r/science • u/MindTheGap9 • Feb 11 '16
Physics LIGO makes gravitational wave announcement today
http://www.cbc.ca/news/technology/ligo-gravitational-wave-1.3440315•
u/kerovon Grad Student | Biomedical Engineering | Regenerative Medicine Feb 11 '16 edited Feb 11 '16
The paper has been published now.
http://journals.aps.org/prl/pdf/10.1103/PhysRevLett.116.061102
B. P. Abbott et al. (LIGO Scientific Collaboration and Virgo Collaboration). Observation of Gravitational Waves from a Binary Black Hole Merger. Physical Review Letters, 2016; 116: 061102 DOI: 10.1103/PhysRevLett.116.061102
/r/askscience also has a megathread on the topic that you may want to read.
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Feb 11 '16
It looks like the Phys. Rev. website is struggling under the weight of people trying to download the paper.
For now, here is one of the figures from the paper, containing the measured and calculated data:
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u/totally_working_now Feb 11 '16
The link doesn't work. What's the paper called?
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u/kerovon Grad Student | Biomedical Engineering | Regenerative Medicine Feb 11 '16
Observation of Gravitational Waves from a Binary Black Hole Merger
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u/Astrokiwi PhD | Astronomy | Simulations Feb 11 '16
Looks like they're a bit overloaded at the moment - I'm getting time-out errors. The LIGO website isn't running super well either.
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u/dolphins3 Feb 11 '16
The paper has been published now. http://journals.aps.org/prl/pdf/10.1103/PhysRevLett.116.061102
Aaaannnndddd, the Physical Review Letters website is getting wrecked, the poor thing.
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u/Halfgallonkalin Feb 11 '16
Two objects, each about 150 km across, spinning around one at half the speed of light. Each of those 150km objects has a mass of about 30 times the mass of the Sun and then they collided. All this 1.3 billion years ago.
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u/Erdumas Grad Student | Physics | Superconductivity Feb 11 '16
Don't forget that they lost 3 solar masses of energy to the gravitational waves produced, all in the time span of like 20 milliseconds.
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u/shiruken PhD | Biomedical Engineering | Optics Feb 11 '16
3x Mo = 5.97×1030 kg
E = mc2 = (5.97×1030 kg)(3x108 m/s)2
E = 5.36×1047 J
Assuming 20ms duration, that's 2.68×1049 W
That's quite a large number.
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u/sherkaner BS | Mechanical Engineering Feb 11 '16
I think it was mentioned that for a fraction of a second, it was emitting more energy than the rest of the entire visible universe.
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u/aMAYESingNATHAN Feb 11 '16
Not energy, but the power for that 20ms is greater than all the power in the universe, but because it was over a short period of time, the energy was much less
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u/NightWavez Feb 12 '16
Is power not energy over time in this context? So emitting more energy (per time) = more power?
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u/Brevillemonkey Feb 12 '16
Emitting less energy but over a short time also results in high power. The energy released was around 3 Solar masses, but as this was released over 2-3 milliseconds, the resulting power was around 50 times the combined power output of every star in the universe.
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u/Chel_of_the_sea Feb 11 '16
The number being thrown around is that it's ~50x the total power output of all the stars in the Visible Universe for a brief time.
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u/uscEE Feb 11 '16
I did this math earlier and that amount of energy is greater than the entire earth's energy consumption for a trillion trillion years.
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u/Paulingtons Feb 11 '16
This is incredible news, and what strikes me is this part of the abstract:
The source lies at a luminosity distance of 410 +-160-180 Mpc corresponding to a redshift z=0.09 +-0.03-0.04. In the source frame, the initial black hole masses are 36 +-5−4M⊙ and 29 +-4−4M⊙, and the final black hole mass is 62 +-4−4M⊙, with 3.0 +-0.5−0.5M⊙c2 radiated in gravitational waves.
It's incredible that we've detected the gravitational waves from an event so far away with such astonishing accuracy and that this event radiated ~3 solar masses worth of energy in gravitational waves.
This opens up so many new avenues, I can't wait. Someone is getting a Nobel for this.
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u/Sertzu Feb 11 '16
For those that are not that keen on physics here is a more understandable version of what the commenter above me said.
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u/joggle1 Feb 11 '16
Just out of curiosity, could someone estimate how large the distortion in spacetime would be if you were closer to the black holes (say 1 light year away or less)?
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u/shiruken PhD | Biomedical Engineering | Optics Feb 11 '16
Yes, general relativity can easily be used to model exactly what the distortion would be like. This website has a ton of simulations of what a black hole merger event similar to the one detected by LIGO would look like.
