Gravitational Waves in Five Years

By Sean Carroll | August 20, 2012 1:15 pm

LIGO, the gravitational-wave observatory, is currently on ice. After running successfully (although without actually detecting any gravitational waves) through 2007, it got a mini-upgrade and ran as Enhanced LIGO in 2009 and 2010. But in October 2010 it shut off, and the original detectors were disassembled. Not because anything was wrong, but because of a long-anticipated upgrade to Advanced LIGO, a substantially more sensitive observatory.

Those upgrades are still going on, with the new detectors scheduled to come online in 2014. Advanced LIGO should provide more than a tenfold improvement in sensitivity, which allows the search for gravitational waves to pass an important threshold: with LIGO, it would have been possible but quite fortunate to actually detect gravitational waves from predicted astrophysical sources. With Advanced LIGO, it will be a surprise if we don’t detect them.

Clara Moskowitz has nice update on She quotes Kip Thorne as predicting that our first definite direct detection of gravitational waves will come in between 2014 and 2017 — within five years. Start your betting markets! Traditionally, looking at the skies in a new way (radio waves, cosmic rays, X-rays, gamma rays, neutrinos…) has always taught us something new and exciting. I’d be surprised if gravitational waves aren’t equally surprising.

  • Josh Andrews

    Won’t the upgrades result in a tenfold increase in headaches due to passing vehcles and earth tremors or will there also be an improvment in the mitigation local effects?

    • Sean Carroll

      Josh– Absolutely. Otherwise we’d be predicting discovery within two or three years!

  • Brian

    In the summer of 2007, when I was doing prospective grad student visits, I remember one of the professors at CalTech telling us that gravitational waves would almost certainly be observed within the next 5 years.

    Here’s hoping that it works out better for the current batch of incoming grad students!

  • Doug Little

    What if we don’t detect them? Could something like looking at gravity as an entropic force gain momentum?

  • Riemannium

    Great news Sean! However, I am not so optimistic! IceCube is not seeing the spectacular neutrino map of the sky we expected. So, either neutrinos are weird, IceCube is working “bad” or we have a problem. There are no as many high energy neutrinos as we wished! Anyway, I really hope to see gravitational waves in my timelife (I am young yet, 34 y.o.) and negative results are as puzzling as true observations. Remember what it happened with ether detection in the 19th century anyway! So, we are living interesting times from the phenomenological aside. Just a question: do you really expect the detection of gravitational waves to happen in the next 5-10 years (being generous with the time)?

    • Sean Carroll

      I really do expect to see them, yes. But there are no guarantees in this life, and certainly not in experimental physics. Not seeing anything would be interesting and disappointing at the same time.

  • Shantanu

    Sean, there are no guaranteed astrophysical sources in the frequency range of ground-based gw detectors, even if sensitivity is increased ten-fold from what it was in 2010.

  • anon

    The time invariance of the universe implies that detection of gravity waves will always happen for the first time in the next 5 years. This has been true since I was a graduate student in the ’90’s.

  • martenvandijk

    The detection of gravitational waves will take just as many years as it will take to admit that they do not exist.

  • John

    Hey Sean,

    Thanks for the update. Great to see this coming on line soon. Whats the story with AMS ? I was expecting some physics from them by now….

  • Biff

    Has any mechanism for the inspiralling behaviour of neutron star binaries, such as the Hulse Taylor system, other than gravitational waves been proposed ?

  • cormac

    what about B-mode polarization signal? might be sooner than that if all goes well at PLANCK surely…

  • Faizan sarwar

    Gravitational waves are related to gravity.Gravity is a process which exists due to both mass and space(both will be required not only one).
    If we let gravitational wave exists then,it must exist on atomic level.
    Because,gravity starts to exist from atomic level.
    Here, a question arises that it don’t exist for such lesser mass?

    But,increase in mass is only gathering of atoms into a particular reason, and if increase in mass is the reason then due to increase in mass gravitational wave will be observable on the level we fill, this view is effectless.
    Hence, gravitation wave has to must exist on atomic level.If not than it don’t exists.

  • Faizan sarwar

    D-: It’s my personal thinking,don’t take it otherwise.It may I am wrong.

  • Richard


    What are you talking about? I have no idea what you just said.

