It looks like you're using an Ad Blocker.
Please white-list or disable AboveTopSecret.com in your ad-blocking tool.
Thank you.
Some features of ATS will be disabled while you continue to use an ad-blocker.
Originally posted by billyjack
If any theoretical physists visit the ATS for laughs I have a question.
Originally posted by billyjack
As I understand, the gravitational effects of the movement of stars in galaxies and the increasing speed of the expansion of the universe requires dark matter and dark energy to account for the observations. This seems like a way to account for error in the theory, similar to the "Zachary variable correction factor" we appled in engineering school. That factor is that number which can be added, subtracted, multiplied or divided into your answer to get the correct answer.
Originally posted by billyjack
In short, could not the observed effects required to account for the observation be accounted for by using a variable gravitational constant instead of some mysterious onobserved mass or energy? If the gravitational constant is actually higher near the black hole in the center of virtually every galaxy observed and becomes less as a function of the distance from a black hole then gravitational equations could be made to balance without without creating the "correction factors'. Since we don't have an effective theory of quantum gravity, maybe we don't understand gravity at inverse Planck distances either.
I remember you! You're the excellent contributor to ATS who made all those knowledgeable and informed posts on the gulf oil spill! Great job on those, I worked in the gulf oil industry, but not as long as you so I appreciated your insights, and I could tell you know what you're talking about.
Originally posted by billyjack
If any theoretical physists visit the ATS for laughs I have a question.
As I understand, the gravitational effects of the movement of stars in galaxies and the increasing speed of the expansion of the universe requires dark matter and dark energy to account for the observations. ...
In short, could not the observed effects required to account for the observation be accounted for by using a variable gravitational constant instead of some mysterious onobserved mass or energy?
That website has some information on the MOND hypothesis, and the author realizes he's in the minority who give it serious consideration. You might want to try some of the links there and read up on it.
Rather than invoking some invisible form of dark matter, it hypothesizes a subtle change to the effective force law at extremely low accelerations (< 10-10 m/s/s).
So at least according to that relatively recent research, MOND isn't looking too good. I'm open minded enough to read research about it and won't bury MOND until there's a good explanation for dark matter observations, and since we don't have a good explanation yet, I would say MOND is not completely dead on that basis. But I don't hold any high hopes for it.
a new study aimed at detecting the Milky Way’s dark disk have come up empty....
Using estimations on the mass from the visible stars and the interstellar medium, the team compared this visible mass to the solution for mass from the observations of the kinematics to search for a discrepancy indicative of dark matter. When the comparison was made, the team discovered that, “[t]he agreement between the visible mass and our dynamical solution is striking, and there is no need to invoke any dark component.”
While this finding doesn’t rule out the presence of dark matter, it does place constraints on it distribution and, if confirmed in other galaxies, may challenge the understanding of how dark matter serves to form galaxies...
Yet while the research may show a lack of our understanding of dark matter, the team also notes that it is even more devastating for dark matter’s largest rival. While dark matter may yet hide within the error bars in this study, the findings directly contradict the predictions of Modified Newtonian Dynamics (MOND). This hypothesis predicts the apparent gain of mass due to a scaling effect on gravity itself and would have required that the supposed mass at the scales observed be 60% higher than indicated by this study.
That is an incomplete formulation of what you mean. If you read the OP you said it needed to be larger nearer to the center of the galaxy (at least that's how I interpreted closer to the black hole).
Originally posted by billyjack
reply to post by Observer99
I aapreciate the responce,but I still believe that the value of G has to be larger not smaller.
I did cite a recent study that seems to directly contradict MOND. However if you read the links I provided on the topic, there are arguments why we might want to keep it on the table until we have some explanations for our observations. The study I cited didn't even confirm the existence of dark matter, though it didn't contradict it, like it did MOND.
I thought the MOND theory had been shot down.
Yes and another one posits that we are all inside a giant black hole. There is a lot of highly speculative stuff out there, much of it consists of a lot of math but zero observable evidence to confirm it so the way I see it, for every 50 theories I hear like that, 49 of them are probably wrong, and one might be right but I have no way to tell which one that might be if none of them have any evidence. So I tend to treat all of them like they have a high probability of being wrong until there's some evidence to back them up.
Finally, I seem to remeber that some theoretical physisist had theorized that gravity some how leaks into our universe from outside; part of string/membrane theory.