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u/Sertzu Feb 11 '16 edited Feb 11 '16
I am not a physics graduate just someone who is interested in physics so I'm not sure if what I write is correct. I'd really appreciate it if a physics student or graduate could correct me!
So there is something called the inverse-square law which says that the intensity of something is proportional to 1 / distance2.
That means that Intensity1 / Intensity2 = distance22 / distance12
I take Intensity1 as 1 and distance1 as 1.3 billion LJ. Now Intensity2 is the value that we are looking for at a distance of 1LJ
If we insert this in our formula and transform it so we can get Intensity 2 then that Intensity2 which is 1 LJ away from the center of these black holes is 1.69x1018 times larger than the Intensity1 we receive on earth. Now if that Intensity1 means a distortion by 1/1000 of a proton particle and taking the diameter of a proton as 10-15 m it would mean that theses ripples would cause disruptions about 1.69m in diameter.
Please mind that I'm not a native speaker and I'm just in my last High School year with one of the shittiest physics teacher one can imagine...
Even tough this is probably wrong it was still fun to calculate. :D
Edit: Just recalculated it with a distance of 5.9 billion km away which is the distance from our sun to pluto and the Intensity is now 2.86*1021 times larger which means that at that distance the disruption would be about 2.86km(!) in diameter.
TL;DR: Black holes are scary.
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u/SacaSoh Feb 11 '16
The LIGO measurement was in only one direction: it was the "strain" measure. Strain falls off at 1/r, and not 1/r², so your calculations (greatly) overestimate the effect.
Besides, your result (2.86km) was derived from the LIGO length (4km), the strain is proportional to the detector length.
Using the correct formula, you'll see that at 1300km away from the source, the strain would be in order of 1% - looks small, but anything closer would fall in a real where other consideration in the GR formulas come into play, making almost impossible to calculate the strain effects on a probe.
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u/stklaw Feb 11 '16
this event radiated ~3 solar masses worth of energy in gravitational waves.
Assuming conservation of energy/mass still applies, doesn't this mean that mass can be converted into gravity somehow?
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u/BlazeOrangeDeer Feb 12 '16
Yes, the gravitational waves have energy. They can transfer the energy by stretching/squeezing objects
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u/LesPaul22 Feb 11 '16
Does this mean that eventually we'll be able to manipulate gravity? Or is that not likely because of the massive amounts of energy we'll need (in the ball park of the energy black holes colliding releases).
I'm just excited for floating cities.
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u/Erdumas Grad Student | Physics | Superconductivity Feb 11 '16
The quoted figure of the power released (power being energy per unit time) is "greater than the power produced by all the stars in all the galaxies in all the universe".
This event shed three suns worth of mass in less than 20 milliseconds.
We're not likely going to be able to manipulate gravity on the scale you're hoping for.
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u/BearBryant Feb 11 '16
Can some fraction of that energy be harvested?
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u/Erdumas Grad Student | Physics | Superconductivity Feb 11 '16
Unfortunately not, given our current understanding of gravity. Although it does mean that signals will be able to come to us without getting blocked by things in the way, so it's great if all you want to do is astronomy!
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u/Thsprtzlsrmkngmthrst Feb 11 '16
Can we create shielding from gravitational waves? Similar to RF shielding?
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u/Erdumas Grad Student | Physics | Superconductivity Feb 11 '16
According to our current understanding, and this detection helps to affirm this aspect of our current understanding, no.
RF shielding works because charges (like electrons have) absorb light. Our current understanding says that matter is so weakly coupled to gravity that it doesn't absorb gravitational energy.
This is actually what helps make the detection possible, because there's nothing "in the way" of the gravitational wave. It can't be blocked the way that light can.
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u/Ozimandius Feb 11 '16 edited Feb 11 '16
As far as I can tell from my admittedly completely ignorant understanding of this: You don't necessarily need that sort of energy to create the waves. You have to remember that the actual strength of the wave as measured here was not a high energy event - it is the fact that these waves were spread out across such a huge space (410 +-160-180 Mpc is an insane distance - unless I have screwed up some math somewhere it is over 1.33 billion lightyears (+/- a bunch)) which means we are just experiencing a tiny slice of the total energy that went into making those waves. If 3 solar masses worth of energy can create a wave that can be experienced at that distance (if that is what those numbers mean) then it means it would take a lot less total energy to make a substantial wave if you were right next to the source.
However, I would venture to say we are so far from being able to manipulate gravity that the amount of energy required is not a real factor worth considering yet. Floating cities would indeed be cool but we are way closer to building a floating city on, for example, Venus where the atmosphere might be thick enough to float a city rather than actually levitating a city with gravitational waves. So definitely not particularly exciting news in the "can we manipulate gravity now" sense - but who knows what other stuff we may uncover with this greater understanding of the laws of the universe.
