New data supports theory of dark matter, but suggests inexplicably that it acts differently depending on the galaxy’s mass
The uncertainty of science: Astronomers analyzing twelve small and faint galaxies have determined that the existence of some form of mysterious undetected dark matter is necessary to explain the motions of their stars, and that another theory dubbed MOND that would make dark matter unnecessary fails to explain the data.
The authors found that the galaxies’ internal gravitational fields cannot be explained by visible matter alone, and that MOND predictions fail to reproduce the observed behaviour. They then compared their results with theoretical models that assume instead that these galaxies are surrounded by a massive halo of dark matter. Run on the UK’s DiRAC National Supercomputer facility, these dark matter models gave a much better match to the data.
Sounds good, eh? Not so fast. The research also found that large and small galaxies inexplicably interact with gravity and dark matter differently.
The research, published in Astronomy & Astrophysics, also challenges a long-standing assumption about how galaxies behave. Astronomers have long believed there is a simple link between the amount of visible matter in a galaxy and the strength of the gravitational pull it produces – known as the “radial acceleration relation.” While this relationship still holds for larger systems, the new study shows that it starts to break down in the smallest galaxies.
In other words, we don’t know enough yet to really explain the formation and behavior of galaxies. This really isn’t surprising, considering the time scales involved (billions of years) and the distances (millions to billions of light years).
On Christmas Eve 1968 three Americans became the first humans to visit another world. What they did to celebrate was unexpected and profound, and will be remembered throughout all human history. Genesis: the Story of Apollo 8, Robert Zimmerman's classic history of humanity's first journey to another world, tells that story, and it is now available as both an ebook and an audiobook, both with a foreword by Valerie Anders and a new introduction by Robert Zimmerman.
The print edition can be purchased at Amazon or from any other book seller. If you want an autographed copy the price is $60 for the hardback and $45 for the paperback, plus $8 shipping for each. Go here for purchasing details. The ebook is available everywhere for $5.99 (before discount) at amazon, or direct from my ebook publisher, ebookit. If you buy it from ebookit you don't support the big tech companies and the author gets a bigger cut much sooner.
The audiobook is also available at all these vendors, and is also free with a 30-day trial membership to Audible.
"Not simply about one mission, [Genesis] is also the history of America's quest for the moon... Zimmerman has done a masterful job of tying disparate events together into a solid account of one of America's greatest human triumphs."--San Antonio Express-News
The uncertainty of science: Astronomers analyzing twelve small and faint galaxies have determined that the existence of some form of mysterious undetected dark matter is necessary to explain the motions of their stars, and that another theory dubbed MOND that would make dark matter unnecessary fails to explain the data.
The authors found that the galaxies’ internal gravitational fields cannot be explained by visible matter alone, and that MOND predictions fail to reproduce the observed behaviour. They then compared their results with theoretical models that assume instead that these galaxies are surrounded by a massive halo of dark matter. Run on the UK’s DiRAC National Supercomputer facility, these dark matter models gave a much better match to the data.
Sounds good, eh? Not so fast. The research also found that large and small galaxies inexplicably interact with gravity and dark matter differently.
The research, published in Astronomy & Astrophysics, also challenges a long-standing assumption about how galaxies behave. Astronomers have long believed there is a simple link between the amount of visible matter in a galaxy and the strength of the gravitational pull it produces – known as the “radial acceleration relation.” While this relationship still holds for larger systems, the new study shows that it starts to break down in the smallest galaxies.
In other words, we don’t know enough yet to really explain the formation and behavior of galaxies. This really isn’t surprising, considering the time scales involved (billions of years) and the distances (millions to billions of light years).
On Christmas Eve 1968 three Americans became the first humans to visit another world. What they did to celebrate was unexpected and profound, and will be remembered throughout all human history. Genesis: the Story of Apollo 8, Robert Zimmerman's classic history of humanity's first journey to another world, tells that story, and it is now available as both an ebook and an audiobook, both with a foreword by Valerie Anders and a new introduction by Robert Zimmerman.
The print edition can be purchased at Amazon or from any other book seller. If you want an autographed copy the price is $60 for the hardback and $45 for the paperback, plus $8 shipping for each. Go here for purchasing details. The ebook is available everywhere for $5.99 (before discount) at amazon, or direct from my ebook publisher, ebookit. If you buy it from ebookit you don't support the big tech companies and the author gets a bigger cut much sooner.
The audiobook is also available at all these vendors, and is also free with a 30-day trial membership to Audible.
