Dark matter is missing from young galaxies

 
bbearren
 
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bbearren
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15 March 2017 17:48
 
 
 
GAD
 
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15 March 2017 23:44
 
 
 
Ola
 
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Ola
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16 March 2017 11:54
 

Both articles are out of my league but I enjoy watching clever people work out this stuff! Thanks for the interesting info.

 
Cheshire Cat
 
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16 March 2017 17:27
 

I heard a physicist say that she thought dark matter was the presence of other universes superimposed over ours, but in other dimensions. We would be inhabiting the same space as these other universes, but wouldn’t be able to detect them.

She thought that one clue to this theory was the weakness of gravity. Of the four fundamental forces – gravitational, electromagnetic, strong nuclear, and weak nuclear – gravity would be the only one that would interact with all universes, thus it’s effects would be spread out amongst them. Gravity is effective over great distances, but is so weak that we can breaks its grip by just raising our arm or standing up.

I think it’s an interesting idea.

 
 
Giulio
 
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16 March 2017 21:48
 

From this wiki article on Entropy (arrow of time):

Entropy is the only quantity in the physical sciences (apart from certain rare interactions in particle physics; see below) that requires a particular direction for time

Is this observation on ‘dark matter’ in earlier vs older galaxies another independent manifestation of the arrow of time?

 
EN
 
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EN
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17 March 2017 14:51
 
Giulio - 16 March 2017 09:48 PM

From this wiki article on Entropy (arrow of time):

Entropy is the only quantity in the physical sciences (apart from certain rare interactions in particle physics; see below) that requires a particular direction for time

Is this observation on ‘dark matter’ in earlier vs older galaxies another independent manifestation of the arrow of time?

Why would evolution not require a particular direction for time???  What is meant by “quantity”?

 
Ola
 
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17 March 2017 15:14
 
Cheshire Cat - 16 March 2017 05:27 PM

I heard a physicist say that she thought dark matter was the presence of other universes superimposed over ours, but in other dimensions. We would be inhabiting the same space as these other universes, but wouldn’t be able to detect them.

She thought that one clue to this theory was the weakness of gravity. Of the four fundamental forces – gravitational, electromagnetic, strong nuclear, and weak nuclear – gravity would be the only one that would interact with all universes, thus it’s effects would be spread out amongst them. Gravity is effective over great distances, but is so weak that we can breaks its grip by just raising our arm or standing up.

I think it’s an interesting idea.

Yes! Mind blowing.

Are you talking about the (membrane) Brane Multiverse? I wish I understood enough maths to have a proper opinion.

Easy speak version:

http://www.bbc.com/earth/story/20160318-why-there-might-be-many-more-universes-besides-our-own

 
Giulio
 
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17 March 2017 16:19
 
EN - 17 March 2017 02:51 PM
Giulio - 16 March 2017 09:48 PM

From this wiki article on Entropy (arrow of time):

Entropy is the only quantity in the physical sciences (apart from certain rare interactions in particle physics; see below) that requires a particular direction for time

Is this observation on ‘dark matter’ in earlier vs older galaxies another independent manifestation of the arrow of time?

Why would evolution not require a particular direction for time???  What is meant by “quantity”?

Evolution (as well as living processes) probably do imply an arrow of time, but I don’t think it is independent of entropy. The earth is an open system that takes as input energy from the sun (low entropy), holds it and transforms the energy in a number of ways, ultimately producing output as heat (high entropy) - paradoxically this process of increasing entropy is what has permitted evolution (which may appear as a local decrease in entropy).

I have wondered if gravity (the fact that things attract into separate clumps) implies an arrow of time independent of entropy.

 

[ Edited: 17 March 2017 17:28 by Giulio]
 
Cheshire Cat
 
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17 March 2017 18:06
 
Ola - 17 March 2017 03:14 PM
Cheshire Cat - 16 March 2017 05:27 PM

I heard a physicist say that she thought dark matter was the presence of other universes superimposed over ours, but in other dimensions. We would be inhabiting the same space as these other universes, but wouldn’t be able to detect them.

