doctorsnuggles
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How LIGO detected gravitational waves
Feb 12, 2016 8:45 AM
doctorsnuggles
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benbar
crazy how gravitation do that
Vegainthemirror
Is it actually that simple?
YannYacobi
What if the (observed) speed of light is, somehow, intrinsicly linked to gravitational forces, and the experiment unwitingly proves nothing?
sonofthemorningstar
So hoverboard is still long way to go or closer now?
SirAlbertNewton
hoverboard in space is closer now.
koed00
Where do the sharks fit in?
daletvak
Thanks to LIGO, all aspects of Einstein's theories on relativity have now been experimentally verified. Interestingly, Einstein didn't 1/2
daletvak
think we would ever be able to detect gravitational waves due to the sheer difficulty of such a feat of experimental design. 2/2
AWizardOfLoneliness
Now I wanna play this again:
YungFoxMain
I went to LIGO for a field trip in HS. My friend tied string to an action figure and threw it out the bus! I highly recommend it.
IfeltlikeIwasonaspaceship
Simple, elegant, clever experiment. 10/10 would science again
Phoenix0rion
As a mobile user, TIL a LASER beam is split up.
squintish
We're so close to finding out some real stuff about life, the universe and everything. I hope we don't make our planet uninhabitable first.
EricFromAccounts
IMMA FIRIN MAH LAAAZEERRR (for science)
myputtanescaisbetter
Laser Interferometer Gravitational-Wave Observatory (LIGO). Because I know you were wondering.
321droidbot
Thanks! You read my mind!
laternerd
Yeah, Science!
Shalala87
PUT THEM ON SHARKS
ravnicrasol
I wonder if it'd be possible to not only make this more precise but also what'd having a third axis imply.
brizzer
You scienced the shit out it. thx
Fishbasket
My old tech teacher, Mr Ingram went there to work. :)
Blastergv9
Also these lasers travel miles and the phase shift is only about 0.0000000000001 meters due to the waves
DontcallmeLen
Now put the cat in the box.
perlcat
I'm stuck on putting the lotion on its skin; I'll get around to the cat later.
ImguriansFillMySaltReservoir
And fire lasers at it. If the lasers go through, then there is no cat in the box.
asumagic
Yes but then it wouldn't be both dead and alive.
dysiode
@OP is the most qualified person to talk about two black holes hugging vigorously to produce these waves.
butttrumpet
isnt this basically an optical coherence tomographer works?
Czck
I thought this was the Michelson-Morley experiment
fujnky
It is. Just a little fancier.
Czck
Where's the compensator lens if it is the M-m experiment
fujnky
This is a radically simplified representation of the actual experiment. The paper has more info. http://arxiv.org/pdf/1602.03837v1.pdf
Czck
Thanks.
ma3axaka
How do they conclude that it is not just a mechanical vibration?
FuckKnows
Carefully.
DavidGriffithsIsMyHero
I work on LIGO: we have a huge array of sensors to monitor every possible vibration and we have extreme isolation system!
Squossifrage
I wonder how they rule out vibrations etc over such large distances?
funkjacket
technically speaking, this is a vibration. also, there's tons of talks online to learn how they conducted this test.
Legend2562
They learn the patterns of things such as radio waves which make a difference at this small of a scale. Everytime they discover a new 1/2
Legend2562
Length, that had the potential to be a gravity wave 2/2
OrionRed
Lawrence Kruass tried to explain it once...I got lost.
Nickaadeemis
They make a curve that takes into account every source of noise possible, called a strain curve, and any waves with a strong enough strain/1
Nickaadeemis
will appear much higher above all of the noise sources in the curve. Strain is essentially the squeezing done by the wave on the object.
Nickaadeemis
So if the gravitational wave strains the detector enough, it's seen as a clear signal.
marylanddd
they suspend parts of it on springs basically, but obviously precisely calculated ones, to diminish the vibrations
StanfordPines
Quadruple suspension mechanisms
WorfRozhenko
That is the exact reason there were two sites widely separated. They both saw the exact same signal, so it could not have been a vibration
MetroidPrimeHesTheBest
Yeah this is the part I don't get, or that the mirrors just weren't equidistant so they were slightly off anti-phase
HolleyRagnarok
that would be a constant signal then which you can either correct physically or mark it as baseline and calibrate any other measurement from
IHateApostrophes
Can someone explain why this is a hug discovery? Did we not already know that black holes had gravity? Quite a bit of it actually.
