Do we still need Dark Matter to make things work?

[laowhoo]

I'm offering this as illustrative of what Andrew said/has been saying, and as our best evidence of dark matter, so "clumping...?" Really? Did you read it? Maybe I'm misunderstanding--I just don't remember that term in the "literature," poorly read as I may be in astrophysics. Strictly a hobbyist. I also like the way Andrew speaks/writes. Maybe Google "does dark matter clump?"

Anyhoo, I was just a little surprised that the cluster hadn't come up. Thought it might be helpful. After all, this is  an astronomy site. Cheers

[andrew s]

1 hour ago, laowhoo said:

 

The Bullet Cluster?

https://astrobites.org/2016/11/04/the-bullet-cluster-a-smoking-gun-for-dark-matter/

 

 

1 hour ago, Stub Mandrel said:

It must have some ability to clump or it wouldn't be associated with galaxies like that...

Indeed it can accumulate on large scales. I was careful to say compact objects like stars in my previous post.

Regards Andrew 

[laowhoo]

7 hours ago, Stub Mandrel said:

It must have some ability to clump or it wouldn't be associated with galaxies like that...

 

Here Stub, it's an excerpt from Lisa Randall's Dark Matter and the Dinosaurs (2015). I've just finished her Warped Passages: Unraveling the Mysteries of the Universe's Hidden Dimensions and can't really recommend her, but here's a taste nonetheless

https://newrepublic.com/article/123226/how-dark-matter-killed-dinosaurs

OTOH, here's a fellow (Rutger's prof--the same Uni that payed Snooki of The Jersey Shore  $32k to speak--so I guess anything's possible) who muses that it might be possible to "build worlds out of DM" and even uses the word "clump" conveniently for his own purposes. (Randall is speculating that there might be a "special type" of DM, w/ its attendant "dark electromafnetic force," wh/ collapses and accretes, and subsequently wipes out everything on the planet every 30 million years or so.) 

 http://blogs.discovermagazine.com/d-brief/2017/07/14/dark-matter-might-form-planets/#.WnKLYqinE2w

Honestly, I just don't have the heart to read the Rutger's guy sound off like Snooki or anything New Jersey. It's hard enough living here. But know that for the time being, DM most certainly does not clump, and if it did, it'd be "special." For maths (wh/ is what a lot of supersymmetry is), I'll take Max Tegmark, and for astrophysics, Leonard Susskind. Just so many wanna-be rock-star scientists who think it's (science) all the second coming, or that they're special--you know, cuz they're "scientists." Am I ranting?

 

[Stub Mandrel]

18 hours ago, laowhoo said:

I'm offering this as illustrative of what Andrew said/has been saying, and as our best evidence of dark matter, so "clumping...?" Really? Did you read it? Maybe I'm misunderstanding--I just don't remMaybe Google "does dark matter clump?"ember that term in the "literature," poorly read as I may be in astrophysics. Strictly a hobbyist. I also like the way Andrew speaks/writes.

Anyhoo, I was just a little surprised that the cluster hadn't come up. Thought it might be helpful. After all, this is  an astronomy site. Cheers

Is that sarcasm? (serious question, I can't tell...)

Clumping is my expression, but a quick google suggests that the words 'dark matter' and 'clump' have a tendency to, ahem, aggregate.

My confusion arises as I'm at a loss to understand how dark matter can have a non-random distribution (in biology we would describe it as clumped) that mirrors the distribution of baryonic matter (which is how I understand the description of that cluster) if it simultaneously lacks a mechanism to do so.

Wikipedia suggest its because it is so cold; but surely if it falls together it will heat up (especially if it cannot radiate the heat energy) and anything with mass falling down a gravity gradient will gain energy, dark or not.

Even more so it is interesting that the dark matter appears to interact differently from the baryonic matter in that pair of colliding galaxies (why do they also describe it as a 'cluster'?)

I realise that intuitive interpretations/handwaving/just so stories about such things are more likely to be wrong than right, but having just read A Short history of Time it's hard not to fall prey to the illusion that the most complex of concepts can be described in plain English.

[laowhoo]

 

Absolutely no sarcasm Stub, and yes, it is  difficult to discern in this format. And I offered the above writings by Randall and the Rutgers fellow to allow for "clumping" as we use the term for baryonic aggregating/accreting under normal electromagnetic interactions/influences. But these examples are extraordinary and purely hypothetical. It isn't gravity that's the operative function here, but electromagnetism, and your example of biological clumping is exactly why DM doesn't clump, unless or until Randall and her buds find the DM equivalent of electromagnetism. But for now, baryonic and non-baryonic are not synonymous in their behaviors, hence no clumping. 

The reason they're called clusters is b/c the Bullet is a cluster of interacting galaxies. As for Hawking, he's been fairly inconsequential since his Hawking radiation, and hasn't made the top 20 list of most influential physicists since I last checked 12 years ago. Moreover, he wasn't received very well when he tried to dodge his 20-year debate loss to Susskind (read The Black Hole War) by claiming Leonard was right, but for the wrong reason (got jeers f/ his peers). Susskind invoked the Holographic Princviple to prevail in showing that info cannot be lost, and the HP is the  working model is standard cosmology. 

p.s. I appreciate your asking. Wouldn't want any unintended animus, eh? Also, check out the astronaut baggie experiment, an example of the electrostatic forces at work in aggregating/clumping particles in microgravity

 

Cheers

Oops. Forgot to add, I visited your site last night and besides the model-making (maybe my first love as a kid), also impressive is your accomplishment on the night sky w/ very little investment. Way cool. 

