Gravitational Waves (extra footage)

Main video: • Gravitational Waves Di...
Discussed by Ed Copeland and Mike Merrifield.
More on Black Holes from Sixty Symbols: bit.ly/Black_Ho...
LIGO: www.ligo.calte...

[@brianpso]

"Space-time tells matter how to move, and matter tells space-time how to curve" So beautiful.

[@holby123abc]

That's possibly the most erotic thing I have ever read

[@Cruuzie]

I love these extra footage videos. I often think they're where the interesting, juicy details are.

[@StreuB1]

I absolutely LOVE watching Prof. Copeland and Prof Merrifield get into this stuff. Its absolutely amazing to watch! I learn SOOOO much!!! :-D

[@Peteminator]

And also Prof. Phil Moriarty, love these guys

[@JeroenDStout]

+Brian Streufert Yes! I always thoroughly enjoy these videos as well.

[@freebiehughes9615]

Me too! Merrifield's enthusiasm is infectious. Copeland has such an avuncular way about him. I could listen to him read a phone book!

[@edwardtcrump5312]

Ed Copeland is basically the ultimate dad

[@KooshanAbedian]

so true!

[@hakkbak]

Prof Merrifield sounds like a genius and the way he talks is so fast and comprehensible: makes me just wonder how intelligent Einstein and Maxwell must've been so that their fame is justified by their intelligence.

[@KingGsterUK]

These conversations are exiting and motivating. I could sit there all day listening and asking questions to these professors. Nottingham is lucky to have them. Great teachers.

[@nikolaos9175]

Thank you so much for the extended footage!!!! I love this! :)

[@ChaosPootato]

"You'd be ripped apart" "Cool." NO IT'S NOT xD

[@sams6306]

"You're tearing me apart, Ligo!"

[@Xe4ro]

Death by gravitational wave sounds pretty cool though.

[@TheGODLIKE100]

I wonder how far away I would have to be to notice those effects in spacetime without being shred to pieces. Great video!

[@IamGrimalkin]

The gamma ray burst actually had significantly worse directional information than the gravitational wave detection did, because it was in the opposite direction to the way the gamma ray telescope was pointing. It did reduce the area by a bit though, because there were bits where the gamma ray and gravitational wave data didn't overlap and bits where the earth would get in the way.

[@MyAvitech]

This is awesome! Would love to hear more on this subject.

[@InshushaGroupie]

It's wonderful to learn something from people so passionate.

[@EbonAvatar]

Professor Merrifield is my favorite Sixty Symbols personality.

[@RedSkyHorizon]

Is it a stretch to suggest that gravitational waves far from being of no consequence might actually help trigger star formation by compressing molecular clouds and initiating their gravitational collapse ?

[@jasonslade6259]

+Tom Mulligan I would think that they could do that, if there happens to be an interstellar gas cloud nearby. I wonder how close it would have to be though.

[@masbaiy4858]

This wave propagates in one direction. In a fraction of time, one molecule got closer to other molecule. That, we imagine, would initiate a preference into a collapse. However, an instant later, the other molecule moves due to the same gravitational wave. The distance between molecules thus would return. Ultimately, the effect of this passing wave would be virtually zero. Now, if there's not one, but two gravitational waves passes...

[@ArnimSommer]

Now I want to see an animation how a black hole merger tears apart a nearby star or planet...

[@Fronema1]

I love how enthusiastic they are

[@kikones34]

8:04 I can't stop listening to that clap, it sounds so satisfying!

[@morgengabe1]

The fact that it took them so long feels very Michelson & Morley - esque..

[@guardyangel]

Thank you for this video!

[@gustavderkits8433]

Someone should point out that G/(c^4) is a really small number! That is the reason why the detector had to be the most sensitive instrument ever built by human civilization to detect this event.

[@andreapaiola]

What a beautiful video! Thanks

[@aMulliganStew]

Cosmic -Microwave- Gravitational-Wave Background Radiation.

[@rens_happy_helmet]

Prof. Ed makes my wife and cat both chill out at the sound of his voice.. My cat tells me that it's something to do with a slow moving mass-less particle called the "chill-on" which Ed emits whenever he talks, however, my wife tells me: "ooh, he's just lovely, it's something about his voice.. it's like sonic cream". Who should I believe??

[@talltroll7092]

The cat, clearly

[@Theraot]

I have a rather simple hypothesis: those gravitational waves are actually the gravitons. Ok, I guess I'm probably no the first to consider the idea... So, a curvature in space time would be a stable flow of gravitons, virtual gravitons?. Curvature oscilations are unbound graviton. Odd, I would be saying that quantum effects of gravitons are macro.

[@nathantonning]

Noticed the board behind the professor's head: double sums, intervals, radii ... Possibly some multi-variable calculus or other fun stuff? :) Great video.

[@petersu13]

Is it just me or do the sound levels vary a lot on this one?

[@U014B]

+Pete Su WHAT?

[@MrGammaGoblin]

+Noel Goetowski Sound was high in the beginning, then lower in the middle and high again in the end.

[@PaterTenebrarum1]

Pete Su That was just a gravitational wave passing through.

[@headness13]

You don't point the LIGO detectors at something. They are just there to record the waves passing through. He said gravitation waves just pass through everything.

[@wingracer1614]

+headness13 True but if you have a bunch of them, the time difference for the detection would allow you to triangulate the position of the source.

[@TheMiracleMatter]

+headness13 actually, maybe there is an orientation that matters; in a 3D space a gravitationnal wave may be oriented just the right way (or should I say _just the wrong way_) so that both "arms" are affected in equal ways and still cancel out each other. Thus no detection.

[@garethdean6382]

+TheMiracleMatter There is, if it hits the detector at or near 45 degrees (The wavefront forming a right angled triangle with the two arms) then both arms will distort the same or nearly the same amount. But that's unlikely.

