How Does Gravity Escape A Black Hole?

[@TheBuzzBen]

Question. What happens if a gravitational wave passes through a black hole? Would we have gravitational lensing of gravity? If so, can gravity be focused on a single point making a virtual black hole without mass?

[@MeesterG]

I'm not sure about your question, but it sounds like a Schwarzschild kugelblitz in that case

[@TheJanitorIsIn]

That is the most insanely cool idea I have ever heard bro omg I absolutely love it

[@BeatBoxBrian]

Yeah very interesting question!!

[@thortor1216]

Woah that is the most spacetime question I have heard in a long time

[@SuperVince1010]

@@thortor1216 It would create a distortion in space time aka mass.

[@Themaniacis_back]

I have the utmost respect for any channel that is willing to admit when they made a mistake and correct themselves. It seems like so many are terrified to admit when they are wrong these days. It's okay to be wrong sometimes. We are human. Anyways, keep up the great work.

[@vblaas246]

It is a science channel, falsifying is kind of a big deal ;) Still appreciated. Also about the DFT. (it is not a cheat, it is molecularly practically functional, e.g. for material science, as any good model needs to be).

[@nate2807]

I agree. I've seen every episode; ST has always shown impeccable intellectual honesty, character, and respect for scientific method. They don't indulge the mysticism and while it is a KZbin show (which does require a certain level of entertainment), they don't overly sensationalize topics or data. They are judicious when simplifying things and explain simplifications. They share what research and experiments tell us and point out different philosophies and interpretations objectively. They take time to read comments and, when necessary, they clarify corrections. These are the sorts of behaviors that build trust.

[@lekhakaananta5864]

Just to play devil's advocate though, it's not hard to admit mistakes in these contexts. The two mistakes mentioned here were 1) about DFT, an extremely technical point where nobody faults them for being wrong when they themselves admit to being slightly out of depth, and 2) trivial facts about historical hardware, where the truth was even more impressive and "yay progress" than their initial claim. Most other humans have no difficulty admitting to mistakes this trivial either. What is harder is to admit mistakes when your identity is attached to them in some way. You see this in even the most celebrated of scientists. Newton, for a historical example, but also many contemporary scientists can be found with their own pet theories that they irrationally defend. Which is not really a bad thing all things considered, but should be noted.

[@GlitchedBlox]

Is that a compliment or human limitations?

[@ReubenCooper]

If you think you understand quantum mechanics, then you don't understand quantum mechanics

[@dannymac6368]

Fact: PBS Space Time is a black hole I’m always happy to fall into. Captivating, radiating information constantly…it fits.

[@Nae_Ayy]

The mild spaghettification is just something you have to get used to while watching Space Time

[@Nae_Ayy]

@Titu Farena Finally, Special love content

[@An_American_Man]

@@Nae_Ayy my mind definitely spaghettifies at times while watching this show

[@Nukepositive]

Fact: the center of black holes are not singularities. Our mathematical models suggest black holes *should* contain singularities, but our observations prove they do not. There's something missing in our mathematical model. It's frustrating that literally the first line is a fiction.

[@An_American_Man]

@@Nukepositive how do our observations prove that they don't?

[@Cucui47]

I play a game with these videos: how far into it can I get before I can feel my brain leaking out my ears. I made it almost 7 minutes with this one. To be clear I LOVE these videos and I learn a lot and Mr narrator guy does an excellent job explaining profoundly complex topics. It's just that a lot of these topics are simply mind-puddling.

[@devinwarrick3660]

We love Mr Narrator Guy

[@TKOfromJohn]

The more you watch the more things start to make more sense

[@frapell]

Same for me... everything is going well, until I can actually feel the exact moment my brain goes over the event horizon and I start feeling stupid xD

[@greyaffliction9752]

I made it 11 seconds

[@feico865]

Quantum mechanics are becoming increasingly hard to understand.

This just made this whole "imprinted on the surface of the event horizon" thing click for me. I simply hadn't connected the dots between that, and the infinitely stretched light. Great video 💡

[@damonedwards1544]

Me too. From our point of view, all the matter that crossed the event horizon is still there, warping spacetime.

[@nenmaster5218]

@@damonedwards1544 "GRAVITY AINT EXIST! ITS FAKE!" -Flat Earther.

[@siahenderson1490]

I wanna take a moment to appreciate Matt .he has unknowingly been my teacher since I was 15...I'm 22 now and a grad student.. Videos like this teach more than schools

[@Hailfire08]

Congrats! In STEM presumably?

[@Mr.Nichan]

I didn't think he was doing it 7 years ago. There are videos only 6 years old with another guy.

[@bastadtroll8922]

@@Mr.Nichan She is a paid commentator

[@Mr.Nichan]

@@bastadtroll8922 I think you're too paranoid (or just trolling, as your name suggests). A lot of people on KZbin comment simple praise like this, including on channels that definitely don't have the money to pay people to. Also, I really doubt paying people to comment would be profitable, and, if not, then your talking about PBS paying people to promote a video at their own expense, either altruisrically, for their own pride or someones job, or for some governmental ulterior motive (e.g., propaganda, getting people to go into a needed field). Also, a lot of people who become grad students in physics or similar probably would watch this channel for a long time before, since it's one of the main modern physics channels at its level and of its quality, so it's not weird that one is here. Maybe you don't think this channel is good because you don't follow it well, or MAYBE because you're an electric-universe/flat-earther type person, or because something else, but, for what it's worth, I usually follow these videos fairly well. Maybe you don't think it's high level enough for a grad student to care, and you might be right, but it's definitely enough for a high-schooler to. EDIT: Actually, I retract the statement that some channels definitely not having the money to pay commenters, since it probably doesn't take much money. It's probably easier to just make dummy accounts yourself or even with bots and pay no one, but paying some people who care very little about honesty in a way that they're not too paranoid or lazy to accept for the amount of money given might help to get commenters who don't look obviously fake when people check their channels. I still doubt many channels would find this worth it, though, nor does this commenter seem particularly like a schill to me (and she DEFINITELY doesn't seem like a bot).

[@bastadtroll8922]

@@Mr.NichanIf she is not paid comenter you definitly are.

[@syntaera]

For SR/GR, it's more helpful to view 'c' not as a speed, but as a geometric *conversion* factor between distances and times in a four-dimensional space-time. The 'speed' of light is an emergent phenomenon of treating different speeds as merely relative rotations of an object into spatial directions and away from the time-oriented observer/rest frame. A 90 degree rotation away from travelling 1 second per second through time results in an apparent motion of 299792458m per second in space - while simultaneously extruding the observed travel-direction length backwards into the time direction, resulting in observed length contraction. Treating 'c' as a mere speed is easier mentally, but ultimately makes SR/GR harder to understand.

[@LuisAldamiz]

Nice reminder of what "speed of light" actually means. In other words, if, Superman-style, you manage to go around earth c. 8 times in a second, you experience no time in that second, that second never ever happened for you, much like the day Pigaffetta reported missing from their first circumnavigation of the world (but different mechanism, of course). That's something quantum mechanics keep forgetting about, as for them, even if they are constantly dealing with hyper-fast particles, including photons, time is Newtonially linear.

[@crackedemerald4930]

so i'm not crazy for measuring my time in meters!

[@asmodean7239]

I think it is also referred to as 4speed (speed in 4 dimensions) - everything always moves at the speed of light, but in space-time, not just in space.

[@sillysausage4549]

I've been researching this all my life, and can finally confirm that the speed of light is... really, really fast.

[@kylelochlann5053]

@@crackedemerald4930 Distance, time, mass, electric charge, and angular momentum are all measured in meters. We call these "geometrized", for example the geometrized mass, m, is m=GM/c^2.

[@mickelodiansurname9578]

This is something I wondered when I was a kid and my physics teacher at the time stated it was compelling evidence of why gravity permeates instantly. He was wrong but you can't really fault his logic... it made sense to me at the time.

[@RC2357]

If the gravity we feel from a black hole is actually from past interactions with the mass, then does that mean that a black hole can have an asymmetric gravitational field? For instance, suppose we kept throwing moons at the left side of a non-rotating black hole. Would the black hole seem to be heavier on the left side since the past mass was added there?

[@viliml2763]

For all intents and purposes, probably not. You can still treat it as a point source, but not a stationary one. It would simply "move" in the direction from which the mass is falling into it to stay in the center of mass of all the stuff. Where it becomes interesting is if you throw heavy electrically neutral mass on one side and light but electrically charged matter on the other...

[@llahneb10]

I think that’s a great question. Also makes me wonder if we had a dipole with constant positive on one side, negative on the other and spun it around, we’d detect the changing field from pos to neg. But when it passes the event horizon, would we see the field from it stuck as positive or negative? I’m just trying to think of a dynamic situation instead of a static one like the example of the electrons in the video

[@nutopio]

even if it becomes heavier on one side that just means the centre moves towards that side. probably by the same amount as it does if you calculate how much the moons you throw in assert their gravity on the black hole (it always works both ways).

[@tonywells6990]

You already have an asymmetric gravitational field where you are throwing them in, each one will slightly distort the event horizon for a short period of time but after they have all entered the event horizon it will quickly become a perfect sphere. So, no. Think of it as all the mass is at the singularity but its imprint is on the event horizon which then becomes symmetric. The 'no-hair theorem' is an explanation.

[@manofcultura]

I doubt non rotating masses, even black holes exist. The way 4d space time curves, it seems all straight lines eventually spiral.

[@ananya.a04]

This video blew out half of my brains, and the other half was blown away after reading the comments. People who can make sense of this and then produce more speculations and theories are geniuses. Thank you PBS Space Time for making this video! :)

[@TKOfromJohn]

A lot of physics students watch these is why

[@neddyladdy]

The other half had already run away to somewhere more sensible ?

[@juan_ta]

People can make foolish comments that sound interesting if you don't realise how they are mixing unrelated concepts, and they may be replied in the same way. Recently I saw a scheme about measuring the length of the shore of England, posted just to raise questions. The "most relevant" comments (after the YT classification) showed a confrontation of a variety of math misconceptions, and none were grasping the subject was about fractal objects. So do not be impressed when you can't follow comments. They are not necessarily good.

[@teathesilkwing7616]

Wait, brains plural? Nice try, octopus

[@pesilaratnayake162]

Question: If an outside observer sees an object slow as it approaches the event horizon of a black hole, and the radius of the black hole event horizon grows as mass falls into it, what happens to the object? Does it disappear as the black hole expands, or does it move outwards with the event horizon? Or do we never observe black hole expansion since we never see anything enter the black hole?

[@lanceallen9875]

I feel like sewing it expand would be very hard because we find them through disturbing light

[@starship3812]

So you are saying that a graviton is carrier of gravity it can travel at any speed that's how it escape black hole gravity means that's how a graviton escape effect of other graviton that's mess a graviton escape other graviton effect to make some gravity for black hole. Mess it's a mess cold mess. Common what the f k . I don't think any theory is be able to describe universe completely at of now not a small percentage. It's a mess

[@planexshifter]

That’s just it though ,it’s NOT a mess. It’s a series of complex equations.

[@LeittenArt]

From your perspective, the observed object passing the event horizon will be there for hundreds of years, until it just disappears.

[@lanceallen9875]

@@LeittenArt you are very correct but I think he was asking if you'd see it expand which I think would be very hard to see if even possible

[@DanHarkless_Halloween_YTPs_etc]

8:06 - "Interactions between particles result from the sum of all virtual particle interactions, possible and impossible, and the speed of light limit actually emerges in a sort of statistical way." 🤯 This really is the best channel on KZbin (according to my information-theoretical measurements, anyhow)!

[@1qazxsw23edcish]

For me, it helps to think of the gravitational effect of getting pulled by spacetime into a black hole as being similar to getting pulled by a chain. Only the first link interacts with the pull source, in this case the singulaity, and only the last link interacts with yourself, but by each link interacting with the ones next to it you still feel the effect.

[@timelapseofdecay9028]

But if you throw a chain into a blackhole, and someone inside the blackhole pulls it harder, you won't be able to feel that outside of the blackhole (because at the boundary of the event horizon, that chain is broken).

[@SeraphX2]

I'm not math smart by any means, let alone physics, but I love watching these shows because while I could never explain it, I feel like I get it. And at first I was like, this seems pretty basic, anyone who knows anything about this should already understand Gravity is not emanating from an object and pulling things in somehow. Even I was capable of realizing this. Then he kept going and I was like geez, I thought I was smart for a whole minute.

