schreef in bericht
...
On Mar 22, 1:55 pm, "Nicolaas Vroom"
wrote:
schreef in
...
On Mar 12, 10:37 pm, "Nicolaas Vroom"
wrote:
I have written a program to simulate galaxies usingMOND.
For a more general discussion related toMONDwhich
includes your references See:http://users.pandora.be/nicvroom/mond.htm
For a copy of the program see:
http://users.pandora.be/nicvroom/prgmond.htm
I am not able to access your site.
There was one . (point) too much.
I hope you took care to apply MOND correctly.
How do you apply MOND correctly ?
It has non-local affects.
What do you mean by that ?
Non-Local effects is explained below.
You did not explain it.
You cannot replace all mass within a sphere with a point mass, for
measuring its effect outside the sphere.
I agree that that gives complications. IMO that is a problem with MOND.
Yes, it is a problem with MOND. It is just slightly inaccurate.
What do you mean by that ?
Do you mean that a0 could have a different value ?
You can try to apply TeVeS if you want completely accurate results
(according to MOND).
For TeVeS See:
http://en.wikipedia.org/wiki/Tensor-...scalar_gravity
Why do I have to use TeVeS.
The bottom line is that MOND works.
If MOND works than why use TeVeS
There are dozens of papers that
show you how to fit the data in galaxies.
I have also studied those curves.
As I have mentioned I have two major problem.
First if the rotation curve is not flat but decreases
at larger distances than you can not simulate those
with MOND.
(MOND can only be used if the speed increases.)
Secondly starting point is a certain visible (baryonic) mass
distribution.
With Newton you can calculate the rotation curve
but this curve does not match the measured curve.
Solution add an halo of darkmatter.
With MOND you should start with this same mass
distribution.
The problem is that the speeds (rotation curves) calculated
based on that assumption with MOND
(assuming that MOND is applicable at scales
larger than 0.1 ly See below) are far too much.
Check the explanation at
http://www.astro.umd.edu/~ssm/mond/mondnbody.ps
Yes I agree there is an issue.
See also my comments See:http://users.pandora.be/nicvroom/mond.htm
at Feedback #4.
At the end of that document is written:
"Note that this does not mean MOND is wrong,
just that this kind of calculation does not work"
IMO that is a serious problem.
It would seem as a serious problem, because we don't have a quantum
theory of gravity, which is bound to be a type of Quantized AdS/CFT
theory,
like the other forces. All AdS/CFT theories have non-local effects.
The rest removed.
The fact that you say that we should use a different theory
IMO is prove that with MOND we have a serious problem.
What MOND predicts is that when you have two colliding BH's
(or large masses) that the speed of a star,
which circulates around the center of gravity of that BH,
after collision, will drastically change.
There will almost be no change when Newton is considered.
I think you are ignoring that MOND only applies to weak
gravitational regimes. In strong regimes MOND is equivalent
to Newtonian Gravity.
My question is more related to two large masses.
If the star is outside the range where a=a0
than with Newton when the two masses collide there
is (almost) no change in the speed of the test object
but with MOND there is.
I have serious problems with MOND.
1. One is for example the above mentioned document.
2. A different one is the value of a0. This is more or less a free
parameter.
It is no longer a free parameter. It is a universal parameter and
must have the same value for all observations. It has already
been fit to 1.21E-8 m/s^2.
I expect you mean 1.21E-8 cm/s^2
This cannot change as it has been
used to fit more than 100 galaxies. If it is changed it will no
longer fit that data. So it cannot have any other value now.
3. Third how do you go from Newton to MOND.
There are more or less three areas involved:
One with Newton at short distance between stars,
one with both Newton and MOND
and one with MOND only at large distances.
There is no distance scale in MOND. There is only an
acceleration scale, ie a0. Above a0 it is Newtonian,
below a0 it is MONDian.
For the Sun the distance for a to get smaller than a0
(1.21E-10m/s^2) is roughly 0.1 ly.
The distance between then sun and the nearest star
is 1.3 pc or 4.3 ly.
That means the behaviour between almost all the stars
in our Galaxy is described by MOND.
Only when two stars become very close the description
becomes Newton.
Is that the correct application of MOND ?
It doesn't matter now why it is so,
because we don't have a quantum theory of gravity. But it
has been proved with the enormous amount of data on
galaxies.
We still don't know precisely the function that should be
used at the boundary ie near a0, to predict the actual
gravity. It will need much more precise observations to
really fix the function.
Other numerical approaches are necessary. For example, Brada's
thesis.
http://www.astro.umd.edu/~ssm/mond/brada.uu
I cannot access that url.
See also MLAPM.
http://www.aip.de/People/AKnebe/MLAPM/
When we have a quantized Ads/CFT theory of gravity, which is the
equivalent of the other forces, nothing will work according to our
intuition. Time Dilation etc are intuitive compared to what we will
have ;-).
Why do you again use the word intuition ?
I don't understand your question. Don't you know what Intuition means?
Non-intuitive means that something does not follow your experiences
in the past. If you think that something should behave one way but it
turns out to behave in a different way then it is non-intuitive.
Science has nothing to do with (my or your) intuition.
Science has to do with experiments under carefully defined
conditions.
There is no personal "dimension" in science.
Nicolaas Vroom
http://users.pandora.be/nicvroom/