If the universe is a simulation, when there gets too much matter in an area to simulate all the interactions, a black hole is the way programmers fixed that - it gets turned into a singularity and isn't simulated anymore except as one point source of gravity (or in a more complex way if black holes preserve entropy - jury is still out on that one.)
Silly and untestable, but fun to think about, like the rest of simulation theory. It would be required to do something like that if you're running a simulation with finite resources. You couldn't just keep piling matter into a finite area without bound, eventually you'd overwhelm what you can compute. Same reason one might want a hard speed limit like the speed of light.
Interestingly this is a not a discrete function, time slows near large masses, which would allow the computer to keep up as matter in an area increased, much as you'd expect in a simulation.
Agree! This is my favorite crazy pet theory: spacetime is simulated on a flat 3d substrate with constant compute and memory per volume, which runs at a fixed rate in time (c) [1], and to account for a high density of mass requiring more compute the simulation is slowed down proportionally. Then, black holes are just the extreme end of this slowing down of the simulation.
[1]: You always move at a constant speed: the speed of light. But that speed can be broken down into two component directions which you can trade off: time and space. You typically move near the speed of light in the time direction, meaning your speed through the space direction is comparatively low.
It's because the stronger the forces and the higher the velocity in a cell of the simulation, the more iterations the numerical integrator needs to perform to maintain acceptable accuracy. It's obvious, really. ;)
Also the universe isn't actually expanding and the red shift we see in distant stars is just a numerical error due to the enormous number of steps between here and there. :)
My crazy pet theory: computational bandwidth is constant for any spacetime coordinate. According to Bekenstein bound the lower the temperature of the system the cheaper it is to flip a bit of information. As time progresses the CMBR gets colder, so it's cheaper to flip a bit, but conversely, as time progresses our Hubble volume gets smaller, limiting our total available energy budget to perform a bit flip.
None of these theories are crazy at all. Special relativity is directly derivable from energy causing a fixed amount of change (action) per unit time.
When the information/computational changes that the energy is allocated, is used for non-local movement, then we consider this to be an aspect of velocity, and the amount of changes leftover for internal changes, which effectively are internal time, is decreased by a ratio equivalent to the standard time dilation formulas.
Movement is change...change requires energy allocation, movement diminishes other interactions, hence time dilation, hence special relativity.
Wolfram talks about this in his new graph based model of physics. Mass is an emergent metric of the amount of internal changes occurring in an object per unit time. Essentially, causal loops in the graph. Feynman had a toy model called the checkerboard model where the amount of bouncing in an area represented mass.
>>You're wrong.
This is no problem. I'm happy to be wrong, I'm happy to be told I'm wrong.
>>What you probably meant is [...]
This is problematic to me. I'm a grown adult, I own what I said, and I said precisely what I meant. When it's wrong, it's wrong, and no, I don't want to retcon that in some feeble attempt to save face, and I certainly don't want others to do that for me.
Obviously, this is not my field. Is movement and motion here the same thing? Motion is relative, so this energy "use" here is relative - in some reference frames where an object would be observed as at rest, is it still "using" energy? You see these quotes? That's because I don't really understand what "use" means here. An object in motion is in motion as a consequence of acceleration, which requires energy, and certainly possesses unrealized kinetic energy, but it isn't consuming energy. So what does "use" mean here?
> in some reference frames where an object would be observed as at rest, is it still "using" energy
There are numerous ways to measure relativistic mass (total energy) of a system from outside of it. As long as there is a measured energy, it is still using energy. Observation tricks usually just juggle energy from potential to kinetic, they don't change the total energy, so they don't change the usage.
> I don't really understand what "use" means here.
Energy causes change. The total amount of energy of a system measures the total number of changes happening every second, essentially actions per second.
Action = Energy x Time = (Action / Seconds) * Seconds = Action
Energy is really only transformed, it is never created nor destroyed, you probably already know this basic tenet that Einstein espoused. The energy of mass is commonly thought to be "at rest" but in actuality, mass is just the phenomena of localizing the changes that the energy must cause. When this localization is upset, you get a nuclear explosion, a lot of change that once was concealed.
We might want to know how many changes per second a single Joule of energy causes. We can calculate this by taking the inverse of the Planck constant. Since Planck constant, h = Joule / Hz [1], the inverse would give us Hz / Joule. Which yields a value of about 10^34 Hz per Joule of energy.