[@lyrimetacurl0]

You may be onto something there because the radius increases proportionally to the mass so it's like a 1D line of mass.

[@emilialittle1002]

@@timelapseofdecay9028 the chain is metaphorical, it stands for the gravitational field in this case, in which case since black holes are incredibly warped regions of spacetime they would be be able to influence stuff directly next to them, and so on and so forth until the gravity reached whatever object was orbiting or falling into the black hole

[@paysour3]

I think they're all wrong. Gravity is not a force that pulls you. I think gravity is a force that pushes. Gravity is a byproduct of the reaction of dark matter with the physical world. Dark matter is the most abundant substance in the universe. To understand gravity it cannot be left out of the equation. Gravitational forces do not pull you into a wormhole. Gravitational forces push you into a wormhole. Water rushes into a drain because it is being pushed by the pressure differential. When a dam breaks it's not because of Any force on the dry side of the dam that is pulling. It is the enormous push of the water on the wet side of the damn. Gravity is a force created by dark matter trying to reclaim physical space occupied by matter. A wormhole allows Dark Matter to flow out of this universe into another parallel universe or to a distant part of this universe where dark matter is deficient. A collapsing star causes a rapid decline in the amount of space that matter occupies. That sets up a "Cascade Effect" in the dark matter surrounding the star. SUMMARY The density of matter has a direct proportional effect on dark matter that surrounds it pushing in on all sides. Dark matter pressure keeps spiral galaxies from flying apart. If all the known mathematical formulas for Gravity are combined in the symbol "N". We can then say that this concept of gravity would be represented by the formula Gravity = -1(N) I'll even go out on a limb and suggest that the instantaneous collapse of matter could open up a wormhole and the possibilities of faster-than-light travel. Dark matter has the capacity to flow in its effort to reclaim the area mass occupies. If there is movement of Dark Matter than there should be turbulence around objects that move. Most likely LaGrange points should be where we start our search. L1 and L2 are particularly interesting because they require regular course Corrections. Plotting that correction data with a precise Mass accounting for the fuel that is used in those course Corrections we should be able to come up with a mathematical signature for dark matter. Fluctuations in the Cosmic Microwave Background maybe another way to detect dark matter.

[@fikretyet]

One of the best eye opening, mind jiggling episodes on this channel. As a person especially interested on these topics I feel adequately satisfied.

[@TheMiracleMatter]

I used to be disappointed in black hole-related videos lately... I don't even recall if it was in part due to this channel or not some of the times... I was shouting at my laptop "no that's wrong, YOU"RE F**KING WRONG !" and was particularly disappointed in how many mistakes there was in each video. But finally, FOR ONCE, one of them answers an interesting question for which the answer is not obvious right away.

[@paysour3]

I think they're all wrong. Gravity is not a force that pulls you. I think gravity is a force that pushes. Gravity is a byproduct of the reaction of dark matter with the physical world. Dark matter is the most abundant substance in the universe. To understand gravity it cannot be left out of the equation. Gravitational forces do not pull you into a wormhole. Gravitational forces push you into a wormhole. Water rushes into a drain because it is being pushed by the pressure differential. When a dam breaks it's not because of Any force on the dry side of the dam that is pulling. It is the enormous push of the water on the wet side of the damn. Gravity is a force created by dark matter trying to reclaim physical space occupied by matter. A wormhole allows Dark Matter to flow out of this universe into another parallel universe or to a distant part of this universe where dark matter is deficient. A collapsing star causes a rapid decline in the amount of space that matter occupies. That sets up a "Cascade Effect" in the dark matter surrounding the star. SUMMARY The density of matter has a direct proportional effect on dark matter that surrounds it pushing in on all sides. Dark matter pressure keeps spiral galaxies from flying apart. If all the known mathematical formulas for Gravity are combined in the symbol "N". We can then say that this concept of gravity would be represented by the formula Gravity = -1(N) I'll even go out on a limb and suggest that the instantaneous collapse of matter could open up a wormhole and the possibilities of faster-than-light travel. Dark matter has the capacity to flow in its effort to reclaim the area mass occupies. If there is movement of Dark Matter than there should be turbulence around objects that move. Most likely LaGrange points should be where we start our search. L1 and L2 are particularly interesting because they require regular course Corrections. Plotting that correction data with a precise Mass accounting for the fuel that is used in those course Corrections we should be able to come up with a mathematical signature for dark matter. Fluctuations in the Cosmic Microwave Background maybe another way to detect dark matter.

[@christianczekalla4188]

I like the way you guys handle mistakes in past episodes. A good example for feedback being taken seriously.

[@GarrettJohnson1986]

Kudos to the simulation of the star collapsing into a black hole and the slowing of space time at each reduction till it finally slows so much that we never see it. Truly amazing stuff and it really helped to understand that the space-time warp could itself cause the fact that nothing comes back from the even horizon because it would simply take infinite time...

[@sid6645]

This episode blew me away.. Black holes are simply collapsing stars relatavistically frozen in time forever, exerting the gravity field it had the instant before it went past our current theories. Fascinating how information emerges from "simple" math equations!

[@theSlimShadyChannels]

your comment blew me away haha

[@davruck1]

They only exist in math. “Physics” has become a joke. If relativity’s predictions do not flawlessly correlate with observable data then it is foolish to use it to predict anything with certainty. If your rifle scope wasn’t calibrated would you use it? You might hit a close target 5 feet away, but there’s no way you can make a snipe kill from 300 meters.

[@warpedwhimsical]

@@davruck1 we literally have pictures of a black hole from a telescope bro what do you mean they only exist in math? We also have tons of gravitational wave measurements, gravitational lensing observations and other supporting evidence for the existence of black holes. This comment is so ignorant lol. By physics has become a joke you mean you’re discounting physics because it’s become too difficult for you to understand Relativity’s predictions correlate with observable to a higher degree than any other model of physics we have. That’s WHY it’s the currently accepted theory. The whole point of science is that if we ever find a better explanation, that will replace the theory of general relativity, how about you go out there and discover it since physics is such a joke. So easy, right?

[@whimsy5623]

@@davruck1 mate you commented this under the wrong video

[@spiralsun1]

I like the waterfall analogy and the event horizon defined by the acceleration reaching the speed of light at that point like a fishie fish 🐠 (they are so cute 🥰) going over a waterfall. Prolly not a salmon though. They swim up waterfalls over and over all pro and stuff like that.

[@j.d.6915]

How does gravity escape a black hole? Very, very carefully.

[@halide33]

I thought gravity caused the black hole in the first place. Can it escape from itself?

[@mdev3987]

Dad joke 👍

[@anywallsocket]

It’s a strange question indeed. Nothing tangible is ‘escaping’, so I’m not sure why they framed it that way. The fact that spacetime is locally connected is enough to explain why the event horizon doesn’t simply cut out a spherical hole in spacetime and disappear completely - as appears to be implied; I.e., how the spacetime inside and outside the horizon stay connected. The idea of coherent ripples in the fabric makes perfect sense across the horizon when you understand it as 4D curvature reaching 90 degrees - just like the water vortex angle.

[@ZYX84]

How do you get to Carnegie Hall?? Practice practice practice!

[@lordgarion514]

@@halide33 “Space-time tells matter how to move; matter tells space-time how to curve”. Can we really say that gravity is the cause? Seems more like a "team event". The only reason space-time curved, is because of the matter. I'm just going to go with I don't know. Lol

[@sebastiendumais4246]

I keep wondering, wouldn't it be "simpler" to consider that gravity is actually not mediated by a particle and the rest of the forces are actually manifestations of space time being modulated in different ways (eg: electromagnetism is a manifestation of how space time is affected by charged particles)?

[@tomkerruish2982]

Look up "Kaluza-Klein". AFAIK currently out of favor.

[@mastershooter64]

it wouldnt work because the universe is inherently quantum, like everthing is determined by probabilities, but GR isn't, it's a classical theory

[@michaelmicek]

I'm under the impression that that is what Einstein was trying to formulate until his death.

[@mastershooter64]

@@hyperduality2838 lol this guy again, i honestly cant figure out if you're trolling or if you actually believe in this pseudoscience

[@Derrowssi]

Since everything in the universe is in motion all the time ''forever'', gravity is but an illusion of objects with mass in motion through space being ''pulled'' towards more massive objects which have curved space around them distorting the direction of their ''flight'' path through space ontowards the center of mass. Unless we find the graviton particle through experiment then the concept of gravitational force remains unproven.

[@MrClivesinger]

Hi Matt, Great video! I actually had no problem with how gravity "escapes" a black hole, but your video now has me concerned about how EM fields escape a charged black hole, and how faster-than-light virtual photons impact the rest of my understanding of QFT. For background, I teach undergraduate physics at a University in the UK, and part of one specific module involves (specifically for this query) virtual particles and the strong force, where I show that virtual pions are really short-ranged because they're massive. To create these little virtual things, you need to borrow that mass from somewhere, and the limit on how long you can borrow it for is given by Heisenberg. However, at one point in the derivation of the "range" of the force, you need to give these "particles" a speed (to convert time into distance), and we just handwave that the speed will be close to the speed of light, and everything just kind of works. You end up with a decent prediction of the range of the strong force between nucleons. But in your video, you state that virtual photons don't actually need to be limited to c! If true, this makes assuming that virtual pions travel close to c an incredibly tenuous assumption. Have I misunderstood something? My students would very much appreciate any help you can give me here!

[@thedeemon]

I would point to Feynman diagrams and the equation terms they denote. A virtual particle is any of the internal lines in the diagram. And corresponding term, in coordinate space, is an integral over d4x for all possible points in 4D where the particle may be created and annihilated. Which means both spatial motion and lifetime can be arbitrarily long.

[@MrClivesinger]

@@thedeemon Thanks for the reply. I am not sure that that answers the question about the virtual pions though, as their lifetime and range certainly seem quite limited. Could you elaborate a bit more?

[@thedeemon]

@@MrClivesinger It's important to recall where logically virtual particles come from, they are mainly a calculational tool. In QFT we look at scattering processes where you have some initial state with one set of particles, they meet and interact and fly apart (here cluster decomposition principle is important) and you get a final state with a different set of particles. In fact you have infinitely many possible final states, so you calculate probability amplitudes for each possible final state, this is a scattering matrix, result of projecting final state to evolved initial state via scattering operator, made with a limit of t -> inf from evolution operator which includes exponent of integral of Hamiltonial operator, so we express this exponent of an operator via a series of terms, each further term having more and more instances of Hamiltonian operator combined, and that operator in the end is expressed via particle creation and annihilation operators, so you get an infinite series of terms with more and more complex interactions, more and more intermediate particles created and annihilated, each such term is represented by a Feynman diagram, where outer lines are our input and output particle states while all internal lines are called virtual particles. And those integrals computing all those imaginable paths usually come as integrals over all spacetime (if taken in position space). When you integrate over time from -inf to inf you can derive total energy conservation. en.wikipedia.org/wiki/S-matrix kzbin.info/www/bejne/sKWpoKmteMaCn80

[@sadderwhiskeymann]

I would give ANYTHING to be *that* smart to understand what you're talking about. I am not kidding, I fail spectacularly at math, which is a must to become a physicist.

[@olubli8844]

Fascinating... so many questions. 1. Is it still feasible today to detect the heavily Doppler-shifted light from the collapsing mass from long ago? 2. Does there exist a similar deformation of gravity with the passage of time, equivalent to the Doppler effect on light? Finally here's something I really struggle to understand: gravity is a force, and we now know that we feel the gravitation of the object preceding a black hole. It feels like the force exerted by such a past object should be somehow diluted in time, and maybe should evolve with time. Is it the case? If not, what is exactly conserved over time?

[@DarthVaderfr]

Well diluted doesn't mean that something is disappearing or decreasing in quantity but just that his density is decreased A liquid is diluted if you added another liquid in more quantity so now the first liquid it's diluted And also gravity its caused by "change" in the spacetime tissue so if nothing changed, than also gravitetional lensing has to remain the same in all of the universe At least in total but not in a local space So a black hole is just a very strong gravitational field caused by the maximum density of matter and energy that you can get so gravity has not to change over time because its caused now by the mass and energy of the black hole Because we are talking about field of the general relativity its a bit odd talking about now" but maybe I've explained myselfe

[@DarthVaderfr]

From the first and the second Probably yes or at least it would be possible to detect, those are waves and every waves has to operate in the same way so probably also gravitational wave suffer of the doppler effect but we measured them for the first time just 6 years ago and we take the first picture of a black hole just 3 years ago and also its cosmologically rare to effectively seing a collapsing of a star in to a black hole so probably it would be visible but because of probability we will never see them sooner

[@kylelochlann5053]

Gravity is not a force, which is a cold brute fact of empirical physics. Gravity is one of 4 fundamentally irreducible phenomena at low energy. The mass of any object produces a curvature to spacetime. The curvature at some location is a constant insofar as the mass that is sourcing the curvature remains constant. Any light we would see from a collapse event would necessarily both be redshifted and emitted long ago.

