When Black Holes Merge (big topic lately, so it seems)

[samoth]

Summary -- Wed, 19 Apr 2006 - NASA scientists have created a new computer simulation that shows what happens when two black holes come together. Einstein predicted that this cataclysmic event should send out a torrent of gravitational waves, rippling the space around them. The simulation was done on the the Columbia supercomputer, which is the 4th fastest computer in the world. The mathematics involved in these simulations are so complex, and so bizarre, that previous attempts have ended with little more than crashed computers.

Full article -- NASA scientists have reached a breakthrough in computer modeling that allows them to simulate what gravitational waves from merging black holes look like. The three-dimensional simulations, the largest astrophysical calculations ever performed on a NASA supercomputer, provide the foundation to explore the universe in an entirely new way.

According to Einstein's math, when two massive black holes merge, all of space jiggles like a bowl of Jell-O as gravitational waves race out from the collision at light speed.

Previous simulations had been plagued by computer crashes. The necessary equations, based on Einstein's theory of general relativity, were far too complex. But scientists at NASA's Goddard Space Flight Center in Greenbelt, Md., have found a method to translate Einstein's math in a way that computers can understand.

"These mergers are by far the most powerful events occurring in the universe, with each one generating more energy than all of the stars in the universe combined. Now we have realistic simulations to guide gravitational wave detectors coming online," said Joan Centrella, head of the Gravitational Astrophysics Laboratory at Goddard.

The simulations were performed on the Columbia supercomputer at NASA's Ames Research Center near Mountain View, Calif. This work appears in the March 26 issue of Physical Review Letters and will appear in an upcoming issue of Physical Review D. The lead author is John Baker of Goddard.

Similar to ripples on a pond, gravitational waves are ripples in space and time, a four-dimensional concept that Einstein called spacetime. They haven't yet been directly detected.

Gravitational waves hardly interact with matter and thus can penetrate the dust and gas that blocks our view of black holes and other objects. They offer a new window to explore the universe and provide a precise test for Einstein's theory of general relativity. The National Science Foundation's ground-based Laser Interferometer Gravitational-Wave Observatory and the proposed Laser Interferometer Space Antenna, a joint NASA - European Space Agency project, hope to detect these subtle waves, which would alter the shape of a human from head to toe by far less than the width of an atom.

Black hole mergers produce copious gravitational waves, sometimes for years, as the black holes approach each other and collide. Black holes are regions where gravity is so extreme that nothing, not even light, can escape their pull. They alter spacetime. Therein lies the difficulty in creating black hole models: space and time shift, density becomes infinite and time can come to a standstill. Such variables cause computer simulations to crash.

These massive, colliding objects produce gravitational waves of differing wavelengths and strengths, depending on the masses involved. The Goddard team has perfected the simulation of merging, equal-mass, non-spinning black holes starting at various positions corresponding to the last two to five orbits before their merger.

With each simulation run, regardless of the starting point, the black holes orbited stably and produced identical waveforms during the collision and its aftermath. This unprecedented combination of stability and reproducibility assured the scientists that the simulations were true to Einstein's equations. The team has since moved on to simulating mergers of non-equal-mass black holes.

Einstein's theory of general relativity employs a type of mathematics called tensor calculus, which cannot easily be turned into computer instructions. The equations need to be translated, which greatly expands them. The simplest tensor calculus equations require thousands of lines of computer code. The expansions, called formulations, can be written in many ways. Through mathematical intuition, the Goddard team found the appropriate formulations that led to suitable simulations.

Progress also has been made independently by several groups, including researchers at the Center for Gravitational Wave Astronomy at the University of Texas, Brownsville, which is supported by the NASA Minority University Research and Education Program.

To see two black holes collide, visit: http://www.nasa.gov/centers/goddard/universe/gwave.htm


Original Source: NASA News Release

 

[Extra_Strong]

cool.

 

[samoth]

cool.

There were already two posts made about this subject, but I checked both, and they seem to be from different sources. Looks like this is a big area of current interest.

Interesting concepts, but I'm not sure how much real science we can pull from this area of astronomy. It's more on the side of theoretical physics, from what I have seen.

Maybe string theorists were tired of banging their heads against the chalkboard and decideded to pursue something of interest that normal people can understand, lol. By 'normal people' I include physics professors and PhD's as well, lol, as the math behind string theory, LQG, and the like are so far above everyone's head that without the mathematical knowledge of Roger Penrose, one is stuck learning advanced group theory just to get an idea of what the string theorists' are talking about.

 

[fortunatesun]

So, the mathematics is able to bear witness. I wonder what is meant by 'bizarre' though.

If you want to see the media presentation of black holes colliding I would try http://www.nasa.gov/centers/goddard/universe/gwave.html instead.

Thanks for posting. I guess I am one of those black hole amateurs.

 

[samoth]

So, the mathematics is able to bear witness. I wonder what is meant by 'bizarre' though.

If you want to see the media presentation of black holes colliding I would try http://www.nasa.gov/centers/goddard/universe/gwave.html instead.

Thanks for posting. I guess I am one of those black hole amateurs.

Everyone's a black hole amature, even the PhD's studying them.

From your link,


Simulations Take Us Inside The Mind Of Einstein

04.18.06


For years scientists trying to visualize the concept of gravitational waves churned by the collision of black holes have relied largely on artists' conceptions. Now, at long last, they have Einstein's conception.

According to Einstein, when two massive black holes merge, all of space jiggles like a bowl of Jell-O as gravitational waves race out from the collision at light speed. This is a mind-boggling notion, to be sure.

