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Concepts Encyclopedia Entry 1779293044

** This encyclopedia entry explores the concept of **Dark Matter**, a mysterious and invisible form of matter that makes up approximately 27% of the universe's total mass-energy density. ## Overview Dark Matter is a hypothetical form of matter that does not emit, absorb, or reflect any electromagnetic radiation, making it invisible to our telescopes. Despite its elusive nature, Dark Matter's presence can be inferred through its gravitational effects on visible matter and the way galaxies and galaxy clusters move. The concept of Dark Matter was first proposed by Swiss astrophysicist **Fritz Zwicky** in the 1930s, and since then, a vast amount of observational evidence has accumulated to support its existence. The existence of Dark Matter was initially proposed to explain the observed behavior of galaxy clusters and the rotation curves of galaxies. In the 1970s, **Vera Rubin** and **Kent Ford** discovered that the rotation curves of galaxies were flat, indicating that stars and gas in the outer regions of galaxies were moving at a constant speed, rather than slowing down as expected due to the decreasing gravitational pull. This observation suggested that there was an unseen mass of matter surrounding the galaxy, which was later attributed to Dark Matter. ## History/Background The concept of Dark Matter has its roots in the early 20th century, when **Albert Einstein** developed the theory of General Relativity. According to this theory, the universe's expansion is accelerating, and the density of matter in the universe is not sufficient to explain this acceleration. In the 1930s, **Fritz Zwicky** proposed the idea of **Dunkle Materie** (German for "dark matter") to explain the observed behavior of galaxy clusters. Zwicky's idea was met with skepticism at first, but subsequent observations and experiments have confirmed the existence of Dark Matter. ## Key Information * **Composition:** Dark Matter is thought to be composed of Weakly Interacting Massive Particles (WIMPs), which interact with normal matter only through the weak nuclear force and gravity. * **Density:** Dark Matter makes up approximately 27% of the universe's total mass-energy density. * **Distribution:** Dark Matter is thought to be distributed throughout the universe, with a higher concentration in the centers of galaxies and galaxy clusters. * **Effects:** Dark Matter's presence can be inferred through its gravitational effects on visible matter and the way galaxies and galaxy clusters move. * **Detection:** Dark Matter has not been directly detected, but its presence can be inferred through indirect methods, such as observing the effects of Dark Matter on galaxy rotation curves and the distribution of galaxy clusters. ## Significance The discovery of Dark Matter has revolutionized our understanding of the universe, providing evidence for the existence of invisible matter that makes up a significant portion of the universe's mass-energy density. The study of Dark Matter has also led to a deeper understanding of the universe's evolution and the formation of structure within it. Furthermore, the search for Dark Matter has driven the development of new technologies and experimental techniques, such as the Large Underground Xenon (LUX) experiment and the Alpha Magnetic Spectrometer (AMS) on the International Space Station. INFOBOX: - **Name:** Dark Matter - **Type:** Hypothetical form of matter - **Date:** 1930s (proposed by Fritz Zwicky) - **Location:** Throughout the universe - **Known For:** Making up approximately 27% of the universe's total mass-energy density TAGS: Dark Matter, Invisible Matter, Galaxy Rotation Curves, Galaxy Clusters, Weakly Interacting Massive Particles (WIMPs), General Relativity, Albert Einstein, Fritz Zwicky, Vera Rubin, Kent Ford.