[@paulwalsh2344]

I have often ruminated on these questions too. When it comes to doppler-shifted light, remember that as light gets redshifted, its wavelength, the distance from peak to peak of the wave gets longer. Blue light becomes redder and redder until it becomes invisible as visible light, turning to near infrared, then infrared, then microwave, then radio frequencies like UHF, VHF, LF and ELF. Presumably that goes on, the peak to peak length getting longer and longer. How all these waves are detected is with dishes or antennae that focus those photons's waves onto receivers that can detect them. So presumably with the extremely long wavelengths we would need dishes or antennae as long as those wavelengths which would become impractical to build with our technology right now. As for your second question, I have often questioned if gravity is redshifted similarly to how photons are redshifted AND if so, just like how light from very distant galaxies that are past the edge of the visible universe that are actually moving faster than the speed of light relative to our vantage, not the space they are travelling in, and therefore are causally disconnected from us, i.e. their light can never reach us. So, do gravitons suffer the same fate AND since gravitons mediate the force of gravity, then if gravitons are causally disconnected then is that what causes the apparent dark energy theorized to be accelerating cosmic expansion... that it's not a new force"dark energy", but simply the limitation of graviton exchange at megaparsec scale that "frees" the matter of very distant galaxies and galaxy clusters, in essence letting them expand faster and faster. That dark energy is to gravity what redshift is to light.

[@Corvaire]

@@kylelochlann5053 lol If gravity isn't a force, how can it be a phenomena at low energy? That's not very brute of you. ;O)-

[@DrZedDrZedDrZed]

I've got this pet theory I keep knocking around my head that gravity is the geometric "buffering capacity" of 3 dimensional space. As in, the background that all quantum fields depend on and exist within, can only communicate their overlapping contents so quickly to neighbouring regions of space, like bottlenecks in transmission speeds. Black holes are simply what you get when the informational content of a 3D region of space exceeds that limit. Transmission fails, and that critical quantity of mass/energy gets "stuck" in relation itself (what I find most fascinating about black holes is that they can MOVE. Implying that they aren't tears in the fabric of space, but tears in the relationships between the mass/energy that fills it). I find this "buffering capacity" view a compelling analogy because with it, you get causal asymmetries that see different regions of space experience communicability at different rates, which creates the time gradient that is the "force" of gravity in GR. You also get the inverse square law of gravity's influence, if you consider, like an infinitely branching network, communication bottlenecks dilute the further out from the source you get, which itself answers some of the mystery of gravity's relative weakness. It also perfectly encapsulates the equivalence of gravity and acceleration, if, when picturing an accelerating reference frame, you imagine an asymmetrical and exponential compounding of information accumulating in the direction of the source of the thrust. The equivalence between the speed of light and gravitational waves fits in just as well, when you consider that that speed simply IS the ability of a region of space to communicate to any other regions of space, its constitution. Just feels like it fits together so succinctly. Especially in conjunction with some of the more philosophical implications of QM, mainly that any component pieces within the universe need to communicate their existence to neighbouring component pieces in order to become determinately "real". That's my 2 cents!

[@VoelhoMobile]

That's really interesting. I've seen a similar idea on other comments, explaining the emergence of time as the universe lags by processing information on regions with high energy density. Does it have a name already? Maybe the "Cosmical Lagging Theory"

[@sircrapalot9954]

It sounds like a nice pet theory. Quantum mechanics is so counter-intuitive. A fair motto about any unifying theory that tries to rectify Quantum and Classical physics is: “if it sounds poetic and straightforward, it’s probably wrong.”

[@User53123]

I have a theory similar to this too. Except I used ripples which dilute as they grow larger. I think the communication differences could be the cause of quantum tunneling.

[@sircrapalot9954]

@CRIMNALSNEAK Did you just vomit science words into a text box and think “yeah, that’s deep”?

[@luudest]

0:45 Amazing! In 1915 they already had awesome animations of curved spacetime

[@skycloud4802]

That's bonkers if it's actual footage.

[@ritemolawbks8012]

That Einstein was ahead of his time. Sometimes they claim his used a rocket in space example for the equivalence principle thought experiments.

[@spacecadet1249]

So many deep thinkers frequent this channel! Thanks for being the conduit that attracts them, their questions, and comments. I've always told people that Gravity is the one thing that can escape a black hole. this added more insight on the matter. thanks!

[@evasilvertant]

I cannot find his account any longer, but I followed a physicist named Harry McLaughlin if I remember correctly, who studies black holes, and he has always argued against physical singularities, and explained how the black hole mass density is distributed over the volume of a black hole. He always made a lot of sense to me, but I am not a physicist nor do I have enough mathematical insight to conclude for myself whether a singularity or distributed mass density makes more sense. Either way, I was a bit surprised when you stated a singularity as fact at the beginning of the video. As far as I can gather, there isn’t necessarily consensus on that in the physics community.

[@grahamhenry9368]

I’m not an expert, but I have heard many physicists doubt the existence of singularities simply because a singularity has historically implied that your model has reached the limits of its capabilities. There are singularities in Newtonian physics that we never observe for example because they don’t exist, they are simply an artifact of the model being pushed past its bounds. As far as the black hole mass density being distributed over the entire volume of a black hole, that just seems obviously incorrect to me, and it would be very easy to determine if this were the case because it would dramatically alter how objects behave near the event horizon.

[@jeffwarrack9059]

Would it be possible to quantum entangle two particles, sending one past the event horizon and still be able to measure the other particle? If it is theoretical possible, what could we expect to learn from it?

[@Mernom]

I'm pretty sure that entanglement is not stable enough to survive something like this.

[@unitedfools3493]

Isn't this that special kind of radiation that Hawking theorised about which leaks information from past the event horizon?

[@LilinRavenholm]

You just described Hawking Radiation.

[@nutopio]

You will only know for example the particle I measured has clockwise spin. So the particle inside the black hole should have anticlockwise spin. But you can't check that because you can't go inside the black hole with your measuring tools.

[@vladyslavkorenyak872]

Well, you would need to wait an infinite amount of time for that no?

[@Siderite]

I love how you ask questions a kid would ask, then answer in a way I can barely comprehend. But keep'em coming :)

[@PlanetXMysteries-pj9nm]

I was born with many difficulties in my life. Although I am not fully educated, I have a strong love for science and the universe. Thank you for bringing it to me. Love you

[@JugheadJonesIII]

I’m a Med student… never studied any quantum physics…but you sure were able to make me understand 75-80% of the quantum physics used here…. Thanks man…. Much appreciated….( fact: my physics was as strong as biology until I chose Medical line…) …. KEEP IT UP MAN💯💯💯💯💯💯💯💯

[@Endoplexer]

Soon quantum physics will change medicine forever.

[@vrbic207]

Question: 6:58: They (virtual particles) don't really travel from one location to another, carrying force with them. But the similar concept is used in description of Hawking radiation. What is the difference?

[@sadderwhiskeymann]

It's just a poor analogy that virtual particle gets trapped inside the black hole and its counterpart escapes as Hawkins radiation. It is all about fields and how the black hole ristricts the "jiggle" of said fields at the event horizon with its insane gravity.

[@ColeSkene]

Would love to see an episode on Stephen Wolfram’s physics project!

[@greengoblin9567]

There already was

[@michelgent7419]

@spacetime please do!

[@ColeSkene]

@@greengoblin9567 send me a link!!

[@ngruhn]

Same

[@ngruhn]

Episode confirmed, boys: kzbin.info/www/bejne/qqjZm2ylqJ53gqcm15s

[@billyte1265]

If you see the mass of a black hole as it was before it entered the event horizon, what happens if the event horizon expands significantly? Like what if two black holes merge? Do you see that mass at the distance from the center where it originally hit the (smaller) event horizon of its original black hole? Or is that influence "pushed out" to the shell that is the event horizon?

[@davidpendrey1736]

Similar question: if gravity/mass and charge are stored on the event horizon then what happens in the (admittedly highly unlikely if not impossible) situation where a lot of mass or change lands on one side of the black hole? Do you get a black hole with gravity stronger on one side than the other, could you make a black hole that is like a battery and has a giant positive and negative charge on different sides?

[@bsadewitz]

What do you mean by "see the mass"?

[@bsadewitz]

That is, we don't see mass. We see light.

[@bsadewitz]

​@@davidpendrey1736 I don't think black holes are defined in that way.

[@bsadewitz]

Take whatever I say about this with many grains of salt, but I don't think charged black holes actually exist, or at least are not expected to exist.

[@itcamefromthedeep]

Your diagram of the sun's gravity at 3:43 suggests that the pull is strongest at the geographic center of the object, which is not the case. It's strongest near the surface. Diagrams like this should have the massive object effectively sitting on a mound rather than at the bottom of a depression in the way a physical object would sit on a physical fabric. (It's easy to see why this mistake will continue to be made for decades to come.) I think this should have implications for the formation of an (inevitably rotating) black hole. What happens to the tiny region of flat-ish spacetime in the middle?

[@dlevi67]

That's why the (theoretical) singularity of a Kerr black hole is not a point, but a ring... methinks.

[@thedeemon]

Penrose and Hawrking demonstrated mathematically that once you have enough matter in a region to form an event horizon, the formation of singularity is inevitable, not matter how the masses were distributed inside. All their paths in spacetime meet in one point. (for a non-rotating BH) For rotating case (non-zero total angular momentum) there will be a ring singularity. en.wikipedia.org/wiki/Penrose%E2%80%93Hawking_singularity_theorems

[@itcamefromthedeep]

@@thedeemon I know that part. Non-rotating black holes will be about as common as hen's teeth so we ignore that case. So the middle goes from being the highest-density region to emptying out. I'm not clear on why (because I haven't learned the math) but I suspect it's due to frame dragging. I'd like to see an episode going a bit deeper on the speculated structure in and around ring singularities.

[@feynstein1004]

This is a common misconception. In our universe, it's change that's limited by the speed of causality, not existence. If there's a change in the gravitational field, then it cannot propagate faster than c. But the field itself, which is static, doesn't have this restriction because it's not changing or moving. It simply exists.

[@fusionspace175]

That title bothered me too, the idea of gravity "traveling". But common language is perhaps better for the laymen, if imprecise scientifically. It's forgivable, I suppose.

[@feynstein1004]

@@fusionspace175 Ahaha fair enough

[@feynstein1004]

@@hyperduality2838 That's some serious tripping, mate 😂

[@theultimatereductionist7592]

@@hyperduality2838 Knowing what I do know from higher mathematics, the word "dual" has strict formal definitions depending upon the context in which they are used. I'll have to check, but most if not all of what you said is garbage word salad. Mathism. In other words, the deliberate misuse & abuse of real words from math but totally out of context.

[@theultimatereductionist7592]

@@feynstein1004 No. It's actually some serious bullshitting. I'll have to check to see if Hyperfoolality got one or two things right, but I doubt even that.

[@ParadoxProblems]

2 questions. 1: Can an event horizon "form" around a body of mass without the mass having to pass through it. That mass wouldn't be "on the event horizon" from a distant observers point of view. (Basically the question is does every black hole start from effectively 0 radius and expand outward or does it form with some non-0 radius?) 2: You said spacetime reacts to neighboring patches of spacetime, but how can a patch of spacetime next to the event horizon react to a patch either crossing it or on the other side of it. (This becomes more obvious when considering the infalling spacetime case but less so when considering the more static sheet)

[@guilhermegrg]

Í por iiiiiiiiiii Ii ii

[@samuelowens000]

To your first question, the event horizon forms with a nonzero radius. As soon as there's enough mass in a small enough space, an event horizon forms around that mass.

[@ThirtytwoJ]

If the spacetime is actually being drawn in itself that could explain the seeming expansion as the parts being pulled in...would def cause a weird effect.

[@drdca8263]

On a small enough patch of spacetime near any point of spacetime, even a point on the event horizon, in an inertial frame, things look normal, I think. I don’t know general relativity, but I know a bit about differential topology, and a little little bit about GR, so, I’m somewhat confident that on a small enough patch, an inertial frame, will basically look like normal spacetime ?