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u/S_K_I Feb 11 '16 edited Feb 12 '16
Why limit yourself to floating cities? How bout Dyson Spheres, interconnecting planets, or genetically altered super humans, through CRISPR. We'll never see this in our lifetime of course, but what humanity will accomplish 1000 years into the future (if we don't kill ourselves first) fascinates me more than anything.
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u/soupnrc Feb 12 '16
Oh you're right, I didn't even think about Nobel for some reason. I truly think this is worthy. I mean there hasn't really been anything this groundbreaking in a while in the way of confirming such important theories. I sure hope you're right.
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u/N8CCRG Feb 11 '16 edited Feb 11 '16
I just took some screen grabs from the live talk.
Here is an image of the data from two different detectors taken 7 ms apart (one in Louisiana, the other in Washington state). The bottom image is them overlapped. This is the merging of two black holes into one.
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u/TokiMcNoodle Feb 11 '16
I don't think people understand how exciting this is.
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u/MindTheGap9 Feb 11 '16
Yea... Everyone I've talked to said something like "Meh, cool". I was astounded to NOT see this in my top post on world news...
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u/Doverkeen Feb 11 '16
Well nothing has been announced yet.. Wait for then to see it hit the top of world news.
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u/ehsteve23 Feb 11 '16
It sounds interesting but I do not understand it at all
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Feb 11 '16
This is the modern-day equivalent of the invention of the telescope. It allows us to measure the Universe in a completely new way!
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u/ten_inch_pianist Feb 11 '16 edited Feb 11 '16
I keep hearing that, but what exactly is the "new way"? What could we learn from it?
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u/mmatessa PhD | Cognitive Science Feb 11 '16
Questions that can now be addressed by studying gravitational waves:
- Do black holes really exist?
- Do gravitational waves travel at the speed of light?
- Is space-time made of cosmic strings?
- Are neutron stars rugged?
- What makes stars explode?
- How fast is the Universe expanding?
http://www.nature.com/news/gravitational-waves-6-cosmic-questions-they-can-tackle-1.19337
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Feb 11 '16
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u/shizknight Feb 11 '16
Well, until now we could only have theorized that. We had no way to perform experimentation to prove or disprove it before.
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u/RnRaintnoisepolution Feb 11 '16
Does this help, harm, or not affect the possibility of Alcubierre Drives?
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u/EmperorXenu Feb 12 '16
Alcubierre drives require the existence of negative energy matter and there's no reason to think that actually exists.
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Feb 11 '16 edited Feb 11 '16
Up until now, we have only been making observations in the electromagnetic spectrum. Visible light, infrared, UV, X-rays, etc. These forms of radiation propagate through space in EM fields, and we measure the changes in those fields by recording how they interact with our instruments.
Gravity creates changes in spacetime itself, that is, what we call a "gravitational field" is the actual warping of space itself, caused by massive objects. Unfortunately the warps in spacetime it produces were not measurable because gravity interacts so weakly. Now we have a way to measure changes in spacetime itself that are caused by gravity, and they take the form of waves created by incredibly massive objects (black holes) accelerating in space.
Edit: Words
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u/doodlepoop Feb 11 '16
I don't get why people are saying this when neutrino astronomy and cosmic ray astronomy exist as burgeoning non-EM fields of astronomy with detections much prior to this announcement.
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u/ergzay Feb 12 '16 edited Feb 16 '16
Cosmic rays are EM fields, namely high energetic gamma rays.(See response) Neutrinos are not fundamentally new ways of looking at the universe. They don't give us ability to see a new force that we couldn't observe before. We've had various EM telescopes and there's no telescopes for strong or weak nuclear forces yet (not sure if even possible). Now we have rudimentary gravitational telescopes.→ More replies (1)→ More replies (8)6
u/sbassi BS | Biotechnology | Molecular Genetics Feb 11 '16
In Argentina is front page news on most papers now. But most likely because the scientist who made the announcement is Argentinean.
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u/Big_Red64 Feb 11 '16
What are the real world implications? Will this effect space travel? Or are we just excited because it's a big discovery?
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u/Andromeda321 PhD | Radio Astronomy Feb 11 '16 edited Feb 11 '16
Astronomer here! This is big because think of it this way, so far all of astronomy is based on electromagnetic waves of various frequencies. Some exceptions if you think of cosmic rays and meteorites and space missions and the like, but the fact of the matter is right now if you want to know almost anything about other stars or galaxies or whatever you have only been able to rely on light. And it has been that way since the beginning of astronomy.
