How does LIGO detect gravitational waves?

[@danksta7103]

Very cool looking forward to your LISA video

[@9813280938]

Wow just , wow.. The way you explain it.

[@SK-cb6wz]

5:54 this is a very good demonstration, great ❤

[@alanweinstein4319]

Required viewing by our grad students! And yes, more videos like this!

[@zhavlan1258]

😅

[@bravofighter]

Thank you for a great explanation!

[@georgiamansell]

Sick animations!

[@luckyshadowtux]

If Mr. Robot was into physics. But seriously, beautiful video.

[@rakinmunim1110]

Great Video. I still don't understand it, but I'm sure once I have fully analyzed it, I will have gained great insight. Thank you!

[@jagdishchandras8593]

Wonderfully explained ! Sharing with grad students.

[@SergioNieCas]

This video is great, thank you very much for the expaination ❤

[@arun_kishor6415]

Thank You! Please, more videos like this !

[@spal3907]

one of the best ❤❤❤

[@SK-cb6wz]

4:24 I'm still struggling to understand what that reference green line mesh is.

[@sergniko]

Very nice and understandable explanation. Thanks for you time!

[@chrisfain3448]

I love this video.

[@hannesaltenfelder4302]

I think this video answered my question "how do they know that what they measure is indeed a graviational wave and not some disturbance from somewhere else?" (22:38) However I still have a hard time imaging how incredibly precise this project must have been built... I mean what kind of construction company would even build the foundation for this 4x4km instrument? Are there specialized ones or is it all done by scientists?

[@TechEsq]

"Now *that* is a highly performing cavity." :D :D :D

[@texsetter]

thanks! two questions: - what is the meaning of the 3 small mirrors on the left? - the gravitational waves modify not only the space but also the time. How does this affects the instruments?

[@craigcahillane1063]

1) The three mirrors on the left form the input mode cleaner cavity. It's purpose is to stabilize the laser light before being input into the main interferometer. Without it, most of the input laser light would be rejected by the main interferometer, because it would not be stable enough to enter. 2) This is true, a GW modulates both space and time. The short answer to your question is the interferometer truly acts as a *timer*, since we are always firing lasers off in two directions, and measuring how long it takes for that laser to come back. If there is a difference in that time, we will detect it as a phase shift in the laser light, since the phase shift produces real light at the antisymmetric port. Maybe I can do an animation of this concept later.

[@texsetter]

@@craigcahillane1063 thanks

[@pritamroy3766]

​@@craigcahillane1063 waitibg for new videos on this topic, Im phd students and I need more videos of you in topic.

[@akta1984]

Why the laser wave lenghy is not changed while the gravitation wave is passing throught the space ? If the gravitation wave affects L it should affect the laser wave length as well.

[@peterkiedron8949]

Good question!

[@ThomasKundera]

To answer you question, it needs a better understanding of GR that I do: you need to know the difference between local coordinates and proper distance, and how a GW can let local coordinates invariant while affecting proper distances. Look for this article (should be in open access): "The basics of gravitational wave theory", by Anna Flanagan and Scott A Hughes, sept 2005 in "New Journal of Physics", Volume 7, 2005. It's explained page 15 and 16.

[@PritamG_YT]

Loved ❤ this video. We want more Physics videos in similar style of 3blue1brown in Mathematics. If there already exists some of those kind of Physics videos please let me know😀.

[@nibydcgrshbdcjd]

EM wave is moving backwards through the input mode cleaner

[@hunterabdo1952]

For understand Time is inside the detector gravitationel waves because is special realtionship between gravitationel waves and time

[@ondtsn1956]

Gravitational waves is not only cause of merging of two black holes but contrary a black hole inside of a galaxy always propogates continous gravitational waves into the galaxy.Ref to :Beyond The Light Barrier.

[@Brandon-rc9vp]

Great video! I had two questions left at the end, 1- Is the triangular gyro-looking interferometer at the front for diagnostics? and 2- shouldn't gravitational waves also have some impact on light itself?

[@cstalt]

Excellent video! One question, you note 1KW transmission power but my understanding is that LIGO uses a ~1MW laser. Just wondering what that discrepancy is about.

[@universityofnextlevelw.c.a7755]

1:41

[@themathsdude763]

hi dude, litte fleedback on the fly sound is not loud enough i think, you should try to level it with your good music ! do theses h values have units ? when you talk about them being small i think you should have added units and reminded of how a mirror has a tau and r number associated, in which they affect the refected and transmitted wave, not to go in the derivation but just quick reminder on the side, which are complex numbers i guess ? don't remember maybe you should add some text alongside animations, i mean explicitly write the nature of your notations of waves and every letter of screen i'll go back to my physics undergraduate course and come back to this video very hard work and very good visual quality, kudos for that !!!

