The data suggest that in fact, dark energy has changed little, if at all, over the course of cosmic history. Though hardly conclusive, that finding lends more support to what has become the conventional theory, that the source of cosmic antigravity is the cosmological constant, a sort of fudge factor that Einstein inserted into his cosmological equations in 1917 to represent a cosmic repulsion embedded in space.
Although Einstein later abandoned the cosmological constant, calling it a blunder, it would not go away. It is the one theorized form of dark energy that does not change with time.
Einstein invented his constant to explain why the universe does not collapse. After he abandoned it, the theory was resuscitated by quantum mechanics, which showed that empty space should be bubbling with staggering amounts of repulsive energy. The possibility that it really exists in the tiny amounts measured by the astronomers has flummoxed physicists and string theorists.Because it is a property of empty space, the overall force of Einstein’s constant grows in proportion as the universe expands, until it overwhelms everything.
So far, he said, the results are consistent with the cosmological constant, but other answers are also possible. The possibility that it is the cosmological constant is a mixed blessing. Physicists concede that they do not understand it.
Dr. Carroll of Caltech said, “Dark energy makes us nervous.”
Hmmm, me too, now that you mention it. Thanks for that guys.
[Hell, didn't we have enough to worry about with the obesity crisis? - ed]