dy156 that article missed out the ultimate irony!
Einstein postualted the existence of such a force, and called it the "Cosmological Constant".
Later on he revoled this, and claimed that this was "the biggest mistake of my life"!
The genius can't be wrong...even when he tries!
With regards to the last paragraph, I don't think any scientist would make the claim that he understands the physical world.
It is only public perception which builds the picture that science is "finished", and that the only things we don't know about are completely insignificant things like what happens when particle A smashes against particle B at a few hundred miles an hour.
Simple fact.
We have two excellent physical theories, General Relativity and Quantum Mechanics, each of which works brilliantly in its own field.
Here's the rub: They are
completely and utterly incompatible.
Einstein spent the latter half of his life trying to bring them together under his "unified field theory", but failed.
Richard Feynmann made a notable attempt with his theory of Quantum Electrodynamics, but ultimatly failed.
All the top modern physicists (Hawking, Penrose, etc) have tried, and are still trying to this day.
EDIT: The unification of Quantum Mechanics and General Relativity is what people are talking about when they refer to a Theory of Everything or a Grand Unified Theory.