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Science

'First Lock' At Laser Interferometer 62

Posted by michael from the hole-in-the-middle-of-it-all dept.
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 ..."
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'First Lock' at Laser Interferometer More

'First Lock' at Laser Interferometer

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  • Ummm... that's not much of a problem. In space you don't have to worry about forces like friction or others that will push and pull on the satalites (except for the rare debris collision every once in a while).

    It's more of an exercise in testing the accuracy of the propulsion/navigational systems they have on the satalite.
  • 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.
  • You wrote:

    >and really good rubber bands from
    >the superstring theory

    Can you elaborate on this. I really have a hard time believing that superstring theory had anything at all to do with any advances in rubber bands that might (but probably didn't) occur in the past 20 years or so.

    PS: "Dicky"???? "Neuton"?????
  • So now we can have a new SETI@home client, analysing gravitational waves !
  • I am not sure exactly what he means in relating superstring theory to rubber bands, but "Dicky" is Richard P. Feynman (brilliant physicist, won nobel prize in physics for an idea that came from watching a spinning dinner plate) and "Neuton" was probably a misspelling of "Newton" (Isaac Newton, need i say more)... Hope I was of some assistance...
  • As soon as I read that guy's post I knew the responses would be exactly like yours. :)

    And from what I've gathered from other Lego obsessed types on /., it's actually Lego bricks, not just Lego when you're referring to the little plastic blocks. :)
  • "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."

    however the energy is evenly distributed over the whole surface of the vacuum vessel, so it wouldn't do much harm if there was a leak (at least not more harm than any other vacuum chamber).

    do you know the exact pressure they have in their interferometer arms ?

  • Firstly, I don't see why there isn't room for multiple projects in this area. Mini-GRAIL doesn't seem to be starving for resources, so I'd say they're not being that adversely affected by the attention that LIGO is receiving.

    Secondly, LIGO and Mini-GRAIL are searching for entirely different phenomena. LIGO is sensitive to low-frequency resonant modes with very low amplitude, and as such are (with luck) going to detect neutron star mergers, black-hole collapses, and such. Mini-GRAIL has much lower sensitivity, and a narrow bandwidth at a fairly high frequency. They may see (and indeed, are looking for) axial asymmetries in spinning neutron stars.

    Finally, while I wish Mini-GRAIL the best of luck, they are being very optimistic about the magnitude of perturbation they can detect, and the amplitude of the incident metric distortions in that band. With the size and type of detector they are using, the most powerful metric fluctuations likely to occur will still only produce signals on the order of 10 times the theoretical minimum noise, limited by quantum effects.

  • 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 [nasa.gov], 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.

  • The superstring thing was a joke... Laugh.
  • I know you were joking, but it's actually a good point. If there is a way to artificially generate gravity waves (very big if) besides crashing suns together, it would probably be the communication method of choice for an advanced civilization. The signals would see no interference and travel way farther than their electromagnetic equivelant could. But like I said, big if.
  • You would think they could use some kind of 3d nano tether system or something? Be interesting to see what kind of gravity independent clock they will use.
  • How about magnetising handles so that peoples hands stick to them? Thats what happened in the film.
  • 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.

    He may actually have a point. IIRC, in big particle accelerators like Fermilab, they create antimatter by sending regular protons through a cloud of gas (Xenon, if memory serves). So obviously you can create antiparticles using regular particles.

  • 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?
  • Shouldn't these, and the clear potential for more down the road, be enough to convice some commercial enterprise to put up the money?

    Not if the payoff is so risky, so unknown, and/or so far in the future that commercial enterprises never desire to invest in it. There's a reason that "basic" R&D isn't done by any but the largest companies...
  • I know who they are. I was criticising his lack of knowledge and lack of respect.
  • how will they detect where the gravity waves are coming from? How is one to tell that the wave is coming from the sun instead of the moon? It would be interesting to see if they could find what the largest source of gravity waves in the sky is.
  • I can see the interest here - after all, it would certainly be one way of solving the 'unified theory' problem if general relativity turned out to be wrong!
    However, does it really help to have multiple countries coming at this in different ways? Surely there could have been some kind of collabaration between nations on this project? It is not as if the results will be state secrets! The more countries working together, the larger the pot of money and in theory the better and more accurate the equipment. I know what some people will say: countries want the glory themselves, more stations increases chances of success, more results independently is better... but due to the complexity of this problem, I think that one amazing site is more likely to get accurate results than a combination of three or four good ones.

