An uneven distribution of stars in several nearby clusters may offer evidence of MOND – a controversial theory of gravity that disputes Newton and rejects the existence of dark matter.

The Hyades star cluster (pink) curls across the sky amid well-known constellations (green). The cluster is at the center of a controversial new study proposing an alternative to Newton’s theory of gravity.

Astronomers observing star clusters in our galaxy have found evidence that controversially challenges Newton’s laws of gravity and could upend our understanding of the universe. The puzzling finding could support a controversial idea that does away entirely with dark matter.

The researchers found this evidence by observing open star clusters, or loosely bound groups of up to a few hundred stars sitting within larger galaxies. Open star clusters have trails of stars, known as “tidal tails,” in front of and behind them. The researchers’ observations indicate that such clusters have many more stars sitting in the overall direction of their travel through space than trailing behind. This throws into question Newton’s law of universal gravitation, which suggests that there should be the same number of stars in both tidal tails.

“It’s extremely significant,” astrophysicist Pavel Kroupa of the University of Bonn told Live Science. “There is a huge effect.”

Kroupa is the lead author of a study published Oct. 26 in the Monthly Notices of the Royal Astronomical Society that argues the observations are evidence of modified Newtonian dynamics (MOND) — an alternative theory of gravity to Newton’s widely accepted universal law of gravitation.

This uneven distribution of stars is noticeable, but not extreme enough for any sort of dark matter — an invisible substance thought to exert a powerful gravitational pull on the universe’s visible matter — to be involved, Kroupa said.

“This is basically a game-changer,” he said. “This destroys all the work done on galaxies and on cosmology assumes dark matter and Newtonian gravity.”

In the star cluster Hyades (top), the number of stars (black) in the front tidal tail is significantly larger than those in the rear. In the computer simulation with MOND (below), a similar picture emerges. (Image credit: University of Bonn)

Dark matter?
Issac Newton’s universal law of gravitation, published in 1687, states that every particle in the universe attracts every other with a force proportional to their masses and inversely proportional to the square of their distance. Albert Einstein later incorporated this law into his theory of general relativity, which was published in 1915.

But Kroupa said that at the time of both Newton and Einstein, astronomers didn’t know that galaxies even existed, and so MOND was developed to bring it up to date with observations.

MOND, also known as Milgromian dynamics after astrophysicist Mordehai Milgrom who developed it in the early 1980s, argues that regular Newtonian dynamics don’t apply on the very large scales of galaxies and galactic clusters — although most astrophysicists think they do.

The main consequence of MOND is that dark matter doesn’t exist — an idea that most astrophysicists dismiss, Kroupa said. “The majority of scientists completely reject Mond,” he said. “Many serious scientists don’t think Mond is serious, and so they wouldn’t consider looking at it.”

Stellar clusters
In their study, the authors report observations of five of the closest open stellar clusters to Earth, including the Hyades — a roughly spherical group of hundreds of stars that is only about 150 light-years from our sun.

The researchers observed that stars had accumulated in the leading tidal tail in all five of the clusters, while the greatest discrepancy from regular Newtonian dynamics was seen in the Hyades cluster, where there are better measurements, Kroupa said.

The observed discrepancies strengthen the case for MOND, but they can’t be a result of the invisible action of dark matter.

In the case of the Hyades, “we would have to have a clump of dark matter there like 10 million solar masses” to explain the results, he said. “But it’s just not in the data.”

Future studies will use more precise data on the positions of stars from new space telescopes, such as the European Space Agency’s Gaia, he said.

However, because MOND is not widely accepted by many scientists, the new study’s findings are controversial.

Sabine Hossenfelder, an astrophysicist at the Frankfurt Institute Advanced Studies, told Live Science in an email that she was pleased to see researchers working on gravitational simulations of MOND.

But “as they admit the paper themselves, they are using an approximate calculation that needs to be confirmed… they haven’t quantified how large the disagreement with data is,” she said. “So I think it remains to be seen how good this argument actually is.”

https://www.livescience.com/star-cluster-mond-disprove-newton

There is a very interesting short NASA video at the bottom of the linked page.

The Hyades star cluster has been studied for yonks.

I distinctly remember reading about a velocity study of the cluster, and seeing a H-R diagram for all the stars in the cluster, back in a book I read in fourth form of high school.

Hard to believe that anything new can be learnt from it now.

Yeah, the H-R diagram for the stars of the Hyades cluster dates back to the year 1940.

