What does modified newtonian dynamics mean?

Definitions for modified newtonian dynamics
mod·i·fied new·to·nian dy·nam·ics

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Wiktionary

  1. modified Newtonian dynamicsnoun

    A proposed extension to Newtonian dynamics that would obviate the need to assume the presence of dark matter

Wikipedia

  1. Modified Newtonian dynamics

    Modified Newtonian dynamics (MOND) is a hypothesis that proposes a modification of Newton's law of universal gravitation to account for observed properties of galaxies. It is an alternative to the hypothesis of dark matter in terms of explaining why galaxies do not appear to obey the currently understood laws of physics. Created in 1982 and first published in 1983 by Israeli physicist Mordehai Milgrom, the hypothesis' original motivation was to explain why the velocities of stars in galaxies were observed to be larger than expected based on Newtonian mechanics. Milgrom noted that this discrepancy could be resolved if the gravitational force experienced by a star in the outer regions of a galaxy was proportional to the square of its centripetal acceleration (as opposed to the centripetal acceleration itself, as in Newton's second law) or alternatively, if gravitational force came to vary inversely linearly with radius (as opposed to the inverse square of the radius, as in Newton's law of gravity). MOND departs from Newton's laws at extremely small accelerations that are characteristic of the outer regions of galaxies as well as the inter-galaxy forces within galaxy clusters, but which are far below anything encountered in the Solar System or on Earth. MOND is an example of a class of theories known as modified gravity, and is an alternative to the hypothesis that the dynamics of galaxies are determined by massive, invisible dark matter halos. Since Milgrom's original proposal, proponents of MOND have claimed to successfully predict a variety of galactic phenomena that they state are difficult to understand as consequences of dark matter.Though MOND explains the anomalously great rotational velocities of galaxies at their perimeters, it does not fully explain the velocity dispersions of individual galaxies within galaxy clusters. MOND reduces the discrepancy between the velocity dispersions and clusters' observed missing baryonic mass from a factor of around 10 to a factor of about 2. However, the residual discrepancy cannot be accounted for by MOND, requiring that other explanations close the gap such as the presence of as-yet undetected missing baryonic matter.The accurate measurement of the speed of gravitational waves compared to the speed of light in 2017 ruled out a certain class of modified gravity theories but concluded that other MOND theories that dispense with the need for dark matter remained viable. Two years later, theories put forth by Constantinos Skordis and Tom Zlosnik were consistent with gravitational waves that always travel at the speed of light. Later still in 2021, Skordis & Zlosnik developed a subclass of their theory called "RMOND," for "relativistic MOND," which had "been shown to reproduce in great detail the main observations in cosmology, including the cosmic-microwave-background power spectrum, and the matter structure power spectrum."

Wikidata

  1. Modified Newtonian dynamics

    In physics, Modified Newtonian dynamics is a hypothesis that proposes a modification of Newton's law of gravity to explain the galaxy rotation problem. When the uniform velocity of rotation of galaxies was first observed, it was unexpected because Newtonian theory of gravity predicts that objects that are farther out will have lower velocities. For example, planets in the Solar System orbit with velocities that decrease as their distance from the Sun increases. MOND was proposed by Mordehai Milgrom in 1983 as a way to model this observed uniform velocity data. Milgrom noted that Newton's law for gravitational force has been verified only where gravitational acceleration is large, and suggested that for extremely small accelerations the theory may not hold. MOND theory posits that acceleration is not linearly proportional to gravitational force at small values. MOND stands in contrast to the more widely accepted theory of dark matter. Dark matter theory suggests that each galaxy contains a halo of an as yet unidentified type of matter that provides an overall mass distribution different from the observed distribution of normal matter. This dark matter accounts for the uniform rotation velocity data without modifying Newton's law of gravity.

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Numerology

  1. Chaldean Numerology

    The numerical value of modified newtonian dynamics in Chaldean Numerology is: 5

  2. Pythagorean Numerology

    The numerical value of modified newtonian dynamics in Pythagorean Numerology is: 7

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"modified newtonian dynamics." Definitions.net. STANDS4 LLC, 2024. Web. 28 Mar. 2024. <https://www.definitions.net/definition/modified+newtonian+dynamics>.

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