Mond theory and dark matter

[Nokton]

Seems, gravity is in question here. A new theory disputes Newtonion
physics, Albert also. Implies dark matter does not exist,
And proposes a rethink on some aspects of Newton and Alberts contentions of gravity
Mond theory is being tested here , now many thinkers are changing their mind.
Never believed in dark matter myself, but have reservations concerning
spiral and elliptical galaxies. Something to do I feel, with the creation of
the black hole that created them, or is it a black star?
Nokton.

[stuart]

MOND is not new, it's been around at least 5+ years. The basic idea behind it is that gravity acts differently at large, local scales, and so objects that "shouldn't" behave the way we observe them to really should because we just have been using wrong equations from Newtonian gravity.

A friend of mine actually gave a presentation in his cosmology class yesterday on why we believe in Dark Matter over MOND, so I'll ask him for a quick summary and post here.

[Diana]

Originally Posted by stuart

MOND is not new, it's been around at least 5+ years.

Actually, I think it has been around longer then that. According to Wikipedia the MOND theory was proposed somewhere in 1981.

As to where I understand many critics have pointed out that MOND cannot explain the observed masses of clusters of galaxys without invoking dark matter, in the form of almost massless particles (neutrinos).

I was reading something on another (new) modified gravity theory called the Scalar Tensor Vector Gravity (STVG). According to researchers this theory can account for both galaxies and galaxy clusters.

I don't quite remember where I read about this at. I found something about it on Wikipedia, but there is not much info there either. If I find more on it I will post the link later.



Diana

[Nokton]

Originally Posted by stuart

MOND is not new, it's been around at least 5+ years. The basic idea behind it is that gravity acts differently at large, local scales, and so objects that "shouldn't" behave the way we observe them to really should because we just have been using wrong equations from Newtonian gravity.

A friend of mine actually gave a presentation in his cosmology class yesterday on why we believe in Dark Matter over MOND, so I'll ask him for a quick summary and post here.

.
Stuart, thanx your reply. Before you do, would ask you to think about
what YOU think? Do you believe in your own thoughts and opinions?
Or rather trust anothers judgement? To the detriment of your own?
Check out Milgrom and Bekenstein. Get back to me.
So many teachers are so locked in knowledge they learned in the past.
Their understanding is in stasis
Stuart, mean it, get back to me.
Nokton.

[Nokton]

Originally Posted by Diana

Actually, I think it has been around longer then that. According to Wikipedia the MOND theory was proposed somewhere in 1981.

As to where I understand many critics have pointed out that MOND cannot explain the observed masses of clusters of galaxys without invoking dark matter, in the form of almost massless particles (neutrinos).

I was reading something on another (new) modified gravity theory called the Scalar Tensor Vector Gravity (STVG). According to researchers this theory can account for both galaxies and galaxy clusters.

I don't quite remember where I read about this at. I found something about it on Wikipedia, but there is not much info there either. If I find more on it I will post the link later.



Diana

Diana,
Unlike in the past. MOND is being is being taken very seriously now.
So is the proposition that 'black holes' are indeed, dark stars, so dense
that matter falling into them becomes changed into a quantum state
we yet not understand.
The proposition of my thread was, and is, did Newton get it so slightly
wrong?. The balance between the earth and the Sun should be null
according to Newton, and Albert, but MOND theory predicts a small variation.
Diana, Nasa Pioneer 10 and 11 seem to be decelerating more than predicted, but the rate of deceleration would hold true if Bekenstein's
theory holds true.
Nokton

[stuart]

Originally Posted by Nokton

.
Stuart, thanx your reply. Before you do, would ask you to think about
what YOU think? Do you believe in your own thoughts and opinions?
Or rather trust anothers judgement? To the detriment of your own?
Check out Milgrom and Bekenstein. Get back to me.
So many teachers are so locked in knowledge they learned in the past.
Their understanding is in stasis
Stuart, mean it, get back to me.
Nokton.