I wish I knew all of this earlier in my life, as a lot of my _energy_ was spent on trying to do Cellular Automata simulations of our universe. Knowing how fast our universe computes, makes any simulation attempts with our current computers seem quite foolish if magnitude matters at all. Some might still argue the rules are more important, but sometimes, as you see in strength sports, even a 50% difference in strength beats any technique advantage a fighter can muster.
An object possessing kinetic energy continues to move unless acted on by an external force/energy. It's literally Newton's first law. It doesn't move for free though. Energy bound to the object is being allocated every Planck second that it moves. That energy could have instead been used for internal interactions, local time for that object, if it were at rest with the same relativistic mass.
Time dilation is a consequence of energy having to be divvied up between external and internal changes.
Nothing I am saying is controversial. But yes, I am making it much easier for everyone to see that movement is just change of state/information, and that all energy causes a constant change of information per unit time.
The universe is computational, not really a surprise...
Although I'm skeptical of the correctness of Wolfram's grand new theory/hypothesis of everything, there are many intuitively appealing aspects of it, and I wouldn't be surprised if some aspects of the theory may help find or understand future discoveries. (Though maybe not; I'm definitely not an expert.)
Why would gravity follow an inverse square law in this model? Wouldn't you expect there to be a hard cutoff as you moved away from a busy region, instead of a gradual decrease?
The steps of granularity would likely be the Planck length.
His proposal does have some unresolved issues. E.g. distance is quantized but the interactions of those quantized variables produce continuous things that affect other things that are quantized. We don't have enough energy to see the limit yet, but it is possible.
It's simply some kind of easing function, and if the universe does have a designer, it's obvious to see that said designer prefers smooth transition and curves for most macroscopic phenomenon.
Also by defining the inverse square law you can maintain a cohesive interaction model between different objects and regions. Their sphere of influence (which can be described by gravity waves) will now just be superimposed on top of each other without extra work.
Or even crazier, maybe it's a combination of both, maybe there is a hard cutoff after all once you pass the event horizon.
> meaning your speed through the space direction is comparatively low
But you do move in space at a great speed if you account for the rotation of the earth around the sun, the movement of the solar system in the galaxy, and the movement of the galaxy relative to other galaxies. It's not like there's a coordinate system with an absolute origin somewhere.
Leaving aside that this completely ignores how relativity works, even if there were a fixed reference point (e.g., the CMB rest frame), our motion through space relative to that frame is ~ 0.07% of c.
This is fun to think about. What is the finite resource though? Time inside the simulation can be simulated so isn't 'real' time. If simulation results were desired quickly that could be a thing, or limited storage of state.
Another good hack is inflation where parts of the universe disconnect and so can be tossed out if you only care about continuing to compute the parts you keep.
In this case I'd say time is the constraint, as you want it to run consistently through your simulation. So you can't let one part get ahead or behind another in a way that breaks causality.
You are likely not running the universe on a Von Neumann machine, so compute and storage would be combined and spread out. You can't just have opposite ends of the universe interacting instantly in that case.
It doesn't have to be that way, but you can see why it would be desirable and seems to fit observations.
However, I'm at a loss how you would explain quantum entanglement if it truly is instant over any distance. That's not really known, but it's at least a lot faster than light.
However, I'm at a loss how you would explain quantum entanglement
You seem to be applying the rules of our simulated universe to the universe outside the simulation. There's no particular reason to think the speed of light or any other rule applies outside.
This is true. The physics outside could be anything and we're unlikely to understand it.
There's a chance us humans are simulating our past for some unknown reason - in which case one would expect the laws to be similar.
It's also not unreasonable to think that there will be many similarities between the laws of the simulation and the outside reality because they'd have what they know to draw on for inspiration.
Entangled particles are stored in the same quantum register. When there are two references and it’s read, the systems says nope can’t do that and it unlinks them.
My point about time in a simulation is that it can be simulated. It's more a computation of a directed graph of causation. 'When' the computation happens in the host environment isn't material within the simulation. Trying to do things in any sort of 'to scale' time is an optimization rather than a requirement.
I don't see the problem with entanglement at all unless it was so prevalent as to direct the shape of the simulation model. If it's a lesser exceptional quantity, they can be handled as special cases, whenever one is evaluated, the universe could even in the most crude implementation, be briefly stopped, the entangled partners updated, and resumed. Pretty much like running in a VM that's doing gc if your real time clock is arbitrary information provided by the host environment.
It's all fun and games until someone underflows velocity.
In all seriousness, finding such a bug in the software would be the best possible evidence of living in a simulation. The hard part is demonstrating that it is a a bug an not a feature.
