Dark Energy - Celestial Objects, Cosmic Forces, Cosmology - Dark energy is a mysterious force that drives the accelerated expansion of the universe. First discovered in 1998 through observations of distant supernovae, dark energy is believed to make up about 68% of the universe's total mass-energy content, making it the dominant force shaping the cosmos. Unlike dark matter, which exerts gravitational attraction, dark energy appears to act as a repulsive force, counteracting gravity on cosmic scales. The most widely accepted explanation is that dark energy is related to Einstein's cosmological constant (?), representing the energy density of empty space, also known as vacuum energy. Alternative theories suggest it could be a new scalar field, quintessence, or a modification of gravity. The cosmic microwave background (CMB), baryon acoustic oscillations (BAO), and large-scale galaxy surveys provide indirect evidence of dark energy's influence. Research efforts, including NASA's Nancy Grace Roman Space Telescope and ESA's Euclid mission, aim to uncover the nature of dark energy and its role in determining the ultimate fate of the universe, whether it will expand forever, slow down, or collapse in a "Big Crunch." Understanding dark energy is one of the greatest unsolved mysteries in modern cosmology, as it dictates the long-term evolution of the cosmos.