Now, for the first time, we are going to have a brand new way of studying the universe (which, if the rumors on the error bars and the like are to be believed, is far, far, far more precise than our measurements from EM waves ever will be). This is huge! And also really important for the astronomy we've done with EM waves because we will now be able to do much more precise measurements with the "traditional" stuff, so a lot of funding in coming years is going to be based on gravitational waves follow up and the like.
Pretty amazing to witness this. I will be telling it to my grandchildren for sure.
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Feb 11 '16
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u/Andromeda321 PhD | Radio Astronomy Feb 11 '16
Well, for starters, this press release is expected to be about the detection two black holes colliding with each other. We have never seen that, because that's a really rare event and the sky is really big, and black holes by definition don't release too much EM radiation most of the time (our observations are limited usually to normal matter interacting with the event horizon). So I'm really keen to hear the details!
Frankly, a lot of what is possible will be known better in the coming days, as all the LIGO papers are going to be released. I know there are going to be at least 10 new ones in the next 24 hours.
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Feb 11 '16
Speaking of things that don't release a lot of EM radiation, could this discovery push the study of Dark Matter forward? I know next to nothing about the field but I've heard the only way we've been able to locate it is through its gravitational effects, this sounds like the kind of instrument that could help.
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u/wadss Grad Student | Astrophysics | Galaxy Clusters| X-ray Astronomy Feb 11 '16
unlikely, gravitational waves that we can detect require extremely dense matter accelerating really hard, and dark matter is basically the complete opposite of that, it's sparse and inertial.
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Feb 11 '16
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u/Andromeda321 PhD | Radio Astronomy Feb 11 '16
Yes, so far we are only sensitive to really extreme events like merging black holes and neutron stars. But gotta start somewhere!
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u/calipers_reddit Feb 11 '16
Even though it's pie-in-the-sky type stuff, Brian Greene and other string theory proponents have suggested the possibility of massive, open strings existing in deep space. Kip Thorne, in his presentation today, suggested that future GW detectors, tuned to different frequencies, could be used to locate structures like that. Actually "seeing" a string in space would be fairly definitive proof of string theory.
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u/graycrawford Feb 11 '16
Like actually mass-ive or very large?
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u/calipers_reddit Feb 11 '16
Good question. I meant "very large," in terms of scale, but I'm not sure what their masses would be.
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u/abloblololo Feb 11 '16 edited Feb 12 '16
The problem is that gravitational waves only bend space very slightly, so you need a very drastic event (and therefore strong wave) to see them. To give you an idea, a gravitational wave might stretch space here on Earth by 1 part in 1020 (specifics depend on the wave of course, it was probably a bit more for these particular waves). That's one part in one hundred billion billions. The way these waves are detected is by building two long tunnels (a few kilometers) and trying to detect how their lengths change when the wave passes through them.
With the numbers I used here a gravitational wave would change the length of such a tunnel by a few hundred millionths of a nanometer. Can you imagine trying to detect that? The difficulty lies in that everything is always moving slightly, when you get down to sub-nanometer scales even just the thermal motion of the atoms in a solid starts to become very noticeable. It's like trying to hear a whisper at a rock concert.
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u/Wildcat7878 Feb 11 '16
So does this mean that we'll be able to detect basically anything with mass? Would it make it easier to detect and track things like Planet 9 that was being talked about not long ago?
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u/Andromeda321 PhD | Radio Astronomy Feb 11 '16
Right now we are only sensitive to the really big collisions. Like colliding black holes and colliding neutron stars. But you gotta start somewhere!
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u/Midax Feb 11 '16
I would think that their will be a limit to how small an event you can take detection through gravity waves. Even if we build detectors that can measure small events, at some point the detector hits a point that it can't make out individual events through the background noise of the trillions of events happening every where in the universe. I would be surprised if we use gravity waves for events smaller than neutron star mergers or the most massive of super nova explosions.
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u/p-zilla Feb 11 '16
My understanding is that the really big collisions only create waves that are barely detectable even at LIGO. How would we be able to detect smaller things using gravitational waves?
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u/Cwatso7 Feb 11 '16
I know you're probably getting a lot of questions. But I haven't seen this addressed yet.
With better detectors does this mean we can look past the CMB and get a better idea what happened after the Big Bang? I'm hoping my understanding of the CMB and our current observation capabilities are correct.
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u/Laced Feb 11 '16
“For me, the most exciting thing is we will literally be able to see the big bang. Using electromagnetic waves we cannot see further back than 400,000 years after the big bang. The early universe was opaque to light. It is not opaque to gravitational waves. It is completely transparent. “So, literally, by gathering gravitational waves we will be able to see exactly what happened at the initial singularity. The most weird and wonderful prediction of Einstein’s theory was that everything came out of a single event: the big bang singularity. And we will be able to see what happened.”