[@georgeisaak5321]

while professor Ed explains things gets endorphin showers inside his brain and that is why you see him getting happy and laugh ! An indication of a brilliant and huge mind and of course the cause to drive his curiosity about gravitation waves and everything !

[@sunnysood8702]

I want to know about the maths on the whiteboard behind professor Copeland - it looked interesting!

[@veronikavasickova4918]

Tell us more about the objects mentioned at the end - pleeease! :)

[@U014B]

1:29 So what you're saying is that the LIGO is a gravitational theremin?

[@MephLeo]

+Noel Goetowski It would be nice to translate the information it outputs into sound and "hear" the blackholes colliding...

[@U014B]

Leopoldo Aranha It would be nice... but what would it sound like?

[@MephLeo]

***** Dunno... not even sure if it is possible, since it is such a short spanned info, milliseconds long.

[@U014B]

Leopoldo Aranha That just means we'd have to put it on repeat and use it as a waveform.

[@MephLeo]

***** Then someone would come and autotune it into a Kanye West song. Maybe its better to leave it alone.

[@cassandra5322]

The more I learn about gravity, the less I understand gravity. Gravity, it just works.

[@kakesen]

Let me see if im getting this right: This rare, split second event where the two black holes merged, 1 billion years ago, produced huge gravitational waves that happened to reach earth within a time frame of a few weeks were instruments designed to detect just such an event were switched on - and thus detected these waves. I mean.. what are the odds of that happening???

[@SreedharVenugopal]

+kakesen There are about 100 million black holes in our galaxy itself. Quite a few of them might be binary black holes. Factor in the 100 billion galaxies in the observable universe. So yeah, I'd say the odds aren't as low as we'd expect.

[@aaronsnell9410]

How are gravitational waves affected by the expansion of space. Does the frequency decrease like with light?

[@ibonitog]

As mentioned at 2:20, why would you get ripped apart? I mean you are in space time and so you are being "moved" the same way as space time is moved itself, so shouldn't you just feel nothing? Excuse my bad english, really love your videos! Keep going Brady, I love all your channels:)

[@Sporkabyte]

Benedikt G. You're thinking of the effects of special relativity. In general relativity, you would experience an acceleration as a result of the curving spacetime, which would tear you apart.

[@Hecatonicosachoron]

Are there some papers / reviews of what is discussed in 11:39 about colliding / interacting gravitational waves? It sounds very interesting. I wish if it could be explained why the wave intensity drops as 1/r instead of 1/r^2 I have read the explanations, but it would be helpful to also hear an actual person explaining it.

[@RoboBoddicker]

+Jason93609 That's just how spherical waves work. It's not something unique to gravitational waves. The energy density in a region of a spherical wave drops off by 1/r^2. But the intensity is the amplitude, which is the *square root* of the energy density. So it drops off by 1/r. It's the same for sound waves and electromagnetic waves too.

[@David_Last_Name]

+Copydot Wait, so whats the difference between energy density and intensity? Like for light, what would be the energy density, and what would be the intensity?

[@RoboBoddicker]

Oops, sorry. Intensity is not amplitude. I got my units confused. Intensity is the energy per time per a given area, and it does diminish as the square of the radius. If you think of a spherical wave as a "squeeze" or a displacement in a medium that's spreading out from a source, then the amplitude at a given point is simply the magnitude of the squeezing at that point (i.e., the distance by which the medium is displaced). And the intensity is the average amount of squeezing (i.e., the energy over time) per *square meter.* That means the intensity is equal to the square of the amplitude. And the intensity must diminish as 1/r^2 so that the overall energy of the wave is always conserved, which means the amplitude will diminish as 1/r. I'm not sure if that makes sense, but I tried my best :D

[@ubergeraldine]

Hysterical! Jokers.

[@bordafro]

Theoretically, can gravitational waves trigger supernovae?

[@unvergebeneid]

So how far apart would the gravitational waves from merging black holes have a noticeable effect? When two galaxies collide and their _supermassive_ black holes merge sooner or later, does this do bad things to the surrounding star systems?

[@massive223]

do some more videos about all the stuff he talks about in response to your very last question of the video, they sound very interesting but idk if google is even giving usefull results in relation to the context of the early universe.

[@JohnnyMotel99]

Could we really see as far back as the origin of the universe with gravitational waves?

[@EcBaPr]

i wonder if there is a point in space far enough away from the black hole collision that the wave doesnt rip you apart but still close enough that you could feel yourself get a bit stretched for a second like a rubber band ? that would be weird..

[@educatedmanholecoverbyrich8890]

The Inverse Square Law will tell you how big the wave was.

[@martinzikmund85]

I've always imagined these distortions caused by gravitational waves as something an object or organism inside the wave can never feel. Like as if somebody watched me through an asymetric lense, they could see me tall and slim or short and fat, but I would't be observing and feeling anything. Or can these spacetime ripples actually cause the matter stretch and shrink, meaning changing the distance between molecules or atoms? What about the Planck lenght? From an observer's point of view, will it stretch and shrink inside the wave too?

[@phillipsmith4979]

Through superimposition of gravitational waves could you have a black hole with no mass?

[@cxpKSip]

His analogy is that photons are a disturbance of the EMF, so a graviton must be a disturbance of the space-time field

[@mikeclarke952]

I don't really understand why gravity waves are constrained to the speed of light? These are ripples in space-time itself like a transverse wave propagating on a taught string. The speed of that wave is given as the square root of the density (of the string)/tension (Force on the string). For c (speed of light) this is written as c= Sqr of e/b (permittivity/permeability) of space. So at the very least there's some fundamental equivalency going on here that looks trivial but probably has a much more profound/ deeper meaning.

[@talltroll7092]

Because the "speed of light" should be more accurately referred to as the "speed of causality". What is really being limited is the speed at which events in one place can affect events in another (light is produced >> light is detected). If the Sun suddenly doubled in mass for reasons, it would be 8 minutes before we saw the light form it, or felt the increased gravitational effects

[@kbuss10]

yes but where is the next detection??? they said several per year is possible, and its april!