  • Faizan sarwar

    I want to say that gravitational wave depends upon gravity and gravity belongs to mass.Mass of anything is the collection of atoms.If gravitational wave exists. On primary level it belongs to atom.So, atom must conduct gravitational wave then molecule and every massly object.

  • Marco

    Hai Faizan,

    If you are saying that molecules should generate gravitational waves just like stars do, then you are right. However, those waves are so feeble that you can not detect them. Rotating double stars or a nova would give a detectable effect, even if you take in account the distance.

  • Matt

    Josh & Sean – Some of the new hardware being installed is exactly for the purpose of reducing the coupling of ground motion to the mirrors of the interferometer. In addition to passive isolation (springs and pendula), there are a number of active systems using accelerometers and feedback to compensate for ground motion.

  • Richard


    Gravity isn’t just produced by mass. It is also produced by energy, momentum, and pressure.

  • Faizan sarwar

    Yes,on atomic level gravitational wave will be feeble though atom itself is almost negligible according to volume and gravity.
    So, thinking on large level like our galaxy Milky way.

    With our sun billion of stars are orbiting the massive black hole due to gravity.Gravity is enormous on this level.
    But,we can say that milky way is 99% empty,so with such large gaps between stars gravitational waves can’t be detectable.But,I think at least nearer to black hole,where density of stars is greater in comparison to outter side, gravitational waves must be detected if it exists. However,these are only the possibilities not the accuracy.To,get accuracy experiment is,I wish ALL THE BEST that we will detect gravitational waves within five years.

  • Georg
  • Bob

    I would not be surprised if gravity waves are detected, but if so, they are perturbations of space itself, not a “flow” of so-called gravitons through space ….

    I say this for two reasons: 1) Relativity Theory is spectacularly successful and suggests only that gravity is emergent in nature as mass causes a curvature of space, and 2) All attempts to integrate Relativity Theory with the equally successful Quantum Theory/Standard Model have been spectacularly UN-successful — probably because gravity IS an emergent property, and not mediated by particle interactions like the electronic, weak and strong forces.

    The reason that nothing can leave a black hole is NOT because “gravity is so strong”, but because that region of space has been curved to the point that it becomes a CLOSED LOOP. Nothing leaves because the space it is IN is twisted into CIRCLES.

    I believe that to ever gain a deeper understanding of gravity, we must first have an understanding of space, which we simply do not yet have.

    Do you really think that a black hole with a mass equivalent of million of suns can actually crush down to a point with no dimension and I N F I N I T E gravity? The math that says so is simply misleading us. Just as the nuclear force sustains the mass of a neutron star, preventing it from becoming a black hole, something likely sustains the mass of a black hole, preventing it from becoming a “singularity” with its attendant infinities. That something is likely to be the structure of space itself — that it has a smallest unit of size, somewhere near the Planck length, which is very, very, very small — but still has dimension, is NOT a mathematical point with no dimension.

    If that unit of space has a minimum size, but can expand to larger size, it could help to explain the expansion of the universe, but may also imply that gravity waves simply get absorbed and don’t travel far. Wave energy can pass though water easily because the units of water are un-compressible. A shock wave travels through air, but is eventually dissipated. I believe the same will be found to be true of “gravity waves” …..

  • http://none Stephen W. Anderle

    supposing gravity were a linear instead of spherical force, in a line directly away from the point source ., this would explain why it is felt all across the universe at a constant rate instead of the up and down ,( stronger and weaker), pulses that a spherical wave would produce.

  • Faizan sarwar


    If gravity is a linear force,it must show a particular direction of force.If a linear gravitational force of sun collisions the linear gravitational force of earth what will happen?Solving it you can say that sun’s gravity would win because sun has larger mass.
    But,when linear gravitational force of equal mass collision what will happen?
    I have lots of trouble to visualize it.

  • Faizan sarwar

    I am satisfied with the thinking that gravity belongs to space and mass.I have an idea to visualize it,
    Today, the gravitational force of earth is well defind related to it If the volume of earth is decreased 100 times and mass be the same desity will be highly increased.Will the gravity be same?
    No,It will be increased.
    Opposite to it, when volume of earth is increased 100 times and mass the same, gravity decreases.
    So,here it is observable that with the same mass, gravity,we can say that mass is not the only factor of gravity,but space around the mass is also the reason of gravity.
    Now,if space has the quality to show gravity it can’t be empty it must be made up of particles.
    According to the above theory how change in density will effect gravity?