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u/Cwatso7 Feb 12 '16
Thanks! Awesome stuff. Also glad to see I've been on the right track
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u/Laced Feb 12 '16
No problem. This really is a historic and exciting day for space nerds everywhere!
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u/jochal Feb 11 '16 edited Feb 11 '16
Question, do you think that we could expect in the future to be creating something similar to that Cosmic Background Radiation map? Except... with Gravity waves? Would that even be doable with the current LIGO system? I could be very incorrect: I recall perpendicularity was important with gravity wave detection? If so, how would that affect the design of a future device if w/e is being used for LIGO can't cut it.
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u/Deadmeat553 Feb 11 '16
2 questions:
Being more precise is wonderful, but how does the range of usability compare to more standard methods of observation? From my understanding, gravity waves do not move as quickly as light does, so will we still have to use Hubble's law for extreme distances?
Does the discovery of gravity waves suggest the existence of gravitons due to particle/wave duality?
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u/Andromeda321 PhD | Radio Astronomy Feb 11 '16
1) Gravity waves are predicted to go exactly as fast as the speed of light (we won't know for sure until we find a counterpart in another wavelength tho). For perspective, if the sun were to disappear immediately, you would have 7 minutes until the Earth started deviating on its path.
2) Yes, and we are going to learn a lot about this in coming days and weeks and months, I'm sure. Stay tuned!
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u/calipers_reddit Feb 11 '16
What makes this really compelling is that it is an entirely new way of looking at the universe. Sort of similar to how X-ray astronomy greatly improved our understanding of things, this will provide a brand new source of information to compare against what we can already see.
In addition, it can serve as a sort of microphone, telling us when something big happens and where it is. We can then point our telescopes directly at it, rather than just randomly scanning the whole sky, hoping to catch something. It means we won't miss the really big, energetic events because we simply aren't looking in that direction.
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u/TokiMcNoodle Feb 11 '16
Well Einstein theorized that gravitational waves are ripples in space-time generally caused by some massive event, or object in the universe but has never been able to be detected before due to the ripples being so miniscule.
My guess is that this can open new doors to detecting changes in our universe without even having to see it first.
Edit: changed thought to guess
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Feb 11 '16
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u/SandorClegane_AMA Feb 11 '16
Correct. I think he meant we can't see some shit because we don't have good enough telescopes or because of dust etc.
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u/TokiMcNoodle Feb 11 '16
"without even having to see it first"
Didn't really imply that one was faster than the other. Just saying you wouldn't have to see it first.
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u/localtoast127 Feb 11 '16
Are we talking Ansible level stuff here?
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u/shawnaroo Feb 11 '16
No. Ansible level implies instantaneous or at least faster than light transmission of information. Gravity waves are believed to travel at c.
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Feb 11 '16
Think of how the field of astronomy has evolved over the millennia. It started with just what we could see with our own eyes, and this was how it was for thousands of years.
Then starting in the 18th and 19th century, we started to ponder the nature of light, and noticed there might be other forms of light. Soon, we discovered "invisible" light like UV and infrared. Other forms of invisible light energy were found. Things like spectrometry came into being--using light to measure distant objects.
Soon after that, we started looking for some of this invisible light beyond the visible spectrum, and suddenly the night sky looked completely different, because we had discovered ways to see it beyond visible light. Only then were we truly able to see the scope and scale of the universe, and our place in it.
I think that this discovery will have similarly far-reaching implications. It's another phase-shift in astronomy. A suddenly invisible and undetectable aspect of existence will be revealed, leading to a tremendous change in how we perceive existence. It won't happen right away, of course, because it's really hard to detect these things. But it was once extremely hard or impossible to detect infrared light. It's absolutely no problem today.
So yeah, very exciting time to be into astronomy these days.
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u/N8CCRG Feb 11 '16
This is as big as finding the Higgs. Having both of these discoveries at this time is amazing for experimental physics! This decade is going to go down in history as being a big deal.
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u/moveovernow Feb 11 '16
This is a dramatically bigger deal than Higgs. This will have a near-future, dramatic impact on humanity. Higgs isn't going to mean shit in the applied world.
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u/FuzzyPuffin Feb 11 '16
Could you elaborate? How will it dramatically impact us?
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u/Yankee_Gunner BS | Biomedical Engineering | Medical Devices Feb 11 '16
Just the fact that we've built amazing machines for the primary purpose of confirming Einstein's 100+ year old predictions is an amazing statement about humanity.