[@craigcahillane1063]

Thanks, glad you enjoyed it. Definitely agree on the sound. "h values" in this video is referring to gravitational wave "strain", and is unitless. We usually think about it as dL/L, where L is some length, and dL is how that length changes with the GW passing through. r and tau can in general be complex numbers (and they are complex for real mirrors). In this video all mirrors are considered simple thin mirrors, and so reflection and transmission are real in this case. I had to balance the length of the video with more explanation (and honestly this video went a lot longer than intended). If you're an undergrad apply to our LIGO SURF: labcit.ligo.caltech.edu/LIGO_web/students/SURF/

[@kallianpublico7517]

How do you make your mirrors lay perfectly still and flat?

[@ezdeezytube]

From the photos it looks like LIGO has suspended their mirrors in a motion-dampening device. Still seems like there is a lot of noise relative to the size of the signal they are looking for.

[@luckyshadowtux]

what is the triangle part at the start of the optics?

[@quantumofspace1367]

Here is a new experiment for you, with wave curvatures of space-time, that is, with gravitational-wave oscillations, which can exceed noise and interference. For balance in movement, two equal angular optical horoscopes are used, installed oppositely, on a special platform made of a mechanical gyroscope, which optical gyroscopes move around each other, without angular velocity, with amplitudes of 50,000 pieces, loads on the optical paths of one loop, gyroscopes from; 1.3 G to 3.5 G and above,

[@telmosanz4734]

Could you please send me the references of the content? I wanted to do a university presentation about gravitational waves and I have to write the sources of the information I write. I would be very grateful if you sent me the information source.

[@RP-pt6qq]

what software is being used to simulate?

[@unflexian]

manim

[@K8URChannel]

How are we sure Ligo is detecting gravitational cosmic waves and not an earthquake, a bird strike or a lightning strike somewhere???

[@craigcahillane1063]

Mostly because the gravitational-wave signal has a very distinct signature. According to numerical relativity simulations, we expect the gravitational-wave emission to increase in frequency and amplitude, producing a chirp effect that increases from very low frequency to around 100 Hz or so (depending on the black hole masses). An earthquake is certaintly detected, but looks more like a low frequency rumbling that shakes the detectors around. A bird strike would look like an impulse with some slow decay, same as a lightening strike. Our black hole merger signals actually *increase* in frequency and amplitude, until they merger with a huge energy emission in GWs, then the final black hole wobbles as it decays to it's smooth final form. If we could hear it, the GW signal would probably sound something like this: kzbin.info/www/bejne/q5iVk355fJmakLs Also, we have two detectors that are a thousand miles apart, and if they see the same chirping signal within a couple of milliseconds we can be really, really sure it came from an astrophysical source.

[@revanwallace]

This sounds like if Steven Wright were a physicist.

[@universityofnextlevelw.c.a7755]

Spiritual mind mass 4:59

[@wakkawakka7624]

Wowwoowowow

[@양익서-g8j]

시각은 우리 모두의 언어라서 맘에 들어요.미적분도 모두의 언어가 되었으면 해요.

[@zhavlan1258]

Всех благ Вашему каналу. Есть физики которые понимают разницу, между прямым физическим опытом и косвенным? В прошлом у *теории светового эфира* было много косвенных подтверждений и много поддержки от авторитетных физиков, как в наше время, но только у СТО Эйнштейна. Но стоило проделать прямой опыт Майкельсону, как физика изменилась. Теперь к Вам вопрос. Вы можете сослаться на прямой опыт по определению константы скорости света? Современные технологии оптического волокна позволяют на *прямом опыте* проделывать это даже школьникам. Два варианта приборов предложены в предыдущем коммент… И мы увидим что "Свет - это упорядоченная вибрация гравитационных квантов и доминантные гравитационные поля корректируют скорость света в вакууме" у приборов в невесомости и в покое относительно ДГП, разница в проходе пути светом - ноль.

[@peterkiedron8949]

How do you know you o not measure blind injection? They did it before and you could not tell.

[@ThomasKundera]

Because they would say it if they would do it.

[@peterkiedron8949]

@@ThomasKundera It all depends who are "they".

[@ThomasKundera]

@@peterkiedron8949 : "they" are the scientists operating the system. I doubt anybody else could do anyway.

[@universityofnextlevelw.c.a7755]

0:08

[@lefterisspanoudakis3152]

My calculations don't agree with yours. For the values given in the video: ΔL = 4*10^(-18) m, P_trans = 0.5 pWatt, dP_trans/dh = 10^9 Watts/strain and h(dP_trans/dh) = 1 pWatt

[@s.a.7895]

I agree with your two first results. However, I got dP_trans/dh=2.76*10^5Watt/strain and h(dP_trans/dh)=2.76*10^(-16) Watt. Hope it helps!

[@pandzban4533]

They didn't. Next question.

[@JohnDunne001]

They didn't what? Please don't say 'detect gravitation waves'