that exists in space even when there is nothing else in that space (basically a vacuum).

You could read http://en.wikipedia.org/wiki/Vacuum_energy to know more.

Oops,sorry for spelling(I didn't realized that).But the wikipedia article hardly explain anything that I asked for.