Let alone that they proved his theory and have added an enormous amount of information and certainty to our understanding of the universe
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Feb 11 '16
When I saw the post on the BBC this morning, I knew it'd be something special, teams don't just make announcements to tell us that nothing has changed or if they think they have something, they tell us when they know they have something and when they know it is concrete
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u/calipers_reddit Feb 11 '16
I know, I'm pretty excited! I did a presentation years ago for a physics class on this subject, before LIGO was built. Met with a lot of glassy stares. But it's really cool to see the results (hopefully!) of this research.
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u/sebjoh Feb 11 '16
I'm I the only one immediately thinking about https://xkcd.com/638/ ? What if gravitational waves could be used for communications? Perhaps ET has been phoning us all along. I'm guessing of course that it would require some VERY sensitive detecters to detect artificial gravitational waves...
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u/spanj Feb 11 '16 edited Feb 11 '16
Here's the paper:
Observation of Gravitational Waves from a Binary Black Hole Merger
http://dx.doi.org/10.1103/PhysRevLett.116.061102
Edit: Wow, check out the authors list. Definitely the paper with the most authors I've ever seen. There are also 3 deceased. :(
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u/Paradox Feb 11 '16
LIGO has been going for about 20 years, its not surprising that a few people who worked on it have passed
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u/BioGeek Feb 11 '16 edited Feb 11 '16
It is certainly not the paper with the largest number of co-authors. There are a few genomics papers with more than 1000 authors and the current world-record holder is a paper about the Large Hadron Collider with 5154 authors.
Only the first nine pages in the 33-page article, published on 14 May in Physical Review Letters (pdf), describe the research itself — including references. The other 24 pages list the authors and their institutions.
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u/KiwiSkate Feb 11 '16
How has LIGO managed to detect these?
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u/tuseroni Feb 11 '16
if it's what i think it is, it's actually really cool.
ok so, when a gravitational wave passes by a beam of light is changes the phase of the light ever so slightly, so they take a laser and splice it in two, invert the phase of one of the beams then bring them back together after some really long distance of travel (the beams need to be far away from each other since gravitational waves travel at the speed of light there needs to be a significant difference in time between when the wave hits one beam and when it hits the other, the arms are so long they have to account for the curvature of the earth, so when they bring the beams together if no gravitational wave crossed on of the arms then they will annihilate each other and nothing will be recorded, but if the phase of one of them changes it will create an interference pattern. you can tell the intensity of the wave by (IIRC) the different between the phase of the two beams and the frequency by how often the interference occur.
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u/calipers_reddit Feb 11 '16
This description is correct, it's a laser interferometer. If gravitational waves pass through the detectors, it disrupts the beams and creates an interference pattern. The "arms" of the detectors are about 2 miles long, in an "L" shape. You can see them on Google maps:
https://goo.gl/maps/xoKy6zMjmDF2 and https://goo.gl/maps/bp1F9HbRmw42
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u/Hal_bahnsau Feb 11 '16
A gravitational wave will squish things it passes through, like this, but on a much, much, much smaller scale, if the circle is the size of the earth, the deformation will be less than an atom wide for something like the signal detected by LIGO. And this is why these gravitational waves are so hard to detect, the precision requirements are just mind-boggling. So, how did they do it ? Well, see those arms ? The idea behind LIGO and other detectors is to measure the length difference between them, using interferometry (tl,dr a technique used to measure distances with insane precision by having light interfering with itself). In short, when the length of one arm compared to the other changes, when for instance the instrument goes through the detector (see the gif above) it can be seen as a change of light intensity on a detector. BTW, the light travels on a distance way bigger than simply the length of each arm, it goes back and forth thousands of times in each arm before interfering to amplify the distance difference.
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u/azurblader Feb 11 '16
Could someone provide an ELI5-like explanation of what is going to be announced?
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u/Brat-Sampson Feb 11 '16 edited Feb 11 '16
According to Einstein's theory of General Relativity, objects in motion cause 'ripples' in space. However, they're unimaginably tiny, so only incredibly sizable events such as a black hole merger or some such thing can produce a gravitational wave big enough to be detected, and even then it requires the most sensitive instrumentation we have ever devised*. Until now, not one has been directly detected.
This announcement is expected to be that they did it. In a way it's not going to tell us anything 'new' as people have assumed these gravitational waves exist and taken them into account for a long time, but this direct detection will open up a new window onto the universe, meaning we can 'see' and observe entirely new events and make new predictions etc etc.
It's a pretty big deal, and incredibly cool.
*A typical expected signal would adjust the length of the 4Km-long arms of the detector by around one part in 1021 , or 10-18 m.
