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swemy
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If DM is immune to the electromagnetic force but not to gravity and the universe is homogenius, would we expect the find DM at the centre of normal matter bodies such as stars and planets trying to form black holes?
Chronos said:No. Unlike baryonic matter, DM is collisionless so it does not accumulate in the center of gravitating bodies. It just falls right through and passes out the other side.
Chronos said:No. Unlike baryonic matter, DM is collisionless so it does not accumulate in the center of gravitating bodies. It just falls right through and passes out the other side.
swemy said:So DM contributes to the gravition force, but is not responsive to gravity? The Wiki suggests it clusters in a large ball around galaxies, what if not gravity causes it behave this way?
Or is it that as it falls toward the centre of a body, the accelertion caused by gravity is enough to give it the escape velocity coming out the other side.
jackmell said:I mean think about it: rather than slightly modify a simple, elementary concept created hundreds of years ago by frail H.sapiens, we'd rather just magically create an entire dark Universe and I personally do not agree with this approach.
The first part is correct. The second is as far from correct as you can possibly get.jackmell said:The only evidence we have for dark matter is gravitational? Is that all? Just the discrepancy between the mass of objects and their observed gravitational influence?
Which ones? I think you'll find that the alternatives to particulate dark matter face significant shortcomings, and are arguably as, if not more, complex than CDM models.jackmell said:The alternative theories make more sense to me.
jackmell said:Ptolemy and his epicycles first come to mind. The alternative theories make more sense to me. I hereby bet one dollar I'm right on this one too or is my support of these theories not consistent with the rules of this forum?
Oh yeah, ether wind too.
I mean think about it: rather than slightly modify a simple, elementary concept created hundreds of years ago by frail H.sapiens, we'd rather just magically create an entire dark Universe and I personally do not agree with this approach.
bapowell said:Which ones? I think you'll find that the alternatives to particulate dark matter face significant shortcomings, and are arguably as, if not more, complex than CDM models.
The most widely accepted explanation for these phenomena is that dark matter exists and that it is most likely[3] composed of heavy particles that interact only through gravity and possibly the weak force; however, alternate explanations have been proposed, and there is not yet sufficient experimental evidence to determine which is correct.[5]
Chalnoth said:The evidence for dark matter is really, really copious.
Well, it was. But the science is pretty solid here. The best evidence, I think, is in the cosmic microwave background, which was emitted back before any structures in the universe formed, and as a result its behavior is independent of the messy physics that deals with the formations of galaxies and stars and the like. The physics back before the CMB was emitted were much simpler, and therefore the detection is much cleaner than worrying about the very complicated nearby universe.jackmell said:Just seems like a tough call to me.
Chalnoth said:It's pretty much impossible to produce this kind of pattern without a weakly-interacting, low-temperature component of the universe that has substantial mass.
jackmell said:Ok Chalnoth. I just don't understand the science and probably should have just stayed out of this. Unfortunately, I like Astronomy and it's difficult for me to not engage even at the risk of getting into trouble. But also I've become skeptical because the science is so deceptive as history has shown us.
Would be nice to have a better handle on what precisely dark matter consists of.
Drakkith said:What do you mean by "deceptive"?
On a side note, I just visited Kitt Peak National Observatory last night. They showed us the telescope where evidence for dark matter was first gathered by Vera Rubin.
This isn't science being deceptive. This is our own senses. Science is the tool we use to see through the deception of our senses.jackmell said:I got a big yard. When I stand in the middle, and look all about, it certainly looks flat to me.
Also, they really do look like they're going backwards and forwards across the sky not to mention the big yellow one looks like it's moving across the entire sky each day from east to west. Andromeda looks like a difusse cloud until you have a nice telescope to resolve the detail and then realize the Milky Way is not the entire Universe. I seriously doubt we've reached the limits of that deception:)
jackmell said:I got a big yard. When I stand in the middle, and look all about, it certainly looks flat to me.
Also, they really do look like they're going backwards and forwards across the sky not to mention the big yellow one looks like it's moving across the entire sky each day from east to west. Andromeda looks like a difusse cloud until you have a nice telescope to resolve the detail and then realize the Milky Way is not the entire Universe. I seriously doubt we've reached the limits of that deception:)
jackmell said:Ok twofish. I appreciate you taking the time to explain that to me so nicely. Seriously. But my understanding is that we do not have sufficient evidence to declare dark matter responsible for the observed discrepancies between mass and gravity
jackmell said:That means we would have to discover some new type of matter. Just seems like a tough call to me. I remain skeptical but I'll accept it when we have some empirical evidence for this new substance.
jackmell said:I got a big yard. When I stand in the middle, and look all about, it certainly looks flat to me.
Also, they really do look like they're going backwards and forwards across the sky not to mention the big yellow one looks like it's moving across the entire sky each day from east to west. Andromeda looks like a difusse cloud until you have a nice telescope to resolve the detail and then realize the Milky Way is not the entire Universe. I seriously doubt we've reached the limits of that deception:)
jackmell said:Ok Chalnoth. I just don't understand the science and probably should have just stayed out of this. Unfortunately, I like Astronomy and it's difficult for me to not engage even at the risk of getting into trouble. But also I've become skeptical because the science is so deceptive as history has shown us.
Would be nice to have a better handle on what precisely dark matter consists of.
Sort of. I don't think this effect has been detected on the level of individual galaxy collisions. At least, not yet.ImaLooser said:There are galaxies which are colliding. The bright matter from each galaxy interacts and slows down. The dark matter does not, it doesn't interact and so keeps moving unaffected. In this way the dark matter has separated from the bright, which is unusual. So there is an area in space which appears empty, but nevertheless bends light via its gravitation. This is what astronomers call "direct evidence" of dark matter, which is sciencespeak for "as direct as we astronomers can hope to get."
As to what dark matter consists of, that could easily take decades to figure out.
Dark matter is a type of matter that is believed to make up about 85% of the total mass of the universe. It does not emit or absorb light, making it invisible to traditional telescopes and difficult to detect. Its existence is inferred through its gravitational effects on visible matter.
Dark matter plays a crucial role in the formation and evolution of galaxies, as it provides the necessary gravitational force to hold galaxies together. It also affects the motion of stars and galaxies within a galaxy cluster. On a smaller scale, dark matter may also influence the formation and stability of individual stars and planets.
While we do not yet have a complete understanding of the nature of dark matter, many theories and experiments suggest that it is made up of particles that interact only weakly with normal matter. Some of the leading candidates for dark matter particles include WIMPs (weakly interacting massive particles) and axions.
Dark matter cannot be observed directly, but its presence can be inferred through its gravitational effects on visible matter. Scientists also use various techniques such as gravitational lensing, the study of galaxy rotation curves, and particle accelerators to search for and study dark matter particles.
Dark matter has greatly influenced our understanding of the universe, as it is a crucial component in many cosmological models and theories. Its presence helps to explain the observed structure and behavior of galaxies and galaxy clusters, and its study provides insight into the history and evolution of the universe.