[HN Gopher] Gravitational-wave detector LIGO is back
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Gravitational-wave detector LIGO is back
Author : gmays
Score : 110 points
Date : 2023-05-26 16:15 UTC (6 hours ago)
(HTM) web link (www.nature.com)
(TXT) w3m dump (www.nature.com)
| fjfaase wrote:
| For observatory status see [0]. It also gives the estimated
| detector range in megaparsecs (Mpc). Initial LIGO's "range" (the
| radius out to which LIGO could detect at least a binary neutron
| star (BNS) merger) was 15 Mpc. With the latest improvements is
| more in the 140 Mpc range. Meaning that it can see more than 9
| times as far and that the area of space is increased by a factor
| of more than 800. This will greatly increase the number of
| gravitational waves being detected.
|
| [0] https://online.ligo.org/
| acqq wrote:
| Do you know if even longer ranges logged there, like 600, are
| practically useful or are they too short (in time) for that?
|
| https://online.ligo.org/grafana/public-dashboards/1a0efabe65...
| dr_dshiv wrote:
| > Meaning that it can see more than 9 times as far
|
| Hear 9 times as far?
| galizar wrote:
| Nice. There's even a citizen scientist initiative for LIGO [0]. I
| wonder what's the status on LISA though.
|
| [0] https://www.zooniverse.org/projects/zooniverse/gravity-spy
| kataklasm wrote:
| One of my professors worked on LISA Pathfinder, the demo
| satellite used to proof-of-concept LISA technology until the
| financial shortcomings in the early 2010s were overcome and he
| recently said that everyone in the project is hard at work
| getting ready for the program review, after which either a
| contract is made or the program is reformulated. But no one
| will put in the gigantic work needed to prepare such a review
| if it is not almost certain the program will pass the review
| and become a contract, so things are looking quite good for
| LISA and its early 2030s launch!
| cubefox wrote:
| I remember reading about LISA as a kid, around 25 years ago.
| Currently it is planned to launch in 2037. I somewhat doubt
| it will ever become a reality.
| wefarrell wrote:
| I think it would be really neat to have a space based
| telescope in close proximity to LISA so that when
| gravitational waves are detected the telescope can point in
| the direction of the source and capture the light from it.
| captainkrtek wrote:
| Big LIGO nerd here. If interested, you can get public alerts of
| LIGO detected activity (on mobile and online):
|
| https://www.ligo.caltech.edu/page/GWPhoneAlerts
|
| https://gracedb.ligo.org/superevents/public/O3/
| Simon_O_Rourke wrote:
| Good, this is a necessary thing to get back up and running
| again. Thanks for the update alerts, will subscribe and see
| what's stirring in the galactic 'hood.
|
| Question though - do gravitational waves diminish significantly
| as a function of distance or intervening mass?
| causality0 wrote:
| The LIGO song is required background music for this article:
| https://youtu.be/degD69wnZcY
| groestl wrote:
| Thank you for this (channel), I was one of the lucky 10k today!
| wwarner wrote:
| haha catchy love it
| whoisthis4chan wrote:
| > Typical gravitational-wave events change the length of the arms
| by only a fraction of the width of a proton. Sensing such minute
| changes requires painstaking isolation from noise coming from the
| environment and from the lasers themselves.
|
| i find it utterly fascinating that we're able to detect such a
| minuscule deviation
| pfdietz wrote:
| Lasers beams are bounced back and forth many times, so the
| deviation builds up. The beams have to be very powerful (100s
| of kW) to reduce photon counting noise sufficiently.
| wwarner wrote:
| Kip Thorne explains it pretty clearly in this 2002 lecture
|
| https://youtu.be/mGdbI24FvXQ
| dekhn wrote:
| interferometry is indeed amazing. When the ultra-important
| Michelson-Morley experiment was run some ~100 years ago, they
| were doing interferometry but in those days there wasn't really
| good vibration isolation technology. They had to float their
| whole experiment on a pool of mercury (!) in the sub-sub
| basement of an idle building, and even then, deliveries nearby
| (by horse) would cause problems.
|
| Nowadays, physics students do the MM experiment in a lab on a
| benchtop in a day.
| acqq wrote:
| I'd like to read how these problems are solved "in a lab on a
| benchtop" today!
| funac wrote:
| you can build very good hydrostatic vibration isolators in
| a home machine shop nowadays; commerical optical tables are
| /very/ steady
| [deleted]
| dekhn wrote:
| the original experiment is pictured here: https://en.wikipe
| dia.org/wiki/Michelson%E2%80%93Morley_exper...
