Is there really a dark matter halo surrounding our galaxy?

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Is there really a dark matter halo surrounding our galaxy?

Postby curiosity on September 18th, 2020, 7:00 am 

Is there a dark matter halo surrounding our galaxy, or is the gravitational discrepancy due to the current theory of gravitation being flawed ?

I suspect the latter is true and even in the unlikely event of hypothetical dark matter actually existing; It is the flaw in the theory of gravity not dark matter, which is responsible for the currently unexplained phenomenon.

The two most prominent theories of gravitation were proposed prior to the acceptance that the universe is undergoing a metric expansion. (due to what we now know as dark energy.) However, once dark energy is thrown into the mix, a reworded amalgamation of the two theories provides a much better explanation for the gravitational anomaly surrounding our and other galaxies, "plus gravitation itself !"
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Re: Is there really a dark matter halo surrounding our galax

Postby TheVat on September 18th, 2020, 9:33 am 

IIRC there are multiple lines of evidence for DM. Here's a link to start with...

https://www.nasa.gov/home/hqnews/2006/a ... exists.%22
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Re: Hot Shot

Postby Faradave on September 18th, 2020, 10:38 am 

Neutrinos are existing hot dark matter (low mass, high velocity) as opposed to the cold dark matter purported to comprise galactic halos.
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Re: Is there really a dark matter halo surrounding our galax

Postby curiosity on September 18th, 2020, 5:59 pm 

Dark matter's unanswered questions.

Dark matter theory has done a reasonable job at predicting many of these measurements, which is why it is well-respected in the scientific community. But dark matter is still an unconfirmed model. All evidence of its existence so far is indirect. If dark matter exists, we should be able to directly observe interactions of dark matter as it passes through the Earth and we might be able to make dark matter in large particle accelerators, like the Large Hadron Collider. And yet neither approach has been successful.

In addition, dark matter should agree with all, not just many, astronomical observations. While dark matter is the most successful model so far, it is not completely successful. Dark matter models predict more dwarf satellite galaxies surrounding big galaxies like the Milky Way than are actually detected. Although more dwarf galaxies are being found, there are still too few compared to dark matter's predictions.

Another big, open question is how dark matter affects the relationship between the brightness of galaxies and their rotational speeds. This relationship, which was first presented in 1977, is called the Tully-Fisher relation, and it has shown numerous times that a galaxy's visible mass correlates well with its rotational speed.


The above are not my own words !!! just an excerpt from an unbiased summing up of the evidence for dark matter, given by a very knowledgeable man who I greatly respect. If direct evidence for dark matter is ever found I will have to accept its existence. but until that time I (Among many others) remain sceptical.
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Re: Is there really a dark matter halo surrounding our galax

Postby curiosity on September 18th, 2020, 6:26 pm 

by Faradave on September 18th, 2020, 9:38 am

Neutrinos are existing hot dark matter (low mass, high velocity) as opposed to the cold dark matter purported to comprise galactic halos.



Hmm, I will have to check that out before commenting Dave... I'm not up to date with neutrinos, the last time I checked they were Fermions, which came in three distinct types, Muon, Tau and Electron type. If they are indeed hot dark matter, why do they react weakly with matter?
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Re: Is there really a dark matter halo surrounding our galax

Postby curiosity on September 18th, 2020, 6:41 pm 

Oops I didn't read your post correctly Dave... I should have noticed the change from cold, to hot dark matter before replying.
I must admit that I have never studied hot dark matter or the evidence for its existence, so I don't have an opinion on it, It is the cold dark matter that I wish to debate.
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Re: Is there really a dark matter halo surrounding our galax

Postby curiosity on September 18th, 2020, 8:41 pm 

Houston I have a problem... It seems that hot dark matter is not proven to exist either, speculation shouldn't be accepted as fact... ( facts are supported by hard evidence.)
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Re: Is there really a dark matter halo surrounding our galax

Postby charon on September 18th, 2020, 8:43 pm 

Is there really a dark matter halo surrounding our galaxy?


