"A galaxy with NO dark matter" Topic

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Hmmmmm…..

Thanks for that. It gets "curiouser and curiouser" all the time.

I must say that reading the "reactions" section of the article was depressing.

And it mentioned that there are "some" galaxies with an over abundance of dark matter.

I remember a college physics course that confidently asserted that the universe was isotropic, and that all constants were constant everywhere. Or was that an Asimov essay? I remember cocking an eyebrow.
At this point we can confidently say that we don't know what we don't know.

Back at the beginning of the previous century, the head of the US Patent Office said there were no new discoveries to be made. It was all engineering.
There were also lists of things "Man will never know". One was the chemical composition of the stars. All were disproven within a decade.

Maybe all physics textbooks more than 50 years old should be burned. Well, perhaps just the back third of the book. Classical is doing just fine.

I remember a college physics course that confidently asserted that the universe was isotropic, and that all constants were constant everywhere. Or was that an Asimov essay? grin I remember cocking an eyebrow.

Well I think it still applies. Isotropism is but one half of the Cosmological Principle.

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Back at the beginning of the previous century, the head of the US Patent Office said there were no new discoveries to be made.

So? Who cares what some bureaucrat incorrectly thought? I doubt that's any indictment on Science.

There were also lists of things "Man will never know". One was the chemical composition of the stars. All were disproven within a decade.

To be fair, that was one guy, August Comte. He said that in 1842 . Kirchhoff proved him wrong in 1859. I don't seem to see the same significance in this as you do. The changes in biology were even more dramatic in those years (Darwin, Mendel, Pasteur, Koch, Lister, etc)

As for Dark Matter, people seem to think it is some recent, fad topic. Except it was first coined in 1906 by the great physicist Henri Poincaré, when describing differences in velocity dispersion in stars. The person who brought that to Poincaré' attention was Lord Kelvin. In a lecture from 1884!

So Dark Matter has a longer track record than you give it credit for.

"So Dark Matter has a longer track record than you give it credit for."

Ok, so what? Does that mean it's suppose to have more credibility?

Ok, so what? Does that mean it's suppose to have more credibility?

Isn't that how science works?

As a concept, it's been around for 110 years or so. In the meantime, our ability to look out into the Universe has increased astronomically (pardon the pun). If it was a BS idea, we should have found that out by now. However, due to observing things like gravitational lensing and perturbations in the Cosmic Microwave Background, the existence of Dark Matter has become strengthened over the last few years.

Same with Darwin's Theory of Natural Selection. Darwin's theory was derived before anyone knew what the chemical nature of inheritance consisted of. The subsequent discoveries in genetics and DNA have only bolstered his theory. It also has withstood intense scrutiny since its inception.

Contrast the above to the concept of the "luminiferous aether". In the late 19th century, people thought this was still necessary as the medium for light to travel in outer space. Early in the 20th century this concept was put to rest.

So ya, surviving 100+ years scientific scrutiny and being supported by modern day observations means that the concept has more credibility.

Since John brought up Comte's statement, I wanted to show that the analogy was not apt.

I'm merely following up on your "curioser and curioser".
All I'm saying is that scientific thinking evolves.
Sheesh.

All I'm saying is that scientific thinking evolves.

I agree

Sheesh.

Sorry.

Contrast the above to the concept of the "luminiferous aether."

Ironically, if one goes with the concept of the Universe as one big electromagnetic field that makes up everything (matter or energy or space or time), then one is somewhat conceiving of a "luminiferous aether" by a different name.

Okay, not really. But some times that actually is how science works: you have observations that given current understanding require an imagined solution that fits those understandings and the observations, until someone does experimentation or more observations which alter (or even remove) the imagined solution. Then you imagine a different one, with a different name. Rinse, repeat.

The OP article is a fascinating example. We have a theorized "something" which explains observations we have made, but which now must be theorized differently in its assumed operation based on newer observations. This doesn't mean the theorized "something" doesn't exist; it just means we have to derive more detailed explanations that fit the newer observations, too. Could this produce a situation where the theorized "something" is completely shown to be a false assumption? Yes, of course. But that only means we will have found or theorized a better explanation for the effects that we have observed. This may be a new theorized "something," or a better understanding of properties and effects of already known "somethings," or a partial retention of the old theorized "something" with new understandings attached that cause us to conceive of it by other categorical terms. But that doesn't change the fact that the effects exist, and if so, aren't explained by the past explanations in a meaningful, scientific way. Do "dark matter" and "dark energy" exist? Well, yes, at least as theorized "somethings" that cause observed effects not explained by those things definitively known to exist. We may one day call these "somethings" by more defined names or terms that don't really fit the words we use today. But that doesn't mean they never existed; it just means we have come to understand them better.

Does this strange galaxy violate the Cosmological Principle in not being homogeneous with the rest of the Universe?

I'm sure the authors' smartass grad students are asking that over a pitcher or three at the bar, and maybe the authors are thinking it too, but are too smart to publish it.

But seriously…
Can Life exist in such a galaxy without Dark Matter?

+1 Parzival

Does this strange galaxy violate the Cosmological Principle in not being homogeneous with the rest of the Universe?

At the scale they are talking about, no. Even on bigger scales we have superclusters of galaxies on the one hand, and then areas of space that are relatively empty. But on the larger scale this is still uniform and isotopic in every direction.

"Although the universe is inhomogeneous at smaller scales, it is statistically homogeneous on scales larger than 250 million light years. The cosmic microwave background is isotropic, that is to say that its intensity is about the same whichever direction we look at."

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But seriously…
Can Life exist in such a galaxy without Dark Matter?

No idea, but it's stumping the astronomers who thought you needed Dark Matter to form galaxies in the first place.

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I have a friend in a prestigious university's
astrophysics department. I sent him an e-mail and asked
how he was going to approach these new findings.

His reply: 'Retirement beckons…'

The explanation for this galaxy is simple.

The Niblonians, simply haven't had time to poop in that galaxy yet.

Paradoxically, the authors said the discovery of a galaxy without dark matter counts as evidence that it probably does exist. A competing explanation for the fast-orbiting stars is that the way gravity drops off with distance has been misunderstood – but if this were the case, all galaxies should follow the same pattern.

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