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'First Lock' At Laser Interferometer
alanb0 writes: "The LIGO project, which is spending hundreds of millions of dollars to look for gravity waves and confirm general relativity, announced 'first lock' on Friday, which is analogous to 'first light' for a new telescope. Here's a story about it ..."
one of the events they are hoping to observe is the collision of black holes. A signal from this event will have a decreasing period as the singularities get closer and they move about each other faster. so it would look lie an inceasing wave, whose wavelength is also decreasing. on the other hand, what do the waves look like when the black holes are actually colliding? incredibly difficult to answer. the models for this situation are incredibly complex and a theoretical nightmare. so part of the problem will be predicting what a signal will look like. at this point there are some very good predictions but for a lot of the events they would like to observe there are no real models.
Believe me, plenty of people would like to. Thing is, space-based interferometry is a tricky business. I believe the first mission to seriously test this technology will be this one, scheduled for 2005. Once space-based interferometry gets developed, though, you're going to see all sorts of cool science come out of these missions, especially since the probes are relatively cheap to build. Just tricky.
I, for one, am eagerly awaiting 10^9 meter baseline radio interferometers. Also, if you build an optical interferometer of that kind of scale, you can pick out the canals on Mars from Alpha Centauri. Or vice-versa.
Quantum mechanics: the dreams that stuff is made of.
You're quite right in saying that rejecting common mode noise is the easiest - you just subtract the common mode out and what's left is siganl. What these guys are doing is just the opposite, from what I can tell. They are looking for a (common mode) signal in the presence of noise that is many orders of magnitude louder.
So as you say, much filtering is needed. I was struck by the similarity of this project to detecting SETI-type signals and I wonder if they could benefit from a SETI@home sort of distributed computing approach. Anybody know more about this?
Admit nothing, deny everything and make counter-accusations.
i listened to a lecture by an applied mathematician modelling gravity waves and he mentioned that the instrument was so sensitive that the scientists were forced to compensate for the movements of the ocean over 300 miles away. it is mindboggling to think that this detector could be thrown off by anything that remote, but that helps to illistrate the challenges the researchers face.
So, first, you would have to detect them, then, perhaps you connect them to events, e.g. Gamma Ray Bursts, then you may be able to tell if it comes from the one direction or the other, and finally, some time in the future (when we're talking LISA), we might talk about angular resolution.
And what that means? It opens a whole new view of the Universe. We're going to see where the matter is, directly. It's just fantastic, I'm telling you....
For an idea of how sensitive these instruments are, I attended a lecture given by a couple of students at a German project, and they once had a signal. Well, not really, it turned out that it couldn't be gravity waves, and they search for a long time to figure out what it could be. Finally, it turned out that a local farmer had bought a heavier tractor, and that shook the ground more than they had thought....
Employee of Inrupt, Project Release Manager and Community Manager for Solid
Also, there will be a unique signature. Having the unique signature occurs simultaneously in distant locations at the same instant is pretty good.
Acumen wrote...
"You are doing it all wrong!"
Heard that before!
"Here's a lead: Create atoms of element 115 in a particle accelerator and investigate them. Element 115's atoms are not only stable, they also have a unique feature: emition of gravity waves!!!. You only need to amplify them, and you got yourself a gravity wave generator."
Erm, firstly creating the damn stuff is hard you get a nucleus of heavy element every n-billionth collision. It generally takes several months of synthesis to create the two or three atoms of a super-heavy element to verify the synthesis.
Element 115 is stable, RELATIVELY speaking, ie. its half-life is measured in the millisecond to second region of things as opposed to elements 109 to 113 which have lives shorter than that of Bill Gates at a Linux Convention.
Finally, wtf are you talking about - gravity wave emission? Jesus, either I am really behind the times or you have being smoking funny tobacco.
"BTW, if you bombard 115 with protons, you get an anti-matter Element 116 atoms"
Hmmm...Anti-matter is (broadly speaking) where the nucleus is made of antiprotons and antineutrons and instead of electrons you have positrons 'orbiting' it. If you bombard element 115 with protons you are unlikely to acheive anything and certainly not antimatter - the superheavy nuclei are made by the fusion of two fairly heavy nuclei in the zinc-lead region of thing IIRC.
Elgon - karma whore to the rescue
I'm sorry to say this but..
My brain just can not help see the similaritys between "First Lock" "First Light" and "First Post"
Each clamming to be "the first" however with "Lock" and "Light" it's scientific..
If Slashdot Trools were scientists I'm sure on any new scientific discovery a bunch of them would search the research and then race to see who can prove it first and all announce a "First" all at once on the same bit of research.
I don't actually exist.
LIGO confirms that Einstein was right the same way that Radio Astronomy confirms that Maxwell was right
Well. Maxwell was confirmed right not by radio astronomy, but by a zillion other experiments. (Radio astronomy did not come into play until the mid 20th century,pioneered by Jansky.) Maxwell did not proposed a theory that was comfirmed by experiments. He proposed a theory which successfully explain a phenomenon (E&M) that was at that time cobbled together by several separate theories.
Also LIGO did not detect gravity waves yet, so it confirmed nothing. Besides, ppl are pessimistic that LIGO will actually detect anything. (It was amazing that they manage to get the project funded with a "BIG IF" probability of success.)
For crazier experiments check out : LISA which plans to fly 6 spacecraft in formation!
Mode (3) smart-aleck mode. Press * to return to main menu.
Check out LISA .
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Another way of accepting a signal is to look for a repetitive signal in a random noise environment. Filtering can help you do this.
