Physics Help Forum Is Dark Matter Real?

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 Jul 28th 2018, 03:56 AM #1 Physics Team   Join Date: Apr 2009 Location: Boston's North Shore Posts: 1,576 Is Dark Matter Real? Way too many times physics amateurs have posted claiming dark matter isn't real and we should listen to them etc. I've ignored those threads because they weren't credible. However there's an article on this subject in Scientific American this month entitled Is Dark Matter Real by two astrophysicists. See: http://www.newenglandphysics.org/oth...DarkMatter.pdf Let me know what you think. topsquark likes this.
 Jul 28th 2018, 09:20 PM #2 Senior Member   Join Date: Apr 2017 Posts: 453 I find it hard to read such articles .. I have problems with nearly every line , just take the first line ... "The stars still have their secrets. We know why they shine .We know why they trinkle . But we ...." Well no , I don't believe established science has an accurate explanation of how they shine . The model is breathtakingly elegant And sounds very reasonable and satisfactory , but many holes in it , also papered over. We do know why stars twinkle ...dust in the atmosphere... But back to dark matter (and dark energy) .... bottomline .... observations didn't fit in with established theories of gravitation , so rather than examine the theory , people assumed the theory HAD to be correct, it was chiseled in stone , and the only answer was to hypothesise some magical , invisible , fairy mater ....sprinkled just where it was needed to make everything right again .... No experiments have ever found or detected evidence of this dark matter ... so it must remain just another unproven theory, and we have plenty of them .... We have other evidence in the fossil record that the assumption that G is constant may not be true ... it could vary over time , hence be different in observations of very distant stars ....
Jul 29th 2018, 08:51 AM   #3
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Quote:
 We have other evidence in the fossil record that the assumption that G is constant may not be true ... it could vary over time , hence be different in observations of very distant stars ....
Perhaps you would like to offer a reference to this claim?

 Jul 29th 2018, 08:55 AM #4 Senior Member     Join Date: Jun 2016 Location: England Posts: 786 In any field of study it is easy to become blinkered by the fashionable ideas. Science history is full of examples of ideas that were initially discarded as being out of sync with standard orthodoxy, but were later proved to be correct. It is also full of examples of ideas that were initially discarded as being out of sync with standard orthodoxy, but were later proved to be total rubbish... All we can do is keep an open mind, and wait for more evidence. topsquark, Pmb and benit13 like this. __________________ ~\o/~
Jul 29th 2018, 02:46 PM   #5

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 Originally Posted by oz93666 But back to dark matter (and dark energy) .... bottomline .... observations didn't fit in with established theories of gravitation , so rather than examine the theory , people assumed the theory HAD to be correct, it was chiseled in stone , and the only answer was to hypothesise some magical , invisible , fairy mater ....sprinkled just where it was needed to make everything right again .... No experiments have ever found or detected evidence of this dark matter ... so it must remain just another unproven theory, and we have plenty of them ....
There are a couple of Relativity replacements that I've heard of to address this. I only know Brans-Dicke Theory (GR with an additional scalar gravitational field) and String Theory by name but there are others. One of the troubles with replacing GR is that GR has passed so many tests. Any replacement theory has to replicate these while also explaining stuff that it doesn't. Not impossible, just hard. That's probably why most Cosmologists I've heard of stick with GR. It could all be explainable by something like String Theory and we just don't know how to calculate it yet.

Either way we'll figure it out sooner or later.

-Dan
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Jul 30th 2018, 04:02 AM   #6
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 Originally Posted by studiot Perhaps you would like to offer a reference to this claim?
I'm referring to fossil records of large creatures with bat type wings which could never flown in the gravity we now have .. dinosaurs over 100 tonnes which could never have walked in the gravity we have now ...

Combine that with the fact that modern measurements of G do not give consistent results , it seems possible that G may change slightly with time ..If it did this could account for the unexplained movements of galaxies , and our fossil record.