Alternate theory. In its core, the universe is a giant one-dimensional loop, which starts "curling" to form multidimensional forms as energy lowers and it's insufficient to keep the string straight (think about small magnets forming a line, but if not strong enough you can form looped shapes with them).
The universe has potentially infinite dimensions defined as n-dimensional Lorenz space: a space where every next dimension is perpendicular to all previous dimensions. The number of spatial dimensions depends on the overall energy level of the Universe, as well as local energy topology.
Black holes represent these inflectional shifts of spatial dimensionality. The surface of a black hole encodes a closed (no beginning, no end) space of a 2D universe, and inside that 2D universe, high-energy regions form two-dimensional black holes, circles, on the surface of the 3D blackhole. The surface (circumference) of those circles is just the original 1D string unentangled, and this is where the set of nested black holes end.
Our own universe is the surface of a 4D blackhole.
We mathematically determine black hole is just a point through which structure doesn't survive, and truly there's nothing at the center of a black hole (i.e. the black hole itself as we define it), but hovering just above the Schwarzschild radius is a whole another set of nested universes, nested in one another, and each of those nested universe is rich with emergent structures, just like in ours 3D+time universe.
We simply can't access it, because the building blocks are of a different category. Basically the building blocks for our particles are made up of what is the particles in a 2D universe (refer to string theory and how vibrating 1D strings in N dimensions form our perception of particles).
So maybe black holes aren't just "we give up, nothing happens" here. Maybe they're rather "we give up, let's unravel one spatial dimension here in order to find new energy-stable configuration".
This actually doesn't contradict your simulation theory, but it adds some unexpected twists to it. Because what looks like just spacetime eating holes may in fact be brimming with life, and maybe our entire universe is one, as well.
Yet the bounds of space are ever increasing, while the amount of matter is not.
This would only make sense if there is some weird arbitrary limitation for matter concentrated in an area. And then the solution would be uncontrollable and happen to fit nicely with the rest of the rules.
Simulation theory is pretty much akin to believing in god as opposed to science. It doesn't lead us to a better description of reality. Just passing off what we don't know one level up.
Not necessarily. Religion, simulation theory, multiverse theory and other currently untestable things could potentially make falsifiable predictions and lead to a greater understanding. I don't think religion specifically is going to achieve that, but neither can I say that with 100% certainty.
Anytime we unlock a new branch of science we potentially refine our knowledge of the physical world. Computer Science was the last branch we unlocked, it might lead us to a better understanding of the universe.
That's besides the point though. In fact, you can treat science ~as~ a religion if you want - this is just semantics. That doesn't diminish that in science, we utilize the simplest models that most accurately represent reality. We don't needlessly suggest an alternative wherein we are left with more complications.
This is the case when we suppose for instance, that the Big Bang is not the beginning. Be it god or a computer simulation, we then wonder how those things came to be. Ergo, more complexity that does not resolve our understanding of the world.
Geocentric for instance works, but heliocentric is simpler because then you don't have wild erratic orbits of other planets around Earth. General relativity over newtonian because while more complex, it affords a more accurate depiction of reality.
> Be it god or a computer simulation, we then wonder how those things came to be. Ergo, more complexity that does not resolve our understanding of the world.
Not necessarily. It could totally explain or universe but leave us clueless as to what lies beyond. To be fair, I expect we'll never be able to answer what lies beyond - so that's fine.
But be it a god or a computer simulation, it needs to make testable, falsifiable predictions to better or understanding of the natural world. Otherwise, true or false, it's useless to us.
> But be it a god or a computer simulation, it needs to make testable, falsifiable predictions to better or understanding of the natural world. Otherwise, true or false, it's useless to us.
true
> Not necessarily. It could totally explain or universe but leave us clueless as to what lies beyond. To be fair, I expect we'll never be able to answer what lies beyond - so that's fine.
You're right. It could totally explain or universe but leave us clueless as to what lies beyond. As does science.
Simulated jet physicists running black-hole simulations in simulated computers in a simulated universe. Imagine the horsepower. It could be 'simulations all the way down' !
I have a theory that the "singularity" will occur when, for purely economic reasons, somebody at one of the big cloud providers decides that it's cheaper to use the other cloud provider's services for their service, not realising that the other provider is already doing that.
I'd recommend the two episodes released right before the one about the black hole information paradox too. They set up for what is covered in the information paradox episode.
