Glossary term: Dark Energy

Description: Dark energy is a proposed cause for the accelerated expansion of the Universe, which has been happening for the past six billion years on the largest scales. Dark energy is often described as exhibiting a "force" opposite to gravity. The effects of dark energy are inferred through indirect observations and measurements of Type Ia supernovae, the cosmic microwave background (CMB) radiation, clusters of galaxies, gravitational lensing, and baryon acoustic oscillations, which seem to indicate that dark energy makes up just over 70% of the Universe’s composition. Despite this, there is much research and debate about the nature of dark energy, whether there are different types of dark energy, whether dark energy changes over cosmic time, and alternatives to dark energy.

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Term and definition status: This term and its definition is still awaiting approval

The OAE Multilingual Glossary is a project of the IAU Office of Astronomy for Education (OAE) in collaboration with the IAU Office of Astronomy Outreach (OAO). The terms and definitions were chosen, written and reviewed by a collective effort from the OAE, the OAE Centers and Nodes, the OAE National Astronomy Education Coordinators (NAECs) and other volunteers. You can find a full list of credits here. All glossary terms and their definitions are released under a Creative Commons CC BY-4.0 license and should be credited to "IAU OAE".