Quintessence (physics)

Quintessence (physics)

In physics, quintessence is a hypothetical form of dark energy postulated as an explanation of observations of an accelerating universe. It has been proposed by some physicists to be a fifth fundamental force. Quintessence differs from the cosmological constant explanation of dark energy in that it is a dynamic equation that changes over time, unlike the cosmological constant which always stays constant throughout time. It is suggested that quintessence can be either attractive or repulsive depending on the ratio of kinetic to potential energy in the universe. Specifically, it is thought that quintessence became repulsive about 10 billion years ago (the universe is approximately 13.7 billion years old).