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Second Gravitational Wave Detected From Ancient Black Hole Collision (theguardian.com)
An anonymous reader quotes a report from The Guardian: Physicists have detected ripples in the fabric of spacetime that were set in motion by the collision of two black holes far across the universe more than a billion years ago. The event marks only the second time that scientists have spotted gravitational waves, the tenuous stretching and squeezing of spacetime predicted by Einstein more than a century ago. The faint signal received by the twin instruments of the Laser Interferometer Gravitational Wave Observatory (LIGO) in the US revealed two black holes circling one another 27 times before finally smashing together at half the speed of light. The cataclysmic event saw the black holes, one eight times more massive than the sun, the other 14 times more massive, merge into one about 21 times heavier than the sun. In the process, energy equivalent to the mass of the sun radiated into space as gravitational waves. Writing in the journal Physical Review Letters on Wednesday, the LIGO team describes how a second rush of gravitational waves showed up in their instrument a few months after the first, at 3.38am UK time on Boxing Day morning 2015. An automatic search detected the signals and emailed the LIGO scientists within minutes to alert them. The latest signals arrived at the Livingston detector 1.1milliseconds before they hit the Hanford detector, allowing scientists on the team to roughly work out the position of the collision in the sky. In February, LIGO scientists officially announced the first-ever observation of gravity waves.
I tried building a sensor that detects gravity but in all my bench-tests it just kept pointing at your mom.
"I like to lick butts!" by MobileTatsu-NJG (#32700246) (Score:5, Informative)
Are the waves smaller than expect, thus harder to detect?
Indeed. They're very small. We're talking about a shift in space the size of a very small fraction of a proton. So yes, with the current detectors they're pretty hard to detect.
FYI, your dick is not a gravity detecting sensor.
You are welcome on my lawn.
It took so long because the signal is mind-bogglingly weak. No detector was sensitive enough or well designed enough to rule out false positives. The LIGO experiment is much more sensitive and a lot of effort put in to detect false positives (including some social engineering). The detectors also underwent a very extensive testing phase before they were considered ready. We also weren't sure how frequent these events were, but now we are expecting a few more events.
But, it must be said indirect evidence of gravitational waves already were detected through the observation of two pulsars orbiting and closing in on each other at a rate predicted by the theory.
Those who do not learn from commit history are doomed to regress it.
Noise. All kinds of noise.
The system is an interferometer - basically two lasers set up in a large L shape with mirrors (massive simplification). When the lengths of the arms are the same, the beams cancel, when they differ a signal is recorded.
Now, the differences in length due to a gravitational wave is tiny, and the problem that kept LIGO from their detection is that there are huge numbers of sources of vibrations around the same frequencies as expected from gravitational waves that have far larger amplitudes. Thermal vibrations, for example, are a killer for experiments like this.
The waves themselves have almost exactly the waveforms that were predicted - the template fits from simulations match amazingly well in terms of amplitudes, frequencies and their evolution. What stopped experiments like this from making the observation was simply a lack of technical skill to make a precise enough instrument. Following the development of LIGO over the last decade, this is precisely what everyone working on the project said - once the noise curve is reduced to form Advanced LIOG (recent upgrade) the noise would be sufficiently small than an integrated signal against a template would be clearly visible, and now it is.
The current detectors are the most sensitive instruments ever developed by humanity, and in and of themselves mark a major leap forward in technical ability.
The world's burning. Moped Jesus spotted on I50. Details at 11.
If I had to hazard a guess, with incredibly fine instruments, there's a risk of experimenter effect.
The world's burning. Moped Jesus spotted on I50. Details at 11.
But gravity waves are like elephants in your fridge compared to the problem of detecting gravity particles.
a detector with the mass of Jupiter and 100% efficiency, placed in close orbit around a neutron star, would only be expected to observe one graviton every 10 years, ...
https://en.wikipedia.org/wiki/...
Correction: It must be very tiny to be sensitive enough to accurately detect such distant large masses like GP's mom.
Still waiting on Serviscope_minor to wake up to fucking reality and realize that Jessica Price isn't going to fuck him.
You have no idea what it will or will not address. When the first scientists were mucking around with electricity in the 18th century they were giving people shocks and making frogs legs jump. Within a hundred years they were rolling out the world's first global high speed communication's system.
So take your contrarianism and stick it up your ass. Your type would have us still beating each other with sticks, because, you know, what good does that shiny shit in the ground do us?
The world's burning. Moped Jesus spotted on I50. Details at 11.
They had a system to inject test data into the final stage analysis. The people doing it did it blind to publication ready point. Partly it was to ensure nobody leaked before the 'envelope was opened'.