[@flashpeter625]

Regarding the bit around 2:10. Does anybody have an idea about the amplitude of spacetime distortion right in the close vicinity of the merging black holes? It is clear it must be much more than the miniscule movement LIGO measures, and Prof. Merrifield says it would rip you apart, but what kind of magnitude of ripping apart would that be? Is it still in the region of stretching by a fraction of a length, or are we talking something humongous like stretching to many times the original length? Unfortunately, this so much beyond my capabilities that I can't even estimate.

[@KingGsterUK]

+flashpeter625 Its not much of an answer but think of a curve, a flat horizontal line means no distortion, a flat vertical line means your subatomic particles are instantly teleported to the end of the distortion. The steeper the curve, the faster and harsher the transition, the higher the curve the more distortion. The *steepness* of the curve is one of the critical factors of what the body can handle. Another factor might be the bond strength of the different matter you're made up of. If those bonds break, you likely die. You'll probably die way before then. The answer lies somewhere in between. Just a theory.

[@360ftw]

One thing I do not understand; As we do not know the origin of these waves, how can we expect that the two detectors weren't both on the line of a tangent to the "sphere" that these waves form as they propagate. Surely it must matter on what line the two detectors lay at the time of detection in regards to this "propagation sphere" - you say the time difference between the two detection were 7 ms if I am not mistaking, which would correspond to the waves propagating at the speed of light. If this were to be true, the two detectors must have laid on a straight line towards the center of the origin of the waves. Any explanation would be highly appreciated! :)

[@markzero8291]

+Martin Johansen I had a similar thought: the time gap between the detections would only be the light travel time if the two detectors and the source of the waves were collinear in space. If the three were not collinear the time gap between detections would be less than the light travel time. In the limiting case you described, there would be no time gap between the detections.

[@RoboBoddicker]

+Martin Johansen Right, if you think of the wave front as a circle, then unless the two detectors were perfectly lined up along a radius of the circle, then it would take a little longer than light speed to hit the second detector. But the thing is, the circle in this case has a radius of 1.3 BILLION light years, and the detectors are just a few hundred miles apart. At that scale, the circle would be essentially a straight line, and any delay due to the curvature of the wave front would fall way below the margin of error for the clocks. Same reason why you don't need to take the curvature of the Earth into account when you're building a patio in your backyard :)

[@360ftw]

+Copydot Thanks Copydot - that explains it! Kinda embarrassed I didn't think of that myself now :) I assume that would make it equally difficult to determine the position of the source then as well?

[@markzero8291]

+Copydot Even if we assume the wave front is perfectly planar, this timing issue would still be a problem: First let's define d1 and d2 to be the distances from the source to the respective detectors, and define x to be the distance between the detectors. Also, let x ≠ 0. We can see that the time gap between detections is | d1 - d2 | / c, where c is the speed of light. Let's imagine the limiting case where the detectors are collinear with the source of the signal. Here we have | d1 - d2 | = x. It's obvious the time gap between detections would be x/c. Now imaging another limiting case in which | d1 - d2 | = 0. The detectors are still at a distance x from each other but instead of being collinear with the signal's source the line in space from one detector to the other is parallel with the signal's plane of propagation (here for simplicity I'm using the assumption that the wave front is approximately planar and not spherical). In this case, the detectors are the same distance from the source of the signal and there is no time gap between the detections (so the time gap is LESS than x/c). The in between cases still have the detectors at a distance x from each other, but now 0 < | d1- d2 | < x. The time gap between the detections is still | d1 - d2 | / c. But because of the above inequality | d1 - d2 | / c < x/c, and the time gap between detections is LESS than the light travel time between the detectors. You might object that this violates special relativity, but it doesn't. There is no signal traveling faster than light, because the time gap between detections doesn't correspond to a signal traveling between the detectors (except in the first limiting case when the time gap is the light travel time). The time gap is the difference in the signals' travel time from its source to the two detectors.

[@ankitmundra]

At 3:38 professor mentioned their may be gamma ray burst associated with black holes collision. But black holes are not supposed to release anything. no Electromagnetic radiation should come out. Can you explain how it all plays out when the event horizon of the 2 black holes touch each other.

[@harry.tallbelt6707]

+ankit mundra I am not a professional in any way (so I won't be able to give you any desent proofs), but I suspect, that there might have been some gas around those black holes, whose particles would start to smash violently into one another and because of that radiate. As professors describe it, it seems it was quite a mayhem there, so it probably could have created a gamma ray burst.

[@rykehuss3435]

+ankit mundra If there is any matter in their accretion disks (which is plausable), then that matter would've superheated and started radiating x-rays and gamma rays and possibly eventually a gamma ray burst

[@xXguzman98Xx]

+ankit tundra Black holes do emit Hawking Radiation (you can look it up on wikipedia).

[@Niosus]

+ankit mundra It's not from inside the event horizon, it's from the area of space around the black holes. It's the same reason why some of the brightest objects we know are black holes: Their surroundings are so wild and energetic that whatever matter is there starts to glow incredibly bright.

[@cinquine1]

+Guus Korver The gamma ray bursts (and x ray sources) are not Hawking radiation, it is way too dim for large black holes to detect.

[@TheTwick]

Since the first event detected at LIGO have there been any more signals? Is that all we have so far?

[@Ni999]

Here's the list so far. en.m.wikipedia.org/wiki/List_of_gravitational_wave_observations

[@Azivegu]

just wondering, but would gravitational waves have an effect on the accuracy of atomic clocks?