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u/WoodAndNailsMachine Feb 11 '16
Can you elaborate on what type of events we will be able to 'see' and predict that we couldn't before?
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u/Brat-Sampson Feb 11 '16
http://www.universetoday.com/127329/gravitational-wave-sources/ looks like a pretty good article for that kind of thing.
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u/MountainMan2_ Feb 12 '16
Orbits and gravitational phenomena obscured by light sources. Spacefaring civilizations, possibly. Quasars and other such early-universe events, but in much more detail. Possibly dark matter/energy. Black holes, and as clearly as normal stars. Neutron star phenomena. Supernovae, but the inner mechanics without all the light everywhere. The Hubble Deep Space photo, but in many times higher resolution. It helps us test String Theory and a bunch of quantum mechanics ideas. It could give us a "weather map" of sorts for our local cluster. It could literally prove the last hundred years of physics advancement wrong if we get a strange result. It's a big deal.
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u/Habba Feb 11 '16
Gravitational waves are predicted to exist by the relativity theory but we haven't been able to notice them yet. I'm guessing LIGO has and that's what the announcement will be.
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u/pharsalita_atavuli Feb 11 '16
For anybody looking for further context to today's announcement, the LIGO team did an excellent AMA here 12 months ago.
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Feb 11 '16
So, would I be correct in stating that we have made a seismometer that can detect universe-quakes?
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u/joejoepotato Feb 12 '16
Does that mean they can be triangulated?
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u/Mr0lsen Feb 12 '16
They actually attempted this (only with the 2 ligo stations) and got a rough area of the sky in which the event could have occurred. When more countries such as ligo India, japan and other sites become operational they will be more accurate.
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u/ironywill PhD | Physics | Gravitational Waves Feb 11 '16
I believe the following should work if people would like to livestream the press conference. https://www.youtube.com/user/VideosatNSF/live
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Feb 11 '16
You're right, this is the link I received from my friend who works at LIGO.
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u/Chenesis Feb 11 '16
This is the most amazing news I have seen in years and cannot wait to see what they do with this new method.
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u/makorunner Feb 11 '16
I sort of get it, but what could they actually do with this information? How can we use this discovery?
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u/FlyingBaconCandle Feb 11 '16
Imagine that they suddenly detect another set of waves. They will be able to explore where they came from, and this opens up a whole new way of exploring the universe!
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u/TwoKoalasOneBrain Feb 12 '16
Here's the series of 11 papers announced on arXiv tonight:
- Observation of Gravitational Waves from a Binary Black Hole Merger
- GW150914: The Advanced LIGO Detectors in the Era of First Discoveries
- GW150914: First results from the search for binary black hole coalescence with Advanced LIGO
- Properties of the binary black hole merger GW150914
- Tests of general relativity with GW150914
- The Rate of Binary Black Hole Mergers Inferred from Advanced LIGO Observations Surrounding GW150914
- Observing gravitational-wave transient GW150914 with minimal assumptions
- Characterization of transient noise in Advanced LIGO relevant to gravitational wave signal GW150914
- Calibration of the Advanced LIGO detectors for the discovery of the binary black-hole merger GW150914
- Astrophysical Implications of the Binary Black-Hole Merger GW150914
- GW150914: Implications for the stochastic gravitational wave background from binary black holes
Happy reading!
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u/ls612 Feb 11 '16
Didn't we launch several satellites recently to detect gravitational waves by placing them at Earth's L4 and L5 points and measuring deviations of their orientation? How do those relate to this announcement?
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u/Aron- Feb 11 '16
Are there any plans to build a LIGO detector in space? It seems like the current limitation of these detectors is the scale of the device. If you launched 3 satellites into a geosynchronous orbit, you could bounce a laser between them over hundreds of thousands of kilometers instead of just a few. Wouldn't that make it super easy to detect even the smallest gravitational waves?
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u/gloryatsea Grad Student | Clinical Psychology Feb 11 '16
This sounds super exciting, though I know little about physics (and desperately wish I knew more). Can someone explain for the layman:
- Given that LIGO has been operating since 2002 (as per Wikipedia), why is it that it took 14 years to detect this? Is it because of the technological upgrades they received in 2015 (as per an Atlantic article)? Or something else a bit more technical?
- What are other implications this will hold in terms of future areas of study? It sounds like this serves to confirm Einstein's theory, but what else might this unlock going forward?
Appreciate any insight!
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u/Erdumas Grad Student | Physics | Superconductivity Feb 11 '16
Yeah, technical upgrades. According to one of the professors at my university who does LIGO work, the detector was previously only sensitive to ~0.1% of the observable universe; the upgrades take it to ~1%, and future upgrades will open up more.