    I think that space has it’s own density.But,when matter replaces it,It is denser around the matter relative to the volume covered by the,when volume of matter increases there is more (space) inside the matter hence particles of space around the matter is less denser and so the gravity and vice versa.
    So,I think this desity of space is the reason of gravity.
    Related to above theory I think distortion of light near mass is caused by the density of space near the mass,In fact it is just like refraction of light.
    But,I aren’t sure by what particles space is made up of,it may be the dark matter.
    Related to the above thinking,It is also predictable that why even light can’t escape from black hole?
    Due to the extremly high density of black hole space(dark matter) around it is also extremly denser.But, the space around black hole hasn’t the property to reflect the,due to high density of space ray of light is trapped in it and can’t able to escape.In such condition availability of worm hole is impossible.
    Related to it I think the density of space is reason of the time.That’s why it get slower and faster according to the mass.

  • Jimbo

    LIGO was `sold’ to congress for about 2% of the SSC cost. Every bit of hype/news about LIGO that I read in the 90s ostensibly predicted the observation of grav waves. Then, after 7 science runs spanning the previous decade, All came up null. Now Kip tantalizes us w/the promise of `Advanced LIGO’. Because its `built’ on Einstein’s GR, which has passed Every observational test, no one can imagine what will happen if grav waves, analogously to SUSY, fail to be Directly observable.
    Fundamental physics is in shock right now, despite the brief Higgsian euphoria. SUSY is dead, likewise extra dimensions, Tev black holes, & FAPP string theory. These theoretical paradigms developed over the last 30 yrs are on life-support, lingering in the hearts & minds of theorists in deep denial that something is terribly wrong.
    We need to be realistic about grav waves’ direct observation, which may never be possible, no matter how sensitive LIGO becomes. GR will be relied upon as the bedrock of grav physics until the next Einstein arrives & replaces it with something grander.

  • realta fuar

    LIGO is unique in the history of “big science”: never before has a project been funded so lavishly, for so long, with no real expectation of success for DECADES! It had damn well better detect something by 2017 as it’s starting to make JWST (ever a WORSE name for a major observatory?) look like a good investment.

  • Phil

    Jimbo and realta fuar,

    Relax. Take a chill pill. Remember that the military has 2 0r 3 telescopes that are much better than Hubble just sitting around doing nothing. Go complain about the military being funded “so lavishly”. So many billions of dollars spent invading other countries.

  • Jimbo

    Phil: Retain yesterday’s news ! Astronomers were Given one of these scopes ~ 6mos ago. Not the point of the post as realtafuar & I emphasize. Grav waves, like SUSY, touted for Decades as a slam-dunk, May go belly-up at ALIGO. At which point we’ll have to accept that GR may have low-energy flaws, so that it’s only 95% correct.
    Similarly, the spectacularly successful standard model of particle physics cannot resolve the Hierarchy problem or the Muon anomaly to name just a few. Something bigger & better is coming down the pike, but we’ll have to wait a while longer.

  • Phil


    Please tell me how you got 95%. If not, shut up.

  • Biff

    @21 Georg

    Thanks for the link. I have to say that I didn’t find his arguments that compelling. It’s the sort of stuff you hear down the pub… Regarding the orbital decay of the Taylor Hulse binary :

    That fact may most probably be explained in terms of tidal friction as suggested in 1976

    I’m afraid you only get points if you do some maths and SHOW that your results match reality. Or at least approximate it better than the rival theory.

  • Kenneth W. Regan

    Announcement today:

    Feeling too queasy to write more—this is the first scientific thing really convincing me to lay off the ice-cream sundaes with their high graviton-inducing count.

  • dmiern r

    Are we still doing pure science or tweaking the gizmo to give us the answer we want??????


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About Sean Carroll

Sean Carroll is a Senior Research Associate in the Department of Physics at the California Institute of Technology. His research interests include theoretical aspects of cosmology, field theory, and gravitation. His most recent book is The Particle at the End of the Universe, about the Large Hadron Collider and the search for the Higgs boson. Here are some of his favorite blog posts, home page, and email: carroll [at] .


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