[@adgalati]

+Azivegu it shouldn't. the detectors that picked up the signal needed to be really really long since the spacetime effects occur over such large distances by the time the waves get here, so the spacetime warping would be negligent in the scale of an atomic clock i would think

[@Azivegu]

Anthony Galati That would be my first guess to, but I would think that the accuracy of the the LIGO detectors is in part only possible with the use of atomic clocks, so I wonder how they would filter out discrepancies it might (but probably doesnt) incurs from what they are observing.

[@garethdean6382]

+Azivegu The effects are very small. As it is LIGO isn't some remarkably precise machine measuring a very tiny distance but instead a carefully calibrated setup that measures two large distances and compares them. Even then it picks up an endless stream of effects from people walking by to traffic to temperature fluctuations. Its data are very messy and any possible signals have to be filtered out then checked repeatedly to confirm their validity.

[@geoffcunningham6823]

+Azivegu I think it probably would, as the rate at which a clock is observed to tick is dependent on the curvature of spacetime locally. That curvature will change slightly due to the waves, even if the local distances basically don't. Not sure how big the effect would be though, it's probably absolutely tiny as the curvature change is tiny.

[@garethdean6382]

Geoff Cunningham The curvature change is also temporary and consists of a change followed by its opposite. (Sometimes called squash and stretch.)

[@0xbaadf00d]

Could you use an array extremely precise Gravitation detector to see what goes on inside a black hole? And why not?

[@foffjerkholes4995]

wouldnt you get the information about what's inside the black hole event horizion from these balck holes violently merging and spewing out all thos grav. waves during the final merge time frame? I dont know.

[@EliotMcLellan]

I HOPE THEY DON'T KNOW ME

[@attentiontodetale]

Can someone clarify something for me? EM waves, i.e. light, will lose intensity following an Inverse square law but the individual photon will retain its energy (momentum) until it interacts with something - (ignoring cosmological red shift) - as mentioned in the video. I assume gravity waves will also follow an inverse square law as they spread out across to universe. However, if they are distorting space time as they propagate, presumably they will also loose additional energy while doing the distorting, i.e. at a greater rate than an inverse square law. Is this correct, and is this what was meant by the wave "damping down" over time? Also, EM waves do not require a medium. If Gravity waves are coupled to space-time does that mean that they do require a medium, and that that medium is space-time itself?

[@unvergebeneid]

Does an object that's rotating and that has perfect rotational symmetry (say, a homogeneous sphere) create gravitational waves? I know about frame dragging but would say a rotating black hole make its presence known (and lose energy) by emitting gravitational waves? And would a perfect sphere of anything keep rotating forever?

[@RoboBoddicker]

+Penny Lane No. A *lumpy* object rotating could produce gravity waves, but a symmetrical one won't.

[@freebiehughes9615]

Can gravity waves diffract into waves of different frequencies in the way light does?

[@matthubsher4500]

at what point would the wave's energy be strong enough to be noticeable but still safe for a human?

[@talltroll7092]

Never. If gravitational waves are strong enough for the effects to be seen by the human eye directly, they would tear you (and the Earth for that matter) to pieces

[@sachamm]

Are gravitational waves subject to gravitational lensing?

[@TheHazyshade]

I supposed the gravitational waves are subject to an expanding universe, is that measurable in their data the why light is?

[@garethdean6382]

+Patrick L Rabun Yes, gravitational waves should obey the same rules and, if you figure out how far away they came from you can calculate their redshift.

[@PaterTenebrarum1]

This is why we never received that extremely important message from Xrrzztrlbnapprrrtx'bnaiggrtzz. Just as he was about to hit the "send" button, he and his equipment were shredded by the gravitational wave.

[@adarshkathiresan9696]

@ 4:42 The professor says that a binary pulsar loses potential energy by emitting gravitational waves. Wouldn't the loss of potential energy be gained as kinetic energy as the neutron stars accelerate towards each other?

[@TheMiracleMatter]

+Adarsh Kathiresan I think both happens *because* the speeds get close to the speed of light: As usual Newtonian physics is valid at low speeds : thus between classical stellar objects orbiting each other, only the kinetic and the potential energy is relevant. But once the speeds involved reach a significant fraction of the speed of light more and more of the potential energy lost turns into gravitational waves *instead* of kinetic energy probably because it's getting harder and harder to boost the kinetic energy (since the speed of light is an asymptote). Furthermore, I would add to that that if all the potential energy lost turns into kinetic energy, then that kinetic energy would perpetually turn back into potential energy since that model describes _exactly_ an elliptic orbit where the closer the objects get, the faster they become and the faster they are "flung" away from each other (cyclically the whole thing would get back to square 1 everytime all the energy lost as potential turns into kinetic energy).

[@lolligerjoj1]

+Adarsh Kathiresan But their distance decreases. Decreased distance, by the gravitational potential E ~ (- G/r) means that you lose energy. Even more so than you increase kinetic energy in this case, I assume.

[@TheMiracleMatter]

***** Yup, what happens is that _both_ the kinetic and the gravitationnal wave energy gets a fraction of what is lost of potential energy.

[@BlackBobby69]

Hearing all about the challanges and interferences and how we currently can only detect cataclysmic events - wouldn't this be the sort of experiment we could easily set-up in space? A base unit with an emitter and a detector and two mirrors far away - sounds like something we could do in space or on the moon with distances orders of magnitudes bigger to detect much smaller waves without any interference by human activity.

[@JimboJamble]

Search for the proposed eLISA mission.

[@BlackBobby69]

Neat! Thanks for the pointer.

[@Orlopzi]

Can we build one of these gravitational wave detectors on the moon?

[@bruinflight]

Do gravitational waves get red-shifted?

[@ufotofu9]

If Gravity is a distortion in Spacetime, I can accept the need for Gravitational Waves. But what I cannot put my head around is the need for Gravitons, or Gravitational Particles.

[@Sporkabyte]

Geoffrey Zoref the thinking is that since other waves that we know of like light, electrons, quarks etc have corresponding particles, it would make sense for gravitational waves to have a corresponding particle.