"Not simply about one mission, [Genesis] is also the history of America's quest for the moon... Zimmerman has done a masterful job of tying disparate events together into a solid account of one of America's greatest human triumphs."--San Antonio Express-News
I prefer Mike McCulloch’s theory about gravitational behaviour at low accelerations. Simpler than MOND. Read his books.
We still haven’t found any Dark Matter and the theory that a halo of Dark Matter surrounds galaxies causing their mass to be higher so the stars orbiting the center of mass move faster than they should based on the visible matter has a problem.
Suppose you descend towards the center of the Earth. At the core gravity acts on you equally in all directions. As you descend, the gravitational pull gets less and less. ONLY THE MASS BELOW YOU COUNTS. The gravitational effect of the mass in the shell above you cancels.
So a shell or halo of dark matter cannot explain the anomalous rotation of the outer stars of galaxies.
Dark Matter, along with Dark Energy, are hacks that grew and grew and got more and more elaborate until they swallowed the theory they were invented to provide little shims for.
No progress will be made until they – and whatever String Theory has evolved into these days – are completely thrown out. Preferably by cancelling existing grants and issuing no new ones to anyone invoking any of this trio of invented garbage in any paper they submit for review.
Mike Borgelt,
You wrote: “So a shell or halo of dark matter cannot explain the anomalous rotation of the outer stars of galaxies.”
You are correct that a mass above your location has an effect on the gravitational forces you feel. perhaps counterintuitively, if you were inside a shell (thick or thin), the gravitational pull from area of the side nearest you would be countered by the pull from the larger area of the side farther away, so you would be floating in zero gravity in ways unlike the free-fall experienced in orbit.
I think that astronomers imagine that there is a mass distribution of the dark matter that can explain the rotations that they see, but I have not yet seen their imagined distribution or the explanation of how it works.
Dark matter is needed, not observed. It is needed to explain observations. The conclusion is that it must exist, but only because the scientists cannot imagine what causes their observations.
Dark matter and dark energy are two concepts that seem more like aether than reality. A century ago, we were certain that we were immersed in an aether for electromagnetic (EM) waves to move through, but later research shows that aether was is not necessary for the EM phenomenon. No one could detect aether, either (sorry, I didn’t mean it to come out that way).
Dark matter and dark energy may be difficult to detect for the same reason aether was never detected.
The universe is a strange and mysterious place. We only accept the reality of what we experience around us because we have experienced it all our lives.
Things fall if we don’t support them. Then someone realized that heavier things fall faster than light things. Eventually, experimentation showed that heavy things and light things fall at the same rate, except where affected by effects (that just keeps happening! and isn’t intentional) such as air resistance. Further investigation concluded that gravity decreased inversely with distance, because that was the only way to get the math to match the observed elliptical planetary motions, and later supported by experimentation. Now there is a hypothesis that gravity is a curvature in space as well as in time (time is curved?). If that is so, then gravity is not a force field, which means that a unified field theory is futile with gravity as a part of it. Could Einstein’s own hypothesis be what stymied him in his unified field endeavor?
And if gravity is a curvature in space and time, then perhaps something else happens on galactic scales that we cannot explain with our usual theories and hypotheses. If something happens on galactic scales, what about universe-sized scales?
But we need, need, dark matter to explain the inexplicable observations.
Did I mention that the universe is a strange and mysterious place? Life was so much simpler when Sir Isaac Newton was around. Maybe that is why they don’t knight modern physicists, astronomers, and astrophysicists. All they do is tell us that the world works differently than we see it work.
I actually hope there is something to the variable speed of light deal…as a sci-fi fan.
Polyhymnia’s odd mass demands a mission.
Edward asked: “(time is curved?)”
Time crystals and the immediate black hole environment would seem to argue that Time can curve back on itself. People in high-stress situations experience time-dilation (raises hand). Einstein theorized, and observation confirms, that Time is not the constant we would perhaps like.
the LIGO results already ruled out MOND
but the sample size here is too small to be very interesting, every galaxy has its idiosyncrasies… there are still recent disagreements on the degree of Keplerian decline in the Milky Way itself
dark matter does still seem to be necessary but I’m not sure I buy their claims it acts differently in large galaxies vs small
I did see “tired light” has become “tired physics” but it still seems like nonsense even if they can make it fit
expecting a nice timescape theory paper using the Euclid QR1 data quite soon… DR1 should be enough to rule out dark energy definitively, if Wiltshire is right
Blair Ivey,
You noted: “People in high-stress situations experience time-dilation (raises hand).”
Time flies when you’re having fun, which may be a curvature of time and a cruel trick by the universe to shorten our enjoyments and lengthen our miseries. A cruel trick indeed.