[@pavelrozhkov3239]

@@samuelowens000 Are you sure this is true? My intuition tells me that the event horizon should gradually increase from one point in the center as the body collapses. And all the particles that make up the body must fall to the event horizon without ever crossing it. If the event horizon appears immediately with a certain radius, then the space-time metric will at that moment have a gap with an indefinite time derivative. Shouldn't this be happening smoothly?

[@paulmichaelfreedman8334]

My thinking is simple: Don't think of gravity as a force, but as pure space time distortion. That distortion was present before and during the black hole creation. It was always there, no need to escape.

[@dimitrispapadimitriou5622]

This video was a good opportunity for addressing several common misconceptions about black hole physics. It succeeded only partially, because it had itself some misleading statements. For example, at 1:00 . Generically, black hole singularities are spacelike. They are not pointlike, of course, and they are not at the " spatial center " of the hole. The center of the coordinate system ( at r= 0) coincides with the spatial center of the collapsing star ( assuming approximate spherical symmetry) only before the formation of the singularity- this is obvious even from the usual spacetime diagrams ( Penrose, Kruskal, Eddington/ Finkelstein etc.). Afterwards, the constant r hypersurfaces are spacelike inside all realistic black holes. That means for example that if two astronauts fall inside the black hole following the same trajectory, but with a difference in ( coordinate) time, their remains won't meet at some center! Instead they' ll end up in causally disconnected "places", very far away from each other. This is also true for the remains of each single astronaut. What is called a spacelike singularity in GR is essentially the unbounded growth of the tidal forces, that is time dependent inside the hole, so there is only a finite amount of proper time before the singularity happens! In that sense, the singularity is,( almost literally) Everywhere inside for an infalling object.

[@samuelthecamel]

How have I never heard it explained this way before? This deserves its own video

[@MinistryOfMagic_DoM]

Have you looked at the research showing black hole ejections are creating new stars? It's quite interesting. I don't understand it, obviously, but it's nifty.

[@danieljensen2626]

I believe it's material/radiation ejected from the accretion disk around the black hole, nothing is actually ejected from inside the black hole.

[@cosmicpickle2659]

Awesome. this same question came to mind about a month ago and I'm stoked you guys did a video on it. If I understood correctly, then a static field, such as the charge of a stationary particle or the mass of a stationary object, is still "visible" indefinitely at the event horizon (makes sense). This seems to imply that black holes could appear "spiky" w.r.t. electric charge from charged particles falling directly into the black hole. Similarly, it would seem a blank hole's gravity could appear to have an uneven topology across the surface of the event horizon due to directly-infalling matter. Although this sounds theoretically plausible, it seems practically impossible given the complex dynamics of black holes and any infalling matter. My take is that anything of the sort would be extremely transient at best, due in part to it's self-defeating nature (inducing rotation of the black hole, etc.). *** Edit *** looks like @Rutvik beat me to it, and does a good job of illustrating an example. Follow-up question - any interesting implications on this subject as a result of an expanding event horizon as the mass of a black hole grows? Would seem to me that the former static fields would appear to now be "inside" the newer, bigger event horizon.

[@Jonathan-ee4rn]

Was coming to ask this too. It seems more plausible if the mass that became the black hole was very lumpily distributed before it reached the threshold to form an event horizon.

[@Wasabiofip]

Repeating someone's answer about charged particles falling into a black hole, as I think a similar idea applies here but I don't really know: the information doesn't just freeze at a point on the event horizon, it gets "smeared" around the whole thing, so that it doesn't become lumpy.

[@talldarkhansome1]

Interesting idea about a black hole eating its past signature. Perhaps we don't understand this stuff at all.

[@tuneboyz5634]

cute dog ☺️

[@garethdean6382]

As noted elsewhere, things get distorted near a black hole. The lines of charge, like the paths of photons, bend and can orbit the black hole before escaping. A single charge then can seem to emit across the whole surface of the hole once close enough, smearing it out over the entire horizon.

[@xani666]

That's kinda like asking "does gravity affect gravity"?

[@ChilapaOfTheAmazons]

What about *rotating black holes?* 🤔 Are their external properties (frame drag and magnetic field) consistent with mass and charge at the event horizon or consistent with a singularity ring of matter deep inside the black hole?

[@Kitsudote]

I will always trust people the most, who admit mistakes honestly and even correct them, because those are the people who seek the truth.

[@adamlaceky8127]

Here's what's wrong with the usual illustrations of gravity warping spacetime. Mass contracts--compresses--space around it, and dilates time. When you stand on the ground, the spacetime you occupy is more contracted near the ground. Length is shorter at your feet, and time is slower. Your feet are in a different inertial frame than your head. It's as if you're being accelerated AWAY FROM the Earth. Your mass expresses an equal and opposite reaction to this apparent acceleration, so it moves toward the center of gravity. Gravity simulates length contraction and time dilation exactly as if you were standing on an accelerating platform in empty space. On Earth, it's as if you're standing on a platform that's moving at 9.81m/s^2. There's no difference between the two. The platform accelerating you makes you feel as if you're moving in the opposite direction--toward the platform. When you're in free-fall, you're weightless. It's as if you're some distance away from the platform, which is accelerating toward you. You're weightless, until the platform smashes into you. Then you feel weight. Gravity doesn't stretch space--it compresses it. Gravity displaces spacetime. The point of space where the singularity is--it has been pushed out from the center of gravity, to the event horizon. All the space "inside" a black hole is on the surface. There is no space on the inside. There's a dimension that's space-like, and time-like, but you can't think of it in the normal way. The center of a black hole is not a point in space, but an instant in time. Near the event horizon, the difference in spacetime distortion--tidal force--is so extreme that you'd be spaghettified. A free-fall into a black hole would kill you terribly. (Except, maybe, for the hypothetical black holes of low density. The Schwarzschild radius is linear, so...)

[@CharlieQuartz]

I'm not an expert in GR but I believe there's a tiny discrepancy in your explanation. It is my understanding that while standing on an accelerating platform and in a uniform gravitational field are the same, they are not the same as standing on the surface of a planet, where the compression of the gravitational field increases to the surface. Length contraction and time dilation would happen at the top of your head and bottom of your feet the same on the accelerating platform but not on Earth. I love the rest of your explanation, though. Edit: corrected "center" to "surface"

[@setcheck67]

Black holes sufficiently large enough like Ton you'd be able to cross the event horizon and be bored for a long while before dying(provided sufficient protection from the now gamma radiation from the normal light entering the black hole).

[@thedeemon]

>Gravity doesn't stretch space--it compresses it. This is the opposite of what GR says. Just look at the Schwarzschild metric. Radial distances grow longer near a mass.

[@jpgalo99]

I did not understand any of it, but I loved every minute of it!

[@Ryan-sx1pz]

Since the expansion of the universe is accelerating, wouldn’t that mean time itself is also accelerating? If so, is the universe 13.7 billion years old in “today’s” sense of time?

[@nenmaster5218]

I love to give scientific Watch-Suggests, but many cant handle the Randomness of this Offer. Can You?

[@muthuramalingam1032]

The expansion of the universe doesn't accelerate the time. For example, a balloon is expanding ( means it doesn't expand by consuming it's boundary objects) it's entirely volume of space inside the boundary is evenly expanding - the thing is we blow air. But in universe, space is created everywhere it is hard to understand, that is why the farther objects move faster than your nearby objects. I give you an simple example for Hubble constant. If ABC are the there objects equally spaced say 1 meter. So the distance between A to C is 3 Meter. After some time due to expansion of space the distance between A to B is 2 meter, Also because of the expansion B to C is also 2 meter. Now the total dist A to C is 4 meter. C moves double time faster than B from A. This means the space is created everywhere. So the acceleration of space doesn't accelerate the speed of light. Light uses space as a path to travel

[@bastadtroll8922]

Even eisntein didnt know the answer to this. He once said gravity is spooky from a distance. Anyway the great thing about physics is that there is no one correct answer.

[@shukrantpatil]

@@nenmaster5218 yes please .

[@nenmaster5218]

@@shukrantpatil Cool. Well, theres many. Professor Dave Explains, Sci Man Dan, Genetically modified sceptic, joe scott, sci show and some more news are just some real-good ones that come to mind.

[@sebas9174]

In a two black hole merger scenario, at the time of the merger, a new event horizon is created that engulfs the two singularities that are still orbiting in a spiral. As they continue to orbit until the singularities merge, gravitational waves escape from this new horizon in a phase called the ringdown. This "escape" of gravitational waves, could not be considered as information that leaves the horizon towards the outside?

[@asmodean7239]

I don't think so, since waves come from 'remembered' mass outside of event horizon. (if we just think in terms of relativity theory)

[@liwoszarchaeologist]

I think an entire episode on ringdown needs to happen soon. In this and previous episodes Matt has already laid the foundations we'll need to follow such a discussion. It sounds like Relativity and QFT will resolve this paradox in slightly different ways. My gut tells me that at the formation of this combined event horizon it will initially be stretched into something far more lumpy and asymmetric than a spheroid/torus and that the ringdown is a part of settling process - but I'm not a physicist so don't trust me on that!

[@tarod3]

Don’t the black holes lose considerable mass in the merger, expended as gravity waves?

[@RME76048]

Is the shape of the merging event horizon more-or-less dumbbell-shaped so long as the singularities still orbit each other at a significant distance from their common center of mass? If they are truly singularities, won't their inward spiral be infinite and never actually merge? I mean, you can always subdivide the distance between two points forever, right? So, in a sense, the ringdown would last forever but perhaps in a rapidly diminished way as the proportion of their distance between the event horizon and their mutual center of mass approaches zero but never quite gets there? As any and all mass falls into a black hole, does it imprint a ringing bell-like series of harmonics upon the surface of the event horizon like waves on the ocean, ones that rapidly diminish but never quite vanish? Yeah, I know. Questions but no answers. Sorry.

[@garethdean6382]

An issue is the definition of 'information'. For information to escape a black hole I must be able to learn something about the hole I couldn't tell from the outside. Such as what it was made of. In the case of a merger what's escaping is the hole's kinetic (and rotational) energy, which is already apparent from the outside. Indeed the total gravitational output of the merger can be predicted ahead of time based on this information. If the holes emitted particles that depended on their composition then THAT would be information escape and quite a revelation.

[@SuicV]

Barely related question, but here it goes: could a warp drive theoretically be used to overcome the expansion of the universe and to travel past the horizon of the observable universe?

[@planexshifter]

I suspect so, however the distance is astronomical!

[@planexshifter]

Also, if you can see it from your warp ship, wouldn’t it BE the observable universe ?

[@SuicV]

@@planexshifter Well, technically it would then be part of your new observable universe, yes. So lets clarify and consider whether it would allow you to travel beyond the observable universe from where you were before you begun the trip

[@jdhenckel2]

Right. Ever played Portal? Warp drives are like a portal that allow you to reappear in a region of higher potential energy, thus they break the law of conservation of energy. Probably other laws also.

[@spikkelkip8128]

To travel to something there has to be something to travel to. there are two possibilities: either the universe is infinite and there is no end to the universe and thus no way to cross this end, or it has an end with no time and space past that point. To travel to a plca there needs to be space, so even if you made it to the edge, there would be nowhere to move to past that edge (this is my view on it of course)

[@austin8179]

A big big thank you Matt ! You’ve answered a question that I has over many years that is how a BH can have a charge if it is beneath the evnt horizon. Your answer is surprisingly simple yet profound : according ro our point of view, it is the past charge that we see, not the actual one… Honnestly, I asked this question around and around and got no answer, you are the first to address it and I am grateful for that.

[@paysour3]

I think they're all wrong. Gravity is not a force that pulls you. I think gravity is a force that pushes. Gravity is a byproduct of the reaction of dark matter with the physical world. Dark matter is the most abundant substance in the universe. To understand gravity it cannot be left out of the equation. Gravitational forces do not pull you into a wormhole. Gravitational forces push you into a wormhole. Water rushes into a drain because it is being pushed by the pressure differential. When a dam breaks it's not because of Any force on the dry side of the dam that is pulling. It is the enormous push of the water on the wet side of the damn. Gravity is a force created by dark matter trying to reclaim physical space occupied by matter. A wormhole allows Dark Matter to flow out of this universe into another parallel universe or to a distant part of this universe where dark matter is deficient. A collapsing star causes a rapid decline in the amount of space that matter occupies. That sets up a "Cascade Effect" in the dark matter surrounding the star. SUMMARY The density of matter has a direct proportional effect on dark matter that surrounds it pushing in on all sides. Dark matter pressure keeps spiral galaxies from flying apart. If all the known mathematical formulas for Gravity are combined in the symbol "N". We can then say that this concept of gravity would be represented by the formula Gravity = -1(N) I'll even go out on a limb and suggest that the instantaneous collapse of matter could open up a wormhole and the possibilities of faster-than-light travel. Dark matter has the capacity to flow in its effort to reclaim the area mass occupies. If there is movement of Dark Matter than there should be turbulence around objects that move. Most likely LaGrange points should be where we start our search. L1 and L2 are particularly interesting because they require regular course Corrections. Plotting that correction data with a precise Mass accounting for the fuel that is used in those course Corrections we should be able to come up with a mathematical signature for dark matter. Fluctuations in the Cosmic Microwave Background maybe another way to detect dark matter.