My opinion, if you really want it, is that MOND seems to be a cop-out. It seems to be something without any real physics behind it, and it was just invented empirically. Whereas MOND has been developed to explain galaxy rotation curves, dark matter explains more, and there is evidence for it in the data for the Cosmic Microwave Background Radiation that should have absolutely nothing to do with MOND (CMB information can be found on NASA's WMAP website http://map.gsfc.nasa.gov/ ). I think that even though dark matter has yet to be really "discovered," it is the more likely of the two explanations to prevail in the long-haul, but really only future observations will tell.

And you say that "so many teachers are so locked in knowledge they learned in the past." I have to disagree with you on this, especially if you're trying to generalize it to me and to other astronomers. Of all the hundreds of astronomers I have met, and the hundreds more that I've read about, I only know of one who refuses to believe lines of evidence that contradict his own ideas. By their very nature, scientists are trained to NOT accept the status quo and to search out what's really going on. That's one of the main reasons why I chose this field -- because it's constantly changing.

[Dragon Star]

I agree that "dark matter" is sketchy in thought, but without any proof it's pointless to say which is correct, if either of them are...or perhaps both.

You can only speculate, so there is no use in arguing.

[Nokton]

Originally Posted by Dragon Star

I agree that "dark matter" is sketchy in thought, but without any proof it's pointless to say which is correct, if either of them are...or perhaps both.

You can only speculate, so there is no use in arguing.

Mean that Dragon, stick my neck out now and contend that 90%
of science is about building on a concept. Since when was 'proof'
required of a concept? The big bang, the event horizon of a black
hole, the cosmological constant are without 'proof', just theories that
have endured because there is as yet, no other concept that would
invalidate the theory. In spite of many diverse arguements, dark matter
is still unknown, and 'unproved', so in order to provide an alternative concept, I posted this thread.
Dragon, the Nasa and Esa's LISA, designed to look for gravitational
waves, ripples in spacetime due to cataclysmic events. At this point in
time, will be operational in 2008. Dragon, who, a hundred years ago,
would have believed in a theory of continental drift?......
Nokton.

[Nokton]

Originally Posted by stuart

My opinion, if you really want it, is that MOND seems to be a cop-out. It seems to be something without any real physics behind it, and it was just invented empirically. Whereas MOND has been developed to explain galaxy rotation curves, dark matter explains more, and there is evidence for it in the data for the Cosmic Microwave Background Radiation that should have absolutely nothing to do with MOND (CMB information can be found on NASA's WMAP website http://map.gsfc.nasa.gov/ ). I think that even though dark matter has yet to be really "discovered," it is the more likely of the two explanations to prevail in the long-haul, but really only future observations will tell.

And you say that "so many teachers are so locked in knowledge they learned in the past." I have to disagree with you on this, especially if you're trying to generalize it to me and to other astronomers. Of all the hundreds of astronomers I have met, and the hundreds more that I've read about, I only know of one who refuses to believe lines of evidence that contradict his own ideas. By their very nature, scientists are trained to NOT accept the status quo and to search out what's really going on. That's one of the main reasons why I chose this field -- because it's constantly changing.

You misinterpreted the point I was making Stuart, but prove it by your
rebuttal. Scientists are trained not to accept the status quo....
Then why not accept ideas different to your teaching????
Tell me your thinking on Black Hole theory. Is it a black hole in the
conventional sense? You envisage a Black hole in 3 dimensions???
or two?
Stuart, I detect hostility in your post, that sorrows me.
All I wanted, contact with you in reason and logic.
Nokton.

[Dragon Star]

Originally Posted by Nokton

Mean that Dragon, stick my neck out now and contend that 90%of science is about building on a concept. Since when was 'proof'
required of a concept?

You have to have something Nokton in order to speculate anything at all, and the truth is we have NO reason to say ether "IT'S MOND!" or "IT'S DARK MATTER!" Because for all we know it could be just a simple explanation for something that is wrong with the current model...our theories are just that, ideas that have ways of explaining the action or reaction...nothing is set in stone at all. Big Bang could be it's self a fluke and totally wrong, but we have evidence that it is what happened! What evidence do you have of Mond? Or Dark Matter?

Because there is nothing more then Missing Mass and some observations of galaxies that say there is something wrong at all, and it's just not enough, our understanding of our universe is highly exaggerated and we know very little about about what goes on outside of our little world and our theories.

Conclusion: Wait for evidence or proof before making wild guesses that can not be proved nor disproved.