Second Gravitational Wave Detected From Ancient Black Hole Collision (theguardian.com) 220
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.
Why? (Score:2)
Re:Why? (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 [space.com]. So yes, with the current detectors they're pretty hard to detect.
Re:Why? (Score:5, Informative)
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.
Re:Why? (Score:5, Insightful)
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?
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When scientists first started mucky around with electricity it had an affect that could be understood and felt. same goes for lasers, and everything else you use.
To detect TWO gravity waves we had to wait for TWO massive blackholes to combine. And space itself moved by a proton fraction.
Do you have any idea how tiny of fraction that is to be useful? Right about now earth is about the best space ship we can hope for. As it is the only way to get one gravity.
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When scientists first started mucky around with electricity it had an affect that could be understood and felt. same goes for lasers, and everything else you use.
To detect TWO gravity waves we had to wait for TWO massive blackholes to combine. And space itself moved by a proton fraction.
Do you have any idea how tiny of fraction that is to be useful? Right about now earth is about the best space ship we can hope for. As it is the only way to get one gravity.
Your argument is selective at best, some of the most profound invention in history fell out of some obscure research that no one including the people researching them had ever imagined would be of practical use. Turing accidentally invented computer by investigating the nature of information, a fundamental property of the universe.
Put yourself in the position of those people, you are focusing on applications that you already know about - you can't think about the ones you don't know about unless you open yo
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Do you have any idea how tiny of fraction that is to be useful? Right about now earth is about the best space ship we can hope for. As it is the only way to get one gravity.
Earth is not a space ship. It has no propulsion. At most it's a space probe, and even then, it's not just Earth. You'd need the whole solar system. Since it's not going anywhere (the idea that we're not part of the milky way has been debunked) it's not that, either.
Unless, maybe, the whole galaxy is a space ship. I suppose that's an idea which merits further investigation.
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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
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And the only reason we achieved so much in such a little amount of time is because the INFORMATION WAS SHARED FREELY. each scientist was able to use the work of the previous.
Now the stupidity of copyright and patents are slowing down progress at an alarming rate.
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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.
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And the only reason we achieved so much in such a little amount of time is because the INFORMATION WAS SHARED FREELY. each scientist was able to use the work of the previous.
Now the stupidity of copyright and patents are slowing down progress at an alarming rate.
And who is stopping the free sharing of information? It's not the government. It's not the public. It's the universities. Why? so they can capitalize on the monetization of their findings. This was less of a problem before there was large scale public funding (government grants).
One way to fix it is by having any royalties go back to the public coffers in proportion to the public spending on the research. If 10% of the funding is from the government, then 10% of the resulting royalties go back to the gove
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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 usefulness of gravitational waves to society will probably not be on the equivalent of electricity. Electricity always existed. However, prior to being able to generate it for ourselves, it was random in occurrence (lightning), much like gravitational waves. So, unless you think we are on the verge of being able to generate our own gravitational waves, it is unlikely that the confirmation of Einstein's theory of their existence will have a practical application any time soon and almost certainly, not
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In the short term perhaps not. But no one can really say what the value of basic research is. Even if takes centuries for an application to be found, well, we know they exist, and further we now have an instrument capable of measuring some of the smallest known perturbations in space-time.
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In the short term perhaps not. But no one can really say what the value of basic research is. Even if takes centuries for an application to be found, well, we know they exist, and further we now have an instrument capable of measuring some of the smallest known perturbations in space-time.
I am not saying the research isn't valuable, it is. It just isn't the same thing as the early research into electricity. Maybe some day it will bear fruit, but that isn't likely as the theories that predict gravitational waves also preclude them being very useful (kind of like Einstein's theories also posit that time travel is possible. Of course, it would require virtually all of the energy known to exist in the universe, but it is possible, if not very practical.).
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At least gravitational waves are real. That alone makes it more useful to study than things like global warming. Humans aren't causing the Earth to get hotter, no matter how much you insist that your pseudoscience is real. Let's stop spending money to study fiction like global warming and then we'll have enough money to fund real research.