[@talltroll7092]

Not just that "it makes sense", but rather "it is a fundamental requirement". There is no light without photons, there is no gravity without gravitons. As far as we can tell, that's just how things work

[@TimmacTR]

What would the gravitational waves "look" like close to the black holes? Like would we notice them?

[@lennutrajektoor]

+TimmacTR As they said - you would be killed by the massive energy they emit. Remember - it's not explosion that kills but rapid spike in air pressure.

[@TimmacTR]

lennutrajektoor Then, let's say halfway, you know, between the killer waves and the atmoic level wave..

[@bellsTheorem1138]

+TimmacTR Half way would not be half the initial energy. The fall off follows the inverse square law like light. But there would be a point close enough to the event that would be very uncomfortable for a very brief moment. Probably something akin to rapid and painful vibration throughout your entire body. Get much closer an you would probably suffer internal injuries. And closer still would turn you into jelly.

[@TimmacTR]

Bell's Theorem What I try to understand is would it be similar in effect to a large mechanical wave? Because obviously this seems a little different..

[@garethdean6382]

+TimmacTR The waves act to stress structures. Large structures suffer the most stress followed by smaller structures as the waves become more intense. Strong enough waves would have the same effect as falling onto the ground at speed, your body would be crushed by the sudden changes in dimensions, as well as being heated due to a unique form of friction. Less intense waves would be detectable as a 'jolt' to your body as certain delicate things like long neuron fibers were stressed. Possibly larger things like buildings might suddenly crack.

[@SupremeCommander0]

Could anybody please explain me, if two massive objects (neutron stars, or black holes), which are spinning around each other, loosing energy into gravitational waves, why do they moving towards each other?

[@SupremeCommander0]

+Supreme Commander ok, I've come up to this answer, please confirm if it is true (at least following current theory): the actual resulting vector of object 'a' movement, which moving around 'A' object is not perpendicular to radius of orbit, but turned to the object 'A'. Since Solar and Earth masses are so small, that we can eliminate counting on it, but very massive objects, such as black holes, or neutron stars (if neutron stars are close to each other) has this vector of movement turned towards another object much more.

[@SupremeCommander0]

+Supreme Commander so to sum up, every moving object in space-time is slowing down

[@TheGrundigg]

+Supreme Commander Just go to your secondary school physics book and check the chapters for dynamics, circular movement and harmonic oscilations. You'll see why this happens.

[@garethdean6382]

+Supreme Commander An orbiting object has a certain amount of kinetic energy that stops it from just falling into what it's orbiting. If the moon were not moving around the Earth it'd just fall down and hit us. It also has gravitational potential energy, the energy you get from not being all smashed together in one lump. (This is the energy you give to a heavy rock when you lift it off the ground.) As orbiting objects lose kinetic and potential energy to gravitational waves they can't stay far apart anymore, they don't have the energy to.

[@foffjerkholes4995]

You answered your own question.

[@bockmaker]

Can you surf a gravitational wave?

[@madmatthew1]

+bockmaker I guess if you're a photon, then yes. But since they travel the speed of light anything will mass cannot do this :(

[@666Tomato666]

+bockmaker are you Australian, mate?

[@bockmaker]

+666Tomato666 No but I did meet quite a few in my travels through Whogivesafvckastan. Really was just asking a ridiculous question to make the mind expand to find an answer. I did have a few thoughts but my math isn't up to the task.

[@SreedharVenugopal]

+bockmaker I think that's the idea behind the Alcubierre drive.

[@TheMarvymart]

Zaphod would

[@u_wind_sprint4393]

What would we need to see an all-sky gravitational survey?

[@MushookieMan]

+Kevin Gorman Since gravitational waves pass through Earth unaffected, I think we would only need the third detector online, Ed was saying that allows you to calculate a vector pointing to the source. Also, increased sensitivity would probably allow you to calculate the direction much more accurately.

[@49819d]

If gravitational waves can propagate through matter, what would happen if a gravitational wave propagated through some other black hole? Would the wave be affected at all?

[@Momohhhhhh]

If the black hole were not accelerating, I'd imagine not much interesting would happen to the passing gravitational wave. If it is accelerating, though, you might get some neat interference between multiple gravitational waves, assuming they interfere in the way that other waves do.

[@garethdean6382]

+mathfreak123 Nothing gets out of black holes, including gravitational waves. It would go in and never come out. Black holes could also lens gravity waves, which would be interesting.

[@lamp-stand7]

At 2:09 We would be "ripped to shreds by gravitational waves" if too close? If these waves are nothing more than a distortion of the Space/Time we share, wouldn't anything in its path simply roll with that distortion like a gull on an ocean wave?

[@pipertripp]

+Lamp- Stand It's a quadrapole wave so you'd be compressed along 1 axis and stretched in the other. But since it's the space you occupy that's expanding/contracting... I'm not sure how things like molecular bonds would respond. Glad we won't have to find this out.

[@David_Last_Name]

+Lamp- Stand No, the forces on you are real. Think of a simple example, 1 positive and 1 negative charge at a set distance apart. These 2 charges feel a force on each other determined by the distance between them. Now, lets say a gravity wave comes by and they move slightly further apart for a brief moment. Even though they didn't actually move through space, the distance between these objects still increased. That means that the force each one experiences will decrease a tiny bit for that moment, exactly as if you had actually moved them. The fact that the movement comes from space expanding instead of real motion through that space won't matter. All that matters to the force is: are the charges further apart? If yes, the force between them goes down. Now consider that the electric charge between atoms is literally the only thing holding you together. As a gravity wave passes through you and changes those distances all of those forces will get weaker, and then stronger, and then return to normal. Make that effect too drastic and bad things will happen. lol.