Maybe the episode before those two also. I vaguely recall that something from the information paradox episode used something from that (and if I'm misremembering, it was still a neat episode):
I have a question about the episodes you cited. They cover how beyond the event horizon space becomes time and time becomes space. They go over how that means that inside you can't go backwards in space for the same reason that out here in the normal universe you can't go backwards in time. You are doomed to only go forward, which inside means toward the singularity.
(Much better than the ridiculous analogy often given that you can't get out of a black hole because the escape velocity equals or exceeds the speed of light. That's a ridiculous analogy because it only explains why you can't get out ballistically).
But all their explanations used a simplified black hole in a spacetime with just 1 space dimension and 1 time dimension. We've actually got 3 space dimension. Does that mean that in a real block hole past the event horizon, you end up in a spacetime with 3 time dimensions and 1 space dimension?
If so, does anything interesting happen due to having more than one time dimension?
From the perspective of an outside observer, nothing ever reaches past the event horizon- it just asymptotically approaches it. The same goes for the whole mass of the black of hole- from an outside perspective, it's smeared across the surface.
There isn't an object that messes with the warping of spacetime- the black hole IS the warp in spacetime. If changes in spacetime couldn't propagate away from the black hole, it wouldn't exist.
I understand that from an external POV things that fall into a black hole never seem to reach the event horizon, but there must be material that is inside the event horizon. When the original star collapsed and the black hole formed, there was material inside the volume enveloped by the new event horizon. Also as more matter accumulates in the accretion disc of the black hole the event horizon will expand. With these enormous super-massive black holes, with event horizons the size of earth's orbit, there must be something inside the event horizon.
Or is that wrong, and everything just smears out even more finely as the event horizon grows?
That one, anyway, is easy. Sort of. Gravity is our perception of space itself being stretched, squeezed, even twisted. So, no gravity is escaping; instead, the black hole is warping the space it is in.
The mathematics describing this process are intractable except in very special cases. In most cases, physicists are obliged to use an approximation that produces an answer that they hope has much of the character of the correct answer. At one extreme, they just use Newtonian gravity, which produces almost-exactly correct answers for small-scale systems involving just regular stars and planets. It is only when warpage gets very large compared to the size of the system, or when e.g. galaxy-scale mass is involved, or the differences between Newtonian gravity and reality are what is interesting, that they have to resort to more complicated approximations.
It was recently discovered that calculations of the motion of galaxies were using an insufficiently accurate approximation that made it seem like stuff is orbiting too fast for the visible mass, requiring "dark matter"–extra, invisible mass–to hold the galaxy together. But using a more accurate approximation makes the need for dark matter evaporate. This created a problem because astrophysicists and cosmologists have come up with lots more uses for dark matter, to explain lots of other things. Without dark matter, they have dug themselves into a hole. The response has generally been to ignore the more accurate galactic gravitational model, and double down on dark matter. They can do this because ultimately it is all just a matter of papers being published and careers advanced or blighted; there are no other real-world consequences.
This is not correct - electric charge can also escape from a black hole.
The actual answer is that it is energy that can not escape and a static gravitational field (or electromagnetic field) is not energy (in and of itself).
However keep in mind that time is frozen by a black hole, so if you have a black hole with a certain charge, and a new charge falls in, the "change" in charge never escapes (it takes infinite time to escape) so you have no issue of non-static gravity or charge escaping from a black hole.
Like the scrunching comment says about the shape. Light travels in straight lines. It just happens that all the straight lines from inside a black hole curve back in on itself. So the light travels as far as it wants but only within the confines of this curved spacetime.
There are a handful of replies already and I'm not any sort of authority on this subject. But, I'd like to share a few of the things about this that have made sense to me; maybe someone will add to or correct one of them and I'll learn something more.
Black holes and gravity are hard to get a satisfactory grasp on for laymen (like me) because they behave in ways that are unlike anything else in the natural, observable world around us. People try to understand difficult concepts by relating them to familiar things, but gravity and black holes don't relate to anything we're familiar with.
Gravity for example isn't, we think, a "thing". It's a property, or a consequence. [1] Lots of people are looking for some way to relate it to the physics of particles and electromagnetic forces, but that hasn't happened yet. So, gravity doesn't escape, or travel, because it isn't a "thing". There's no particle of gravity. There is a force, in that when we observe large masses, they seem to be acted upon by some kind of invisible action, but that force is actually a consequence of things attempting to travel in straight lines along a curved surface.