How would one know whether or not humans are causing the earth to get hotter, unless one were to research 1) if indeed the earth is getting hotter and 2) if so, the cause? Isn't that what research is all about -- forming a hypothesis and then conducting research to prove it true or false?
With global warming, there seem to be two possibilities -- either thousands of scientists with different political, spiritual and ethnic backgrounds have come to the conclusion that the planet is getting warmer or they all
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Scientists that where mucking around with electricity in the 18th century was not government funded...
If society, today, practiced the same amount of philanthropy and charitable given as in the 18th (and 19th) century, the government wouldn't need to fund research today.
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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
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Yes, all of those civilizations you mention, did many public works projects that had technologies come from them. But, they did not fund research for the sake of research, but instead to solve a problem. In most cases, it was not the government, per se, funding things, but the ruler. When one is organized in a monarchy or pseudo-monarchy, there is no real distinction between public funds and personal funds so the funding of projects is not truly by the government, any more than when the Renaissance popes co
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Most taxes were a lot lower back then as well. Most Astronomers had to make their living casting horoscopes for the idle rich back in the day.
Re:Why? (Score:5, Insightful)
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.
Re:Why? (Score:4, Interesting)
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.
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That's not the kind of "technical ability" nor the kind of instrument we need.
You think you know what we need. You're wrong. You don't.
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> Doesn't matter. That's not the kind of "technical ability" nor the kind of instrument we need. It won't help us to address a single pressing or practical problem here on Earth in the foreseeable future.
It most certainly does matter. If the alcubierre drive (aka "warp drive") is to ever become reality, we need to more fully understand how gravity works, and then we need to develop a way to create and manipulate gravity waves and development of the sort of power sources required will likely take centurie
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Fuck you -- how dare you try to dictate the good of humanity
You are a vile and clueless piece of shit that would hold humanity back in your asshole attempt to tell us how to think and live our lives
Let me guess -- you're a progressive liberal. Probably want to tell me what to eat as well
Isn't your condemnation of whomever you were responding to, just another example of of somebody trying to tell others how to think and live their lives?
Re:Why? (Score:5, Interesting)
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/... [wikipedia.org]
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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 ;-)
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Re:Why? (Score:5, Informative)
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.
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The LIGO experiment is much more sensitive and a lot of effort put in to detect false positives (including some social engineering).
How can social engineering be useful at all in this case?
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If I had to hazard a guess, with incredibly fine instruments, there's a risk of experimenter effect [wikipedia.org].
Re: Why? (Score:2, Informative)
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'.
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So the graviton was both there and not there as long as you didn't open the envelope?
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We also weren't sure how frequent these events were, but now we are expecting a few more events.
I'm no statistician, but assuming that the intervals between detectable events are exponentially distributed (seems reasonable to me), the fact that we detected the first event pretty quickly within a certain time period would seem to suggest that too high or too low values of lambda (not fitting the first successful observation) are unlikely.
Re:Why? (Score:5, Informative)
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.
Re: Why? (Score:2)
And why isn't it detecting waves on a daily basis? The universe is supposed to contain billions of black holes.
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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.
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Wouldn't it be able to detect weaker events if they happen closer to us?
Re: Why? (Score:5, Informative)
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It detects weaker events all the time. They can detect the gardeners mowing the lawn outside. But the gardeners aren't interesting to astronomers, black holes are.
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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.
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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
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>remember that the strength of waves decays according to the square of our distance from them.
But the detector's detection rates increase with the cube of the sensitivity distance of the detector. That's why it works.
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For a while I was starting to wonder if we would need space-based interferometers to solve the noise/vibration problem. But fortunately that wasn't needed.
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The waves aren't smaller than expected, this recent upgrade is actually the first time they had an instrument they thought would be sensitive enough to detect a gravity wave.
Small black holes, right? (Score:2)
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To be precise, it's size would be zero. It's a singularity, no actual size.
