"Gravity's River" --New Black Hole Research Points to Gravity as a Fluid (Weekend Feature)
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June 07, 2014

"Gravity's River" --New Black Hole Research Points to Gravity as a Fluid (Weekend Feature)

 

Black_Hole



The accepted wisdom among gravitational researchers has been that spacetime cannot become turbulent. New research from Perimeter, though, shows that the accepted wisdom might be wrong. Gravity, it’s thought, can behave as a fluid. One of the characteristic behaviours of fluids is turbulence – that is, under certain conditions, they don’t move smoothly, but eddy and swirl.

Perimeter Faculty member Luis Lehner explains why it might make sense to treat gravity as a fluid. “There’s a conjecture in physics – the holographic conjecture – which says gravity can be described as a field theory,” he says. “And we also know that at high energies, field theories can be described with the mathematical tools we use to describe fluids. So it’s a two-step dance: gravity equals field theory, and field theory equals fluids, so gravity equals fields equals fluids. That’s called the gravity/fluids duality.”

The gravity/fluids duality is not new work – it’s been developing over the past six years. But hidden at the heart of it is a tension. If gravity can be treated as a fluid, then what about turbulence?

“For many years, the folklore among physicists was that gravity could not be turbulent,” notes Lehner. The belief was that gravity is described by a set of equations that are sufficiently different from fluid dynamics equations, such that there would not be turbulence under any circumstances.

Lehner highlights the emerging paradox: “Either there was a problem with the duality and gravity really can’t be fully captured by a fluid description, or there was a new phenomenon in gravity and turbulent gravity really can exist.” A team of researchers – Lehner, Huan Yang (Perimeter and the Institute for Quantum Computing), and Aaron Zimmerman (Canadian Institute for Theoretical Astrophysics) – set out to find out which.

They had hints about what directions to go. Previous simulations at Perimeter, and independent work out of MIT, had hinted that there could be turbulence around the non-realistic case of black holes confined in anti-de Sitter space. “There might be turbulence if you confine gravity in a box, essentially,” says Lehner. “The deeper question is whether this can happen in a realistic situation.”

The team decided to study fast-spinning black holes, because a fluid-dynamics description of such holes hints that the spacetime around them is less viscous than the spacetime around other kinds of black holes. Low viscosity increases the chance of turbulence – think of the way water is more swirly than molasses.

The team also decided to study non-linear perturbations of the black holes. Gravitational systems are rarely analyzed at this level of detail, as the equations are fiendishly complex. But, knowing that turbulence is fundamentally non-linear, the team decided a non-linear perturbation analysis was exactly what was called for.

They were stunned when their analysis showed that spacetime did become turbulent.

“I was quite surprised,” says Yang, who has been studying general relativity (GR) – Einstein’s theory of gravity – since his PhD. “I never believed in turbulent behaviour in GR, and for good reason. No one had ever seen it in numerical simulations, even of dramatic things like binary black holes.”

“Over the past few years, we have gone from a serious doubt about whether gravity can ever go turbulent, to pretty high confidence that it can,” says Lehner.

How did this behaviour hide until now? “It was hidden because the analysis needed to see it has to go to non-linear orders,” says Yang. “People didn’t have enough motivation to do a non-linear study. But, this time, we knew what we were looking for. It gave us the motivation to do a more in-depth study. We had a target and we hit it.”

This is theoretical work, but it might not stay that way. There are next-generation detectors about to come online which might soon be able to detect gravitational waves – ripples in the gravitational “fluid” that result from big events like the collision of two black holes. If gravitation can be turbulent, then those ripples might be a bit different than previous models suggest. Knowing about these differences may make gravitational waves easier to spot. And, of course, actually detecting these differences would be direct evidence of gravitational turbulence.

“There are potential observational consequences of this discovery,” says Lehner. “LIGO or LISA or some future gravitational wave experiment may be able to detect them.”