[@austin8179]

Thank you for your answer, but I think you should rather submit it to Matt or any expert rather than me. My comment does not aim at guessing a new physics law, but rather understanding the already accepted laws of physics. All in all, if I follow your reasoning, gravity is a by-product of dark matter flowing (btw what is the engine causing the DM to flow?). If so, there exists already an equation governing a fluid in motion, it is the Navier Stokes equation, and you may want to compare its results VS GR when applied to strong fields (NS is linear vs GR is not, so others probably already did and they certainly proved GR to be more effective, else why use a more complicated set of eqn rather than 2 more simple ones?). The theory you have around turbulences is very close to Descartes’s theory which I know was later discarded after Newton published his laws. This also is probably an indication that further insight is needed. Your theory looks to be based on classical / pre relativistic physics, and this would surely be a very pleasant theory that simplifies physics if it works. But seen this way, any expert (which I’m not) can confirm or falsify your theory, so don’t hesitate to ask them.

[@paysour3]

@@austin8179 I was like you more inclined to accept the established laws of physics. That is until I saw those Tic Tac objects defy all known laws of physics. They play games of tag with America's best fighter pilots. They have no heat signature that would correspond with their acceleration, they produce no Sonic Boom, and maneuver without any aerodynamic flight structures, and seem to be oblivious to g-forces. That sent me back to the drawing board because we are obviously missing something. I have always believed that there was a medium in space undetected as of yet but we can see the affect on the spiral galaxy. The engine, as you call it, powering this effect I believe is a result of Dark Matter trying to reclaim physical space. The greater the mass the greater the pressure. I also believe that the instantaneous collapse of matter has a corresponding effect on dark matter. That would include the subatomic level as well as massive stars. I believe those Tic Tac Unidentified Aerial Phenomena are defying current laws of physics because they are able to collapse matter around them. I'm going to take your suggestion and the next time I have to investigate I am going to review those laws of fluid dynamics. I sincerely don't think that there is a enough Force within a black hole to produce the enormous amount of gravity pull. Instead I believe you are pushed into a black hole dragged along with dark matter. I'm more inclined to believe that the enormous gravitational pull of a black hole is related to the flow of dark matter through the black hole itself. Like pulling the plug on a bathtub and to scale it up slightly the collapse of a massive water dam. The dam is not destroyed by the forces pulling on the dry side of the damn. It is the forces on the wet side of the dam that causes the collapse that drags along everything within the vicinity. 40 years ago when I had physics in College I believed space was not a void. I believe the universe is swimming in a sea of dark matter. Pushing in on all sides of the physical world. I would even go so far as to say that a black hole terminates with a "BIG BANG" somewhere else in the Multiverse or expanding this universe. Controlling the collapse of matter I believe could open up a wormhole. As I see it unless we can render time and space irrelevant we will never see the far reaches of the universe. I speculate that wormholes and black holes can be shortcuts across the vastness of time and space.

[@paysour3]

@@austin8179 oh no I respect your opinion. You seem to be a very knowledgeable person. We cannot abandon our responsibility to provide ideas. Keep in mind we owe the development of the Aerospace industry because of two bicycle mechanics. Oval and Wilbur Wright were not aerodynamic engineers they repaired bicycles for a living

[@MrRyanroberson1]

One problem i've had lately with "all the black hole's mass is in the center" is the following: as time slows down around the black hole, how are we to know that the mass has even had the time to get that dense? As matter crushes in the center of the black hole, surely time dilation would slow the event down exponentially, until finally it (effectively) freezes in some finite state (even if time for most of the mass still elapses at a rate of about one quadrillionth)

[@dodatroda]

Time isn’t a physical thing. It’s just something we measure about nature, a dimension. A black hole is a place where everything is stopped, ceases to move, to be. I can’t understand why everyone thinks it’s so much more complicated.

[@frankn254]

Time slows down around the black hole *from an outside observer*. If *you* fell in, you'd experience time as normal and the universe would appear to speed up and see the heat death of the universe before you fell completely inside.

[@dodatroda]

@@frankn254 Which is the exact same thing as you never fall inside. There's no such thing as falling into a black hole.

[@ShadeAKAhayate]

@@dodatroda *but that applies only to the perception of ones that are outside of the event horizon. And even to the outside observer it isn't stopped, it continues to fall, just continuing to slow down exponentially. That obviously won't stop an object itself that's dropping through the event horizon like nothing happened.

[@dodatroda]

@@ShadeAKAhayate No. That makes no sense at all. To "slow down exponentially" means to stop. And there is absolutely nothing obvious about "dropping through" an event horizon, a concept that is literally impossible. The observer-dependent physics belongs to Special Relativity and does not apply here, no matter what physicists say. If you don't move you don't move. And in a black hole there can be no motion. You can disagree of course and believe what you want, no one knows anything about what goes on inside black holes. It's just not logical, let alone obvious, to postulate that you can fall in perpetuity into a singularity.

[@DanielDogeanu]

You don't need a mediating particle for gravity (graviton), the space-time itself is the mediating particle. Meaning, the space-time itself is made out of some kind of particle, or maybe something like rubber bands (strings) interconnected with each other. That is what transmits the information from one region of space-time to another. The reason we can see/feel the gravitation from a black hole, is because space-time itself transmits that information. Each space-time particle interacts to the one next to it (as explained in this video). The reason space-time itself can send information pass the event horizon is because the space-time never becomes causally disconnected with itself! It's still just one piece of interconnected things, a singularity exist on top of the framework of space-time! I hope it makes sense...

[@juzoli]

Science never claimed otherwise either. The smallest unit of spacetime which can mediate gravity IS the graviton. The term graviton as particle only means that there is an elementary unit of gravitational wave (as wrinkle in spacetime), and it cannot be smaller. Which is hypothetical, but makes sense, since matter what can cause gravity has a smallest unit too... So graviton only means that gravitational wave can be quantized. If it can be...

[@eriknelson2559]

Science Asylum has a video about how elastic / stiff is the fabric of spacetime, turns out to be ultra-rigid. The fabric of spacetime could unify all of Physics. Per QFT, "particles" could be viewed as oscillations of the fabric, "reverberations" or "sounds" which have been "ringing" in the fabric since the Big Bang and propagating away from that "event" in our "forward" time direction... vaguely like seismic waves through the earth. The fabric of spacetime could be the only actually existing substance, all other quanta "particles" and "photons" could just be "vibration oscillations" of the same

[@juzoli]

@@eriknelson2559 That would be a nice resolution for the theory of everything, but at this point it is highly theoretical. Right now the biggest question is that we know how large masses of material curves spacetime, but we don’t know what is the mechanism of a single elementary particle curving spacetime, what is the the way one particle tells all the other particles to curve in their motion in spacetime Maybe once we find this fundamental building block, we might see that they are the reason behind other types of interactions too.

[@phillipsusi1791]

Hrm... that's an interesting paradox. So things falling into the black hole appear to freeze at the event horizon. But as more things fall into the black hole, the event horizon expands. So how can the older matter still appear to be frozen on the surface of the event horizon after it has later expanded to a larger size? Does it now appear to be frozen inside the event horizon? Or does it appear to have moved outward to the new event horizon?

[@jacobfreeman5444]

It only appears frozen to outside systems. If you were part of the system of the black hole you would be able to see its true state. Think of the event horizon as the point where the system of the black hole quarantines it's interactions from all outside systems.

[@phillipsusi1791]

@@jacobfreeman5444 My question wasn't what it is like inside the black whole. My question is, how can it appear to us, on the outside, that it is both frozen, and expanding at the same time?

[@MedicAthlete24W]

⁠@@phillipsusi1791 it looks frozen to the observer because you are seeing it from a specific and fixed moment or place. Think of it like a puddle. It may look shallow staring down at it, but once you step in it you realize that it is ankle deep.

[@phillipsusi1791]

@@MedicAthlete24W But how can it grow without changing its appearance? New things would have to fall onto the surface and appear frozen there. How can that happen without covering what was "frozen" before?

[@MrSJPowell]

This is one of the few episodes where I intuitively understood the answer to the topic, and (more importantly) why, before I clicked the video. I'm going to say that it's because you've taught the topic well enough in previous videos that I was able to understand at least the underlying GR to get it.

[@Luper1billion]

Its like in the infinite hotel analogy, but where whenever someone first enters their room, a confirmation is sent to the front desk (gravity). As the rooms are being filled faster then the speed of light (blackhole), it takes time for the signal to reach the front, so you could never know the current number of rooms filled (aka mass) but only the delayed count as the numbers keep rolling in. You could never run fast enough to see the rooms as they fill up, nor could you convey anything more then the frontdesk is already getting (the event horizon)

[@KalebPeters99]

This is such a cool analogy, thank you

[@harrybridges8258]

Can I just say, what an absolutely amazing question! I had never ever considered this. And the answer is actually really amazing, and helped me understand more about how the universe works. I am going to be thinking about this for a long time. Thanks!

[@henrysmith9484]

Why don't we introduce a Born Infeld like modification to gravity to regularise gravitational dynamics so that we can rid the misbehaving singularity produced in GR.If blackhole mass is distribution everywhere then is it possible that the gravitational self energy is the energy of blackhole mass itself since mass and energy is same according to E=mc²? There might be a maximum finite curvature of spacetime at r=0 of a point like mass instead of infinite curvature around the shell of schwarzschild radius.

[@kelast203]

I came in confused, since this is basically asking how the gravity of a black hole escapes the gravity of a black hole, and came out multifold more confused. Excellent video.

[@SGTRandyB]

Ok, before watching this I’m going to say ‘it doesn’t’. Gravity is a physical property of bent spacetime while being influenced by any given mass, like a black hole. Therefore the well of gravity is a physical 3D shape in reality, extending not only down to the core of the black hole, but outwards to every other part of the universe’s physical spacetime. If anything, spacetime is being pulled into the black hole to some degree, not escaping it. The shape of spacetime’s affect on objects outside the event horizon is not gravity escaping, but spacetime itself being bent towards to the black hole, creating a well to fall into. Alright PBS ST, educate me. If I got it even close to right it’s probably because your channel taught it to me.

[@RoganGunn]

Wrong! Just kidding you were pretty much spot on. 😜 I like to think of it as, how does the water know to move towards the waterfall, when the water that's fallen over the edge already has gone? Well, because the water next to it moved closer, in a chain. Same with spacetime flowing 'over' the event horizon. This is merely the point where that flow reaches c. As you say, the curvature and flow has already been imparted on it by the previous chunk of spacetime that flowed 'over' the horizon. This is why we can only see a black holes 'past mass' not it's exact present mass, as this past mass is encoded on the surface of the event horizon by time dilation. But also, we have to remember, that while what we perceive as gravitational force propagates _through_ spacetime at c, IIRC the flow of spacetime _itself_ is not limited by c, it's just wherever it exceeds c an event horizon forms. Hence why Alcubierre type drives are _hypothetically_ possible, and the expansion of space itself has a horizon from our POV.

[@WormholeJim]

Ah. So it was a trick question, after all. I got a little nervous when Matt said that gravity travels with the speed of light, suddenly remembering stuff like gravitational waves and virtual particles blinking in and out of existence. But it turns out that good, old Einsteinian visualisation of gravity being a dimple in the space fabric caused by a heavy object still holds out.

[@mattiasselin4955]

Hi Matt! What if we drop a bunch of positively charged particles on one side of a black hole and a bunch of negatively charged particles on the other side? From our perspective the charges will "freeze in place" on the event horizon creating a non-uniform electrical field around the black hole. Wouldn't that contradict that whole thing about black holes not having any hair? Seems quite hairy to me! What am I missing?

[@DarthVaderfr]

Maybe I'm wrong but doesn't the no hairy theorem just say that any black holes have just three characteristic, one including the charges?