[@lamp-stand7]

But still, hasn't the distance between the charges changed only in respect to the outside observer? e.g. I understand how I would feel the effects of an ordinary pulling apart of particles/bonds, etc., but where space/time is concerned, it remains counter-intuitive (to me) that the object acted upon could perceive the distortion (ie. changes in distances) much as an orbiting body experiences no sense of inertia when following a curved path. To the orbiting body, it follows a straight course. Why does the same not hold as to an object through which a gravity wave passes? If I understand Pipertrip's point as being that the distortion is felt because it operates along a single axis, that raises a few thoughts; one being, even if that is the case, how would an object feel an internal distortion of itself acting at the speed of causality? (ie. all internal relationships would appear set aright before they could causally react.)

[@David_Last_Name]

Lamp- Stand No, it's not just to an outside observer that the distance has increased. The real distance between the particles will have increased. Consider another example we have of space expanding, the expansion of the universe. Galaxies aren't actually moving away from each other, rather the space between galaxies is expanding and that drags the galaxies along with it. Now, this doesn't change the fact that galaxies are moving apart from each other, and so things like gravitational forces between them start decreasing. Gravitational waves do the same thing, just on a smaller scale. So when a gravity wave passes the actual distances between particles starts changing.

[@Konstantinos340]

whats a soliton??

[@TheCoenetje]

Can gravitational waves escape a black hole?

[@MariusKruger]

yes

[@Shinsei01]

I am curious, how do they filter noise in that if you have 2 gravitational events occurs in the same path or near each other how can anyone know its actually 2 events overlapping one another instead of just one event? Even if the first event was greater but by the time it reaches the second event its of similar power/intensity of the second could they tell them apart?

[@garethdean6382]

+Shinsei01 It's similar to having two people talking at the same time; the signal is very specific, it follows a definite pattern like words in a sentence. if you have two events they will 'garble' each other. If you record them both it should be possible to play them back and analyze them to pick out the two different events in the same way you can take a recording and pick out individual voices.

[@hcheyne]

This is great. I have one question. Why do gravitational waves move at the speed of light?

[@grieske]

+hcheyne I know that this is not much of an answer, but the answer is on page 369 of volume 2 of Landau and Lifschitz

[@m8e]

Why do light travel at the speed of gravity? Why do light travel at the speed of radio waves? It isn't really about light, it's kind of a universal speed limit.

[@hcheyne]

m8e Not really the point of my question. Why do they go that fast, and why, since spacetime can expand faster than the speed of light are ripples in spacetime restricted to the speed of light? My assumption is because the ripple is caused by energy transfer, but I don't know if that is true. hence my question.

[@SreedharVenugopal]

+hcheyne They are carrying energy and so are restricted to the speed of causality. Spacetime can expand faster than that because they do not carry information.

[@hcheyne]

Sreedhar Venugopal Thankyou.

[@noddwyd]

This is really interesting. So it's really possible to produce gravity waves, it just takes some insane event like two black holes colliding. But normal everyday gravity is not the same thing? I was really confused about this. I always feel like Mass/Spacetime/Gravity interrelationship is very confusing. Mass comes from some kind of field "sticking" to certain particles and not others, then these things with mass distort spacetime which is the effect we call "gravity", but we're not sure exactly how this is done. But there's also "gravity waves" which are a different thing (but not really) resulting from relativistic events and will stretch spacetime out like a rubber band back and forth in a detectable way. But presumably, like the lightspeed limit, perhaps it can't stretch spacetime hard enough to actually snap it. I mean, that would fit with relativity. Or maybe it is possible. Would we even be able to notice if a relatively small part of the universe was torn?

[@garethdean6382]

+noddwyd You may have misunderstood some things. Energy distorts spacetime, sometimes this energy can be in the form of mass, sometimes not. Mass is just contained energy, a system of things bound together. Most particles are massive because they are in fact two particles bound into one by the Higgs field. Gravity waves are produced by anything that's moving mass around in an odd (asymmetric) way. You waving your hands makes gravity waves, just very, very, very weak ones. It takes a powerful event to make waves strong enough to detect. As far as we know there's no limit to how fast space can be stretched or warped, it should never 'tear' though it may be possible to twist it up in weird ways.

[@noddwyd]

Yeah, my understanding is simplistic. At the end of the day, I just end up confused. So, essentially, there's just energy and space time here. And they follow some rules. This makes it seem like space-time "backdrop" is the only actual "stuff". Also, if I think about it, inflation pretty much rules out the "tearing" thing. If anything, it would have torn then. Maybe it did though, and that's the reason for the "great attractor". It's all being pulled towards the hole. A hole that could be outside the observable and still affect us because it's just part of the overall topology. I think I'll go look for more info about that.

[@garethdean6382]

noddwyd For a long time space was seen as just a 'backdrop', something for events to happen in, unrelated to anything. It was Einstein who showed us that in fact it is inseparably coupled with the energy and mass in our universe. Indeed empty space has its own energy, the 'vacuum energy' and is filled with fields and 'virtual particles'. There's a very real sense that all the stuff we're made of is just vibrations in spacial fields, floating atop the sea of spacetime. Holes in space are problematic, what happens when you reach the edge? Do you vanish? Change? Go somewhere else (In which case it's not a hole but a tube.) In general it's held space can't rip because there's nothing to fill the hole. tear a shirt and the hole fills with air, smack a hole in the air and it's filled with space. But what is a hole in space filled with?

[@SamuelHauptmannvanDam]

Question: Does the moon or the Earth lose mass by orbiting the sun and how quickly? Resulting in us diving into the sun? Or is that calculated to be far less significant than the time it will take the sun to expand out towards us?

[@IamGrimalkin]

It's not only far less significant than that, it is also far less significant than other effects perturbing our orbit.