But one of the most exciting consequences of this research relates not to gravity, but to ordinary, Earth-bound turbulence. From hurricanes to cream stirred into coffee, from the bumblebee’s impossible flight to the vortices shearing off the end of airplane wings, turbulence is all around us. Yet we don’t fully understand it. It’s considered one of the greatest unsolved problems in classical physics.

This research strengthens the idea that gravity can be treated as a fluid – which also means that fluids can be treated gravitationally.

“We’ve been stuck for over 500 years on achieving a full understanding of turbulence,” says Lehner. “This gravity/fluid correspondence tells us that there is a way to use gravitational tools and gravitational intuition to take a fresh look at turbulence. We may end up as stuck as we are in our standard approach, or we may end up shedding completely new light that helps the field go forward. It’s very exciting.”

Read the original paper on arXiv.

The Daily Galaxy via Perimeter Institute for Theoretical Physics

Image credit: http://img3.wikia.nocookie.net/__cb20081031154246/spore/images/9/9d/Black_Hole.png

Comments

I think I will get a shot of Black Label and try reading this again.

The whole concept of universe can be imagined as an inverted sun. Black holes can be imagined to be solar flares. They have an angle that later will be used to calculate the size of the universal bubble size. We live on the surface and can only sense that dimension.
Electromagnetic waves is a surest sign that the shortest way (energy efficient) is to move in a wave like motion (through another dimension) rather that what we would consider to be straight.

I think it just goes to show that scientists don't have a clue as to what gravity is.

OF COURSE "GRAVITY" IS FLUENT - EVERYTHING IS.

Excerpt:
"The accepted wisdom among gravitational researchers has been that spacetime cannot become turbulent. New research from Perimeter, though, shows that the accepted wisdom might be wrong. Gravity, it’s thought, can behave as a fluid. One of the characteristic behaviours of fluids is turbulence – that is, under certain conditions, they don’t move smoothly, but eddy and swirl".

This is exactly what I´ve been writing of for some years in this forum.

“Space-time” is connected to motions of gas; particles, stars and planets, and it all can be distorted and reformatted in swirling motions as in our galaxy. That´s how our Solar System was formatted in the first hand in the galactic center.

“Gravity”:
Deals with weight; motion and direction. Weight is achieved by magnetic lumping and not by “gravity”.

Cosmic Flow:
Is made by thermodynamics and electromagnetics and it´s motions turns both right- and left handed; inwards and outwards and up and down - and the magnetic fields works perpendicularly of an electric current – all creating constantly swirling motions and thus also constant turbulence.

These entire patterns can be observed all over the place in micro- and macrocosm and this gives the natural explanations to everything.

Take for instants the “galactic rotation anomaly”: If looking at the Milky Way galactic formation as a circuit of formation, some amount of gas and particles are flowing into the center and mini-galaxies and solar systems etc. etc. are formatted in the center and flows out of the center in this circuit.

The outflow of stars from the galaxy is the ONLY way one can explain how all objects are orbiting the galactic center with the same relative velocity compared to the galactic center.

That is: “Gravity” really flows according to the actual direction of an inwards and an outwards motions in a circuit.

Newton are partly right in his attractive theory when it comes to the galactic issues – but his theories fails explaining the opposite motion, which is why the “galactic rotation anomaly” was stated and “dark matter” was invented, keeping cosmologists and astrophysicists in mind- and hand locks for many decades.

Regarding the Newtonian “gravity theory” supposedly working in our Solar System, this also may be wrong since the Solar System is a directly integrated part of the galactic formation and rotation.

But maybe scientists now are at the right track by this “new” discovery which really could have been achieved studying ancient Myths of Creation and interpret these in a modern way, taking “deities” as “creative forces” and “heavenly objects”.

This is really my primary approach to the theories of modern science.

Regards
Ivar Nielsen
Natural Philosopher

Thanks for providing a link to a high resolution picture. It has been converted to my new full-HD black hole wallpaper!

Ditto. Thanks for the picture. I like crazy high-res pictures on my 1440p monitor.

I'm sure I learned this in Star Trek, a couple of decades ago. 'Gravity waves' etc - anyone else remember?


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