From a science article published in 1933. The lopsidedness of the Hyades star cluster is because it consists of two clusters moving through each other.

mollwollfumble said:

The Hyades star cluster has been studied for yonks.

I distinctly remember reading about a velocity study of the cluster, and seeing a H-R diagram for all the stars in the cluster, back in a book I read in fourth form of high school.

Hard to believe that anything new can be learnt from it now.

Yeah, the H-R diagram for the stars of the Hyades cluster dates back to the year 1940.

Why don’t you just read the article instead of assuming you know what it is about. That’s the thing about NEW research, is that it is NEW and if you read it, you might even discover something that you did not know.

PermeateFree said:

Why don’t you just read the article instead of assuming you know what it is about. That’s the thing about NEW research, is that it is NEW and if you read it, you might even discover something that you did not know.

Tell that to Berkeman. He keeps rejecting my physics and mathematics research without even bothering to read it.

As for article. No. Simply no.

There have already been at least five nails put in the coffin of MOND. Do you want me to list them?

And if the MOND simulations show asymmetry then they must be wrong because the equations of MOND have nothing in them that could generate that kind of asymmetry.

I would guess that the asymmetry both in real life and in the simulations is due to initial conditions. Because stars form from clouds of dusty gas and the motions in that initial cloud of dusty gas are highly anisotropic, some asymmetry is left over when the stars form.

If you want an example of real asymmetry, look at the Magellanic tidal streams.

mollwollfumble said:

PermeateFree said:

Why don’t you just read the article instead of assuming you know what it is about. That’s the thing about NEW research, is that it is NEW and if you read it, you might even discover something that you did not know.

Tell that to Berkeman. He keeps rejecting my physics and mathematics research without even bothering to read it.

As for article. No. Simply no.

There have already been at least five nails put in the coffin of MOND. Do you want me to list them?

And if the MOND simulations show asymmetry then they must be wrong because the equations of MOND have nothing in them that could generate that kind of asymmetry.

I would guess that the asymmetry both in real life and in the simulations is due to initial conditions. Because stars form from clouds of dusty gas and the motions in that initial cloud of dusty gas are highly anisotropic, some asymmetry is left over when the stars form.

If you want an example of real asymmetry, look at the Magellanic tidal streams.

Why don’t you just read it, then you can sensible comment. And it does mention MOND and why he deserves a second look.

PermeateFree said:

mollwollfumble said:

PermeateFree said:

Why don’t you just read the article instead of assuming you know what it is about. That’s the thing about NEW research, is that it is NEW and if you read it, you might even discover something that you did not know.

Tell that to Berkeman. He keeps rejecting my physics and mathematics research without even bothering to read it.

As for article. No. Simply no.

There have already been at least five nails put in the coffin of MOND. Do you want me to list them?

And if the MOND simulations show asymmetry then they must be wrong because the equations of MOND have nothing in them that could generate that kind of asymmetry.

I would guess that the asymmetry both in real life and in the simulations is due to initial conditions. Because stars form from clouds of dusty gas and the motions in that initial cloud of dusty gas are highly anisotropic, some asymmetry is left over when the stars form.

If you want an example of real asymmetry, look at the Magellanic tidal streams.

Why don’t you just read it, then you can sensible comment. And it does mention MOND and why he deserves a second look.

Trying to take down Einstein is almost blasphemy, he’s likely correct but who knows, could shut off entire areas of research by not considering them.

Cymek said:

PermeateFree said:

mollwollfumble said:

Tell that to Berkeman. He keeps rejecting my physics and mathematics research without even bothering to read it.

As for article. No. Simply no.

There have already been at least five nails put in the coffin of MOND. Do you want me to list them?

And if the MOND simulations show asymmetry then they must be wrong because the equations of MOND have nothing in them that could generate that kind of asymmetry.

I would guess that the asymmetry both in real life and in the simulations is due to initial conditions. Because stars form from clouds of dusty gas and the motions in that initial cloud of dusty gas are highly anisotropic, some asymmetry is left over when the stars form.

If you want an example of real asymmetry, look at the Magellanic tidal streams.

Why don’t you just read it, then you can sensible comment. And it does mention MOND and why he deserves a second look.

Trying to take down Einstein is almost blasphemy, he’s likely correct but who knows, could shut off entire areas of research by not considering them.

It is like the religious types that condemn books, films. etc, that they think denigrates their faith, but do not read the book or watch the film themselves. They trap themselves in their own little bubble.