[@SamuelHauptmannvanDam]

Thanks. :)

[@Niosus]

+Samuel Hauptmann van Dam They don't lose mass, they lose orbital velocity. It's a bit as if there is just a tiny bit of drag on the Earth. In the case of these black holes, the collision was so violent that a significant chunk of mass was turned into energy (or whatever that would mean when dealing with black holes). As long as there is no collision, you don't lose any mass. This is also why they were spiraling in on each other to begin with: They were bleeding off orbital speed through those gravitational waves. Paradoxically when dealing with orbits, slowing down actually makes you go faster because you fall deeper into the gravity well of whatever you're orbiting. In the case of these black holes, they slow each other down, which makes them fall closer to each other and thus speed up again. This makes them slow down even more, fall more, and speed up more... Rinse and repeat and that's how you get something 30x the mass of the Sun moving at a significant portion of the speed of light.

[@SamuelHauptmannvanDam]

Insane. Of course. Yea that makes sense. Do you by any chance know if you'd really would be shred to pieces coming to close as relatively - everything would be at "normal" distance to each other? Or is the connections between the atoms getting that much weaker by expanding space? Thus - Shredding you apart.

[@Niosus]

Samuel Hauptmann van Dam I have no clue, although given that 3 solar masses worth of energy were released, I don't think there would be much left of you if you were anywhere near this collision.

[@dirfgiS]

So, if gravitational waves don't care what's in their way, would it lose more of its energy if it propegated through a period of space where there were a lot of mass? For example, would the gravitational wave "decay" (not sure how to properly word it) faster if it were to travel through the sun than it would if it traveled through complete vacuum but the same diameter of the sun. Does the gravitational wave lose its energy because it has to distort mass, or because it has to destort spacetime?

[@garethdean6382]

+Sigge Stjärnholm It loses energy when distorting mass. Space has no mass, no inertia. It can be distorted without 'friction' or resistance. But mass takes energy to move about and distort so gravitational waves should lose energy as they pass through mass, mainly as heat.

[@dirfgiS]

+Gareth Dean Would that not make it harder to calculate how big the black holes were? We would see it as a lower energy gravitational wave than it should have because it has traveled through some mass, most of it would be vacuum with a small amount of particles but it could also have traveled through some stars, asteroids or anything else which would have made the wave smaller as it had to distort that mass. It makes sense that it would lose its energy by distorting space and if it distorted a period of space where there were a lot more mass it would lose a lot more energy to distort the mass. I might be on a completly wrong trail, but I see gravitational waves as something that doesnt travel through space in the way that electromagnetic waves do, but rather in some kind of dimension above spacetime. It affects spacetime by distorting it, and spacetime affects it by taking more energy if there is a lot of mass. Its interacting, but not interliving. Thanks for the reply, I'm really curious about this!

[@garethdean6382]

Sigge Stjärnholm That is an issue, but gravity is very weak and the energy loss is very small indeed. How small? passing a wave through a light year of lead would reduce its energy by less than half. This means that the cumulative effect of an entire galaxy's worth of rather thinly-spaced material is quite negligible. The waves can actually be seen as exactly like electromagnetic waves if you treat gravity as a force. It would be carried by gravitons, massless, light-speed-traveling particles. The issue is affecting spacetime; nobody knows how you work that into the graviton approach, an area known as 'quantum gravity'. This is in fact part of why we're looking at gravitational waves, they could hold clues to a new approach.

[@dirfgiS]

+Gareth Dean Oh, that cleared up a lot for me. I can't wait what science has for us during the next couple of years if we can find more information. Again, thanks for the indepth replies!

[@comprehensiveboycomprehens8786]

The speed of light ........ We tend to think that light is deciding what the speed is for itself. Maybe it's space time fixing this speed.

[@foffjerkholes4995]

just think about it as the spees of causality

[@origamigek]

Being to close to a source of gravitational waves will tear you apart? Why? If spacetime is being stretched and squeezed doesn't that mean that everything will return to normal?

[@MD-pg1fh]

+ᴠᴧᴨᴛᴧᴃᴌᴧcᴋ If that was true, there'd be no waves at all. Spacetime is alternatingly stretched in one direction and squeezed in the other; and vice versa.

[@demaloe]

+ᴠᴧᴨᴛᴧᴃᴌᴧcᴋ I was wondering the same.

[@Stericify]

+ᴠᴧᴨᴛᴧᴃᴌᴧcᴋ The issue is what happens during the period of time when stuff is stretched. If you stretch something, it moves around, and then you try squeezing it back together, it's not necessarily going to go back to the same place.

[@origamigek]

As I understood: Experiencing length contraction, by for example moving at great speeds, is relative. So in your reverence frame you won't actually contract. So you're fine after having been 'squeezed' by length contraction, because the spacetime itself contracted with you. And in the same way you might be 'torn apart' by gravitational waves in an outside reverence frame but from your perspective you don't change, your surroundings do. Typing all this makes my doubt my understanding, so I'd love some clarification.

[@Stericify]

Length contraction in special relativity is indeed relative, but distortions caused by gravity work differently. If you are in a gravitational field, you experience an acceleration as a consequence of the curvature of space. This acceleration exists in any inertial reference frame. As a gravitational wave passes you, parts of your body will be accelerated as a result of space being curved. This acceleration is not uniform so different parts of your body will be accelerated at different rates.

[@michaelsheffield6852]

Who is Laurie?

[@JimboJamble]

Must be a famous truck driver, since all Brits seem to mention her when talking about trucks. ;)

[@KrzysztofWierzbicki777]

Tow Ting’s, why someone didn't build interferometer on deserted Island, second thing is interesting coloration neutrinos and gravitons are behaving the same, I know I know, It is'n causation

[@MelindaGreen]

How difficult would it be to detect gravitational waves generated in the laboratory?

[@Algebrodadio]

+Melinda Green A better question would be "how difficult would it be to GENERATE detectable g-waves in a laboratory?" The answer: Really really difficult. Impossible with today's technology.

[@MelindaGreen]

Aaron Wolbach That's the same question. You just arranged my words in a different order.

