NASA: Dark Energy Looks Like Einstein's "Greatest Blunder"

Einstein called the cosmological constant his "greatest blunder" but according to NASA, new evidence suggests Einstein was right after all:

The study strengthens the evidence that dark energy is the cosmological constant. Although it is the leading candidate to explain dark energy, theoretical work suggests it should be about 10 raised to the power of 120 times larger than observed. Therefore, alternatives to general relativity, such as theories involving hidden dimensions, are being explored.

Since dark energy acts as an "antigravity force" the physics behind the observed phenomenology is now one of the greatest scientific problems of the early 21st century.