Skip to comments.How to Listen to the Background Hum of Gravitational Waves From all the Black Holes Colliding...
Posted on 04/19/2018 3:27:17 PM PDT by LibWhacker
The first-ever detection of gravitational waves (which took place in September of 2015) triggered a revolution in astronomy. Not only did this event confirm a theory predicted by Einsteins Theory of General Relativity a century before, it also ushered in a new era where the mergers of distant black holes, supernovae, and neutron stars could be studied by examining their resulting waves.
In addition, scientists have theorized that black hole mergers could actually be a lot more common than previously thought. According to a new study conducted by pair of researchers from Monash University, these mergers happen once every few minutes. By listening to the background noise of the Universe, they claim, we could find evidence of thousands of previously undetected events.
Their study, titled Optimal Search for an Astrophysical Gravitational-Wave Background, recently appeared in the journal Physical Review X. The study was conducted by Rory Smith and Eric Thrane, a senior lecturer and a research fellow at Monash University, respectively. Both researchers are also members of the ARC Center of Excellence for Gravitational Wave Discovery (OzGrav).
As they state in their study, every 2 to 10 minutes, a pair of stellar-mass black holes merge somewhere in the Universe. A small fraction of these are large enough that the resulting gravitational wave event can be detected by advanced instruments like the Laser Interferometer Gravitational-Wave Observatory and Virgo observatory. The rest, however, contribute to a sort of stochastic background noise.
By measuring this noise, scientists may be able to study much more in the way of events and learn a great deal more about gravitational waves. As Dr Thrane explained in a Monash University press statement:
Measuring the gravitational-wave background will allow us to study populations of black holes at vast distances. Someday, the technique may enable us to see gravitational waves from the Big Bang, hidden behind gravitational waves from black holes and neutron stars.
Drs Smith and Thrane are no amateurs when it comes to the study of gravitational waves. Last year, they were both involved in a major breakthrough, where researchers from LIGO Scientific Collaboration (LSC) and the Virgo Collaboration measured gravitational waves from a pair of merging neutron stars. This was the first time that a neutron star merger (aka. a kilonova) was observed in both gravitational waves and visible light.
The pair were also part of the Advanced LIGO team that made the first detection of gravitational waves in September 2015. To date, six confirmed gravitational wave events have been confirmed by the LIGO and Virgo Collaborations. But according to Drs Thrane and Smith, there could be as many as 100,000 events happening every year that these detectors simply arent equipped to handle.
These waves are what come together to create a gravitational wave background; and while the individual events are too subtle to be detected, researchers have been attempting to develop a method for detecting the general noise for years. Relying on a combination of computer simulations of faint black hole signals and masses of data from known events, Drs. Thrane and Smith claim to have done just that.
From this, the pair were able to produce a signal within the simulated data that they believe is evidence of faint black hole mergers. Looking ahead, Drs Thrane and Smith hope to apply their new method to real data, and are optimistic it will yield results. The researchers will also have access to the new OzSTAR supercomputer, which was installed last month at the Swinburne University of Technology to help scientists to look for gravitational waves in LIGO data.
This computer is different from those used by the LIGO community, which includes the supercomputers at CalTech and MIT. Rather than relying on more traditional central processing units (CPUs), OzGrav uses graphical processor units which can be hundreds of times faster for some applications. According to Professor Matthew Bailes, the Director of the OzGRav supercomputer:
It is 125,000 times more powerful than the first supercomputer I built at the institution in 1998 By harnessing the power of GPUs, OzStar has the potential to make big discoveries in gravitational-wave astronomy.
What has been especially impressive about the study of gravitational waves is how it has progressed so quickly. From the initial detection in 2015, scientists from Advanced LIGO and Virgo have now confirmed six different events and anticipate detecting many more. On top of that, astrophysicists are even coming up with ways to use gravitational waves to learn more about the astronomical phenomena that cause them.
All of this was made possible thanks to improvements in instrumentation and growing collaboration between observatories. And with more sophisticated methods designed to sift through archival data for additional signals and background noise, we stand to learn a great deal more about this mysterious cosmic force.
I'll say! From the first detection of gravitational waves generated by a single merger of a couple of black holes three years ago to "looking up" and being able to "see" thousands of mergers going on at once. That's comparable to looking up and seeing a single star one minute and looking up a few seconds later and being able to see thousands... What will we learn?
That’s racist as John Wiley Price once stated about black holes. He really did, he is that dumb.
They need to put a stop to these black hole mergers. Pretty soon we’re going to have a black hole that’s too big to fail.
I didn’t hear any hum.
Actually, I'm a little disappointed in this article. The title says "How to...," but doesn't say how they plan to do it at all, just that they figured out how to do it. Guess we've got to go read the original paper. But original papers are almost always waaaay over my head.
“The title says “How to...,” but doesn’t say how they plan to do it at all”
I actually expected something people could do at home. Something along these lines:
Luckily, its possible to learn something from the host of weaker signals that collectively form an unresolved background (Fig. 1). Think of listening to frogs croaking in a swamp: We can pick up clear songs from the nearest frogs, but we can also hear an indistinct hum from the thousands of frogs that are farther away. The volume of this background hum provides a measure of the frog population. Similarly, the amplitude of the unresolved background in LIGO and Virgos detectors can tell us about distant black hole mergers that occurred when the Universe was much younger.Source: https://physics.aps.org/articles/v11/36
The traditional way to distinguish this gravitational-wave background signal from noise is to compare the outputs of two or more detectors with a so-called cross-correlation analysis. Noise is uncorrelated between detectors, so its contribution will average to zero in a cross-correlation, while any gravitational-wave signal should survive. Predictions suggest that, using the cross-correlation technique, the LIGO and Virgo detectors should be sensitive enough to detect the gravitational-wave background within several years.
I already do. It’s called tinnitus!
not fun is it
I already do. Its called tinnitus!
You just thought it was tinnitus. Now you know. ;-)
Yeah but this is more like Dynamo Hum
Maybe you could post this one too... interesting stuff:
‘Time is elastic’: an extract from Carlo Rovelli’s The Order of Time
What does it really mean to say that time passes? Why does time pass faster in the mountains than it does at sea level? The physicist explains in this extract from his latest book
Interview with Carlo Rovelli
Interesting about the frogs’ background noise. Any chance of this link to the “Windsor Hum” or “Taos Hum”?
Mine is not as bad as most, I believe. Mine does not affect the audio on videos and music. But when quiet, it’s definitely noticeable. For some reason, I can hear all the neat things outside, birds, winds, etc. I just hope it does not get worse.
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