Jul 30th 2018, 04:35 AM   #7
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Hi Oz./.. just wanted to clarify some things:

Quote:
 Originally Posted by oz93666 I find it hard to read such articles .. I have problems with nearly every line , just take the first line ... "The stars still have their secrets. We know why they shine .We know why they trinkle . But we ...." Well no , I don't believe established science has an accurate explanation of how they shine . The model is breathtakingly elegant And sounds very reasonable and satisfactory , but many holes in it , also papered over.
Oz... we have decades worth of quantitative experimental evidence that verifies not only how many different kinds of stars burn their fuels, but also the transport of thermal energy from the interior to the exterior and the subsequent light (not just as a brightness, but also a frequency-dependent curve). I have direct research experience with this and can fill you in on the evidence if you wish.

As far as I remember from my PhD, the main unknowns with stellar physics being researched today are the following:

1. MHD phenomena (corona, mass ejections, loops, heliosphere) are very difficult to model
2. supernovae models (SN 1a and SNII models) are still very uncertain and very difficult to do
3. thermal pulses, novae, oscillations are still difficult to model and observables are sometimes difficult to obtain
4. Extreme environments (black holes, neutron star equation of state, binary accretion) are difficult to observe and model
5. triple-alpha, $\displaystyle ^{12}$C($\displaystyle \alpha, \gamma$)$\displaystyle ^{16}$O reactions are uncertain in the lab, introducing uncertainties to stellar models and galactic chemical evolution models
6. Low-mass regime: brown dwarfs, hot Jupiters, dwarfs are hard to observe because they are faint (lower part of Salpeter curve)
7. Mixing models are crude (convective-boundary mixing, thermohaline mixing and entrainment models often use diffusive approximations)
8. Interior state: direct observations are difficult, so helioseismology could be an important test of stellar models
9. Population studies of massive stars are difficult, because a lot of them have exploded already (upper part of Salpeter curve)
10. Origin of r-process elements

Among others.

Quote:
 We do know why stars twinkle ...dust in the atmosphere...
We know the twinkling effect is caused by intervening matter between the stars and telescopes, including the Earth's atmosphere and the interstellar medium. There are extensive reddening maps of the Milky Way and interstellar medium to predict the effect. We also have adaptive optics at observational facilities to help eliminate the effect of twinkling and other aberrations (such as coma).

Quote:
 But back to dark matter (and dark energy) .... bottomline .... observations didn't fit in with established theories of gravitation , so rather than examine the theory , people assumed the theory HAD to be correct, it was chiseled in stone , and the only answer was to hypothesise some magical , invisible , fairy mater ....sprinkled just where it was needed to make everything right again .... No experiments have ever found or detected evidence of this dark matter ... so it must remain just another unproven theory, and we have plenty of them ....
Since the original observations of galactic rotation profiles, scientists have explored both possibilities (additional mass and modified Newtonian dynamics) and it is still one of the longest unsolved problems in astrophysics. There's the occasional idiot who claims to "know" the answer as being in one camp or the other, but any honest scientist will admit that the solution could be either.

Quote:
 We have other evidence in the fossil record that the assumption that G is constant may not be true ... it could vary over time , hence be different in observations of very distant stars ....
Those papers were really, really shite though dude. I don't think there's any compelling evidence yet for any of the fundamental constants not being constant.

Imho, the dark matter article doesn't really shed light on anything new. It's probably just not well reported about the MOND efforts or the TEVES models, so they're just getting round to reporting on it.

Jul 30th 2018, 08:25 AM   #8
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 Originally Posted by benit13 Imho, the dark matter article doesn't really shed light on anything new.
It would be odd if it did since Scientific American is not a peer-reviewed journal. Its purpose is not to publish the results of new research but to explain to the general reader the state of an area of science.

See - https://www.scientificamerican.com/p...-instructions/
Quote:
 Generally speaking, Scientific American and Scientific American MIND present ideas that have already been published in the peer-reviewed technical literature. We do not publish new theories or results of original research.

Last edited by Pmb; Jul 30th 2018 at 08:28 AM.

 Mar 29th 2019, 01:30 AM #9 Junior Member   Join Date: Mar 2019 Posts: 2 Excellent information here. Thank you. __________________ java online training
 Apr 2nd 2019, 07:47 PM #10 Member   Join Date: Mar 2019 Location: cosmos Posts: 93 neila9876 vs htam9876 @pmb Dear sir, I am not knowing if it's correct to say something here. Because astronomers have spent so much money to do it and they have done so much endevour to explore the cosmos, should we say something congraturation? Sorry Sir.

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