[@kylelochlann5053]

@@DarthVaderfr No, you're correct, and that's exactly what is implied by the No Hairs Theorem.

[@kylelochlann5053]

The charges vanish but field of the charges spreads out over the surface of the black hole.

[@Xboxiscrunchy]

The charge doesn’t just hit a point and stay there it gets sort of stretched and smeared over the whole surface of the black hole. At least that’s how I understood it. Someone correct me if that’s wrong.

[@sid6645]

@@Xboxiscrunchy yeah if we look at it with the time snapshot perspective, then the problem of a lopsided electric field arises. But I have a sneaking suspicion that the hawking radiation is just time flowing at an infinitely slow pace (especially on the large black holes), and thats how the charge would "distribute" itself across the horizon. Maybe it gets caught in lightspeed or greater than lightspeed orbit (though an orbit would make a magnetic field, which violates the no hair theorem) around whatever the singularity looks like like, and that to us would be either an instant process or something that would never happen.. idk. Or maybe it decomposes into something that just happens to make a uniform electric field. I should stop guessing lol

[@jfxl1977]

I love science because it continuously questions itself about what it doesn't know. Theories show we have a very thought-out and experimented understanding of what reality looks like, why we function as we do, but it never supposes we have all the answers. This is amazing, appropriate, and exciting! It is how we better ourselves, and how we continue to work toward more knowledge.

[@DJCornelis]

1) Wouldnt a real graviton need to be messaged by another graviton to be attracted to the mass of the singularity? 2) Do two gravity waves interfere like sound or do they pass through each other? 3) How could gravity exist in the first place if its mediating particle is affected and therefor cancelled out by itself? It doesn't because gravity is not a polar force. Only polar forces self-interact. Gravity waves come in at the speed of light so there is no reason to assume a newer graviton could catch up to the older one unless the older graviton was slowed down which would require a graviton to catch up with it to tell it to be attracted. Detecting a graviton would require measuring the local properties of the gravitational field, like sticking your finger in a lake or using a pressure meter on a stretched out canvas. Unfortunatly such a device seems impossible, for now. I think virtual particles, or maybe rather real particles are a misconception. Aren't all particles virtual? Just momentary snapshots of a wave in a certain field. It's only a particle when we make a measurement of the field.

[@Anonymous-df8it]

You solved the renormalization problem for gravity! Gravitons can't self interact, thus the gravitational influence of every particle remains finite!

[@guyedwards22]

To me, the idea that other gravitating bodies can have an effect on the Black Hole's motion is even stranger than the black hole itself exerting a gravitational influence. If you and a black hole were chilling out in otherwise empty spacetime, you would accelerate towards each other, which means that your mass' warping of spacetime is "felt" by the black hole, even though in principle you would never directly observe your own wave of gravitational curvature cross the event horizon.

[@bastadtroll8922]

to quote you "If you and a black hole were chilling out in otherwise empty spacetime, you would accelerate towards each other, which means that your mass' warping of spacetime is "felt" by the black hole, even though in principle you would never directly observe your own wave of gravitational curvature cross the event horizon." wouldnt dark energy expansion cancel out the long reach efects of very far away objects of mass?

[@shiinondogewalker2809]

I'm not mega sure about this but couldn't you observe them if you follow them into the black hole?

[@shiinondogewalker2809]

@@bastadtroll8922 still, if you cancelled out dark energy expansion then that's the way it's "felt", even if you just cancel it out by a fraction there's still an effect. Also you could always get closer to the black hole, or lay on a couple of pounds lol

[@GreatCollapsingHrung]

If the event horizon grows due to in falling matter, wouldn’t these past charges have to move with the event horizon out away from the central singularity, in order for charge to be conserved? If so, wouldn’t that mean when a black hole first forms and grows, say from a Planck length to dozens of kilometers across, all the mass and charge appears to be pushed out along with the event horizon, leaving the space within empty?

[@zackfair7913]

you did not listen. the accumulating charges truly fall into the black hole. it is only from your perspective, if you're a distant observer. that they appear frozen at the event horizon.

[@thedeemon]

@@zackfair7913 I believe the question was "how does a distant observer's perspective on those charges change when the horizon grows?" Which is a sane question.

[@NiflheimMists]

Maybe the infalling matter's gravitational field pulls the old matter, and they reach an equilibrium at the new, larger event horizon?

[@garethdean6382]

Firstly, tissue at hand is what we see from outside the hole; there aren't 'really' charges stuck on the horizon that have to move out, more like 'shadows' where they crossed the horizon. You can think of it like having a depth gauge in a river. It is ten feet tall but only six feet stick out of the water. If the water rises two feet the gauge doesn't float, two feet of it sink under the waves. The total amount of gauge is the same. Charge, like gravity, can be treated as coming from a 'charge singularity' of zero volume. If I move twice as far from a charge I feel half the charge density. If a charged hole grows twice as large the charge density at it surface will be half as strong. In both cases we calculate the same total charge. The amount of charge, like the amount of mass isn't constantly being sent out from the hole like a GPS signal, it's imprinted on the space surrounding the hole and going out to infinity.

[@frankcrawford416]

There is nothing inside a black hole. Everything gets converted to energy before falling in. A black hole is a separation between our universe and not our universe. There is nothing good in there. No life, no stars, no joy, no nothing.

[@Chad_Thundercock]

One of these days, I'd like to see Matt be at a loss for how to wrap up with the signature ending, and just pause for 10 seconds, stare deadpan at the camera, and just say "... Spacetime".

[@adis7080]

Question: If I understood it correctly, somewhere inside the black hole, time stands still? So if a person was standing inside a black hole, that person would perceive it as an eternity? But for us that are outside the black hole, time passes and if one was to live long enough, the black hole would eventually evaporate and disappear? Assuming a black hole could evaporate into a white hole, and objects could then leave the white hole, and time would start ticking again (to the objects that once were inside the black hole). What's the "eternity" that someone was experiencing inside the black hole?

[@redi4deth]

I don't think they would actually experience eternity. Time is relative and always seems to flow normally for the observer. Maybe the fall towards the singularity and (assuming they survive it) the creation of this white hole you're talking about would only seem like minutes or hours to them. But relative to them, we on the outside would see the entire lifespan of a black hole until it evaporated.

[@ToThisEndWasIBorn]

"Fact, mass concentrated at the singularity at the the very center." Frankly, I'm ok with this but in my experience a lot of people get tripped up with the singularity concept. Is there any reason to say "point at the center," or even "infinite density." Does this add meaning to say singularity or is this instead a guess about the arrangement of matter inside of this extreme object of which such a guess provides no value? I believe a previous episode also talks about another possible shape for the concentration of mass, a torus if I'm not mistaken. Sure the math says it collapses and there really is a lot of room for matter to collapse with atoms being largely "empty space." To jump forward in my idea here. Perhaps we think this most collapsed matter is a single point for a similar reason as humans classically believed Earth was the center of everything. It fits in with a healthy sense of logic. But why a singularity? I am surprised to hear this episode say as Fact, infinite density point. At least one previous episode talks about infinities usually being errors in math or holes in our understanding. Is this intended to be a correction of that previous episode? Or rather does current science overwhelmingly agree upon that infinite density single point? My mind keeps this as an area of known unknown. Maybe it's a singularity, maybe a torus, maybe it remains every bit as spaced out as the volume of the black hole itself, maybe time dilation plays a huge role in the situation and not once has a black hole fully collapsed internally because time stopped inside and prevents absolutely everything inside from changing in any sense. I just don't see any good reason to conclude the singularity to be a specific spacial arrangement,

[@ebenolivier2762]

I'm as uncomfortable as you are that this is called "fact". GR predicts it yes, but there are many theories that predict singularities that turned out not to exist.

[@ASeventhSign]

Noob question #672: Can we detect any of these virtual particles or are they theoretical? i.e. Is there a Virtual Particle Detector 5000?

[@gareththompson2708]

From what I've been told, virtual particles don't exist in any sense. They are just a math trick for calculating the interactions between real particles.

[@passintogracegoldenyearnin6310]

In the purest vacuum we can make, virtual particles are inferred from interaction between two neutral bodies with a small gap between them. And gravitational interaction as well as the theoretical ratio G are derived from experiments done with neutral bodies in a vacuum also. If there is no gas, no electrical charge etc, then any sympathetic interaction between the objects must come from a quantum process and/or a spatial process. They also claim that even objects as small and light as the Earth can produce measurable Frame Dragging due to the interaction between our gravity and our rotational velocity. As we head out of nanometer-scale microchips and move into the angstrom scale, virtual particles and quantum tunneling become primary concerns. On very small scales it appears to be possible for a particle to go out of phase with a barrier and appear on the other side of it. This is only possible if particles are not as solid and physically real as we once imagined them to be. Photons and Phonons are considered proven but the Graviton may not actually be real. There are also questions as to whether 'empty' space has its own material properties; if it does, then Space can flow from one place to another and carry matter along with it. You can have cosmic strands and even rivers, effects like the Great Attractor, and still not have a Graviton. The only problem is that this would not explain why Space then flows _into_ matter, or what happens to the Space that falls into a gravity well.

[@ClintonAnderegg]

They know a lot about virtual particles. Temporarily they do exist and a have a very real effect on the non virtual particles around them. kzbin.info/www/bejne/j4usnnRug7GCrpo

[@passintogracegoldenyearnin6310]

@@ClintonAnderegg There have also been claims that a very powerful magnetic field can 'boost' or capture virtual particles, holding them in our space before they can disappear again. I think this is far from proven, but I saw it mentioned in context of whether time itself has a vector of motion. Along the lines of only matter in a very specific time vector can interact, even tiny differences keep them from trouching, but weak interactions could drive what we see as random events on the quantum scale. Probably just a fun mental exercise for someone.

[@mishagjata7374]

I am a time traveler. I am watching this video on January 18, 2022, 9 days before it's going to be published. Love science.

[@yuvalne]

If we still maintain a causal connection to the past mass and charge of the black hole, shouldn't it apply to other things as well? Shouldn't other fields propegate out of the black hole, making the No Hair theorem discernably false? Or is that taken care of (how?) by the infinite redshirt and time dilation?

[@gnidarap]

Mass and charge actually interact with the outside world, so their influence can be observed, like the no hair theorem says. But things like the type of matter or particles it was made from doesn't make a difference, so it "disappears" behind the event horizon. I mean an antimatter black hole is indistinguishable from a regular matter black hole I think Don't quote me on that I'm no physicist

[@frede1905]

I could be wrong, but I believe that the no hair theorem would apply to actual black holes (that presumably must have existed for all time), not the things we see in the universe, which are extremely close approximations to the real thing. As he explained in the video, matter would never cross the horizon, as seen from a distant observer, meaning the infalling matter is always slightly above the horizon.

[@garethdean6382]

Other fields propagate. The issue is that the sum total propagates and not the details. So a hole made of neutrons would have the same external fields as one made of electrons and protons (And electron neutrinos.) What we want is a way to identify the constitution and history of the hole, a way to rewind time and see what went into it, not just the sum charge mass and what have you.

[@ArchangelApollo]

Curious, if black holes are, indeed, fuzzballs, with all the mass of a black hole stretched across the event horizon, would that have any effect on how its gravity affects surrounding space?

[@RedRocket4000]

Noting is stretched across the event horizon for an object crossing an event horizon nothing changes with larger black holes with smaller it might be torn apart well before hitting the event horizon. Matt is going for the effects on something a distance away from the effect horizon the past mass of the object effecting the present. This is needed for the Quantum Gravity idea but not for relativity. Relativity gravity is just the curve of spacetime. The singularity create a very curved space time which does ignores the idea of a event horizon.

[@ArchangelApollo]

@@RedRocket4000 Just in case you missed this upload back on Nov 17, 2021 kzbin.info/www/bejne/aWaUe3aFq7CWj9k

[@CleverNeologism]

Intuitively, just apply Newton's argument in reverse: any radially symmetric mass distribution can be modelled as a point source of gravity, and vice versa. Any object of a given mass and radius is a black box (hole?) when it comes to the external gravitational field.

[@paulmichaelfreedman8334]

I've been considering the event horizon as the source of gravity for some years now. My brain uses though experiments to validate scenarios, and this seems the most plausible to me. The event horizon is simply the physical manifestation of the boundary between our reality and for lack of a better word, nothingness. A bubble of nothingness, its size determined by the amount of mass it has accumulated. It also explains why black hole diameter is directly proportional the the mass and not inversely cubed. Black holes have only a single dimension, and the apparent size in our 3 dimensions is just a projection of its single property/dimension,/degree of freedom (mass) into our 3 dimensions. I don't believe charge has any significant impact, and rotation is an external property, not an internal one.

