Comments on: Astronomers discover galaxy with no dark matter

By: pzatchok

pzatchok — Fri, 10 Dec 2021 07:05:41 +0000

I might be barking in the wrong tree.

How do they know the actual specific gravity of a galaxy?

They can measure the spin rate.
They can measure pretty accurately the diameter.
Can they detect and measure the expansion or contraction of the galaxy? This would effect the speed.

If they do not know the actual gravity in the galaxy how do they know whats to much or to little?
Thus the whole reason for dark matter.

By: markedup2

markedup2 — Wed, 08 Dec 2021 18:08:37 +0000

So much for MONDS.

I don’t think anyone _likes_ dark matter, but it explains (in a vague, mysterious sort of way) the problems with current models.

By: Blair Ivey

Blair Ivey — Wed, 08 Dec 2021 04:28:47 +0000

Thank you for the comments, MadRocketSci. Things to consider.

By: Jay

Jay — Tue, 07 Dec 2021 19:17:53 +0000

You are correct MadRocketSci about the rotation rate of galaxies. Some parts of galaxies, like are our own are going the other direction due to the absorption of smaller galaxies. I was surprised to hear that finding when they deduced it from the data from the Gaia satellite.

By: MadRocketSci

MadRocketSci — Tue, 07 Dec 2021 14:59:33 +0000

Of course, if the rotation rate of the galaxies doesn’t correlate with the perceived dark-matter mass, then this model is busted. If the percieved dark matter mass varies independently of everything else, then it’s hard to escape the “something is there we can’t see” hypothesis. Will have to look into the statistics sometime.

By: MadRocketSci

MadRocketSci — Tue, 07 Dec 2021 14:54:30 +0000

I had read a paper earlier claiming that gravitomagnetism (the analogue of magnetism for the gravitational force. I think it’s also called Lenz-Thirring or frame dragging force in other contexts/more complete GR treatments) can explain the increased rotation rate of stars attributed to dark matter, and also some other structural aspects of galaxies. I’m intrigued and it’s been on my to-do list to set up a simulation of this as soon as I can bash enough GPU code together to do that. If this is true, it could solve the mystery in a way that doesn’t require crazy amounts of invisible mass.

In special relativity, forces that act in one frame between stationary objects give rise to other forces acting between moving objects. In the SR context, magnetic fields *are* electric fields: The 3-d field vector is replaced with a 4-d tensor that acts on the world-line segment of a particle to bend its path. The resulting covariant equation is something like dv/dtau_j = F^ij * v_j The space-time components of the tensor are electric fields. The space-space components are magnetic fields. When transforming to a moving frame, the tensor tilts over and space-space components appear. I imagine soemthing similar happens with gravity in a weak-field limit – how I intend to simulate it.

By: George C

George C — Tue, 07 Dec 2021 12:58:53 +0000

If some galaxies have dark matter and some do not then it tends to refute those alternative formulations of the law of gravity as a way to model what we observe.

By: pzatchok

pzatchok — Tue, 07 Dec 2021 06:01:45 +0000

Could there be a super massive black hole increasing the gravity in that low population galaxy?

I sometimes just think they are calculating the expected gravity wrong.

By: Col Beausabre

Col Beausabre — Tue, 07 Dec 2021 04:51:30 +0000

In defense of theoeretical physics, Pauli proposed the neutrino in 1930 to account for observed interactions. It took another 26 years to detect them. Although I do hve to admit I remain skeptical of dark matter and dark energy. It reminds of the shape of physics around the turn of the 20th century. It took relativity to solve those contradictions.

By: Jay

Jay — Tue, 07 Dec 2021 04:44:26 +0000

Wayne,
That was an excellent series that played on PBS. I know many physics teachers, high school and college, that have used that series to compliment the lessons.

By: wayne

wayne — Tue, 07 Dec 2021 03:36:10 +0000

Joe-
good stuff.
I’m reminded of “The Structures of Scientific Revolutions” by Thomas Kuhn.
(Had an entire class on that topic, and while not an actual techie-scientist per se, I was trained in (skinnerian) applied behavior analysis, and they drilled into my brain I wasn’t allowed to Appeal to Stuff we couldn’t actually get a grip on. I did adopt more cognitive methodologies later on, but I always try to remember — those most likely don’t actually represent the underlying mechanism in play. )
((The more ephemeral Stuff is very poetic, but it’s not really science, ya’ know?!))

By: Joe

Joe — Tue, 07 Dec 2021 03:11:24 +0000

It has always been the issue with established science. They circle the wagons around the prevailing theories. Everyone know that gravity does not bend light. Everyone knows that the Earth is static and there is no such thing as plate tectonics. Everyone knows dinosaurs did not evolve into birds. Everyone knows CO2 is the leading cause of global warming (I mean climate change).

Until they are proven wrong over and over again.

The second you need some force that cannot be measured, cannot be seen, and cannot be experimented against, then you are in the realm of magic. If they find a way to measure it instead of just creating models, then they might actually have something.

By: wayne

wayne — Tue, 07 Dec 2021 01:56:47 +0000

Good stuff, by all.

I’ll drop this in here— an excellent resource for homeschoolers.

The Mechanical Universe, Episode 41
“The Michelson Morley Experiment”
Caltech 1985
https://youtu.be/Ip_jdcA8fcw
28:46

“A series of 52 thirty-minute videos produced by Caltech covering the basic topics of an introductory university physics course.”

By: Chris

Chris — Tue, 07 Dec 2021 01:30:26 +0000

My comment is not whether Dark Matter exists or not – It is about the current state of science.

I get the strong feeling that through the government funding processes worldwide Science has adopted a Go-along-to-get-along attitude that creates the biggest and (in some eyes) the best of science. But often the biggest is build on a house of cards. I do not think this is the way of science – science is not a beauty pageant nor a fundraising campaign. As Prof. Mike Bright (Grove City College) once stated to me about engineering – a science: “It is the search for Truth.” Todays science seems to be a search for money, power, political power or some combination of the three.

Open, verified data, repeatable experiments (Not repeated ONLY if they can’t be repeated again – more scrutiny required here), open debate over theory, data, methods, results and non-partisan, non-outcomes based funding. This is science.

By: Patrick Underwood

Patrick Underwood — Tue, 07 Dec 2021 01:23:21 +0000

Dark matter is evidence of Iain M. Banks’ “sublimed” civilizations. :)

By: Jay

Jay — Tue, 07 Dec 2021 00:23:21 +0000

You are right Chris,
Dark Matter is just a hypothesis. Historically it reminds me of the “Aether” that people once believed that the Earth and other celestial bodies traveled through. Remembering my physics, the Michelson-Morley experiment proved that the aether did not exist. I sure there will be another Michelson-Morley-like experiment to prove or disprove the existence of dark matter.

By: Mike Borgelt

Mike Borgelt — Tue, 07 Dec 2021 00:21:11 +0000

Go back through this guy’s posts:
https://physicsfromtheedge.blogspot.com/

He has alternative explanations that do not require Dark Matter.

By: sippin_bourbon

sippin_bourbon — Tue, 07 Dec 2021 00:20:43 +0000

So no dark matter. Does that mean it is on the lighter side?

By: Chris

Chris — Mon, 06 Dec 2021 23:22:13 +0000

The mystery to me is that scientists are willing to invent, create or otherwise pull out of their hat an “explanation” for data that does not fit their model instead of looking harder at their model.
One would think that if they were to look to other branches of science such as sun modeling, climate modeling ….or
Oh never mind..