MOND gravity, an explanation please.

In summary, the conversation revolves around the theory of Modified Newtonian Dynamics (MOND) and its ability to explain the rotation of galaxies. The main questions discussed are how MOND differs from the inverse-square law, what problems in science it addresses and the level of support it receives from the scientific community. The conversation also touches on the topic of metric skew tensor gravity, which is related to MOND but not fully understood. Overall, while MOND offers a potential alternative to dark matter, it has not yet been conclusively proven and has limitations when applied to larger structures.
  • #1
Chaos' lil bro Order
683
2
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 address and what solutions does it offer?

3) How serious does the scientific community take MOND and who are the main proponents of the theory?


Thanks a bunch guys, I'm excitedly awaiting replies.
 
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  • #2
Have a browse of the "Pioneer Anomaly" thread, Chaos. It won't answer your question directly, but there's some interesting related stuff in there.

https://www.physicsforums.com/showthread.php?t=121897

I still don't know what metric skew tensor gravity is. Maybe it's to do with massive rotating masses generating more gravity because of frame drag or something. Not sure.
 
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  • #3
MOND is an alternative to the dark matter halos proposed to explain the rotational velocity of the arms in most galaxies. It mostly fails when applied to large scale structures. The MOND conjecture, however, has not yet been disproven, merely that it works no better than existing models.
 
  • #4

1. What is MOND gravity?

MOND (Modified Newtonian Dynamics) gravity is a proposed modification to the laws of gravity that attempts to explain the observed discrepancies between the predicted and observed motion of galaxies without the need for dark matter.

2. How does MOND gravity differ from Newton's law of gravity?

In Newton's law of gravity, the force of gravity between two objects is directly proportional to the product of their masses and inversely proportional to the square of the distance between them. In MOND gravity, the force of gravity is modified at low accelerations, specifically when the acceleration is below a certain threshold called "a0". Below this threshold, the force of gravity is no longer inversely proportional to the square of the distance, but instead follows a different function.

3. What evidence supports the existence of MOND gravity?

Some of the evidence for MOND gravity comes from the observed rotation curves of galaxies, which do not follow the expected relationship between orbital velocity and distance from the center of the galaxy. Additionally, MOND gravity has been able to successfully predict the dynamics of galaxy clusters without the need for dark matter.

4. How does MOND gravity explain the observed discrepancies in galaxy rotation curves?

MOND gravity proposes that at low accelerations, the force of gravity is stronger than predicted by Newton's law. This means that the outer regions of galaxies, where the acceleration is lower, experience a stronger gravitational force and thus do not require the presence of dark matter to explain their observed rotation.

5. Is MOND gravity widely accepted by the scientific community?

MOND gravity is a controversial theory and is not widely accepted by the scientific community. While it has been able to explain some observations, there are still many unanswered questions and inconsistencies. The majority of the scientific community still supports the existence of dark matter as a more well-supported explanation for the observed discrepancies in galactic motion.

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