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Dark Matter & Dark Energy

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posted on Jun, 28 2011 @ 11:52 PM
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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. 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.

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.

Thanks, Just curious where I am wrong by someone who remembers and uses differential equations on a daily basis.




posted on Jun, 29 2011 @ 12:56 AM
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reply to post by billyjack
 


Either way they're just making things up. I'm starting to sense more people are under the same impression now...

Formulas don't detail the exact root mechanics, nor does pitching dark energy, dark matter, and dark flow.



posted on Jun, 29 2011 @ 02:27 AM
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Originally posted by billyjack
If any theoretical physists visit the ATS for laughs I have a question.


I don't think it takes a physicist with a Ph.D, just anyone who is educated and learned enough about the topic.


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.


It is most certainly the biggest fudge factor I've ever heard of in science. Dark matter & energy are laughable attempts to cling to failed theories of cosmology. Reminds me of epicycles in the Earth-centric solar system model. Humans so rarely learn from past mistakes.


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 like your idea, but it's backwards in your example. If G was larger near the black hole, the orbiting stars would be spinning around faster, and we would estimate a heavier black hole than what is actually there. In that situation, barring any other factors (like dark matter / energy) they'd be trying to explain the "slower" galactic motion in the face of "the extra mass of the central black hole which doesn't show itself."

Since their dark matter speculation is trying to account for "faster galactic motion based on mass which is not apparent", then if variable G were the culprit, it would be weaker nearer to the black hole.

I haven't done the calculations myself for the specific star speed / distance in the milky way, but F = G*m1*m2 / r^2 is universally applied. I have to imagine they've tried the calculations for stars of various distances. Wouldn't any kind of variable G be immediately apparent? Ehhh who knows, good luck.



posted on Jun, 29 2011 @ 02:47 AM
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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?
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.

Anyway on to your question. First, the terms "dark matter" and "dark energy" are just "placeholders" for some future theory. We don't know what they are, though we have found part of the missing dark matter but there's still plenty unaccounted for.

Gravity is an attractive force, so it can't explain the repulsive force apparently observed causing the expansion of the universe to accelerate. Some things could explain it, but the ideas so far aren't accepted by any consensus. So dark energy won't be explained by variable gravity, at least not by any variable gravity theory I've heard of.

It's possible that some kind of variable gravity might explain some dark matter observations, and there's a hypothesis related to that referred to as MOND, but it's either a fringe or minority view:

The Modified Newtonian Dynamics (MOND) s a scientific theory proposed by Moti Milgrom as a solution to the missing mass problem in extragalactic astronomy.


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).
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.

Some recent observations have posed problems for the MOND hypothesis however:

Missing Milky Way Dark Matter


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.
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.
edit on 29-6-2011 by Arbitrageur because: clarification



posted on Jun, 29 2011 @ 03:02 AM
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reply to post by billyjack
 

Send the starter of this thread a u2u. Always assuming he’s still around and still willing to play – he was unbelievably shabbily treated by the membership and the board staff – he may answer your question. And yes, he is almost certainly the genuine article.


edit on 29/6/11 by Astyanax because: URL was malformed.



posted on Jun, 29 2011 @ 03:06 AM
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reply to post by billyjack
 

In the meantime, with my undergraduate-level understanding of the subject, I’ll attempt an answer to your question.

If the gravitational constant has differing values depending on its location, then it isn’t a constant but a variable, and as such must be a function of other physical quantities. What are those quantities and how do they effect this ‘gravitational function’? Answer that, and you’re in business.



posted on Jun, 29 2011 @ 02:59 PM
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reply to post by Observer99
 


I aapreciate the responce,but I still believe that the value of G has to be larger not smaller. The creation of dark matter is to account for increased mass to make the current equations balance in light of the observed acceleration. The two point force of gravity problem as you described therefore requires that the center of gravity of the dark matter mass be relocated at the center of the galaxy and that the black hole has significantly more mass or that the accelration of the stars observed is accounted for by an increase in the gravitational constant. In the equation F= m1 X m2X G/r^2, we can get the same F by increasing m or increasing G.

I thought the MOND theory had been shot down.

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.

Anyway, it is an interesting problem to ponder.



posted on Jun, 29 2011 @ 03:05 PM
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reply to post by billyjack
 


Another alternative to dark matter and dark energy is a modified theory of gravity called Scalar-Tensor-Vector Gravity (STVG), theorized by John Moffat. It predicts the existence of a vector field akin to anti-gravity, which works over smaller distances (out to about the radius of the solar system). Beyond that point, gravity takes over - but the effect is that true gravity is stronger than the gravity we observe.
The theory accurately reproduces many cosmological observations, from the accelerated expansion of the universe, to the masses of galaxy clusters, to the Pioneer anomaly.

STVG
edit on 29-6-2011 by CLPrime because: (no reason given)



posted on Jun, 29 2011 @ 06:51 PM
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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.
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).

Now you just said it needs to be larger. It's correct to say it needs to be larger, but observer 99 is correct that it needs to be larger further away from the center of the galaxy, not closer to the center as you suggested in your OP.


I thought the MOND theory had been shot down.
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.


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.
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.



posted on Jun, 30 2011 @ 03:47 PM
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My uncle is an engineer and I had him visit ats, and he said that people on this site are full of b/s

true story.



posted on Jul, 15 2011 @ 03:44 PM
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reply to post by DuceizBack
 


sounds like your uncle is a typical pocket protector, short sleeve type who has no imagination; should have smoked more dope while he was in college and then he could see a little beyond his calculator. What a waste of intellect from someone capable of passing differential equations. If your uncle didn't take diff e he's not a real engineer anyway. Sorry he has no intellectual curiosity.




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