  • sensitivity (Score:4)

    by jimmy_whacked ( 246255 ) on Friday October 20, 2000 @11:26PM (#687665)
    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.

  • First Light? (Score:1)

    by Anonymous Coward
    Bull***t is it analogous to "First Light" - First Light is when you first detect something with the telescope, usually the image of a star or galaxy. They've detected sweet FA with this thing and they never will. Wake me up with LIGO 2 comes on line - or better yet - LISA.
  • While it's mentioned nowhere in articles, I know for sure Russians provide low-end theoretical work (measurement scheme) and mirrors support. I don't know the exact status of this, possibly some kind of subgranting. Russian key person's name is Braginsky.
    ---
    Every secretary using MSWord wastes enough resources
  • I want one in my backwayrd!

    During the day I can dump all this unused sun light into it and light my house all night!

    Think of the costs savings for Las Vagas or New York!

  • Re:This is good, but... (Score:4)

    by KjetilK ( 186133 ) <kjetilNO@SPAMkjernsmo.net> on Saturday October 21, 2000 @02:58AM (#687669) Homepage Journal
    Patience, my friend, patience.... :-) It's really, really hard. First, spherically symmetric objects don't send out gravity waves, so the moon, the sun, most stars, etc, will emit very little. However, there are lots of things that will, some things are very far out in the Universe. In my personal opinion, it's not so much a matter about testing GR, I think that it is very certain that gravity waves exist, I think it is a matter of learning how to use them.

    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 [nasa.gov]), 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....

  • Re:Distinguishing Noise/grav waves. (Score:2)

    by Anonymous Coward
    That's why there are two in seperate locations.

    Also, there will be a unique signature. Having the unique signature occurs simultaneously in distant locations at the same instant is pretty good.

  • ... gravity waves is yours. If you are 15 or younger today, then you'll be exactly at the right age when LISA [nasa.gov] is going up, you'll be in the middle of the revolution when gravitational wave detectors get some kind of angular resolution, that means, you'll get pictures of the actual mass in the Universe. So, that's my advice to you, start reading about gravity waves!
  • I toured the LIGO at Hanford about 4 months ago. Very interesting. It was interesting to hear how while they were running some tests that the cars rumbling on the road, freshly graveled and about 10+ miles away, were showing up in their readings. Also saw the control room. I have never actually seen so many machines running solaris with my own eyes.
  • All right. First, let me point out that I am absolutely fascinated by science and the many advances that have been made in the past few years. We're learning so much about the universe we live in through this research.

    That having been said, I need to respond to your point about politics. Why should the governemnt be sponsoring this research? In the first part of your post you list all of the benefits that we get from the work that's being done in this area. Shouldn't these, and the clear potential for more down the road, be enough to convice some commercial enterprise to put up the money?

    My point is... government isn't the answer to everything. If you want to support this research, why not reduce your tazes, so you can do what you like with your money? There are better ways to do things than government [lp.org].
  • 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
  • Heh, you learn something new every day. Lets just hope I don't get bitchslapped for improper plurals. :)
    -
  • 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.
  • [Ignoring other responces that say basicly you don't know what your saying]
    This would be cool.. so we could like build a gravity wave gun by building up a massive amount of element 115?
    And then launch them and protons right behind them so they spontaneously convert to 116 in fight creating.. an antimater gun...
    Now we can make an SDI (StarWars) Satlight that accually works.. oh wait that wasn't using anti-matter.. that was using "Dosen't matter" (as in.. all replys to press questions "Dosn't matter")
  • 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 [uni-hannover.de] which plans to fly 6 spacecraft in formation!
  • The big problem is that the noise far exceeds the signal that they are looking for. It is possible to detect a signal in a lot of noise - However. There are certain things necessary to do it. The easiest noise to reject is common mode noise with a differential signal; have differential detectors each of which gets the same noise while the signal comes in in differential form. The noise cancels itself out while the signal gets amplified.

    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?

  • Not to be rude but if you're referring to something related to EBE's etc... then I'm afraid it is a crock. Matter does not spontaneously turn from normal matter to antimatter (fortunately)

    OTOH, if you wish to provide me with a few references etc... I will be more than happy to admit I am wrong.

