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Verlinde's new theory of gravity passes first test


kunok

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Interesting indeed. As far as I understand it, this new theory - or rather, a hypothesis still at this point - works out only in a few specific circumstances so far. That's not ideal, but perhaps it can be expanded, or somehow meshed together with Einstein's theories to form a coherent whole picture. I would certainly prefer the visible matter explanation over a vague and mysterious dark matter explanation. Whether or not reality is that convenient remains to be seen.

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Not my field either, but it sounds like yet another one feels uncomfortable with and tries to work around the dark matter. Cosmologists might have problems with that. Dark matter and energy are widely accepted concepts.

I don't understand this:

"However, the mass of the dark matter is a free parameter, which must be adjusted to the observation. Verlinde's theory provides a direct prediction, without free parameters."

From my understanding the portion of dark matter is quite well determined and it's stable, or am i wrong ?

 

"The question now is how the theory develops, and how it can be further tested. But the result of this first test definitely looks interesting."

Also i understand that the test was not an observational one. Dark metter and energy on the other side explain observations very well and have passed many tests, or not ?

 

Edited by Green Baron
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14 minutes ago, Green Baron said:

Not my field either, but it sounds like yet another one feels uncomfortable with and tries to work around the dark matter. Cosmologists might have problems with that. Dark matter and energy are widely accepted concepts.

I don't understand this:

"However, the mass of the dark matter is a free parameter, which must be adjusted to the observation. Verlinde's theory provides a direct prediction, without free parameters."

From my understanding the portion of dark matter is quite well determined and it's stable, or am i wrong ?

 

"The question now is how the theory develops, and how it can be further tested. But the result of this first test definitely looks interesting."

Also i understand that the test was not an observational one. Dark metter and energy on the other side explain observations very well and have passed many tests, or not ?

 

The amount of dark matter is well measured and stable.

However, the problem with it is that how we came up with it: We observed the orbits of the stars around the centers of the galaxies and noticed that they orbited faster than the observed total mass of the galaxy. So we added mass to the galaxies to make the observations agree with the theories and we called that mass dark matter.

So we don't have an actual proof for the existence, it is just the generally accepted solution to the problems of our gravitational theory. So exploring theories for the actual nature of dark matter or theories not needing dark matter isn'ta bad idea.

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25 minutes ago, Green Baron said:

I don't understand this:

"However, the mass of the dark matter is a free parameter, which must be adjusted to the observation. Verlinde's theory provides a direct prediction, without free parameters."

From my understanding the portion of dark matter is quite well determined and it's stable, or am i wrong ?

Oh, that was the interesting part, to me! What it means is, the amount of dark matter is determined by observation.

In a simplistic way, we look at (say) a galaxy, it behaves differently than it should based on its visible mass alone. We (I just got a ninja notification as I type this, let's hope it's not the same thing I'm saying here...) say "there's X more mass there that we don't see", and assuming that's true, it then fits the observation (and can predict some other not-yet-made observations, which is why he call it a 'theory' and not just 'whatever some guy said'). That's why it's a free parameter, there's nothing in our current understanding that says how much dark mass should be in some place a priori, we can only tell by looking.

However, this statement means that his new theory (if we can call it that already, I'm not sure. See below) can predict the the behaviour from visible mass alone. If that's true, than in my opinion that's great evidence for this new theory, except...

Quote

The new theory is currently only applicable to isolated, spherical and static systems, while the universe is dynamic and complex. Many observations cannot yet be explained by the new theory, so dark matter is still in the race

I take "Many observations cannot yet be explained" to mean "some results the theory predics disagree with direct observation". That's text-book science for "this hypothesis is wrong, and thus as currently worded cannot become a theory. Period. Some future variation of it might, but until you change your premises, no amount of further testing will prove it."

(well, the ninja post complemented my point)

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3 hours ago, monstah said:

I take "Many observations cannot yet be explained" to mean "some results the theory predics disagree with direct observation". That's text-book science for "this hypothesis is wrong, and thus as currently worded cannot become a theory. Period. Some future variation of it might, but until you change your premises, no amount of further testing will prove it."

Not necessarily, it can also mean that the mathematics behind this new theory are so overwhelmingly complicated that noone has yet solved them for more complicated systems.