In the David Weber's "Honor Harrington" universe he uses gravity waves. His gravity waves are faster than light (cue interesting plot details, of course), but the real ones detected by LIGO seem to propagate at something more on the order of 0.01 c. Does someone have a more exact value?
0.010000000c
Strangely enough humanity as a whole can multitask. Individuals can too.
For your complaint to be valid humanity could only do one thing at a time, that specialization doesn't help when developing something (humans are replaceable cogs) and that somehow your idea what is important is the key to future advancements. You also disregard the fact that basic research often helps progress in unexpected ways - including the area of microscopy.
However you seem to think that just throwing monkeys (read: humans) on typewriters (research) is the best way to develop solutions. That in itself should be a huge warning sign that you shouldn't be taken serious.
There are three main detectors; two in the USA (LIGO) and one in Italy (Virgo). Currently, a detector is under construction in Japan and a fifth one using LIGO components will be built in India. Additionally, there is a smaller detector in Germany that is only sensitive in higher frequencies. It is mainly used to test technology, but it is also used for certain types of sources.
Having multiple detectors is very useful, because coincidence is used to determine the sky position. A single detector can only determine the distance, but with three or more detectors, a spot on the sky can be identified by triangulation. Moreover, having multiple detectors increases sensitivity, so weaker signals can be detected and more accurate measurements can be done on the properties of the system that is observed (e.g., the masses of merging black holes).
LIGO is detecting the gravitational storm that happens when two black holes, each 10-30 times the mass of the sun, actually collide and merge. Standalone black holes shouldn't generate gravity waves unless disturbed by something massive close by.
Orbital binary systems should generate gravity waves, but those would be a couple of orders of magnitude less powerful than two colliding black holes and LIGO isn't sensitive enough to detect those out of the noise.
Trying to become famous by taking photos. Visit my homepage please.
Actually, given the level of some comments here, better microscopes are really needed just to detect the presence of a brain in some people.
I just don't know who to believe. Albert Einstein and several generations of cosmologists, or a AC blowhard on Slashdot. TORN.
I do not want your cheap brainburning drugs. They are useless for work. And I am a working man today.
How do you know they are not just reflections off the edge of the glass jar the universe is in?
Do not look at laser with remaining good eye.
but the real ones detected by LIGO seem to propagate at something more on the order of 0.01 c. Does someone have a more exact value?
Sure, as far as we know, the exact value is c. Where did you find 0.01c?
The distance between Livingston and Hanford is 3002 km, and the signals were received 1.1 milliseconds apart. In a straight line that would be rougly 3 million km/sec, or 10c. But obviously the signal came in at an angle. If it had come in perpendicular to the line between the two detectors, they would have detected it simultaneously. So it must have come from somewhere in between, I would say around 6 degrees off the perpendicular plane between the two detectors.
But I'm detecting gravitons all the time! I wouldn't be sitting in this seat if it wasn't for gravitons. I think someone misunderstood something here. Possibly me ;-)
So the graviton was both there and not there as long as you didn't open the envelope?
Money invested into a specific scientific discipline has greatly diminishing returns. Couple that with no one knowing which scientific discipline or combinations of will cause the next breakthrough, and spreading our money around is the best investment. Many domains already have huge amounts of private funding, little point in the government throwing money at better optics for microscopes.
Yes, but it's how much weaker. For a brief moment, those two blackholes released more energy that the rest of the entire observable Universe, that includes all of those quasars. Even gamma ray bursts only outshine their local galaxy.
Unless you have a testable theory to show that its size is is anything less than the event horizon, you just have faith that its size is 0 and nothing more.
the growth in cynicism and rebellion has not been without cause
gravity waves propagating through spacetime faster than the speed of light would mean that the universe doesn't work the way we thought
FTFY.
Science.
All my liberal friends think I'm a conservative, all my conservative friends think I'm a liberal.
And why isn't it detecting waves on a daily basis? The universe is supposed to contain billions of black holes.
The black hole merger that was first detected had a peak power output that was 50 times greater than the total power output of all the stars in the observable universe.
The waves from that merger caused the arms of the LIGO detectors to differ in length by 0.000000000000000000001 meters, which is roughly like the earth getting wider by 10 protons.
This latest merger involved less massive black holes which should mean it had a lot less peak power.
INFORMATION WAS SHARED FREELY. each scientist was able to use the work of the previous.
That was most certainly not the case.
Or Newton and Leibnitz had not accused each other for stealing their ideas about differential equations and integrals.
Cost free eBook I read (by iBook/Kobo/Amazon/ObookO/Gutenberg etc.): "The Green Odyssey" by Philip Jose Farmer.
You also disregard the fact that basic research often helps progress in unexpected ways - including the area of microscopy.
