In physical cosmology, astronomy and celestial mechanics, dark energy is a hypothetical form of energy that permeates all of space and tends to increase the rate of expansion of the universe.
Dark energy is the most accepted theory to explain recent observations and experiments that the universe appears to be expending at an accelerating rate.
In the standard model of cosmology, dark energy currently accounts for 73% of the total mass- energy of the universe.
Dark energy certainly counts as frontier science. The discovery a decade ago that the universe is speeding up, in defiance of common sence or cosmic gravity, has thrown in to doubt notions about the fate of the universe and of life with in it, not to mention gravity and even the nature of laws of physics. It is as if, when you drop your car key, they shoot up to the ceiling.
Physicists have one ready-made explanation for this behavior, but it is a cure that many of them think is worse than the desease: a fudge factor invented by Einstein in 1917 called the cosmological constant. He uggested, and quantum thory has subsequently confirmed, that empty space could exert a repulsive force blowing things apart. But the best calculation predict an effect 10 to the exponent of 120 times greater than what astronomers have measured, causing physicists to metaphorically tear their out mutter about multiple universe.
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