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20 minutes ago, Tullius said:

Not necessarily, it can also mean that the mathematics behind this new theory are so overwhelmingly complicated that noone has yet solved them for more complicated systems.

I always wonder about this. What do mathematicians do all day? I asked some theoretical chemists, apparently they do just write on chalk boards allot (I must be the only scientist I know who prefers dry erase boards) and then put the equations into mathematica. Still can't wrap my head around that, the thought process that goes into just staring at an equation until some new way forward pops up.  

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1 hour ago, todofwar said:

 

I always wonder about this. What do mathematicians do all day? I asked some theoretical chemists, apparently they do just write on chalk boards allot (I must be the only scientist I know who prefers dry erase boards) and then put the equations into mathematica. Still can't wrap my head around that, the thought process that goes into just staring at an equation until some new way forward pops up.  

Knew an mathematician, he did doctorate after engineering on university,  he was doing modeling, as in trying to make simulations work. 
Kind of edge with programming as you have to know how the computers do math. Think that is the main employment, same as most software developers end up making custom modules for firms. 

Theoretical chemistry has become big because of simulations, you try loads of stuff in an simulation and you find something interesting, then the next part is to make it real. 
You also need people to set the strategy for the search. 
And yes they have found multiple materials harder than diamond, don't know if any is commercial, know that stuff who is a bit weaker and way cheaper is.
And the real big ones is in biochemestry. 

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Can someone put in one or two sentences how this "Verlinde's Theory" is "new?"

The article did not make that clear to me . . . okay hold on, Wikipedia to the rescue Entropic Gravity.

So . . . seems we're all holograms now!? :D

Quote

gravity is a consequence of the "information associated with the positions of material bodies". This model combines the thermodynamic approach to gravity with Gerard 't Hooft's holographic principle. It implies that gravity is not a fundamental interaction, but an emergent phenomenon which arises from the statistical behavior of microscopic degrees of freedom encoded on a holographic screen. The paper drew a variety of responses from the scientific community. Andrew Strominger, a string theorist at Harvard said “Some people have said it can’t be right, others that it’s right and we already knew it — that it’s right and profound, right and trivial."[7]

 

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1 hour ago, todofwar said:

 

I always wonder about this. What do mathematicians do all day? I asked some theoretical chemists, apparently they do just write on chalk boards allot (I must be the only scientist I know who prefers dry erase boards) and then put the equations into mathematica. Still can't wrap my head around that, the thought process that goes into just staring at an equation until some new way forward pops up.  

Dry erase boards are in briefing rooms and are pretty common these days.  Chalkboards are disappearing.  They make me feel more academic.  Seriously.  Holding chalk makes me feel more intelligent.  As soon as I realize this newfound sense of self satisfaction comes from holding chalk in my hand I immediately feel stupid.  And I should.  I am still embarrassed that those thoughts even cross my mind.  

 

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4 hours ago, Jonfliesgoats said:

Dry erase boards are in briefing rooms and are pretty common these days.  Chalkboards are disappearing.  They make me feel more academic.  Seriously.  Holding chalk makes me feel more intelligent.  As soon as I realize this newfound sense of self satisfaction comes from holding chalk in my hand I immediately feel stupid.  And I should.  I am still embarrassed that those thoughts even cross my mind.  

 

I will agree a marker just doesn't have the feel of chalk, but it's not enough to outweigh the other benefits for me. Of course, chalk is much more eco friendly too.

5 hours ago, magnemoe said:

Knew an mathematician, he did doctorate after engineering on university,  he was doing modeling, as in trying to make simulations work. 
Kind of edge with programming as you have to know how the computers do math. Think that is the main employment, same as most software developers end up making custom modules for firms. 

Theoretical chemistry has become big because of simulations, you try loads of stuff in an simulation and you find something interesting, then the next part is to make it real. 
You also need people to set the strategy for the search. 
And yes they have found multiple materials harder than diamond, don't know if any is commercial, know that stuff who is a bit weaker and way cheaper is.
And the real big ones is in biochemestry. 

No, you're describing computational chemistry which is different from theoretical. Computational chemists apply the theory others come up with, not to say theoretical chemists don't apply their own theories. 

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