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."
So I was googling around and I happen to see several references to MOND theory, Modified Newtonian Dynamics.
Anyway, it proposes that there is this other new constant a_{0} that is a very very very low acceleration that exists. Basically, as far as I can tell so far the whole idea is that...
http://www.nasa.gov/home/hqnews/2006/aug/HQ_M06128_dark_matter.html
press conference Monday 21 August
CHANDRA team has been watching the highspeed collision of two clusters of galaxies
they can see the GAS of the clusters colliding and getting hot so it radiates Xrays
they may have also seen...
I need some help with the formula from the MOND Theory. I just want to understand it and be able to do it myself without any help, but that just didn't happen. so i need some help from professionals. the formula is:
F=mµ(a/a0)a
I know that symbol in there is "Micro" (µ) but i don't know...
http://arxiv.org/abs/gr-qc/0606039
for something to gain visibility all it needs is people interested in proving or disproving it. It doesn't need people to BELIEVE it.
Some PF members seem not to have heard of RELATIVISTIC MOND. Or else they may be positive that MOND does not do lensing...
Greetings,
I've heard something to the effect that MOND can explain the rotation of galaxies, but the article was very fuzzy.
Can someone please explain to me MOND...
1) How is MOND different from the inverse-square law? (math please)
2) What 'problems' in science does MOND...
Another "dark" horse in the MOND race
I'm glad there are several competing alternatives to dark matter.
Bekenstein's TeVeS doesn't have the field to itself.
this appeared today:
http://arxiv.org/abs/astro-ph/0605322
Dark energy, MOND and sub-millimeter tests of gravity
I. Navarro, K. Van...
http://arxiv.org/abs/astro-ph/0601478
Modified Newtonian Dynamics, an Introductory Review
Riccardo Scarpa
To Appear in the proceeding of the "First crisis in cosmology" conference, published in the American Institute of Physiscs' proceedings series, Vol. 822. (includes 13 pages and 12...
there must be a lot of ways already proposed to do this.
can anyone list those considered most promising?
has this been the subject of a thread already
today I saw this paper which claims to suggest a way to
observationally distinguish MOND from DM-----to tell which is right.
I think...
in case anyone is interested:
http://arxiv.org/abs/astro-ph/0505017
I know Joe Silk slightly and respect him a lot.
I don't know much at all about this subject (tests of MOND)
but assume that this paper is of interest because Silk
is so highly regarded
http://uk.arxiv.org/abs/astro-ph/0504051
But, in the other direction we have:
http://uk.arxiv.org/abs/astro-ph/0503104
This involves the so called "dark galaxy" and contains the caveat that the measurements are not yet considered definitive.
And, for all around MOND/TeVeS junkies...
http://arxiv.org/astro-ph/0503104
Does VIRGOHI21 Pose a Problem for MOND?
Scott Funkhouser, Occidental College, Los Angeles
March2005
"If the inferred parameters of the recently discovered dark galaxy VIRGOHI21 are verified then thedynamics of the body may represent a counter-example...
MOND (for modified Newtonian Dynamics) is a proposed alternative to the dark matter theory used to explain galatic dynamics that don't follow general relativity if only observed matter is taken into account. Jacob Bekenstein (whose recent paper is first listed here), in 2004, made a major...
I ran across this some time ago (probably in this forum, somewhere or other) - but I thought it was quite interesting at the time.
It's one of the very few alternatives to GR that is actually inspired by considerations of actual observation.
Basically, someone feels that they've discovered...
The gravitational force acting on a particle of mass m, on the
surface of a sphere of radius 10^26 metres and with a mass of 10^52
kg is given by
G x10^52 m / (10^26) ^ 2
The acceleration is given by G x10^52 / (10^26) ^ 2 = 10^ - 11 m/ s^2
This is the magnitude of accleration at which...
The gravitational force acting on a particle of mass m, on the
surface of a sphere of radius 10^26 metres and with a mass of 10^52
kg is given by
G x10^52 m / (10^26) ^ 2
The acceleration is given by G x10^52 / (10^26) ^ 2 = 10^ - 11 m/ s^2
This is the magnitude of accleration at which...
It’s interesting that MOND splits Newtonian gravity into two cases
and the Modified version of Newtonain dynamics seems to happen in galaxies and clusters of galaxies with magnetic fields.What is the physical reason that MOND could be right?
If we assume that there is another force interacting...
Space is filled with gravitons moving in every direction.
These gravitons push masses together and cause "attraction".
When gravitons approach a spiral galaxy parallel to its plane,
they get pushed together and concentrated by the magnetic field lines of the galaxy.
As they double their...
can someone please explain about this theory?
(it's roots, what does it solve, why it's better description than the dark matter proposal).
thanks in advance.