PermeateFree said:

mollwollfumble said:

PermeateFree said:

Why don’t you just read the article instead of assuming you know what it is about. That’s the thing about NEW research, is that it is NEW and if you read it, you might even discover something that you did not know.

Tell that to Berkeman. He keeps rejecting my physics and mathematics research without even bothering to read it.

As for article. No. Simply no.

There have already been at least five nails put in the coffin of MOND. Do you want me to list them?

And if the MOND simulations show asymmetry then they must be wrong because the equations of MOND have nothing in them that could generate that kind of asymmetry.

I would guess that the asymmetry both in real life and in the simulations is due to initial conditions. Because stars form from clouds of dusty gas and the motions in that initial cloud of dusty gas are highly anisotropic, some asymmetry is left over when the stars form.

If you want an example of real asymmetry, look at the Magellanic tidal streams.

Why don’t you just read it, then you can sensible comment. And it does mention MOND and why he deserves a second look.

> Trying to take down Einstein is almost blasphemy

No no no. Einstein must fail – somewhere. I’m quite happy to take down Einstein as it relates to dark matter. But not in this way.

Let me comment more on the mathematical equations and solution techniques involved in this simulation.

The original invention of MOND failed to include Special Relativity. Which mean that it was ruled out even before first publication by such simple experiments as the operation of a synchrotron (any synchrotron), the continued operation of GPS, and the operation of interferometers. All those rely on special relativity, as does the aberration of light, which has been known since the 1600s.

The modern version of MOND is now called f ( r ) gravity. It includes General Relativity and classical MOND both as special cases. In fact it provides a continuity of physical models of gravity between GR and classic MOND.

So far so good. But note the name “f ( r ) gravity”. The force of gravity depends only on the distance between two objects and their masses. It does not have any anisotropic component. And so, given symmetrical initial conditions, the correct integration of the f ( r ) equations cannot introduce lopsided asymmetry into the solution.

Also note that this simulation is of the https://en.wikipedia.org/wiki/N-body_problem. It is quite difficult to integrate the equations out accurately because numerical errors grow exponentially with time. A poor algorithm is very easy to write. I was, while at CSIRO, given an n-body problem numerical code that was accurate only to second order, which wasn’t good enough. I modified it to third order, which proved to be much more accurate for the work I was doing. There are plenty of poor n-body simulation codes out there.

I was being generous when I said that the problem with the MOND simulation is probably due to the asymmetry of initial conditions. It is actually more likely to be due to a poor n-body solution algorithm.

I can illustrate this with a few lines of code. One algorithm for the n-body problem is as follows. n is the number of stars.

for i=1 to n calculate force f(i) on particle i calculate movement dx(i) of particle i
end for
for i=1 to n move particle i using x(i)=x(i)+dx(i)
end for

That’s a first order Euler method. Not great, but it will do for illustration purposes. Such an algorithm retains symmetry, for both MOND and relativity.

However if you get it wrong and write this as

for i=1 to n calculate force f(i) on particle i calculate movement dx(i) of particle i move particle i using x(i)=x(i)+dx(i)
end for

Then computational errors will very rapidly grow to produce the type of asymmetry illustrated in the MOND simulation results of the original article.

mollwollfumble said:

PermeateFree said:

mollwollfumble said:

Tell that to Berkeman. He keeps rejecting my physics and mathematics research without even bothering to read it.

As for article. No. Simply no.

There have already been at least five nails put in the coffin of MOND. Do you want me to list them?

And if the MOND simulations show asymmetry then they must be wrong because the equations of MOND have nothing in them that could generate that kind of asymmetry.

I would guess that the asymmetry both in real life and in the simulations is due to initial conditions. Because stars form from clouds of dusty gas and the motions in that initial cloud of dusty gas are highly anisotropic, some asymmetry is left over when the stars form.

If you want an example of real asymmetry, look at the Magellanic tidal streams.

Why don’t you just read it, then you can sensible comment. And it does mention MOND and why he deserves a second look.

> Trying to take down Einstein is almost blasphemy

No no no. Einstein must fail – somewhere. I’m quite happy to take down Einstein as it relates to dark matter. But not in this way.

Let me comment more on the mathematical equations and solution techniques involved in this simulation.

The original invention of MOND failed to include Special Relativity. Which mean that it was ruled out even before first publication by such simple experiments as the operation of a synchrotron (any synchrotron), the continued operation of GPS, and the operation of interferometers. All those rely on special relativity, as does the aberration of light, which has been known since the 1600s.