[@Algebrodadio]

Melinda Green And yet order matters. The difficulty is not detection. The difficulty is generation.

[@MelindaGreen]

Aaron Wolbach No, every acceleration creates gravity waves so that in itself is not the problem. Creating a strong enough signal is exactly as important as creating a sensitive enough detector. They are dual aspects of the problem.

[@Algebrodadio]

Melinda Green Yes. But LIGO has demonstrated the ability to detect g-waves. And while it is true that all moving masses generate g-waves, almost none of them are detectable. Even the Earth and Moon moving around each other isn't enough to make a detectable signal. So in order to produce one, we would need to take an astronomically large mass and move it with astronomically large acceleration. That isn't going to happen on Earth. So I say it again, detecting g-waves is something we can do. Generating detectable waves is not.

[@RonJohn63]

9:48 How can the EM waves just... peter out? The inability to see the candle is from far away is due to decreased energy DENSITY (computed via the inverse square law) -- IOW, fewer photons hit your eyeballs.

[@morf301]

+RonJohn63 As the waves spread out their amplitudes decrease which corresponds to decreased energy.

[@RonJohn63]

Michael Carradus What about the photons?

[@morf301]

RonJohn63 Yeah, light is strange like that... the photon particle model also works to describe light in certain contexts but really light is neither a particle nor a wave. But yes, you are correct in saying that the intensity of light depends on the number of photons too. Confusing, i know, but hopefully I've answered your initial question.

[@TheGrundigg]

+RonJohn63 both definitions are true. Lower amplitude of the wave = less photons.

[@RonJohn63]

TheGrundigg OK. I had the mental image of individual photons keeping the same energy as they traveled farther from the source, but there "just" being fewer of them per cubic cm the farther they got from the origin.

[@wurth2041]

How you suposed to detect things that dont exist? All you can do is fantasise about their existence...

[@FrancekPirosrancek]

i wish brady would ask better questions

[@naimulhaq9626]

Neither Einstein's nor Newton's theory of gravitation, explain why the planets do not fall into the sun or why the moon is moving away from the earth, rather than falling in? Why?

[@Ni999]

Both Newton and Einstein explain why planets don't fall into the sun. You've either been misinformed or you misunderstood the explanations.

[@nickb4302]

If we don't have a quantum theory of gravity, why does quantum gravity always come into the conversation when we talk about gravitational waves?

[@talltroll7092]

Because right now, gravity is the only fundamental force that doesn't fit into quantum mechanics. Quantum mechanics can explain what the Sun is made of, why it behaves the way it does, but has nothing to say on the matter of why we (or anything else) orbit it, rather than just sailing away into space. Classical physics can explain orbits and why galaxies stick together and so on, but can't explain why your hand isn't burnt off when you put it inside a black plastic bag. Getting the two to play nicely together requires an overarching theory that quantises gravity, and fits everything else we see. That would be a quantum theory of gravity, which is why we'd like to have one so much

[@3877michael]

I don’t think back holes are objects at all. So much to do about nothing.

[@MariusKruger]

Would inflation have caused gravitational waves?

[@Ni999]

Yes, but we haven't detected them yet. en.m.wikipedia.org/wiki/Cosmic_microwave_background#Polarization

[@po-hsuanhuang5200]

Why am I here ?

[@danpop1235]

ha let them use ecwasons it is phisics after all

[@danpop1235]

ops no ha

[@sanxofon]

El profe parece que está pachecón

[@TheElectra5000]

I don't know, but gravitons sound as fishy as midichlorians...

[@talltroll7092]

If gravitons *don't* exist, then you have to explain how a fundamental force exists without a mediating particle to propagate it, which would require us to rethink all of physics from scratch. There are several possible ways of making gravitons fit with what we already know, but they all require things like supersymmetry, or string theory, none of which are well developed theories yet. As we gradually gather more and better data, and better theories to explain the data we have, we should eventually work out how gravity works, and maybe that will let us understand gravitons

[@venkateshbabu5623]

Instance healing is possible because of gravitational waves. Just like MRI and x-rays are useful in diagnosis G-wave will be used for pulling unwanted cells and plugging in new cells something like instant healing and reshaping.

[@MephLeo]

2:13

[@carnsoaks1]

re the first G.W. result, does not accelerating any object, use energy. is not the cosmos filled w objects radiating energy away, ie every Cluster, Galaxy, every star, every planet, comet, moon, etc, is the U getting colder tx to this, or is the Consv-ofE' creating something we cannot see, eg Dark Energy....

[@GiordanoBruno42]

Might an extremely advanced civilization of AIs, robots, cyborgs or organics attempt to capture this energy? Conversion of three solar masses into energy seems like it'd be an extremely attractive prospect. Maybe somebody with more technical knowlege than me could think about whether this is plausible? Might there be a signature effect on the gravitational waves that we could detect if a large portion of the energy from a similar event had been "harvested"? Or is this nonsense?

[@stefans4562]

hknuddv Very hard to imagine that. Gravitational waves just pass through matter like it's nothing. So how to turn it into usefull energy? However I don't want to rule out anything.

[@GiordanoBruno42]

Stefan Sierraoneoneseven I had that suspicion, but somebody in the comments claimed that the spacial distortion very close to the event would be more like several football pitches than a single proton. I feel like there'd be some way to capture a load of this energy but for now it'll have to remain fantasy :(

[@IamGrimalkin]

+hknuddvI suspect such a signal might be assumed to be noise by the data filtering algorithm, because it would no longer match the expected signal for a merger.

[@GiordanoBruno42]

IamGrimalkin Yeah I thought as much. Hmm, maybe I need to get thinking about how G-waves' energy could be captured? Then I could work out what such a system's signature would be and it could be added to the algorithms' list. Nobel Prize here I come! Ahaha I'm being hilariously optimistic, it'll probably take somebody much smarter than me a lifetime of work a century from now :P