No, it's a rumour.
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No Problemo

Postby Faradave on September 18th, 2020, 8:48 pm 

"An example of a hot dark matter particle is the neutrino. Neutrinos have very small masses, and do not take part in two of the four fundamental forces, the electromagnetic interaction and the strong interaction. They interact by the weak interaction, and gravity, but due to the feeble strength of these forces, they are difficult to detect. A number of projects, such as the Super-Kamiokande neutrino observatory, in Gifu, Japan are currently studying these neutrinos." - Wikipedia*

*clicking on underlined text in my posts brings up a source link.
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Re: Is there really a dark matter halo surrounding our galax

Postby curiosity on September 19th, 2020, 5:09 am 

No, it's a rumour.




Do I detect a note of sarcasm?

I'm not questioning the fact that there is a gravitational anomaly, which encompasses our and many other (but not all) galaxies. I am simply not convinced that the anomaly results from the proposed presence of hypothetical dark matter. I believe the discrepancy could be due to a misunderstanding of the underlying cause of gravitation.
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Re: Is there really a dark matter halo surrounding our galax

Postby TheVat on September 19th, 2020, 9:54 am 

Not sure why I had to repost this. Was there a difficulty opening the link??


TheVat » September 18th, 2020, 6:33 am wrote:IIRC there are multiple lines of evidence for DM. Here's a link to start with...

https://www.nasa.gov/home/hqnews/2006/a ... exists.%22


The team was granted more than 100 hours on the Chandra telescope to observe the galaxy cluster 1E0657-56. The cluster is also known as the bullet cluster, because it contains a spectacular bullet-shaped cloud of hundred-million-degree gas. The X-ray image shows the bullet shape is due to a wind produced by the high-speed collision of a smaller cluster with a larger one.

In addition to the Chandra observation, the Hubble Space Telescope, the European Southern Observatory's Very Large Telescope and the Magellan optical telescopes were used to determine the location of the mass in the clusters. This was done by measuring the effect of gravitational lensing, where gravity from the clusters distorts light from background galaxies as predicted by Einstein's theory of general relativity.

The hot gas in this collision was slowed by a drag force, similar to air resistance. In contrast, the dark matter was not slowed by the impact, because it does not interact directly with itself or the gas except through gravity. This produced the separation of the dark and normal matter seen in the data. If hot gas was the most massive component in the clusters, as proposed by alternative gravity theories, such a separation would not have been seen. Instead, dark matter is required.

"This is the type of result that future theories will have to take into account," said Sean Carroll, a cosmologist at the University of Chicago, who was not involved with the study. "As we move forward to understand the true nature of dark matter, this new result will be impossible to ignore."

This result also gives scientists more confidence that the Newtonian gravity familiar on Earth and in the solar system also works on the huge scales of galaxy clusters.


Thoughts?
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Re: Is there really a dark matter halo surrounding our galax

Postby curiosity on September 19th, 2020, 4:48 pm 

Not sure why I had to repost this. Was there a difficulty opening the link??



Sorry... No there is no problem with the link. I just happen to be burning the candle at both ends, which is crazy really as I have recently retired, I should be taking things easy but have ended up working harder and longer than I was while still employed.

I really wanted to discuss the reason for the gravitational anomalies that surround many galaxies including our own, but due to my tiredness I have made a bit of a hash of getting the ball rolling
I don't disagree with Einsteins premise that gravitation is an effect caused by the proximity of matter altering the geometry of space-time. It is just the means by which it is proposed to do so, that I disagree with.
Such is the genius of Einstein that he can be right even when he is wrong, In the case of gravitation though I think he is only half right. Being fifty percent wrong however, in this instance really screws things up. I see no reason to invoke dark matter in the attempt to make the sums add up. I believe it is the theory of gravitation itself which needs a little tweak.
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