https://phys.org/news/2016-11-theory-gravity-dark.html

A new theory of gravity might explain the curious motions of stars in galaxies. Emergent gravity, as the new theory is called, predicts the exact same deviation of motions that is usually explained by invoking dark matter. Prof. Erik Verlinde, renowned expert in string theory at the University of Amsterdam and the Delta Institute for Theoretical Physics, published a new research paper today in which he expands his groundbreaking views on the nature of gravity.
In 2010, Erik Verlinde surprised the world with a completely new theory of gravity. According to Verlinde, gravity is not a fundamental force of nature, but an emergent phenomenon. In the same way that temperature arises from the movement of microscopic particles, gravity emerges from the changes of fundamental bits of information, stored in the very structure of spacetime.

..

According to Erik Verlinde, there is no need to add a mysterious dark matter particle to the theory. In a new paper, which appeared today on the ArXiv preprint server, Verlinde shows how his theory of gravity accurately predicts the velocities by which the stars rotate around the center of the Milky Way, as well as the motion of stars inside other galaxies.
“We have evidence that this new view of gravity actually agrees with the observations, “ says Verlinde. “At large scales, it seems, gravity just doesn’t behave the way Einstein’s theory predicts.”
At first glance, Verlinde’s theory presents features similar to modified theories of gravity like MOND (modified Newtonian Dynamics, Mordehai Milgrom (1983)). However, where MOND tunes the theory to match the observations, Verlinde’s theory starts from first principles. “A totally different starting point,” according to Verlinde.

It’s easy to dismiss it as a MOND – but it seems to be gaining some traction.

I’m not sure if dark matter and dark energy are one and the same, the boffins tend to talk of them individually.
Anyway I’ll vote for anyone that can get rid of one or both of the elusive dark bastards.

Dropbear said:

https://phys.org/news/2016-11-theory-gravity-dark.html

A new theory of gravity might explain the curious motions of stars in galaxies. Emergent gravity, as the new theory is called, predicts the exact same deviation of motions that is usually explained by invoking dark matter. Prof. Erik Verlinde, renowned expert in string theory at the University of Amsterdam and the Delta Institute for Theoretical Physics, published a new research paper today in which he expands his groundbreaking views on the nature of gravity.
In 2010, Erik Verlinde surprised the world with a completely new theory of gravity. According to Verlinde, gravity is not a fundamental force of nature, but an emergent phenomenon. In the same way that temperature arises from the movement of microscopic particles, gravity emerges from the changes of fundamental bits of information, stored in the very structure of spacetime.

..

According to Erik Verlinde, there is no need to add a mysterious dark matter particle to the theory. In a new paper, which appeared today on the ArXiv preprint server, Verlinde shows how his theory of gravity accurately predicts the velocities by which the stars rotate around the center of the Milky Way, as well as the motion of stars inside other galaxies.
“We have evidence that this new view of gravity actually agrees with the observations, “ says Verlinde. “At large scales, it seems, gravity just doesn’t behave the way Einstein’s theory predicts.”
At first glance, Verlinde’s theory presents features similar to modified theories of gravity like MOND (modified Newtonian Dynamics, Mordehai Milgrom (1983)). However, where MOND tunes the theory to match the observations, Verlinde’s theory starts from first principles. “A totally different starting point,” according to Verlinde.

It’s easy to dismiss it as a MOND – but it seems to be gaining some traction.

Agreed. “It’s easy to dismiss it as MOND – but it seems to be gaining some traction.”

MOND went through a couple of transformations until it ended up as f® gravity. By that time, people had forgotten it was MOND and had exactly the same problems as MOND – ie. the impossibility of getting the dark matter density right simultaneously for galaxies and galactic clusters – wrong dark matter predictions for many dwarf galaxies – and over-suppressing the oscillations seen in the Big Bang spectrum by the Planck spacecraft.

You can see oodles of f® gravity papers published every year. In addition to its inability to explain astronomical observations, f® gravity is called f® gravity because it contains a completely arbitrary function of distance called, not surprisingly, f®. There is no ‘a priori’ reason whatever for choosing one function f® over any other such function. That means that the f® function is nothing more than an ad-hoc interpolation.

Unlike f® gravity, emergent gravity does have a theoretical underpinning. But I have yet to see anyone dare to prove that it’s any better than MOND – ahem,
I mean f® gravity – at predicting the observed occurrences of dark matter.

for “f®” read “f ( r )”.