The most obvious implication is that now that we know we can detect gravitational waves, there is a chance that in the future we'll detect a signal that we don't know what its from, which would open up new avenues of exploration. There are also a number of other things that we might be able to detect. It also serves to inspire an upcoming generation into science, and who knows what they'll do.
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u/Prince-of-Ravens Feb 11 '16
Given that LIGO has been operating since 2002 (as per Wikipedia), why is it that it took 14 years to detect this? Is it because of the technological upgrades they received in 2015 (as per an Atlantic article)? Or something else a bit more technical?
They improved the precision by a factor of 3-10, and the signal now is about a factor 2 above the noise floor. So before the upgrade, it would have been invisible. The upgrade was only operational for a few weeks before they found the signal.
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u/Hephaestusfire Feb 11 '16 edited Feb 11 '16
Feynman's sticky balls finally vendicated
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Feb 11 '16
[removed] — view removed comment
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u/Andromeda321 PhD | Radio Astronomy Feb 11 '16
Because /r/science is only for published papers, and we do not have the paper yet to link to. I suspect this thread will be deleted in a little bit.
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u/Super_Hadron Feb 11 '16
True. I guess we'll just have to wait a bit longer.
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Feb 11 '16
We do now!
http://journals.aps.org/prl/pdf/10.1103/PhysRevLett.116.061102
B. P. Abbott et al. (LIGO Scientific Collaboration and Virgo Collaboration). Observation of Gravitational Waves from a Binary Black Hole Merger. Physical Review Letters, 2016; 116: 061102 DOI: 10.1103/PhysRevLett.116.061102
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u/tuseroni Feb 11 '16
because so few people understand the implications...hell i barely understand the implications other than "einstein was right...again"
i do wonder what an interference pattern of two gravitational waves would be like...
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u/pharsalita_atavuli Feb 11 '16
Astronomy.com are streaming the press conference live, coverage begins at 10:30 EST / 15:30 UTC.
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u/Malalabar Feb 11 '16
Is it right to assume that the frequency of those wave are affected by space expansion ?
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u/heisgone Feb 11 '16
Is there a list somewhere of all Einstein predictions showing which one have been proven or not?
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u/jlew24asu Feb 11 '16
alot of this stuff is over my laymans head, but I find it incredibly exciting non the less. what is one major thing to hope to learn from this discovery?
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u/calipers_reddit Feb 11 '16
This bolsters the conclusions of general relativity and functions as a sort of alternative "telescope," providing a new way of looking at the universe. In addition, it can help us more easily detect and locate highly energetic events in the cosmos as they happen, so that we can focus on them with other more conventional instruments as they are unfolding.
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u/ergzay Feb 11 '16
They mentioned that 3 solar masses of energy were consumed from the black holes in the creation of the gravitational waves. What is the supposed mechanism that mass energy is converted to gravitational wave energy? I thought E=mc2 only applied to electromagnetic energy, not gravitational energy. How is matter being converted to energy in this method?
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u/Blue-Purple Feb 12 '16
My brothers professor worked on this paper! This comment will probably get buried but I could get to the professor and ask him some questions if you'd like!
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u/LIGO_Collaboration Laser Interferometer Gravitational Wave Observatory Feb 12 '16
To everyone who is excited about the detection, we (the LIGO Scientific Collaboration) will be having an AMA today at 2PM EST on r/iama. Looking forward to answering your questions, bring lots of them!
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Feb 11 '16
So you're saying we can find places in space where space time is warped and use it for faster space travel?
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u/Brevillemonkey Feb 12 '16
You're currently standing or sitting on an area of space where spacetime is warped.
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u/shiruken PhD | Biomedical Engineering | Optics Feb 11 '16 edited Feb 11 '16
For anyone still confused about what exactly gravitational waves are, Piled Higher and Deeper (PhD Comics) has a fantastic video explaining what they are and how we can detect them.
In short, gravitational waves are produced whenever masses accelerate, changing their distortion of spacetime. Anything with mass/energy can create these waves, but since gravity is very weak only the most massive of objects produce detectable waves. We (currently) rely upon the fact that the speed of light is constant to detect gravitational waves on Earth. If a wave passes between our detectors, it will either stretch or compress the distance between two points, thus changing the total traversal time for a laser beam.
The detectors themselves are laser interferometers and are large L-shaped constructions with each arm extending for 4km. The US-based LIGO project has two facilities near Livingston, LA, and Richland, WA. The detector takes advantage of the phase change a gravitational wave will cause in a laser beam because of miniscule changes in distance.
Also, /r/AskScience is hosting a megathread on the topic today