[@falseprophet1024]

It should make the surface gravity of the blackhole stronger than predicted, since our predictions think of gravity coming from the singularity, and we know gravity becomes weaker with distance..

[@jwb52z9]

I wonder how close Science is actually getting, if at all, toward being able to explain and show things in the various related fields to cosmology that are actually happening without needing to use the idea of "virtual particles"?

[@glowingfatedie]

That's a bit like asking how close mathematicians are to not needing to use the imaginary unit. It doesn't imply progress.

[@adelelopez1246]

We already don't need them, in the sense that we know they aren't real. Science Asylum has a video that gets closer to the real explanation: kzbin.info/www/bejne/qKO4p3-ip9uarrM

[@JJ-zr6fu]

@@glowingfatedie You don't understand imaginary numbers.

[@JJ-zr6fu]

When you're using stats as an explanation for an interaction I don't think you're close.

[@JohnBaleshiski]

@15:06, we have all done that. Great of you to call yourself out, allow yourself to feel a bit like an idiot for a moment, and then being more careful in the future. I've certainly been there!

[@ianthorvaldson5120]

You brushed right up against a question I've had in the back of my head for a while - From an outside observer's perspective, it seems like infalling matter "slows" down as it falls into the black hole as its clock is stopped from our perspective. As you mentioned, this is also true for the matter that originally formed the black hole. However, within finite time the black hole will also evaporate due to hawking radiation, which will either fry that infalling matter or propel it out of the black hole. From this picture, could we just avoid the need for a singularity altogether? Since from an outside observer's perspective, the matter forever falls into the black hole slower and slower until it (or at least its constituent particles) are catapulted from the black hole by hawking radiation. Of course, I feel like this probably isn't the answer (because otherwise physicists wouldn't have spent so long trying to resolve the singularity problem) but I'm not entirely sure why it's not the answer.

[@xintophotography9848]

I have wondered this for a long time, as well. I hope PBS Space Time eventually covers exactly this. It has covered every individual aspect of this question, but it isn't clear how the aspects play together.

[@Laff700]

No no, that is the answer. The structure you're talking about is called a shell collapsar. They have no singularities and no event horizons. I'm a physicist myself and even I don't understand why physicist still wonder about the black hole information paradox. While GR allows black hole solutions to exist, it doesn't actually let them form. Therefore, black holes, as well as their singularities and event horizons, don't exist, and neither do the problems they would cause.

[@dcsignal5241]

Glad I'm not the only one who sees the paradox of having Black holes in the Universe without enough time for them to form. (According to the way I'm interpreting the explanation in this video)

[@ianthorvaldson5120]

@@Laff700 Interesting... Would you happen to know if there is any observable difference between a shell collapsar and a traditional black hole (one with a singularity at the centre)? Would we perhaps be able to tell the difference between black holes that formed from collapsing stars (ie. shell collapsars) and primordial black holes which could have potentially formed with a significant amount of matter below the event horizon? Also, what happens to the mass interior to the event horizon in a shell collapsar? I know that interior to a hollow (spherical) shell, gravity is zero so perhaps it just stays in a super high pressure state?

[@coreylehman8741]

I've had this same question in my head for a few years now. If black holes evaporate over time, and from an outsider's perspective nothing actually crosses the event horizon, it's hard to imagine what you would see if you stared at something trying to cross an event horizon long enough.

[@harrybutts8098]

If the analogy of space flowing at the speed of the observer in that space towards a black hole is more realistic than the analogy of space as a rubber sheet stretched by an object placed on it, then is it possible that space created by dark energy is subsequently dragged into objects with immense gravity?

[@xtear0]

What would happen if you put a sphere of exotic matter “anti gravity” around a black hole? Would it just exist but not do anything anymore? Great video by the way! Always love your videos!

[@samuelthecamel]

I would assume that the black hole would continue inside the sphere, but someone outside the sphere would feel no effect if the black hole's positive mass and anti-gravity's negative mass canceled each other out.

[@xtear0]

@@samuelthecamel possibly!

[@olbluelips]

I imagine the force towards the black hole from inside the shell would be increased, and the force towards the black hole from outside the shell would be decreased

[@YIPPEE2468]

This show is LIGHTYEARS ahead of its time

[@darke-minecraft]

Great vid as always. Possible future topic that interests me; why do we think the centre of black holes collapse to a singularity? Could they not simply be a super dense dark star made of a quark soup that resides inside the event horizon? The vanishing to a single point concept is hard to comprehend, especially at super massive scales. Could make a great explainer?

[@russhamilton3800]

If it's a soup then it would have height, depth and width, so how would those exist without time?

[@Laff700]

In all likelihood, they're probably just shell collapsars instead of black holes. All their mass-energy is stored infinitesimally above where the event horizon would otherwise form. They are supported purely by gravitational time dilation.

[@feynstein1004]

Because GR predicts that they do. However, GR doesn't work at quantum scales. So I personally believe that once the core collapses to a certain size, quantum effects prevent further collapse and give the black hole a non-zero size. That is the logical viewpoint, I believe. GR simply gives us the behavior of spacetime at large scales. However, at the quantum scale, spacetime itself behaves differently and so GR is no longer applicable.

[@olbluelips]

Once you've crossed the event horizon, all possible spacetime paths point towards the singularity. Resisting the downward pull is impossible (would need infinite energy). However, we don't have a theory of quantum gravity, so there could certainly be some other principle which prevents the formation of a singularly! I think it would be really cool if there was some kind of spacetime-related "exclusion principle", but no one currently knows

[@Ceelvain]

I knew that we cannot see anything go through the even horizon, making black holes virtually immutable objects. But I never thought that it also applies to the star it comes from. *Mind Blown*

[@Ceelvain]

@CRIMNALSNEAK Would we? Wouldn't the background light be subject to the same space and time dilation as the light from the back hole itself?

[@nekdozahadny4846]

So if everything stays on the event horizon (time stops for the object here from the view of the observer), that means we could detect everything that had fallen to the black hole since the day of its forming?

[@nekdozahadny4846]

@CRIMNALSNEAK wow... Thank you for the answer. I think I might get it now :D

[@poulthomas469]

The question is so obvious but I never even thought about it. Well done Space Time.

[@benhalpin7306]

"The blackholes gravity doesn't care about the event horizon at all"... that's OK event horizon, I care, I care.

[@limiv5272]

If you're on the surface of a planet that is falling into a black hole, what would be your cause of death? My current thinking is that the atmosphere would be ripped off the planet and you'd suffocate long before the black hole could tear you apart, but I'd like to hear more thoughts.

[@undercoveragent9889]

Surely the force that rips the atmosphere would rip you long before you ran out of breath. lol

[@tyronelannister9922]

But if space time itself compresses, wouldnt everything around you appear to shrink?

[@henrytjernlund]

As an object heads toward becoming a black hole, does the EH simply form around the object or does it expand from zero distance out. If it simply forms is the information inside the EH become lost to the Universe? Or does the EH expanding out from zero sweep up all that information on it's surface? Is there anything at all inside the EH? Is there even space-time inside the EH?

[@happmacdonald]

It forms from small diameters (probably larger than zero; the first clump(s) of matter in the core that happen to reach sufficient local density) which nucleate and grow at relativistic speeds. Bekenstein theorizes that all of the information that fell into a black hole is encoded upon the surface of the event horizon. But we're not clear on how said information is able to leak back out via Hawking radiation; every model we have predicts perfect non-correlation of the hawking radiation. So that's a bit of an unanswered question.

[@nenmaster5218]

@CRIMNALSNEAK I love to give Watch-Suggests, but many cant handle the Randomness of this Offer. Can You?

[@dodatroda]

The EH isn’t a physical thing. It’s simply the point in space where light stops. A black hole isn’t an object, it’s concentrated energy, a region of space where nothing can happen.

[@dodatroda]

@CRIMNALSNEAK "there’s No Escape" because there is nothing that can escape. Yes, everything stops, including light, because everything is made of light (EM waves). The point is that there is no light inside a black hole that "can't escape". When the velocity of light is zero there is no light. Then after you agree that everything stops, you say "Something is Happening". That is wrong. Happening means physical processes. There are none in a black hole. You say you know but you don't. The event horizon is the boundary between spacetime, where light propagates and things happen, and the black hole. And no, there are no singularities in nature, and you don't know they exist because you can't.

[@henrytjernlund]

@@dodatroda Most illustrations show the gravity well being like a funnel that goes infinitely small and thus the math breaks down. So a non-infinite event horizon sphere, empty of space-time, might be an alternate way to consider it that doesn't involve infinities.

[@TallinuTV]

0:30 Initial thoughts were: Uhhh... isn't it *_changes_* in gravity that travel at the speed of light? And all of the matter that entered the black hole's event horizon originated outside it, where its passage into that region, adding to the total, could still be communicated to the outside world. So, I don't see the problem. Fascinating video. Looks like I was actually pretty close. Thanks!

[@deusexaethera]

If the present mass of a black hole is hidden behind the event horizon and all we can perceive is the gravitational field of the black hole's past mass, then how do black holes develop increased gravitational fields as they absorb additional mass?

[@eriknelson2559]

Think all of the mass which you've observed accumulate towards the BH has generated corresponding curvature / warpage in the fabric of spacetime, which curvature / warpage manifests as the effects of gravity

[@Thomas.Wright]

Because it's not as though mass is actively radiating gravity, but rather gravity is the observed distortion of spacetime. The distortion in spacetime doesn't go away, but persists as long as the mass remains within the black hole. Erik Nelson probably explained it better than I just tried to.

[@zerrideas2286]

You stated that virtual particles can travel faster than light, but information can't. Trouble is, the analogy of the travel of virtual particles sounded a lot like information travelling. It looked like the real particles kind of compare notes on every possibility before they continue to move.

[@badlydrawnturtle8484]

I'm skeptical whenever physicists start treating information as a "thing", rather than a convenient quantifier. It doesn't help that it's most often trotted out as an unconvincing hack to let the speed of causality be violated without admitting that it's being violated.

[@ThePowerLover]

@@badlydrawnturtle8484 This. _"It doesn't help that it's most often trotted out as an unconvincing hack to let the speed of causality be violated without admitting that it's being violated."_ More like "is almost never violated, please think as is literally never violated"...

[@MrJdcirbo]

So, according to the hypothesis that Hawking radiation causes black holes to evaporate, and your relative time slows to zero from the point of view of an outside observer, wouldn't that mean that the relative time of the rest of the universe sped up according to you as you fell into a black hole? Furthermore, since time is so warped, wouldn't that also mean that the eons it takes a black hole to evaporate would pass by in a flash according to you? Basically, if you fell into a black hole, wouldn't it look like the event horizon shrank under you as you got closer, and the black hole just evaporates in front of your eyes. Wouldn't you experience trillions of years in the blink of an eye?

[@glowingfatedie]

Not exactly, because - well, think about the way you would observe that. Realize that since it's taking YOU forever and ever and ever to fall in, it also takes whatever falls in after you (the light carrying to you your view of the rest of the universe) even longer to catch up to you. It's slightly paradoxical - observers outside the EH see you slowing down, but to you it would also look like they were slowing down too. The first phenomenon happens for the reason you're already thinking about. The second phenomenon happens because there's all this other stuff happening between the falling observer and the outside stuff they're trying to observe.

[@MrJdcirbo]

@@glowingfatedie wouldn't you still see the black hole evaporating quickly as you approached the event horizon?

[@glowingfatedie]

@@MrJdcirbo No - we already know that, looking down, you see what appears to be a frozen past because spacetime is falling out from under you toward the singularity. Light from events "below" you (closer to the singularity) cannot reach back up to you. Weird, eh? You see time slowed and frozen in both the inward and outward directions as you fall in. The light from what's below you falls in even faster than you fall, and the light from what falls in after you can't catch up to you. There is a PBS SpaceTime episode about this.

[@MrJdcirbo]

@@glowingfatedie I'm going get finally address one my comments in the comments section of the next video. Lol. I'd like a more mathy explanation. 😂

[@MrJdcirbo]

@@glowingfatedie not that I don't appreciate your feedback, though. Thank you.

[@Gounesh]

It gives me chills knowing these guys know much more than they teach. What a big pipi.

