Quintessence, a term borrowed from the Greeks who identified it as a mysterious fifth element, is a term used to describe a theoretical form of dark energy that could describe why the universe is accelerating its expansion. If it exists, quintessence could be responsible for pushing particles away from each other.
Quintessence is a way of explaining a peculiarity in cosmology that no scientist expected. The standard prevailing theory, in the 1980s, was that the universe was expanding. However, at some point, scientists thought it would end. There was so much gravity-generating matter out there that it would eventually take over and bring the universe back to together.
However, given the rate at which the universe is expanding, many scientists are now questioning whether the expansion will stop at all. In other words, the forces at work to expand the universe more than counteract the forces working to bring it all together -- and by a wide margin. This is at the heart of what quintessence may be all about.
The existence of quintessence may be further bolstered by exploding stars, events known as supernovas. Based on the constants that scientists know exist in the universe, they have been able to conclude that supernovas farther away are moving away from us as a much faster rate than closer supernovas. If that is true, that means the outer edges of the universe are expanding faster than the interior.
Still, quintessence has yet to receive broad acceptance. Some say the evidence for a rapidly-expanding universe is weak. They argue the observations of the supernovas are so distant that many other things could be affecting what scientists are seeing, including minute particulate matter, or space dust.
If quintessence does exist, its presence could provide a number of benefits. It may help us better understand not only the nature of the universe, but also how it came into existence. In addition, if quintessence is truly a form of dark energy, there is a chance that it could be harnessed and used as a virtually inexhaustible supply of energy. However, this is still highly theoretical and may be decades, if not centuries, away from having a practical application.