The modern version of MOND is now called f ( r ) gravity. It includes General Relativity and classical MOND both as special cases. In fact it provides a continuity of physical models of gravity between GR and classic MOND.

So far so good. But note the name “f ( r ) gravity”. The force of gravity depends only on the distance between two objects and their masses. It does not have any anisotropic component. And so, given symmetrical initial conditions, the correct integration of the f ( r ) equations cannot introduce lopsided asymmetry into the solution.

Also note that this simulation is of the https://en.wikipedia.org/wiki/N-body_problem. It is quite difficult to integrate the equations out accurately because numerical errors grow exponentially with time. A poor algorithm is very easy to write. I was, while at CSIRO, given an n-body problem numerical code that was accurate only to second order, which wasn’t good enough. I modified it to third order, which proved to be much more accurate for the work I was doing. There are plenty of poor n-body simulation codes out there.

I was being generous when I said that the problem with the MOND simulation is probably due to the asymmetry of initial conditions. It is actually more likely to be due to a poor n-body solution algorithm.

I can illustrate this with a few lines of code. One algorithm for the n-body problem is as follows. n is the number of stars.

for i=1 to n calculate force f(i) on particle i calculate movement dx(i) of particle i
end for
for i=1 to n move particle i using x(i)=x(i)+dx(i)
end for

That’s a first order Euler method. Not great, but it will do for illustration purposes. Such an algorithm retains symmetry, for both MOND and relativity.

However if you get it wrong and write this as

for i=1 to n calculate force f(i) on particle i calculate movement dx(i) of particle i move particle i using x(i)=x(i)+dx(i)
end for

Then computational errors will very rapidly grow to produce the type of asymmetry illustrated in the MOND simulation results of the original article.

You obviously have a closed non-scientific mind that rejects new research that conflicts with your understanding, but that is not how science works.

PermeateFree said:

mollwollfumble said:

PermeateFree said:

Why don’t you just read it, then you can sensible comment. And it does mention MOND and why he deserves a second look.

> Trying to take down Einstein is almost blasphemy

No no no. Einstein must fail – somewhere. I’m quite happy to take down Einstein as it relates to dark matter. But not in this way.

Let me comment more on the mathematical equations and solution techniques involved in this simulation.

The original invention of MOND failed to include Special Relativity. Which mean that it was ruled out even before first publication by such simple experiments as the operation of a synchrotron (any synchrotron), the continued operation of GPS, and the operation of interferometers. All those rely on special relativity, as does the aberration of light, which has been known since the 1600s.

The modern version of MOND is now called f ( r ) gravity. It includes General Relativity and classical MOND both as special cases. In fact it provides a continuity of physical models of gravity between GR and classic MOND.

So far so good. But note the name “f ( r ) gravity”. The force of gravity depends only on the distance between two objects and their masses. It does not have any anisotropic component. And so, given symmetrical initial conditions, the correct integration of the f ( r ) equations cannot introduce lopsided asymmetry into the solution.

Also note that this simulation is of the https://en.wikipedia.org/wiki/N-body_problem. It is quite difficult to integrate the equations out accurately because numerical errors grow exponentially with time. A poor algorithm is very easy to write. I was, while at CSIRO, given an n-body problem numerical code that was accurate only to second order, which wasn’t good enough. I modified it to third order, which proved to be much more accurate for the work I was doing. There are plenty of poor n-body simulation codes out there.

I was being generous when I said that the problem with the MOND simulation is probably due to the asymmetry of initial conditions. It is actually more likely to be due to a poor n-body solution algorithm.

I can illustrate this with a few lines of code. One algorithm for the n-body problem is as follows. n is the number of stars.

for i=1 to n calculate force f(i) on particle i calculate movement dx(i) of particle i
end for
for i=1 to n move particle i using x(i)=x(i)+dx(i)
end for

That’s a first order Euler method. Not great, but it will do for illustration purposes. Such an algorithm retains symmetry, for both MOND and relativity.

However if you get it wrong and write this as

for i=1 to n calculate force f(i) on particle i calculate movement dx(i) of particle i move particle i using x(i)=x(i)+dx(i)
end for

Then computational errors will very rapidly grow to produce the type of asymmetry illustrated in the MOND simulation results of the original article.

You obviously have a closed non-scientific mind that rejects new research that conflicts with your understanding, but that is not how science works.

My earlier comment does not mean you should accept the new research, only to view and consider it fairly, not dismiss it out-of-hand without investigation.