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It’s strange to imagine, but physicists cannot accurately describe nearly three quarters of the matter and energy in the universe. Because as it turns out, nearly 73% of the universe is composed of a mysterious substance called dark energy. In physical terms, no one knows exactly what dark energy is. Instead, dark energy is a theoretical construct that permeates all of the space in the universe and can provide an explanation as to why the expansion rate of the universe is increasing. Simply put, Dark Energy is a force that is intrinsically found in space and is causing the expansion rate of the universe to increase.

There are different opinions as to how and when Dark Energy was discovered. Although physical observations have only recently confirmed the existence of dark energy, some say that Einstein discovered Dark Energy way back when he was formulating his General Theory of Relativity. While making the General Theory of Relativity, Einstein originally added the “cosmological constant” into his equations in order create a static universe. In this original formulation of General Relativity, the cosmological constant acted as a mysterious force that caused the universe to expand; this was necessary in order for General Relativity to predict a static universe, which Einstein wanted. However, Einstein then removed this cosmological constant when observations by Hubble indicated that the Universe was expanding. But since the cosmological constant causes the Universe to expand and would permeate all of space, it is essentially dark energy.

However, others say that dark energy was really discovered in 1998, as this was the first time a physical phenomenon that required the existence of dark energy to be explained was observed. Scientists from Berkeley and scientists from Australian National University observed two supernovas that were farther apart than models would predict in a universe that lacked dark energy. Consequently, others say that these scientists discovered dark energy.