[HN Gopher] Gravitational-wave detector LIGO is back ___________________________________________________________________ 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. ___________________________________________________________________ (page generated 2023-05-26 23:00 UTC)