[andrew s]

58 minutes ago, Stub Mandrel said:

My confusion arises as I'm at a loss to understand how dark matter can have a non-random distribution (in biology we would describe it as clumped) that mirrors the distribution of baryonic matter (which is how I understand the description of that cluster) if it simultaneously lacks a mechanism to do so.

Wikipedia suggest its because it is so cold; but surely if it falls together it will heat up (especially if it cannot radiate the heat energy) and anything with mass falling down a gravity gradient will gain energy, dark or not.

Neil, the only mechanism to impact dark matter as currently proposed is gravity. Simulations of structure formation that  include as much physics as the simulation can currently handle show that dark matter and normal matter can indeed form large scale structure similar to those we observe today. So gravity can pull normal and dark matter into galaxy, clusters of galaxy scale and larger structures.

However, once you try to form smaller structures then the conservation of angular momentum becomes a serious obstacle.  This was indeed an issue for simulations of star formation regions where it was impossible to get the (normal matter) molecular clouds to collapse into stars until the physics of viscous hydrodynamics and radiation losses were added.

The scale of the issue is to be seen in the high energy jets and radiation from quasars, young stars and the accretion disk of cataclysmic variables as they dissipate the energy associated with increasing angular momentum from accreting matter. 

Hope this helps.

Regards Andrew

[laowhoo]

 

Andrew, VH and radiation loss are properties of established stars. What's at issue is the electromagnetic component of how space dust aggregates to a point wherein gravity plays a role

https://www.cfa.harvard.edu/news/2009-20

Hope this helps

[andrew s]

1 hour ago, Stub Mandrel said:

Wikipedia suggest its because it is so cold; but surely if it falls together it will heat up (especially if it cannot radiate the heat energy) and anything with mass falling down a gravity gradient will gain energy, dark or not.

Giving this some more consideration the reality is that on the scales currently modeled the potential wells are not that deep on average and like  shallow sea rather than a well. There maybe some local hot spots (black holes etc.) but they are relatively few. So as long as the increased velocity of the cold dark matter does not exceed the escape velocity it can remain gravitationally bound. This maybe why dark matter seems to be in halos around galaxies rather than uniformly distributed. 

Regards Andrew

[andrew s]

8 minutes ago, laowhoo said:

 

Andrew, VH and radiation loss are properties of established stars. What's at issue is the electromagnetic component of how space dust aggregates to a point wherein gravity plays a role

https://www.cfa.harvard.edu/news/2009-20

Hope this helps

They are also major issues in star formation. The more physics we added (e.g.) magnetism etc. the better model we get. The viscosity in accretion is due to EM forces.

Regards Andrew

[laowhoo]

Yes, they follow. But Stub's most recent Q was confusing gravity for EM in earliest aggregation scenarios vis a vis soil, etc. It's also why I linked the Lisa Randall conjecture (apologies to mathematicians). EM is crucial. Love reading your stuff. Many thanks, and remember everybody, "The universe is made of stories, not atoms."

[Stub Mandrel]

1 hour ago, laowhoo said:

Also, check out the astronaut baggie experiment, an example of the electrostatic forces at work in aggregating/clumping particles in microgravity

I always suspected the little blue salt bag was really an advanced physics experiment.

[andrew s]

34 minutes ago, Stub Mandrel said:

I always suspected the little blue salt bag was really an advanced physics experiment.

I remember them well. It was impossible to get an even distribution of salt on the crisps. 

Regards Andrew 

[Stub Mandrel]

16 minutes ago, andrew s said:

I remember them well. It was impossible to get an even distribution of salt on the crisps. 

Regards Andrew 

yes... it clumps...

[Paul67]

This is all new to me but something I am very interested in (the maths and physics).  So I have bought myself some books and am launching myself into teaching myself maths to start with, with a view to try and understand the universe as best I can.

In one of my books, Higher Dimensions, and the Future of the Cosmos by Michio Kaku he talks about experiments planned to measure gravity on a quantum scale that might lead to proof for parallel Universes using M theory, with speculation that this could account for the hidden mass required.

How has this line of thinking progressed, given that this book was published in 2006? 

[leibek]

hi

dark matter is75 % of the universe its a considerable amount of matter its like jelatine for me its made of wimps particulses  its like huge magnet . with an attraction

force inward .dark matter is probably made of micro black holes  like some theories argue.

dark matter is a huge magnet.

i hope that in the near future we can discover the real nature of this mysterious matter the ghost matter.

thanks

[philthy]

Maybe we can't find Dark Matter because it doesn't exist?

How can we use gravity to show its existence, when we don't understand how gravity works, and therefore don't know if our mathematical equations describing gravity are correct.

[leibek]

Darkmatter  ?

The enigma stood still.?