Dropbear said:

“We have evidence that this new view of gravity actually agrees with the observations, “ says Verlinde.

What about the Bullet Cluster?

KJW said:

Dropbear said:

“We have evidence that this new view of gravity actually agrees with the observations, “ says Verlinde.

What about the Bullet Cluster?

What about it

Dropbear said:

KJW said:

Dropbear said:

“We have evidence that this new view of gravity actually agrees with the observations, “ says Verlinde.

What about the Bullet Cluster?

What about it

The Bullet Cluster is a collision of two clusters of galaxies. The dark matter interacts minimally compared to the ordinary baryonic matter. Therefore, as the two clusters collide, the dark matter continues on its trajectory unabated while the bulk of the ordinary baryonic matter is slowed down, leading to the dark matter being displaced relative to the bulk of the ordinary baryonic matter. This means that the dark matter is some form of material and not some modification of the gravitational law.

• The Bullet Cluster is a collision of two clusters of galaxies. The dark matter interacts minimally compared to the ordinary baryonic matter. Therefore, as the two clusters collide, the dark matter continues on its trajectory unabated while the bulk of the ordinary baryonic matter is slowed down, leading to the dark matter being displaced relative to the bulk of the ordinary baryonic matter. This means that the dark matter is some form of material and not some modification of the gravitational law.

I read a description of the bullet cluster today where it was explained without invoking dark matter…

KJW said:

Dropbear said:

KJW said:

What about the Bullet Cluster?

What about it

The Bullet Cluster is a collision of two clusters of galaxies. The dark matter interacts minimally compared to the ordinary baryonic matter. Therefore, as the two clusters collide, the dark matter continues on its trajectory unabated while the bulk of the ordinary baryonic matter is slowed down, leading to the dark matter being displaced relative to the bulk of the ordinary baryonic matter. This means that the dark matter is some form of material and not some modification of the gravitational law.

Some would disagree.

There’s an article about it in the latest New Scientist.

• There’s an article about it in the latest New Scientist.

That’s the one I read…

Here’s an analogy to make you think.

The late 19th century paradox:
Question: Is light a particle (photon) or a wave in the ether?
Early 20th century solution:
Answer: Both, it can appear as either.

Early 21st century paradox:
Question: Is dark matter a particle (WIMP) or a distortion of gravity (emergent gravity)?

Answer: Both?

mollwollfumble said:

Here’s an analogy to make you think.

The late 19th century paradox:
Question: Is light a particle (photon) or a wave in the ether?
Early 20th century solution:
Answer: Both, it can appear as either.

Early 21st century paradox:
Question: Is dark matter a particle (WIMP) or a distortion of gravity (emergent gravity)?

Answer: Both?

That’s what quantum loop gravity says, isn’t it?

By the way, why is the possibility that space has mass never discussed in public?

The Rev Dodgson said:

mollwollfumble said:

Here’s an analogy to make you think.

The late 19th century paradox:
Question: Is light a particle (photon) or a wave in the ether?
Early 20th century solution:
Answer: Both, it can appear as either.

Early 21st century paradox:
Question: Is dark matter a particle (WIMP) or a distortion of gravity (emergent gravity)?

Answer: Both?

That’s what quantum loop gravity says, isn’t it?

By the way, why is the possibility that space has mass never discussed in public?

Golly, you’re right. I’d forgotten about quantum loop gravity, I haven’t seen a paper about it for several years. Worth resurrecting, perhaps.

Checking Google and Google scholar, I don’t see any paper that attempts to explain dark matter using loop quantum gravity. Perhaps I’m not looking far enough. There are papers about both, but either they’re looking at loop quantum gravity as just one of many possibilities along with string theory, or they’re looking at how standard dark energy and dark matter interact gravitationally with standard loop quantum gravity.

> By the way, why is the possibility that space has mass never discussed in public?

Because it encourages the nutters?

mollwollfumble said:

The Rev Dodgson said:

mollwollfumble said:

Here’s an analogy to make you think.

The late 19th century paradox:
Question: Is light a particle (photon) or a wave in the ether?
Early 20th century solution:
Answer: Both, it can appear as either.

Early 21st century paradox:
Question: Is dark matter a particle (WIMP) or a distortion of gravity (emergent gravity)?

Answer: Both?

That’s what quantum loop gravity says, isn’t it?