|
| what makes it possible to do in a desktop lab course
| combination of a large number of different innovations. The
| first is that we know how to make extremely
| stiff/rigid/strong/flat/thermally stable tables
| (https://www.thorlabs.com/navigation.cfm?guide_id=41) which
| can optionally be placed on active vibration-cancelling
| struts (https://www.thorlabs.com/newgrouppage9.cfm?objectgr
| oup_id=10...). The second is using cage systems for
| mounting things with everything lined up parallel and
| centered
| (https://www.thorlabs.com/navigation.cfm?guide_id=2255).
| The third is precise kinematic mounts which make real-time
| angle tuning a lot easier/more reliable (https://www.thorla
| bs.com/thorproduct.cfm?partnumber=KM100#ad...). The fourth
| is now we have powerful lasers and LEDs that make
| generating lots of light all pointing in the right
| direection easier (https://www.thorlabs.com/thorproduct.cfm
| ?partnumber=CPS532-C...). The fifth is that high quality
| standardized optical parts (mirrors, lenses, etc) are
| easily available from a wide range of vendors (https://www.
| thorlabs.com/newgrouppage9.cfm?objectgroup_id=10...).
|
| There are a number of other innovations in material
| science. but I'd recommend taking a look at Thorlab's
| Michelson-Morley educational kit. For $3K you get basically
| everything you need to carry out the experiment:
| https://www.thorlabs.com/thorproduct.cfm?partnumber=EDU-
| MINT... plus a nice manual https://www.thorlabs.com/drawing
| s/5d9e11209b7d4536-820A3379-... that walks you through
| physical setup and theory behind the experiment (which
| among other things helped lead to special relativity).
|
| if you want more like this, see https://www.thorlabs.com/ne
| wgrouppage9.cfm?objectgroup_id=11... which is a hardware
| kit that accompanies an actual optical lab class. The
| course is online: https://www.thorlabs.com/drawings/5d9e112
| 09b7d4536-820A3379-... and gives a fairly straightforward
| introduction to optics. With this, you can easily build a
| microscope from components or any number of other nifty
| optical systems.
|
| Non-optics people (IE, programmers, etc) with enough time
| and money can learn how to do real-world optical
| experiments in their garage (this applies to astronomy
| too). For example after a significant time/money
| investment, have started building my own microscopes which
| use real-time object detection to track tardigrades to do
| behavior analysis (lest anybody feel imposter syndrome,
| trust me it took a ton of time and money and even then I'm
| not quite at the level of a good grad student).
|
| It's not my favorite but you can also read
| https://www.amazon.com/Perfectionists-Precision-Engineers-
| Cr...
|
| If you want to truly go down the rabbit hole,
| https://pearl-
| hifi.com/06_Lit_Archive/15_Mfrs_Publications/M...
| acqq wrote:
| Wonderful answer, thanks!
|
| Do you know if the "Michelson-Morley educational kit" is
| really enough to achieve the accuracy of the original
| experiment or is it just to make "any" functioning
| interferometer?
| dekhn wrote:
| I'm pretty sure it exceeds the accuracy of the original
| experiment. I think not being based on a trough of
| mercury is pretty important as well. But the manual shows
| several types of interferometers that can be built in lab
| courses.
| acqq wrote:
| Still, I see it is actually called "Michelson
| Interferometer Educational Kit", not "Michelson-Morley"
| and the user guide I'm reading (your link gives "The
| resource you are looking for has been removed", so I've
| clicked on the "User Guide" on the page instead) also
| takes care to never directly mention Morley or to suggest
| that the same experiment can be reproduced with that kit.
| epberry wrote:
| I absolutely love LIGO. YC actually did a great interview with
| one of the lead physicists on the project where he described some
| of the technical hardware and software challenges -
| https://www.youtube.com/watch?v=1D2j8nTjOZ4
| jackmott42 wrote:
| That's the guy who when someone told him they got their first
| detection was incredulous "I don't have time for this" or
| something to that affect, because he assumed it was a false
| positive to have gotten something so quickly, but it was real!
| throwawaymaths wrote:
| How do we know it was real and not overinterpreting noise
| again?
| kmote00 wrote:
| It's my understanding that it was correlated by data from
| the twin facility on the other side of the country.
| Gare wrote:
| https://en.wikipedia.org/wiki/GW170817
| bsder wrote:
| That event is _amazing_.
|
| I had no idea how much cross correlation they produced
| (see the "Scientific Importance" sections). I love the
| fact that measurements got like _10 orders of magnitude
| or more_ better--that 's just absolutely absurd.
