Astrophysics (Index)About

modified Newtonian dynamics

(MOND)
(alternative theory to "dark matter")

Modified Newtonian dynamics (MOND) is a variant on Newton's laws developed in 1983 by Mordehai Milgrom, offering an explanation for the same observations that motivate the concept of dark matter. MOND is not widely accepted in physics, but often gets consideration in studies if they might provide evidence for or against it.

MOND affects gravity by modifying the law, "F=ma", its modification being insignificant within daily life and throughout the solar system, but significant when forces are extremely small, such as that of gravity over the distances between stars, galaxies, etc. It can be considered a radical change to physics (as was general relativity), but because the evidence for dark matter depends so much on large-scale dynamics, science demands that alternatives should be explored. MOND does not offer a fully-defined law, but a template that fits laws which could produce the effects attributed to dark matter. In place of the law, F=ma, MOND has:

F = m μ(a/a0) a
μ( x>>1 ) ≈ 1
μ( x<<1 ) ≈ x

Various functions are tried as a workable μ(x), one example being:

μ(x) = x / (1+x)

Research into MOND has continued and continues: variants consistent with relativity have been produced, as well as studies specifically looking for evidence, and ideas developed of how it might be tested, one such idea being tracking wide binaries.


(physics,theory,gravity)
Further reading:
https://en.wikipedia.org/wiki/Modified_Newtonian_dynamics
http://www.scholarpedia.org/article/The_MOND_paradigm_of_modified_dynamics
https://ui.adsabs.harvard.edu/abs/2006AIPC..822..253S/abstract
https://ui.adsabs.harvard.edu/abs/1983ApJ...270..365M/abstract
https://ui.adsabs.harvard.edu/abs/1983ApJ...270..371M/abstract
https://ui.adsabs.harvard.edu/abs/1983ApJ...270..384M/abstract

Referenced by pages:
alternative cosmologies
bigravity
Bullet Cluster
cosmological model
dark matter (DM)
entropic gravity
gravity
stellar stream

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