By the way, why is the possibility that space has mass never discussed in public?

Golly, you’re right. I’d forgotten about quantum loop gravity, I haven’t seen a paper about it for several years. Worth resurrecting, perhaps.

Checking Google and Google scholar, I don’t see any paper that attempts to explain dark matter using loop quantum gravity. Perhaps I’m not looking far enough. There are papers about both, but either they’re looking at loop quantum gravity as just one of many possibilities along with string theory, or they’re looking at how standard dark energy and dark matter interact gravitationally with standard loop quantum gravity.

> By the way, why is the possibility that space has mass never discussed in public?

Because it encourages the nutters?

Nearly finished reading “Reality is not What it Seems” by Carlo Rovelli (the journey to quantum gravity). An excellent book, but I don’t think it has much to say on dark matter.

As for encouraging nutters, I’d suggest that any hypothesis outside the current standard models would encourage the nutters, even if it turns out to be true.

The Rev Dodgson said:

mollwollfumble said:

The Rev Dodgson said:

That’s what quantum loop gravity says, isn’t it?

By the way, why is the possibility that space has mass never discussed in public?

Golly, you’re right. I’d forgotten about quantum loop gravity, I haven’t seen a paper about it for several years. Worth resurrecting, perhaps.

Checking Google and Google scholar, I don’t see any paper that attempts to explain dark matter using loop quantum gravity. Perhaps I’m not looking far enough. There are papers about both, but either they’re looking at loop quantum gravity as just one of many possibilities along with string theory, or they’re looking at how standard dark energy and dark matter interact gravitationally with standard loop quantum gravity.

> By the way, why is the possibility that space has mass never discussed in public?

Because it encourages the nutters?

Nearly finished reading “Reality is not What it Seems” by Carlo Rovelli (the journey to quantum gravity). An excellent book, but I don’t think it has much to say on dark matter.

As for encouraging nutters, I’d suggest that any hypothesis outside the current standard models would encourage the nutters, even if it turns out to be true.

Loop quantum gravity now goes by the name of “spin foam”, and looking up “spin foam” with “dark matter” I did find one paper that linked the two. From 11 Oct 2001.

https://arxiv.org/pdf/gr-qc/0110060.pdf
A NEW APPROACH TO THE GEOMETRIZATION OF MATTER by Louis Crane

The model we are referring to is in the class of spin foam models. It is based
on state sums on a triangulated manifold, rather than differential equations on a
smooth manifold. The model has passed a number of preliminary mathematical
hurdles; it is actually finite on any finite triangulation. The biggest hurdle
it still has to overcome is an explicit physical interpretation, or differently put,
a classical limit.

Because it doesn’t have a physical interpretation, it’s fair to say that it’s not very advanced.

The purpose of this paper is to outline a radically new way to include matter
in this type of theory. If one accepts the approximate arguments
we make, the bosonic part of the standard model, rather than any random
collection of matter fields, is what appears. The approach yields a fermionic sector
as well. Also a natural family of candidates for dark matter appears in it.

The low energy interacting world would
contain only toroidal and Klein bottle singularities, leaving the higher genus
surfaces to decouple and form dark matter.

mollwollfumble said:

Loop quantum gravity now goes by the name of “spin foam”, and looking up “spin foam” with “dark matter” I did find one paper that linked the two. From 11 Oct 2001.

https://arxiv.org/pdf/gr-qc/0110060.pdf
A NEW APPROACH TO THE GEOMETRIZATION OF MATTER by Louis Crane

The model we are referring to is in the class of spin foam models. It is based
on state sums on a triangulated manifold, rather than differential equations on a
smooth manifold. The model has passed a number of preliminary mathematical
hurdles; it is actually finite on any finite triangulation. The biggest hurdle
it still has to overcome is an explicit physical interpretation, or differently put,
a classical limit.

Because it doesn’t have a physical interpretation, it’s fair to say that it’s not very advanced.

The purpose of this paper is to outline a radically new way to include matter
in this type of theory. If one accepts the approximate arguments
we make, the bosonic part of the standard model, rather than any random
collection of matter fields, is what appears. The approach yields a fermionic sector
as well. Also a natural family of candidates for dark matter appears in it.

The low energy interacting world would
contain only toroidal and Klein bottle singularities, leaving the higher genus
surfaces to decouple and form dark matter.

Looks interesting.

The Rovelli book is full of spin foamy stuff by the way.