| borissk wrote:
| Since learning about gravitational waves I was always curious if
| a type III civilization could potentially use them as a weapon.
| abecedarius wrote:
| Pretty hard to direct.
|
| If you've set up a close-orbiting neutron star binary and
| you're in a military frame of mind, one thing you could do is
| accelerate missiles to a good fraction of lightspeed. (Same
| principle as the gravity assists used by planetary probes like
| Voyager.) The tides would limit the practical size of the
| missile, though I haven't tried to compute this limit.
|
| (I don't consider this comment to be aiding the interstellar
| enemy, it's too obvious.)
| saiya-jin wrote:
| I dont think so, they go in all directions as a shockwave, pass
| through everything including black holes (even though it would
| warp it a bit), so its dark forest signalling basically to
| whole universe.
|
| Since we came to exist so early in the overall age of universe,
| there is absolutely no chance we are the only sentient civ
| across hundreds of billions x hundreds of billions/trillions x
| nr of planets realm.
|
| Super focused super dense ray of very hard gamma rays/cosmic
| rays should do any trick required for anything made out of
| matter. Or just swipe left with a black hole or two.
| MaxikCZ wrote:
| Correct me if I am wrong, but since not even spacetime can
| escape blackholes, even gravitational wave would get
| swallowed, wouldn't it? Of course, since we can't "point"
| gravitational waves in a certain direction, because of the
| rest of the wave traveling around the hole would basically
| propagate it even directly behind blackhole (from perspective
| of source), but that's because the wave goes around, not
| trough.
|
| Or do grav waves really pass ~trough~ black holes?
| borissk wrote:
| Hmmm, gravity does escape black holes, so maybe
| gravitational waves do too.
| sparker72678 wrote:
| Maybe? There would be far less energy-intensive ways to wipe
| other civilizations out of the universe, though.
| dekhn wrote:
| step 1: arrange two black holes near your enemies step 2: wait
| 2 billion years
| kadoban wrote:
| Seems orders of magnitude too difficult to be worth it. If you
| can approach that level of energy, pointing a gamma ray burst
| sounds more fun. Or just throw some rocks at fractions of c.
| cde-v wrote:
| Anything can be used as a weapon.
| bsder wrote:
| Any sufficiently advanced propulsion also qualifies as a
| weapon.
| HansHamster wrote:
| First thing that comes to mind is a lethal dose of neutrino
| radiation: https://what-if.xkcd.com/73/
|
| Now the tricky part is probably to build a neutrino /
| gravitational wave / whatever source that is intense enough
| to be useful as a weapon without just evaporating everything
| in a supernova scale explosion before...
| mhh__ wrote:
| See also neutrino HFT
| causality0 wrote:
| One of the most interesting yet sadly least rigorous What-
| Ifs. He relies on simply scaling up a calculation in
| absorbed dose at the distance of one parsec. Neutrinos do
| not interact with nuclei the same way gamma rays do, and
| the effects of a particular amount of neutrino radiation on
| living tissue is unstudied and unknown. The paper he cites
| explicitly points this out but he ignored it.
| raverbashing wrote:
| Of course it doesn't, I think that was given by the
| relationship between neutrino count and sieverts
|
| But make no mistake, there is such a thing as a fatal
| amount of neutrinos. It's just that's a supernova mind
| boggling amount, but it exists. They do interact due to
| the weak force, which is more than neutrons do (and a
| lethal dose of those is well known)
| tommywiseausmom wrote:
| detect this gravitational wave. oh!
| _Microft wrote:
| Beside the mentioned laboratories in the US, Italy and Japan,
| there is another one in Germany albeit of much smaller size [0].
| The length of its arms are only 600m (1/3mi) each but it serves
| as testbed for technologies [1] that might later be used for
| other observatories.
|
| [0] https://www.geo600.org/ ,
| https://en.wikipedia.org/wiki/GEO600
|
| [1] https://en.wikipedia.org/wiki/GEO600#Advanced
| quercusa wrote:
| Michelson and Morley smile
|
| https://en.wikipedia.org/wiki/Michelson%E2%80%93Morley_exper...
| waynecochran wrote:
| The image at the top of the page is not a real image is it? We
| don't have real photos of black holes yet right? (except the one
| at https://www.nasa.gov/mission_pages/chandra/news/black-
| hole-i...)
| [deleted]
| sp332 wrote:
| The image is credited to the SXS Project, which does black hole
| simulation.
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