Fenriswaffles
Another step in reinforcing the accuracy of GR, in this case the einsteinian model of spacetime would call for gravitational waves 1/2
Fenriswaffles
This result is the first direct observation of those waves (there have be indirect observations before)
annoyingjoe
it took a tremendous amount of gravity (2 black hole) to create a signal strong enough to measure
Freshtodeaf
Everything has gravity. The fact that its a "wave" is the discovery... "Fact"*
annoyingjoe
and part of the reason it was a theory was because, in theory, such waves are very weak and difficult to detect.
dysiode
It's a hug discovery because these waves originated from two colliding blackholes "hugging" if you will
tontoj
Nicely done
Fenriswaffles
I mean...that image is of 2 neutron stars generating G-waves rather than black holes, but same thing in the end.
whatwedoinlifeechoesineternity
This is a brand new way of exploring the "dark" components of the universe, the things that don't generate light in any form. 1/2
whatwedoinlifeechoesineternity
Everything we have used up to now has been on the EM spectrum: Radio, UV, Gamma rays, etc. It's a whole new way to explore the universe 2/2
KickMeElmo
Simple, clear, has lasers. Sounds good to me.
GingerOverlord
Most of the big experiments going on are simple and clear, it's just that the science behind it makes it convoluted.
Iwanttofingeryou
train etiquette, super simple stuff
CP3oh
Yeah, I mean what's the big fucking deal? I have a laser and a couple mirrors at home. Science, pshhh...
Ohond
[deleted]
[deleted]
FrostInks
Budget cuts
jdlsharkman
Hello, am I late?
Taafish
Advanced lasers!
graehall
This feels as significant as when the Higgs was confirmed by the LHC at 125 GeV in 2013. German Fusion reactor was weeks ago too! Science!
Squossifrage
...except for the Comic Sans
graehall
I was watching a video about it just now that compares it to the discovery of XRay!
Squossifrage
Did Wilhelm Röntgen use Comic Sans?
graehall
I suspect he, and these folk, were more focused (hah, laser joke) on the information, rather than someone using a dumb font :)
Dominian
I really think that we are living in the future, now. The unpredicted new age. Feels kinda great, even though we could fuck it up royaly.
graehall
Right? Like, next to me is a small rectangle I can hold in my hand that gives me access to most of the world's knowledge, & pizza. By touch
Fenriswaffles
I mean, this is just another step in confirming a theory someone a century ago came up with. GR is ground-breaking. Still an awesome time.
Dominian
By using lasers. Also possible thanks to the same theory.
Kidiri
FUN FACT: this type of interferometer is called a Michelson Interferometer, named after Albert Michelson. Along with Edward Morley, he has[1
80percentlegs
Albert's daughter was Milly Michelson, the young girl that famously dated an autistic boy who could fly.
PermenantlyBannedClubMember
how was his landing? could he do a barrel roll?
80percentlegs
No he just kinda hovered awkwardly
Trecares
So with the result of the LIGO experiment, the luminiferous aether is confirmed, yes? XD
boobcat
a HUGE COCK!
codylishush
THE BIGGEST PHYSICIST DIIICK!
doopbasementlife
Michelson-Moorley interferometer. It was made to discover whether there was ether
cat7e
That was it, thanks. I thought the setup really looked similar to some experiment setup I had seen. But didn't remember the name.
helicotrema
That was a fun fact. I had fun.
twfeline
Michelson measured the speed of light, using a simple device that you can build.
DrMcSnugglepaws
Yeah CWRU!! Home of Michelson and Morley!
DeadBodyMovement
I wrote an exam about this today :) they also used interferometers to show that the "nether" does not exist.
whitewolf2759
I would think a fabry-pérot interferometer would be more sensitive.
roastedLAM
What's the difference between the Michelson-Morley experiment and the LIGO one?
marylanddd
Michelson-Morley was originally looking for phase changes due to the 'ether.' LIGO looks for changes due to gravitational waves/contraction
marylanddd
I can try to explain any of this further if you want
dhaves
Please!
marylanddd
will do. what in particular?
dhaves
In what way they're exposed to the gravitational waves? just lying or how?
Thra11sBa11s
Each arm of LIGO is 2.5 miles long and can detect shifts in the two beams smaller than the width of a proton. And it's getting improved!
CocoaMaster
Also, LIGO added Fabry-Perot cavities to each arm and some "power recycling" mirrors to improve sensitivity.
CocoaMaster
https://www.ligo.caltech.edu/page/ligos-ifo for those looking for the details
marylanddd
and like a million other things to make it precise
Kidiri
And accurate.
Kidiri
performed an experiment in 1887 to prove the existence of aether. However, the results were negative, and they discovered that the speed [2]
WhyAmINotASaiyan
Ey that's my last name. Also, Arther?
WhyAmINotASaiyan
Aether*?