    Elgon

  • Re:Space anyone? (Score:3)

    by Bryan K. Feir ( 11060 ) on Saturday October 21, 2000 @09:41AM (#687682)
    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 [isas.ac.jp] satellite, part of the VSOP [isas.ac.jp] project. This was the first working satellite for a Space VLBI [isas.ac.jp] 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 [asc.rssi.ru] 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 [nasa.gov] 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 [crestech.ca] which is used at a number of radio observatories around the world for VLBI.)

    -- Bryan Feir
  • Actually, I heard a talk from this guy back in 1993 when they were in the planning stages. He showed a lot of the math behind it (which I didn't get) and mentioned that they would like to put 3 space based systems way far away from anything and have them with lengths approaching millions of kilometers. But he admitted that there were some problems with that approach as well (space dust, alignment, etc.)

  • The article on MSNBC indicated that two gravitational wave observatories are required to determine the direction of an incoming gravitational wave; presumably the time separation between signal detections at the two observatories would determine which observatory the wave passed through first. There's one LIGO facility in Hanford (which is the subject of this article) and another in Livingston, Louisiana.

    -Gabe

  • 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.
  • I completely agree with you that government should be as small as possible. But if there's anything governments and tax dollars can do well, it is fund important and long-term research projects which corporations would never be able to convince their shareholders was in their interests.

    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.
  • Please get your facts right. A telescope you buy at a department store could be off by 1/2 lambda, which would be on the order of 10^-7 meters. As explained in the article [msnbc.com], the distance scales they're talking about for the LIGO mirror are more like 10^-17 m, which is smaller than an atomic nucleus. (Of course it can only be in an average sense that the surface of the mirror is controlled this accurately, since the mirror is made of atoms.)
  • the LIGO interferometer is a michelson interferometer with fabry-perot interferometers in each arm and an additional fabry-perot on the input side (bright port). i have inside (ha!) information that this lock was acheived without the power-recylcing mirror aligned, so the laser power resonating in the system was a couple of orders of magnitude below nominal.

    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.
  • When the observations begin.

  • If the LIGO project was like Slashdot... (Score:3)

    by faeryman ( 191366 ) on Friday October 20, 2000 @10:14PM (#687692) Homepage
    ...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*

  • screw the inferometer, i just want my own interoceter.

  • More information at LIGO (Score:3)

    by tmarsh_p1 ( 112710 ) on Friday October 20, 2000 @10:07PM (#687694)
    There is more information on the LIGO site: http://www.ligo-wa.caltech.edu/news /00 10han [caltech.edu].
  • And they would probably publish the same papers month after month.

  • 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. Not exactly. There's a proven aisle of stability aound the 115 area. A certain isotope of 115, is *much* more stable than you think. It's very stable. Colored orange. Has a density of 31.5 g/cm3. Melting point: 1740 C, boiling point: 3530 K

    . The transition from 115 to 116 is very unique. I don't know exactly what causes the created 116 to be antimatter.

  • LEGOs (Score:4)

    by GigsVT ( 208848 ) on Friday October 20, 2000 @10:10PM (#687697) Journal
    Its amazing what they can build with Lego's these days.
    -
  • ... 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.
  • 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 [leidenuniv.nl].

    vinylat33 [mailto]

  • Yeah, I've got one of them. Its great. It gives neutrons a positive charge and makes the human body magnetic.

    Got to love the scientific accuracy of that film.

  • Re:no waves, just particles... (Score:1)

    by Anonymous Coward
    The human body, being the bag of water it is, does react to magnetic fields and is therefore magnetic. It's not ferromagnetic, though, which means that the fields will have to be extremely strong to cause levitation, for instance. It's been done with frogs (no, not the European ones), already.

  • I saw the explination.. (Score:2)

    by Anonymous Coward
    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.
  • Fool! It's Lego. There is no Lego's. In some places, you could be pelted today with small plastic blocks for saying Legos or lego's. Lego is plural, like Moose.

    ---
  • The problem with that is, aside from making the cost even higher, is that the two satellites must be in exactly the same frame of reference. If the drift even 1nms^-1 rel each other, the experiment won't work, and getting them so still is almost impossible.
  • There is another project, Gravity Probe B [stanford.edu], that is planning to launch a satellite. The project is trying to measure the effect of the Earth on the space-time fabric, something different than gravity waves.
  • LIGO confirms that Einstein was right the same way that Radio Astronomy confirms that Maxwell was right.

    There is a lot more going on here than just proof of concept. I have been hearing that gravitational wave astronomy will "open a new window to the Universe" for almost twenty years now, but that doesn't make it any less true.

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