What exactly is dark energy?

Dark energy is a hypothetical form of energy believed to be responsible for the observed acceleration in the expansion of the universe. Unlike ordinary matter or dark matter, it exerts a negative, repulsive pressure, causing space to stretch at an increasing rate.

How much of the universe is composed of dark energy?

According to current cosmological models, dark energy makes up approximately 68% of the total mass-energy content of the observable universe. Dark matter accounts for about 27%, and ordinary (baryonic) matter constitutes only about 5%.

When and how was dark energy discovered?

The existence of dark energy was inferred in 1998 by two independent teams of astronomers studying distant Type Ia supernovae. Their observations showed that the expansion of the universe was accelerating, not decelerating, as previously thought.

What are the leading theories about the nature of dark energy?

The most widely accepted theory is that dark energy is the cosmological constant, a constant energy density inherent to space itself, as proposed by Albert Einstein. Other theories include 'quintessence,' which posits a dynamic, time-varying energy field.

Is dark energy the same as dark matter?

No, dark energy and dark matter are fundamentally different. Dark matter is a form of invisible mass that exerts gravitational pull, helping galaxies hold together. Dark energy is a mysterious force causing the universe's expansion to accelerate.