The diameter given when describing size of a black hole is the diameter of event horizon created by the black hole. It's still just "empty space", but that's a point-of-no-return, and whatever's inside, will not escape (minus Hawking Radiation, but that's nitpicking) and that's an important characteristic that describes a limit beyond which everything is "as good as inside the black hole", the 3km from the center not doing a squat of
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It's unlikely there is a literal singularity at the center of a black hole, but we have no theories that can make sense of what's actually going on beyond the event horizon.
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It's easy if you just think of it in terms of kilopounds per megainch.
No km is kibibytes per millimeter.
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Is it just me or black holes just slightly bigger than the sun sound small?
I think it's a reference to the overall idea there are two size ranges of black holes. Small (stellar) and super massive. For technical reasons there seem to be a lack of many holes in the 100 to 100k solar mass size range. Supermassive mergers are thought to happen sometime after galaxies merge, but this is far less common than thier smaller counterpart mergers. Intermediate holes seem to be quite rare. [wikipedia.org]
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Don't forget Australia (Score:2)
https://en.wikipedia.org/wiki/AIGO
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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 det
Getting close to design sensitivity (Score:2)
Every time they get closer to the design sensitivity the detector can spot signals coming from farther away, as the wave amplitude follows the inverse square law.
This increase in range will result in a great increase in the _volume_ they can observe, and remember that these detectors do not need to be pointed they way telescopes do.
The project can clearly follow the Type 1a supernova project (which brought the Nobel Prize to Saul Perlmutter) and go from detecting one signal every few months to detecting a f
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Counter-intuitively, the strain amplitude goes as the inverse of the distance, not the inverse square!
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Actually, let me rephrase that -- it's not counter-intuitive at all that amplitude goes as 1/r, but what's odd is that with gravitational waves, you directly detect the wave amplitude, so detectability falls off as 1/r. For most waves, you detect the wave intensity, which goes as amplitude squared and therefore 1/r^2.
Good that it was ancient (Score:2)
I guess I wouldn't want to observe something like that if i was only a light year away.
Collision? (Score:2)
"Collision" might be a bit of a stretch. It implies immediacy. I didn't RTFA and I am no physicist, however I expect that the "Collision" took an extraordinary amount of time (galactic even as opposed to geologic time periods). Millions of years maybe? I have no idea. Seems if that is the case the summary is a bit sensational, in that it could more accurately be described as the waves of two black holes that slowly eventually merged into one... The end may have happened a lot quicker I suppose, but the lead
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Yes, the black holes had been circling each other for billions of years and slowly leaking energy in the form of gravity waves which resulted in them gradually moving towards each other. As their orbits tightened their orbital velocities increased and it was only in the very last fraction of a second before this long process ended that they were orbiting fast enough to create waves we could detect.
So far away (Score:2)
Both supposed gravitational wave detections were >400 megaparsecs (1.3 billion light years) distant. That is really, really far.
For example, the CfA2 Great Wall [wikipedia.org] of galaxies is only 300 million light years from Earth.
Are there really no black hole collisions happening closer to us? Are these really so rare?
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We are only detecting the last split second of a multi billion year process, so yeah pretty rare that the orbiting black holes are in a detectable state.
Not black holes (Score:2)
Re:ALIENS. (Score:5, Funny)
I tried building a sensor that detects gravity but in all my bench-tests it just kept pointing at your mom.
Re:ALIENS. (Score:5, Funny)
FYI, your dick is not a gravity detecting sensor.
Re:ALIENS. (Score:4, Informative)
Correction: It must be very tiny to be sensitive enough to accurately detect such distant large masses like GP's mom.
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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?
Re: ALIENS. (Score:5, Funny)
0.010000000c
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Can you elaborate what makes you think, that the detected gravity waves propagate at 0.01c?
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I was interested in the maximum possible speed, distance between the two points divided by 1.1 ms. Of course speed can be much less; if gravity wave propagation is orthogonal to the line between the two points then the wave should have been detected at the same instant. You might take into account the speed of the Earth and its rotation, but that should be insignificant and it gets complicated. That is why I asked if someone had a more exact (read: better) value :)
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How do you know they are not just reflections off the edge of the glass jar the universe is in?
