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Author Topic: Is Gravity Not An Entropic Force?  (Read 2830 times)

Offline yamo

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Is Gravity Not An Entropic Force?
« on: 25/08/2011 09:42:00 »
I don't understand the argument that it is and i don't understand the experimental refutation.  Could someone here hand hold me through an explication taking baby steps, please? 


 

Offline imatfaal

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Is Gravity Not An Entropic Force?
« Reply #1 on: 25/08/2011 11:40:31 »
I am not sure that it can really be explained easily.  The claim that gravity is an entropic force basically says that gravity is not a fundamental force mediated by a force carrying boson, nor an artefact of the geometry of spacetime; but is in reality an emergent consequence of thermodynamical laws and the necessary increase in entropy in any statistical system.  My quick impression is that an understanding of the argument requires a good understanding of string theory and the holographic principle both of which are beyond me.  I do not see any mention of an experiment that clearly refutes the theory.
 

Offline graham.d

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Is Gravity Not An Entropic Force?
« Reply #2 on: 25/08/2011 12:29:27 »
I am unfamiliar with this too, however your question prompted me to spend a little of my lunchtime browsing. This is the simplest explanation I could find for how the Entropic Gravity works - well I liked it :-)

http://www.science20.com/hammock_physicist/it_bit_entropic_gravity_pedestrians-66244
 

Offline imatfaal

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Is Gravity Not An Entropic Force?
« Reply #3 on: 25/08/2011 15:28:04 »
Great spot - and a nice intuitive article. 

[I was reminded by Wolfram's mega-opus a new kind of science and was pleased as punch when the author brought it up in the comments]
 

Offline yor_on

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Is Gravity Not An Entropic Force?
« Reply #4 on: 29/08/2011 05:13:31 »
No, gravity is no more entropy, than that it is coupled to mass, accelerations and energy (whatever now 'energy' is:)

As it follows matter, and matter has a entropy you might want to argue that is, but that's not true. If you don't want to define our classical nothing 'space' as being entropic too of course? After all, gravity is the metric of space giving it its definition and shape. There's a lot of new terms going around those days, but they remind me more of some sort of 'new meta science' than really explaining something.

The main problem is ignoring the way the arrow seems to be connected to the room, becoming one whole thing, as I see it. Exchanging our macroscopic arrow for 'entropy' is to me more of a name change than a explanation. And it will also meet some consternation when considering QM:s 'time reversals' as that then should mean entropy turning around :)

But I still need to read that article and see.
This is my gut reaction.
 

Offline Geezer

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Is Gravity Not An Entropic Force?
« Reply #5 on: 29/08/2011 06:48:30 »
If gavity was related to entropy, would it not have to be viewed as "anti-entropic"? (If there is such a thing.)
 

Offline MikeS

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Is Gravity Not An Entropic Force?
« Reply #6 on: 29/08/2011 07:21:20 »
I don't understand the argument that it is and i don't understand the experimental refutationCould someone here hand hold me through an explication taking baby steps, please? 

This is to answer the direct question (Is Gravity Not An Entropic Force?) and is not based upon Verlinde’s work.
Gravity increases entropy by the following mechanism:-
1)When two masses combine time dilates for them more than it did for them individually.  
2)Time dilation is equivalent to a loss of useful energy.  
3)Time dilation is equivalent to a loss of useful energy because it requires more energy to do anything in a higher gravitational field than in a lower one. (In that way gravity 'ties up' energy rendering it of little use.  Entropy increases)

Gravity is probably the universes main source of entropy and both gravity and entropy are the main arrows of time.

Here is a link to the supposed refutation of Verlinde’s paper
http://www.technologyreview.com/blog/arxiv/27102/
« Last Edit: 29/08/2011 11:41:21 by MikeS »
 

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Is Gravity Not An Entropic Force?
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