She thought that one clue to this theory was the weakness of gravity. Of the four fundamental forces – gravitational, electromagnetic, strong nuclear, and weak nuclear – gravity would be the only one that would interact with all universes, thus it’s effects would be spread out amongst them. Gravity is effective over great distances, but is so weak that we can breaks its grip by just raising our arm or standing up.

I think it’s an interesting idea.

Yes! Mind blowing.

Are you talking about the (membrane) Brane Multiverse? I wish I understood enough maths to have a proper opinion.

Easy speak version:

http://www.bbc.com/earth/story/20160318-why-there-might-be-many-more-universes-besides-our-own

Yes, that’s got to be the model she was talking about.

I was pretty bad at math in school, but I still love science. It’s the concepts, ideas and results that I find fascinating. It also adds greatly to my sense of mystery and awe about being alive in this universe.

 
 
Ola
 
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18 March 2017 15:45
 
Cheshire Cat - 17 March 2017 06:06 PM
Ola - 17 March 2017 03:14 PM
Cheshire Cat - 16 March 2017 05:27 PM

I heard a physicist say that she thought dark matter was the presence of other universes superimposed over ours, but in other dimensions. We would be inhabiting the same space as these other universes, but wouldn’t be able to detect them.

She thought that one clue to this theory was the weakness of gravity. Of the four fundamental forces – gravitational, electromagnetic, strong nuclear, and weak nuclear – gravity would be the only one that would interact with all universes, thus it’s effects would be spread out amongst them. Gravity is effective over great distances, but is so weak that we can breaks its grip by just raising our arm or standing up.

I think it’s an interesting idea.

Yes! Mind blowing.

Are you talking about the (membrane) Brane Multiverse? I wish I understood enough maths to have a proper opinion.

Easy speak version:

http://www.bbc.com/earth/story/20160318-why-there-might-be-many-more-universes-besides-our-own

Yes, that’s got to be the model she was talking about.

I was pretty bad at math in school, but I still love science. It’s the concepts, ideas and results that I find fascinating. It also adds greatly to my sense of mystery and awe about being alive in this universe.

Same here. I owe all my understanding, such as it is, to BBC programmes and the internet (people like Sean Carroll, for example, or kindly folk on message boards).

 
bbearren
 
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bbearren
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18 March 2017 18:50
 

Gravity isn’t a thing.  It’s the shape of space/time that is the result of the presence (or absence) of mass/energy.  “Dark matter” is a place-holder.  Astrophysicists don’t have a clue as to what it might be.  NdGT says we could just as easily call dark matter and dark energy Fred and Wilma.  The only things we know about it are its effects on space/time in the regions of the universe where it is concentrated.

The experiments that have been at work trying to detect WIMPS (Weakly Interacting Massive Particles) have not come up with anything.  “LUX has delivered the world’s best search sensitivity since its first run in 2013,” said Rick Gaitskell, professor of physics at Brown University and co-spokesperson for the LUX experiment. “With this final result from the 2014 to 2016 search, the scientists of the LUX Collaboration have pushed the sensitivity of the instrument to a final performance level that is four times better than the original project goals. It would have been marvelous if the improved sensitivity had also delivered a clear dark matter signal. However, what we have observed is consistent with background alone.”

 
 
EN
 
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EN
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19 March 2017 10:49
 

So you don’t believe that gravitons exist?

 
bbearren
 
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19 March 2017 13:11
 
EN - 19 March 2017 10:49 AM

So you don’t believe that gravitons exist?

No, I do not.

 
 
Cheshire Cat
 
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19 March 2017 19:24
 

From a few things I found on the internet, gravity as the curvature of space fits with Einstein’s model in General Relativity, and gravitons fit within the mathematical formulas of Quantum Mechanics. They can’t seem to reconcile the two, however. The equations for Quantum Mechanics relate to a flat universe and Einstein’s to curved space time.