NASA scientists have reached a breakthrough in computer modeling that allows them to simulate what gravitational waves from merging black holes look like. The three-dimensional simulations are a manifestation of Einstein's equations, pure and simple. And they are the largest astrophysical calculations ever performed on a NASA supercomputer.

Previous simulations had been plagued by computer crashes; the equations needed, based on Einstein's general relativity, were far too complex. But scientists at NASA Goddard Space Flight Center in Greenbelt, Md., have found a method to translate Einstein's math in a way that computers can understand.

Left image [below - ed.]: Ranked the fourth fastest supercomputer in the world on the November 2005 Top500 list, Columbia has increased the NASA’s total high-end computing, storage, and network capacity tenfold. This has enabled advances in science not previously possible on NASA’s high-end systems. It sits at the NASA Advanced Supercomputing (NAS) Facility at the Ames Research Facility. It consists of a 10,240-processor SGI Altix system comprised of 20 nodes, each with 512 Intel Itanium 2 processors, and running a Linux operating system. Click on image to view large resolution. Credit: Trower, NASA

Click here for huge version of above picture.

The simulations provide the foundation to explore the universe in an entirely new way. You see, there's more to the universe than what meets the eye.

Our eyes detect light in the optical waveband. Since the dawn of mankind until only about a hundred years ago, this was the only form of "radiation" humans knew. Then scientists discovered radio waves, infrared light, ultraviolet light, X-rays and gamma rays. Suddenly a new window to the universe was open.

Einstein predicted the existence of gravitational radiation. Similar to ripples on a pond, gravitational waves are ripples in space and time, a four-dimensional concept that Einstein called spacetime. They haven't yet been detected directly.

"These mergers are by far the most powerful events occurring in the universe, with each one generating more energy than all of the stars in the universe combined," said Dr. Joan Centrella, who leads the Gravitational Astrophysics Laboratory at Goddard.

Gravitational waves hardly interact with matter and thus can penetrate the dust and gas that blocks our view of black holes and other objects. The gravitational waves from the big bang itself could still be rolling through the universe.

The National Science Foundation's ground-based Laser Interferometer Gravitational-Wave Observatory (LIGO) and the proposed Laser Interferometer Space Antenna (LISA), a joint NASA - European Space Agency project, hope to detect these subtle waves, which would alter the shape of a human from head to toe by far less than the width of an atom. This is one of the hottest fields in astronomy, the new (and final?) frontier.

Black hole mergers produce copious gravitational waves, sometimes for years, as the black holes approach each other and collide. Black holes are regions where gravity is so extreme that nothing, not even light, can escape its pull.

Black holes alter spacetime. Therein lies the difficulty in creating black hole models: Space and time shift; density becomes infinite and time can come to a standstill. Such variables cause computer simulations to crash.

These massive, colliding objects produce gravitational waves of differing wavelengths and strengths, depending on the masses involved. The Goddard team has perfected the simulation of merging, equal-mass, non-spinning black holes starting at various positions corresponding to the last two to five orbits before their merger.

With each simulation run, regardless of the starting point, the black holes orbited stably and produced identical waveforms during the infall, collision and aftermath. This was a first. The combination of stability and reproducibility assured the scientists that the simulations were true to Einstein's equations. The team has since moved on to simulating mergers of non-equal-mass black holes.

Right image [below - ed.]: Funded by the National Science Foundation, LIGO was designed and constructed by a team of scientists from Caltech and MIT. In an effort to detect passing gravitational waves, researchers bounce high-power laser beams back and forth in each arm. Passing gravitational waves alter the length between the mirrors in the LIGO arms, which the lasers detect. There are two separate LIGO sites; the Hanford, Wash. site is pictured here. Full-time observing commenced in November 2005. Click on image to view large resolution. Credit: LIGO Laboratory

The simulations were done on the Columbia supercomputer at NASA Ames Research Center near Mountain View, Calif. Dr. John Baker of NASA Goddard, the lead author on papers about this work in Physical Review Letters and Physical Review D, described the complexity of the simulations.

Einstein's theory of general relativity employs a type of mathematics called tensor calculus, which cannot be inputted directly into computer coding, Baker explained. The equations need to be translated, which greatly expands them. The simplest tensor calculus equations require thousands of lines of computer coding. The expansions, called formulations, can be written in many ways. Through mathematical intuition, the Goddard team has found the appropriate formulations to lead to suitable simulations.

Progress also has been made independently by several groups, including researchers at the Center for Gravitational Wave Astronomy at the University of Texas at Brownsville.

"These simulations enable us to visualize Einstein's equations," said Dr. Paul Hertz, Chief Scientist, NASA's Science Mission Directorate. "Now when we observe a black hole merger with LIGO or LISA, we can test Einstein's theory and see whether or not he was right."

As of November 2005, LIGO is up and running and could, in theory, detect gravitational waves from stellar-size black hole mergers any day. LISA, in the planning stages, could detect longer-wavelength gravitational radiation from supermassive black holes. The beauty of the NASA simulations is that they can be scaled to fit either scenario.

Source: http://www.nasa.gov/centers/goddard/universe/gwave_feature.html

 

[fortunatesun]

Interesting concepts, but I'm not sure how much real science we can pull from this area of astronomy. It's more on the side of theoretical physics, from what I have seen.

I think that one reason that we extend ourselves in this direction is that space exploration captures the public's imagination. As we move towards a more technologically advanced society, these types of inquiries will provide a basis for creating economic stimulus and employment opportunities at a major level.

String theory, as you point out, is still a little counterintuitive to the layman.On the other hand, the basics aren't too difficult to explain. I think it will eventually prove itself as a source of much inventive thinking and a bit of fun and magic for non-scientists as well. The string theorists need to bring us a harder sell.