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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 plan
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That there's millisecond delays at all at the scale we're talking has me unconvinced that we've detected a gravity wave.
Hyperskeptical I see. I presume you've read up on all the measures that they take to find the real signal and subtract noise? They weren't sufficient for you?
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If the gravity waves were travelling faster than the speed of light, we would not have detected them. We wouldn't be here to detect them because gravity waves propagating through spacetime faster than the speed of light would mean that the universe doesn't work and that would be the end of everything. I suggest Misner, Thorne and Wheeler [amazon.com], an appropriately weighty tome, for more information on the nature of space time.
whenever I have trouble sleeping, this book, saved from my graduate school days always do
Re:ALIENS. (Score:4, Insightful)
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.
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If the gravity waves were travelling faster than the speed of light, we would not have detected them.
Not necessarily, C, the speed of light (In Vacuum) in is available to both sub-luminal and super-luminal events, so a super-luminal particle could cause a flash of light that could be seen by us in our sub-luminal universe.
The effect would be similar to but not the same as Cherenkov radiation [wikipedia.org] where neutrons travelling faster than the speed of light in water cause a blue glow in reactor pools.
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I think you slipped a decimal. The LIGO observatories are roughly 3000 km apart, so a straight line lag between them is around 10 milliseconds. A lag of 1 millisecond meansi that the (essentially plane) wave came in at a small angle relative to the perpendicular plane separating them. The triangle involved would (conveniently enough) have a short leg around 300 km long, and that's still a small angle so without a calculator roughly 0.1 radians on one or the other side of the perpendicular plane. I'm not
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If I had any ligoites in my addressbook, sure, but lacking that, posting on /. is a good way to proceed. OTOH, reading the wikipedia page would probably do it too. At the moment I'm making up a physics final and don't have time -- I was just dangling bait to see if I could get a lazy answer in the meantime...;-)
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I'm not certain how they manage to set the azimuthal angle
See: Rapid Bayesian position reconstruction for gravitational-wave transients [aps.org]
"We introduce BAYESTAR, a rapid, Bayesian, non-Markov chain Monte Carlo sky localization algorithm that takes just seconds to produce probability sky maps that are comparable in accuracy to the full analysis. Prompt localizations from BAYESTAR will make it possible to search electromagnetic counterparts of compact binary mergers."
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If the detectors arms aren't parallel and perpendicular to each other and the source that would give them an additional data point and make it possible to triangulate; 4 arms in two locations, could give you 3 data points.
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Doesn't all technology that we know of depend on gravity in some form or another?
Technology does not exist in nature, it is created. For people to exist to create the technology, they need a planet capable of sustaining life. To have a planet with an atmosphere or even to have a planet at all, requires gravity.
Ergo, all technology depends on gravity.
Re:Why LIGO is a scam (Score:5, Funny)
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Quit bogarting, dammit.
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[emphasis added]
If true, this was the most interesting part of your article, Louis. Got an external link to back it up?
It's not true. I don't have a link to back it up, but I did read it somewhere plausible written by a real physicist. The motion of the planets fits the relatavistic model. One of the problems with Newton's laws is that the motions of the planets did not fit the predictions of Newton's laws. Relativity made up for the discrepancy. The motion of the planets is conditionally stable, just like any control system in the real world (as opposed to your simulator).
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No, instead of reading a scientific report on these findings you went to the mass media and complained it was the mass media. The problem lies with you not knowing where to find what you're looking for, not that what you're looking for doesn't exist.
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"Massive ego, detecting an accomplishment that did not originate from itself, quickly moved into action to diminish it, causing the fabric of noosphere to ripple in a disgusted reaction."
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A real physicist on the radio called it "swimming in jello" (That's jelly for the rest of the world).
That seems a pretty good analogy. Radiating gravity waves seems fine too. People are so picky.