Kidiri
of light is constant. This has led Albert Einstein to think about how it would influence physics, and thus the creation of relativity.
v3rmilion
Einstein made use of the aether concept and later regretted the cop-out. Then even more later turned out he was right. HA, bitch
OSCgal
And that is why being wrong isn't such a bad thing. They discovered something else instead!
evostars
speed of light is dependent of medium. Actually it is rate of induction. Further more, a wave is not a thing. A wave is what something does.
AlaSnackbar
Just imagine what this discovery could do to the future of science and thus make life better.
voidyman
Yeee for the Michelson Morley experiment!!
kkus
This is important not just for science but for the scientific method. Science won't stick to the hypotheses when evidence is on the contrary
bothDeadAndAlive
Sorry, you are wrong. At a speech about the MM experiment, he said he got the idea for relativity out of elektromagnetic forces
marylanddd
I thought the impetus for relativity was more about electrodynamics, but I could be wrong. That was a good explanation tho
IMayOrMayNotHaveTroubleFindingAndOrChoosingAUsername
BS summary; Black hole is MASSIVE gravity due to lack of anything (incl. electrodyn & light). Outside BH-weirdness; more realm of electrodyn
endeavour1a
Electromagnetism is very much related to electrodynamics, yes.
IMayOrMayNotHaveTroubleFindingAndOrChoosingAUsername
2 Lack of anything-Conversely too much of everything in a small space. It's a sliding scale between gravity and electrodyn. Bohr vs Einstein
CT1space3DX
heard about the discovery but had no idea this old experimental method was used to discover it. thanks so much for sharing
moedisaster
I had my "mündliche Abiturprüfung" (a final presentation to finish german high school) in physics about Michelson-Morley. I was so confused.
H3X0
You have to give a presentation to finish high school in Germany? I'd have been fucked. o.O
moedisaster
It depends where you go to school. Germany has 16 states ("Bundesländer"), all of which have different school-systems. It´s fucked up
TotalSharknado
So, since light is supposed to be he same speed, it should always be in phase when it returns. If it isn't, gravity wave. That the jist?
MagicalMeows
I like how you broke this down
CaptainBergatron
If it's the same wavelength yup
Freudberg
doesn't really sound like hard proof when put that way tho. could be some other factors at play. oh nasa...
gph456
They spent months eliminating every other possible factor to make sure. They don't want to say it was, and then find out it wasn't
Freudberg
if we're just discovering proof of gravity all these years later, we likely do not.
Freudberg
the nature of the process of elimination is such that we assume all possible factors are known.
RobertBaker
Is it bad I pictured a skeptical Christian Dad being told dinosaurs are real?
MoxRavager
They discovered this in Sept. Every day between then and now was examining other factors and they were all ruled out.
DarthFutuza
Also, gravity waves have a very specific signature so even if there's other interference like loud noises, earthquakes etc, is accounted for
Fuish
Sorry this is months later, but how? Couldn't a tiny movement (atomic radius sized) change the distance enough to interfere?
DarthFutuza
3 something else, and signifies a positive match.
DarthFutuza
Yes, but that's why the signature they're looking for is very specific. They have redundant systems as well, so even if one is bogged down
DarthFutuza
2 or malfunctioning in some way, not all of them will. If all systems show the exact same specific gravitational wave signature, it's not
eggmuffin
Exactly. Something must have changed the distance the laser had traveled. And if other variables can be eliminated, gravity remains.
MisterAmazing
Question though, how did gravity change one of the distances or rather why would it affect the two differently?
eggmuffin
1/2 A wave has a length, width, and direction of movement. Based on those values, it will interact with the two targets differently.
eggmuffin
2/2 "Wave", in this case, isn't just a metaphor, it's a description of how the spacetime literally flexes and warps.
MisterAmazing
I guess I just can't wrap my head around why it would interact with the two beams differently when they both are hit by the same wave.
eggmuffin
That's why the two stations are set miles apart, at a 90°. It only hits one of them head-on. The difference is tiny, but measurable.
MetroidPrimeHesTheBest
And there's no possibility of the mirrors not being placed in phase?
YoDaLayEWho
well if they're constantly getting the reading of waves when they shouldn't be, they'd recalibrate it
DSPKevlar
the idea is that the phase detected would be changing, so they would be constantly going in and out of phase, it isn't just a static value
eggmuffin
Yes, of course there is. Why are you assuming the dozens, if not hundreds of engineers working on this are clueless dolts?
ShirouBlue
Not only the numbers...they are probably the best ones too....
dysiode
The paper cited 1,000+ names. Are you going to get butt-hurt for them all? Better take some time off work! Take a smoke break and chiiiiiill
nacko
Why are you assuming it was a criticism of their work and not an honest question about how they account for this?
eggmuffin
If so, it was very clumsily worded. You didn't actually ask that at all. Instead, you asked something to which the answer is obvious.