Indeed. My research is in making better microscopes (to cure cancer and whatnot...) and I've been personally looking at some of the advances in interferometry that allowed LIGO to be built (and the analytical techniques that allow useful data to be recovered).
So Midas' criteria has been fulfilled and he can quit his bitching now.
If you want a vision of the future, imagine a youtube comments section scrolling - forever.
Governments have always invested huge amounts in technical advancement, although historically much of it has been military advancement. But if you look at Rome, it made huge investments in public works, and out of that investment came numerous technical advancements, some still incredibly stunning, The Pantheon in Rome, built by state funds, is still the largest freestanding unreinforced concrete dome ever built.
But the Romans were hardly the first. The Greeks, Egyptians, Akkadians, Chinese, Sumerians, Inca, Aztecs and numerous other civilizations made great technological and engineering advancements, all largely financed by their governments. Even in the US, many of the major technical innovations made by private enterprise have either rested in part on taxpayer-funded research, or in some cases, like the development of the space and maritime technology, and even Internet itself, via direct funding by government.
The world's burning. Moped Jesus spotted on I50. Details at 11.
And why isn't it detecting waves on a daily basis? The universe is supposed to contain billions of black holes.
I went to a talk by one of the LIGO scientists where pretty much this questions was asked.
It's a simple answer. Two black holes colliding is fantastically rare, but very the universe is fantastically big, so it happens a hell of a lot if it happens at all.
The LIGO experiment is limited by noise and can 'see' out to some distance. So all the events happening within the sphere of that radius get detected. The rate of detection is a function of the radius of detection. The rate of detection tells us something about the actual density of black holes in the local part of the universe.
The nice thing is as they increase the sensitivity, the volume goes up as a the third power of the radius, so the rate of detection should go up by the same amount. The rate of detection at the increased ranges tell you lots of things about the uniformity of distribution and the tightens the statistics on the detection rate. If they improve the sensitivity by a few db, they might well be detecting on a daily basis. Before the upgrade they were getting nothing. After the upgrade they have got 2 in a year.
I think they should build a couple more of these things around the globe and so get a higher resolution of direction determination. If you have a few billion, you should fund that.
I should use this sig to advertise my book ISBN-13 : 978-1501515132.
And space itself moved by a proton fraction.
You must have a sense of scale.
Space moved a tiny amount, yes, but at a distance of 1.3 billion light-years. It is so small because we are so far away.
Imagine saying light waves are useless because a distant galaxy is so dim that it is barely detectable. But when you account for the distance, you realize that there was some serious energy in that light, and the light traveled a vast distance without being concentrated or guided in any fashion.
Where would telecommunications be now, if we looked disdainfully at a dim galaxy and decided not to research lasers?
Gravity is the weakest of the fundamental forces, but it is the one to study if you want to manipulate space.
If gravity wave intensity follows the inverse square law, that would be a ripple in space of roughly 1500 meters at a distance of 1 light-year from the collision (for a local deflection of 1 photon's circumference).
Since the article indicates the detector is sensitive down to 1/1000 of a photon's circumference, it would indicate at least a 1.5-meter ripple at one light-year for the smallest detectable ripple. This would be at least a 10cm change on Earth if it happened in Alpha Centuari. Obviously, this number should be multiplied by the actual detected change, but unfortunately the article does not report it.
This translates to a ripple of ~196 km at a distance of one light-day, or 1.6 million km at 8 light-minutes (the distance from the Earth to the Sun).
I don't know what a 1.6 million km ripple in space would do to something within it, but I doubt I would like to experience it.
We've done amazing things with optics in the century or two after we figured out how light worked. Clever ways of generating it, filtering it, focusing it, etc.
Now that we know with certainty that gravitational waves exist, we can work on better observations and a better understanding of this force.
We won't have interstellar warp travel in the next decade---but looking back, we didn't build the first laser until 50 years after the first detection of photons. This is just one step on a long road.
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According to the latest ruleset, this post should be modded as Vorpal Flamebait +5.
Nope, it was dismissed out of hand. There was never any kind of test done to discredit it, the scientists simply said it couldn't possibly be and refused to even entertain the idea.
I disagree with one thing. Cosmology is not at risk of becoming as dogmatic as religions, it has been at least that dogmatic for many decades.
Larry Niven was a friend of Robert Forward, a physicist and aerospace engineer who made various proposals for gravity wave detectors and other over-the-horizon technologies throughout the 1960s to 1990s. He (Forward) is considered one of the doyens of "hard" SF. (As is Niven himself.)
Birds are not dinosaur descendants;birds are dinosaurs, for all useful meanings of "birds", "are" and "dinosaurs"