What these people are trying to do is listen for a cricket chirping outdoors while they are inside and a rock band is playing full volume next to their microphone. They can filter for the expected cricket sound, but there is no guarantee that what they detect isn't the drummer's pant leg brushing against a snare drum. The noise isn't random. If the noise is repetitive at the expected signal frequency there isn't any way to know which is which.
Does anyone have any insight on how they are going to reject noise at the expected frequency?
I, for one, am eagerly awaiting 10^9 meter baseline radio interferometers. Also, if you build an optical interferometer of that kind of scale, you can pick out the canals on Mars from Alpha Centauri. Or vice-versa.
Well, there's always the Japanese HALCA satellite, part of the VSOP project. This was the first working satellite for a Space VLBI mission, and it had the expected problems with dealing with interferometry between quickly moving objects. True, it's apogee is only at 21 400 km, so it's not quite at the 10^9m level, but it's close.
While HALCA itself is nearing the end of its useful operating lifespan (There were some problems with the satellite losing its targetting that resulted in using up the maneuvering fuel faster than planned), the success of the mission has helped get the Russian Radioastron project back on its feet, and pave the way for other Space VLBI projects.
The main problems in space interferometry have already been tested and dealt with, and there's been some work in the radio astronomy community for dual-satellite interferometry, once some of the second-genaration systems like VSOP-2 and ARISE are in space in a few years. With two satellites each with a 50 000km apogee, we can actually hit the 10^9 meter baseline level.
(Yes, I know a moderate amount about this from my work with the S2 data recording system which is used at a number of radio observatories around the world for VLBI.)
-- Bryan Feir
As someone who did an internship in a small branch of a small branch of Ligo, I feel pretty safe in saying that the problem with this project won't be an abundance of false results, but more likely a lack of results altogether. Firstly, the mindset in the project is not one of weeding out noise to get clean results, but more of searching the noise for possible results. The project is actually looking for a very specific signal, namely the gravitational wave signature given off by a pair of neutron stars falling into each other. This event isn't something that is expected to happen within our signal range very often: estimates range from once a month to never. Given that it will be a surprise to everyone when and if there is a signal that appears to be what they're looking for, I don't think you should be worried about overzealous scientists being duped into thinking an insect is actually a pair of neutron stars.
Corporations worry primarily about the next quarter's results, or at most a five-year plan, so researching gravity waves just makes no sense, even if in 25 years time it could result in, say, levitating cars. In fact, corporations would often prefer not to make such breakthroughs because of the degree to which it upsets the status quo.
If you want to eliminate useless government programs that compete unnecessarily with the private sector, go pick on the Postal Service or something. Leave research alone, unless you want to see real progress in scientific knowledge stopped in its tracks.
I know its hard, but it is sure taking a long time.
the trick is that when the power recylcing mirror is locked in, the whole thing undergoes a 180 degree phase shift, which no one really knew about until recently. so you have to make all sorts of tricky modifications to your control electronics to compensate for this.
also, the gravity waves they are looking for come in quadrupole form (don't know? don't ask), mostly from binary stars, supernovae, etc. one guy told me that the biggest signal came from the actual physical expansion of the earth due to the tidal effects of the moon that increased the length of one of the arms about 100 microns over the 2 km distance.
some truly impressive physics will be done one everything is truly fine tuned enough to detect strain levels down to 1E-27.
as a sidenote, the beam arms are about 1m in diameter, and 2 km long each, under high vacuum. something like 1/2 ton of dynamite in potential energy each. hope it doesn't crack.
i worked on ligo, so if you have any other questions just ask.
Although the article acknowledges that noise could upset the measurements, it doesn't acknowledge the full extent of this problem
The locking may appear accurate in the tests, but there is no way to tell whether noise has caused the mirrors to move forward 1/2 lambda or there is a true grav. wave. This means that the results from the observations mean nothing.
Air movement, insects, electromagnetic interference in the locking devices are the most likely cause of error, and in many cases can not be detected.
X-Has-Sig: yes
...they'd be running around chanting 'first lock d00d!' and pouring hot grits down each others pants right now.
But then Taco^H^H^H^Hthe project leader would bitchslap them and make them all get back to work. *sigh*
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faeryman
There is more information on the LIGO site: http://www.ligo-wa.caltech.edu/news /00 10han.
Its amazing what they can build with Lego's these days.
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I've had enough abrasive sigs. Kittens are cute and fuzzy.
... to confirm that Einstein was right? You bet your ass. Of all the theortical physics to date has translated into some kind of everyday usefull product [a very small subset of academic physics], we now have computers from Dicky Feynman's work in quantum mechanics, space travel from Neuton's laws and really good rubber bands from the superstring theory.
I spend a ton of money on taxes in this fine nation of ours. I write to my government officials and tell them to spend what they can on pure research and space exploration. Aside from the pure joy of knowing there is a unified theory to explain it all, it's just too cool not to do some of this stuff.
Use my backyard for the next one of these.
Pay no attention to the man behind the curtain with all your metadata.
GRAIL (acronym for Gravitation Radiation Antenae In Leiden) is also looking for gravitational waves using a copper sphere with a diameter of 3 meters at a temperature of 1 mK.
Interested in reading this stuff, see here.
vinylat33
There was a student at the International Science fair doing some work on Gravity waves. I believe he was using multiple seperate detectors to remove noise and detectors at multiple angles to find direction.
I believe LIGO is using his research for that purpose.
Considering the interferance that comes about tiny tremors to windy conditions, couldnt they have launched 2 satellites for better results?
Ok this stupid ass java ad is screwing with my cursor. Move all the ads to ads.slashdot.org please. Thanks.