Dark Energy is a theoretical kind of energy that exerts a repulsive force; the reverse effect of gravity. We are unable to directly observe dark energy, but we are able to confidently infer its existence based on observations of astronomical bodies and clusters.
Two major discoveries are essential to the fundamental concept of dark energy. In 1929, astronomer Edwin Hubble was researching supernovae when he came to the conclusion that the universe is growing in size. Since then, researchers have tried to ascertain just how quickly this expansion is decreasing due to the decelerating effects of gravity. However, two independent teams of researchers working in the 1990s discovered the expansion of universe wasn’t decreasing: The expansion was actually accelerating! The force driving this acceleration was dubbed “dark energy.”
After calculating the amount energy required to overcome the gravity of known matter in the universe, researchers established that dark energy comprises approximately 68 percent of the universe. Known matter comprises less than 5 percent of the universe and the rest of the universe is made up of mysterious “dark matter”, which appears to be completely unrelated to dark energy.
In his famous theory of general relativity, Albert Einstein initially included a cosmological constant to take into account what he thought was the static nature of the universe. But after Hubble’s discovery that the universe is expanding, Einstein removed the constant and thought of it as one of his biggest mistakes.
However, Einstein’s miscalculation may be the best way to describe dark energy. Einstein’s constant suggests that space can have its own energy. It also suggests that as more space is created, more dark energy would also be created, increasingly counteracting gravity.
Even though Einstein’s constant matches observations, researchers still aren’t sure why it does.
Problems with Dark Energy Theory
While dark energy is a widely accepted concept, not everybody is onboard and alternative explanations for dark energy have gained traction.
One of the major hurdles is the staggering disparity between the expected power of dark energy, and its detected strength. Calculations based on quantum field theory produce a strength value that is 10120 times bigger than the observations tell us. If dark energy were as strong as calculations indicate, the universe would grow so fast, individual atoms would be pulled apart from one another, making stars incapable of forming.
Clearly, there is a massive fundamental flaw in the theory behind dark energy. This disparity has led some researchers to put forward other, fairly controversial alternatives, or even refuse to acknowledge the existence of dark energy.
Some researchers have proposed that our observations of the universe are skewed because the Milky Way is located within an area of low density that was created by a density wave. Possibly caused by the Big Bang, this cosmic wave in space-time would have left a low-density ripple that is tens of millions of light-years wide. While theoretically possible, this perspective-altering difference in space-time would defy the Copernican principle that says the universe is largely homogenous.