Science, Tech, Math › Science Dark Energy in Physics Share Flipboard Email Print NASA / WMAP Science Team Science Physics Physics Laws, Concepts, and Principles Quantum Physics Important Physicists Thermodynamics Cosmology & Astrophysics Chemistry Biology Geology Astronomy Weather & Climate By Andrew Zimmerman Jones Andrew Zimmerman Jones Math and Physics Expert M.S., Mathematics Education, Indiana University B.A., Physics, Wabash College Andrew Zimmerman Jones is a science writer, educator, and researcher. He is the co-author of "String Theory for Dummies." Learn about our Editorial Process Updated on November 24, 2019 Dark energy is a hypothetical form of energy that permeates space and exerts a negative pressure, which would have gravitational effects to account for the differences between the theoretical and observational results of gravitational effects on visible matter. Dark energy is not directly observed, but rather inferred from observations of gravitational interactions between astronomical objects. The term "dark energy" was coined by the theoretical cosmologist Michael S. Turner. Dark Energy's Predecessor Before physicists knew about dark energy, a cosmological constant was a feature of Einstein's original general relativity equations that caused the universe to be static. When it was realized the universe was expanding, the assumption was that the cosmological constant had a value of zero--an assumption that remained dominant among physicists and cosmologists for many years. Discovery of Dark Energy In 1998, two different teams--the Supernova Cosmology Project and the High-z Supernova Search Team--both failed at their goal of measuring the deceleration of the universe's expansion. In fact, they measured not only a deceleration but a totally unexpected acceleration (Well, almost totally unexpected: Stephen Weinberg had once made such a prediction). Further evidence since 1998 has continued to support this finding, that distant regions of the universe are actually speeding up with respect to each other. Instead of a steady expansion, or a slowing expansion, the expansion rate is getting faster, which means that Einstein's original cosmological constant prediction manifests in today's theories in the form of dark energy. The latest findings indicate that over 70% of the universe is composed of dark energy. In fact, only about 4% is believed to be made up of ordinary, visible matter. Figuring out more details about the physical nature of dark energy is one of the major theoretical and observational goals of modern cosmologists. Also Known As: vacuum energy, vacuum pressure, negative pressure, cosmological constant Cite this Article Format mla apa chicago Your Citation Jones, Andrew Zimmerman. "Dark Energy in Physics." ThoughtCo, Aug. 26, 2020, thoughtco.com/dark-energy-2698971. Jones, Andrew Zimmerman. (2020, August 26). Dark Energy in Physics. Retrieved from https://www.thoughtco.com/dark-energy-2698971 Jones, Andrew Zimmerman. "Dark Energy in Physics." ThoughtCo. https://www.thoughtco.com/dark-energy-2698971 (accessed June 6, 2023). copy citation