[@whatlifeis1069]

Q: A falling object should never reach the singularity. From an outside observer the object will move slower and slower and appear to stop. it will remain stopped until the blackhole evaporates. The object falling in will see itself reach the event horizon and at that point the black hole (and object) evaporates. So all the mass should be on the event horizon until this happens. Why is this wrong?

[@happmacdonald]

I never get anyone to clarify to me what the Lorentz position of the infalling observer is to the deep field observer. The light from the infalling observer redshifts infinitely at the event horizon, so the deep field observer will "see" an infinite fall broadcast by light coming to them, but deep field observer ought to also be able to correct for that light aberration and calculate where the infalling observer *is* relative to them. Does the infalling observer ever reach the singularity *in the deep field's reference frame?* That nobody ever clarifies for me. If not then we have a problem, because an evaporating blackhole over a google years or so will shrink to nothing and presumably explode at Planck scale. In the hypothetical circumstance that the infalling observer "never" reaches the singularity in the deep field reference frame, where would that infalling observer be after evaporation is complete? "torn into hawking radiation" would be a reasonable guess, for sure. That is after all the only way that the infalling mass can be accounted for. OTOH they might also say "Light aberration makes it LOOK as though the infalling observer freezes on the horizon in infinite redshift, but after correcting for aberration a deep field observer can confirm that the Lorentz position of the infalling observer reaches the singularity in some relatively short time after crossing the EH". That would support the standard "nah you fall in" model, but then it raises the question of what a hyperplane of simultaneity can even *look* like across an event horizon? Especially since the speed of light can only be defined bidirectionally in SR and GR?

[@happmacdonald]

@CRIMNALSNEAK But that horizon isn't eternal, and models which treat it as such (such as the original Schwarzschild model) are counterfactual. The horizon increases in radius as more matter is consigned to it, and decreases whenever hawking radiation dominates infall. Even if worldlines freeze at the horizon in the Deep Field's reference frame (which I'm not even getting confirmation that they do after light aberration is accounted for) that doesn't "end" them (like a singularity might), and they would be thawed by a retracting horizont. So what would *that* lead to? The horizon does have to retract to nothing given our present best models, and by that time every inbound worldline would either have to participate in the Planck-scale explosion or find some tunneled exit through Hawking radiation prior. BUT that presupposes that worldlines *actually* freeze at the horizon instead of just looking like they do as a result of difficulties sending any signal back out. And they CANNOT while remaining consistent with GR's prediction of the inertial reference frame of the infalling observer crossing the horizon. That is an example of an inconsistency that should be mathematically tractable on this side of the horizon, and I would like someone who's been in the weeds of the actual baseline math to share their perspective on that.

[@ChrisBarnes73]

Could the expansion of the universe be related to space “flowing toward massive objects”? In other words, could the expansion of the universe actually be just spacetime being stretched by the massive objects that occupy it?

[@spindash64]

I honestly imagined it more as the opposite: that space on large scales naturally creates more of itself, while massive particles essentially “eat” the space around them

[@falseprophet1024]

If the multiverse theory is correct, and gravity acts to infinity (which it does), then expansion could be explained by the mass outside our universe (other universes) pulling on our universe. If this was true, you would expect the matter near the edges of our universe to be accelerating faster than near the center (which we see), and that the expansion wouldn't be the same in every direction (which we just observed recently)...

[@robk5865]

I rather like the idea of cosmic ping pong being played between 2 supermassive "paddles" at either end of the universe. All that matter gathering on one paddle and exploding right back to the opposite end.

[@TreyRuiz]

At 7.16, Matt references the consensus understanding and possible ASSUMPTION that any one particle considers every possible path. Would it be more physically accurate to say that an individual particle is perturbed by the virtual particles in the non zero point space it travels through? This is analogous to releasing a toy motor boat on a lake with ripples and seeing where it ends up on the other side. If you do this millions of times you will see that there is a distribution on the other side where it ends up. Are we interpreting the results of millions of outcomes (from our particle accelerators) and applying this outcome to each individual particle?

[@starship3812]

So you are saying that a graviton is carrier of gravity it can travel at any speed that's how it escape black hole gravity means that's how a graviton escape effect of other graviton that's mess a graviton escape other graviton effect to make some gravity for black hole. Mess it's a mess cold mess. Common what the f k . I don't think any theory is be able to describe universe completely at of now not a small percentage. It's a mess

[@TreyRuiz]

@@starship3812 my thought here may be a little off topic from the main video. I'm just saying there may be an incorrect interpretation of the many paths theory. In either interpretation, the logic of the main video send the same. That either the curvature of space time is "above" being affected by the horizon, or that it is the gravitons from the creation of the black hole and shortly after (many years ago) that are providing the gravitational affect we see today.

[@starship3812]

@@TreyRuiz the most suitable explanation for this I think is last things Matt points that blackhole mass exists every where. that's how it's gravity works

[@shanxmonappa870]

Gravity to Black holes: Oh, you think Gravity is your ally. But you merely adopted gravity; I was born as it, moulded by it

[@chillyman1459]

If we can "see" the mass of the star imprinted on the outside of the event horizon, with its time stretched out approaching infinite, then what would happen to what we are seeing when the black hole completely evaporates? To an outside observer, does the star ever pass the event horizon since the event horizon disappears?

[@Pfhorrest]

This is why nothing ever actually enters a black hole. It's all just smeared around the horizon, and there isn't actually anything at all inside the horizon.

[@paulmichaelfreedman8334]

I've been hammered for this thought, but here it is: If you were to try to fly into a black hole, it would start evaporating faster and faster until it disappeared the moment you were to hit it, also shrinking the event horizon as it evaporates, so you'd never even reach the event horizon. The experience would still be lethal as the black hole shrinks (before your very eyes, time accelerating at a boggling pace) and gravity starts funneling more and more (So spaghettification is still possible) Could cosmic strings be remnants of matter that was extruded through an evaporating black hole? Food for thought.

[@paulmichaelfreedman8334]

@@Pfhorrest One possibility is that the event horizon is the physical boundary between our reality and actual nothingness: The space-time distortions around the event horizon is what gives it it's apparent size in our 3 dimensional world. A literal hole of size x in our space time. Perfectly spherical (A 0-dimensional object projecting its single property, mass, into 3 dimensions) literally frozen in time, shrinking only by hawking radiation

[@chillyman1459]

@@paulmichaelfreedman8334 the assumption of infinite time at the event horizon is based on an inertial frame, so I'm not entirely sure how it would work, but that was the logic I was thinking

[@Pfhorrest]

@@paulmichaelfreedman8334 That's exactly my line of thinking too. A way I like to put it is that "toward a black hole" is literally "toward the future", and the reason why nothing escapes from a black hole is the same reason as why nothing goes back in time (since FTL travel and time travel are equivalent, and FTL travel would be necessary to escape a black hole). If you fly a ship toward a black hole, you are flying toward the infinitely distant end of time, and you can never actually reach that. But you can reach a time far enough in the future that the black hole doesn't exist anymore, in the ridiculously (but still finitely) far future. That is, as you say, *if* you could somehow survive spaghettification -- and then the collision with everything else that had been spaghettified swirling around you as it also arrives, annihilated, in that distant future with you (i.e. the explosive end of Hawking radiation). But from the point of view, as it were, of a single particle flying into a black hole, you'd basically run up quickly behind a traffic jam of other particles slowed on the event horizon in front of you, until right before you reached them a few at the front start to make it out of the jam, and then more after them, and even more and more rapidly until you and the rest of the particles arriving around the same time as you all escaped followed by HOLY CRAP where did this huge sea of other particles behind you suddenly come from? Well, they've accumulated over the aeons of dilated time that have passed since you neared the horizon, and now they're all about to escape behind you as well, and even more from behind them, and so on. You, particle, and all the rest of the particles before and behind you, *are* the Hawking radiation of the evaporating black hole, which was never anything more than this traffic-jam of particles getting too close to each other and stuck in each other's time dilation as a result.

[@8dgrooves334]

Question : According to Relativity if spacetime bends objects start falling inwards ,something that we experience as gravity ,so if gravity is just a curvature in spacetime then why are we trying to find a particle which causes gravity (graviton as hypothesis) in particle physics and why unification is being so hard? and yea why do we treat gravity as a force when its a mere curvature of spacetime?

[@gamingcreatesworlddd2425]

Yes graviton how can be real its impossible gravity is not force your comment is correct 🤝

[@taelim6599]

Gravity is only purely the curvature of spacetime in general relativity. In quantum physics, fundamental forces are excitations in various fields, and gravity is a fundamental force. This contradiction is one of the reasons unification is so difficult. Another reason is because the equations we use to describe quantum physics only works in locally flat spacetime, so anywhere with curved spacetime (ie anywhere where relativity is relevant), the quantum equations we use just do not work at all. My hypothesis on gravity is that it is an excitation of a field... it's just that that "field" is spacetime itself.

[@physikistrelativ3991]

First of all awesome video like always! I’d have one question though: If it is the „past“ matter we observe/feel the gravitational pull, how does this affect if a large chunk of mass is approaching the event horizon anisotropically? Lets say a massive object is approaching the event horizon of a non-rotating black hole and „freezes“ there doesnt this cause an anisotropic distribution of mass, hence a totally different gravitational/elektromagnetical effect on surrounding matter? Only if the mass is distributed along the surface of the event horizon (so not „frozen“) this would be equivalent of the center of mass approaching the singularity, right? Thanks for anyone who could help me answer that question! See you somewhere in spacetime!

[@garethdean6382]

The light, charge and gravity of the approaching object is distorted as it approaches the hole. In the same way photons from the object can bend around the black hole and appear on the other side of it, you'll be able to 'see' the gravity of the object on one side of the hole 'spread over' the hole as it nears the horizon. The field will TECHNICALLY be asymmetrical, but to a degree that's vanishingly small after only a short amount of time.

[@Pferdekopfnebel]

@@garethdean6382 In what way is gravity distorted? As I understand the video, gravity does not fight against itself, so what distorts it? I understand that light is distorted by gravity and, thus, sort of wraps around the black hole. But just as gravitational lenses only distort our view of the object, not the object itself, the actual object plummeting perpendicular to the surface into the hole should only be stretched in the same direction. Or am I missing something? Most likely I am.

[@kylelochlann5053]

There's nothing "frozen" anywhere. The in-falling object vanishes over the horizon and the horizon expands outward. There is no asymmetry anywhere as this would violate the No-Hairs theorem. During the infall and collision the spacetime is perturbed and asymmetrical which are quickly radiated away as gravitational waves and the black hole settles down.

[@physikistrelativ3991]

​@@kylelochlann5053 Thanks a lot! Also had similar things in mind but just wasn't sure about it.

[@zzantares]

singularity, horizon, causality and geodesic, are this guy's favorite words.

[@rolirolster]

I'm sitting here with my family gathered around me and a tear in my eye as I get my first ever question read out on PBS. I had some comment about whether graviton information transfer could be akin to electrons in a copper wire, whereby none of them move at the speed of light or anywhere near that, but still manage to transfer information at great speeds because of their density. But I'm too overwhelmed! 😁 Thank you!

[@LuisSierra42]

Congratulations!

[@1adamgriffin1]

I’d like to know how so much mass gets converted into gravitational waves and escapes when 2 black holes collide

[@WeeklyDosisofScience]

Whoa, mind-blowing stuff! When black holes collide, the intense gravitational forces cause ripples in the fabric of spacetime, which we call gravitational waves. It's like an epic cosmic dance where a tiny fraction of their immense mass-energy is transformed and radiated away as these elusive waves, carrying the signature of their cataclysmic encounter. Truly mind-boggling physics in action! 🌌🔭

[@oneandzero6251]

I've always wondered. Why does "reality" have a speed limit? By my logic I see no reason why it should. Gravity almost reminds me of objects in a video game. The bigger and more complex something is to render, the more computing power is needed. And if you try to render too much it creates lag. Light itself experience no time. From perspective of light it cross the entire universe in an instant. So the closer you get to the speed of light, the slower you age compared to f.ex humans on earth. Almost like the universe has less time to spend on processing the information that you are made of. Same as lag. It will process all the information, but requiring a lot more time. Inside a black hole the time is basically standing still while the world around doesn't. The only thing that apparantly can defy speed of light is if diving into quantum physics. Like quantum entanglement. Comparing that again to a computer, would be like changing the computer code of the video game. That would would appear as instant changes within the "game". My reflections may be totally wack though. Im not no expert into these things

[@aybaer3668]

On the topic of the apollo mission computers vs smartphones, I gave a presentation in college on the topic for IT called "Smartphones to the Moon" and explored the differences.