Changes in gravity do travel, apparently at the speed of light. So, in that sense, the gravitational effect of a black hole does extend beyond its event horizon. But, that's totally okay, because gravity itself isn't a thing and doesn't travel and therefore doesn't need to escape a black hole.
Rather, a black hole is a consequence of gravity, or relativity. It's a division-by-zero [2] in the equations that describe matter, gravity, and curved spacetime. Thinking of black holes as being somehow similar to really really dense planets is one of the misconceptions that misled me for a long time. They are instead more of a place where physics, as we understand it so far, stops working.
That place has a boundary region where physics still mostly works, and things happen there that we can sort of understand and relate to. We can observe some of the effects of this extreme curvature of spacetime in this boundary region.
But beyond that, the curvature goes to infinity and volume goes to 0 and time stops existing.
There's an old joke about black holes being where god divided by zero. Since god can do all things, dividing by zero is not impossible. Once we can comprehend how dividing by zero is possible, the mysteries of black holes will be revealed.
As best as I understand: light travels in space. Thus, if space is scrunched up, light can't escape. Gravity IS space. The scrunching up IS gravity. There is no "escaping", because gravity is literally the substrate.
For most 3+1 dimensional theories containing gravitons they do so in exactly the same way classical gravitational waves do in our universe. (Somewhat more technically: most such graviton theories define them in terms of variations of the Ricci curvature tensor R_{\mu\nu}, much like we can describe a photon in terms of the electromagnetic tensor F_{\mu\nu}.)
So when-and-where does classical gravitational radiation appear?
Spherically symmetric static sources do not generate gravitational waves. However, if we raise a bump on such a source thus breaking both spherical a symmetry and staticity in favour of a dynamical bumpy spheroid -- then with a light-crossing time of the spherical source, the nearby external spacetime will have settled back down to a spherically symmetrical state. The near-region will also return to static (the curvature in the near-region stops varying) while at ever-further removes from the source one can find a perturbation in the curvature there-and-then.
This also works (although it takes much longer than about a light-crossing time) for objects which are slowly-rotating, roughly spherical, but not shrouded in a horizon. Such objects' bumps will eventually flatten, and the flattening is typically faster for more-massive bodies. We see this in the rocky bodies throughout the solar system. Gravitational radiation is shed during the flattening process, but at much lower amplitudes than on a bumpy black hole.
How do black holes get bumps? When something falls onto them. In particular, we study the collision of neutron stars and other black holes onto black holes at LIGO, Virgo, and soon other gravitational wave observatories. The more massive the infaller, the bigger the bump, and the larger the amplitude of the gravitational waves. Indeed, in several observations the black holes are of comparable mass, so they raise bumps on each other, and this can be seen in the multipole wave form.
Back to gravitons. A classical "chirp" of light can be seen as a large number of photons in the theories of quantum electrodynamics or of the Standard Model. A "chirp" of gravitational radiation detected at LIGO can be seen as a large number of gravitons in theories such as perturbative quantum gravity.
The spacetime outside but nearby a spherically symmetrical essentially-non-rotating object is boringly quiet, whether that object is a cold rocky body or a black hole. There won't be gravitational waves of non-negligible amplitude there. But if we induce a large perturbation by breaking that symmetry, the spacetime outside but near the object is much less boring, and filled with gravitational waves. That freshly-dynamical spacetime will eventually settle down, depending on the properties of its sources (the matter configuration), and thus eventually we get the nice quiet spacetime outside (but nearby) the body again. However, that's because the local gravitational perturbations have run away from the local area as gravitational waves.
A rocky body has a solid surface on which a solid bump can rest for very long times (but compare something that can melt or sublimate, deposited onto the surface of such a body). A black hole does not have a solid surface at the horizon: an infalling object passes right through the horizon. Some treatments (putting it very roughly) think about such an object very quickly melting and spreading all over the "surface" of the horizon. This is mathematically convenient sometimes, but conceptually misleading. The horizon cannot support anything -- nothing can rest on it. That's why the time it takes to flatten a bump on a black hole is about the light-crossing time of the black hole.
However, the gravitational radiation comes from the dynamical spacetime outside the horizon at the time the perturbation is raised. Once things settle down, there is just a bigger horizon.
Not covered above: extremely fast black hole rotation, such that we don't have sphericity or staticity in the first place. This doesn't really change the picture much: an infaller raises a bump, the bump is dragged around because of rotation, and settles down. The spacetime outside the rotating black hole with the bump is enormously dynamical, and emits gravitational waves, which fly away from the rotating black hole. In short order, even to observers many galaxies away (e.g. at LIGO), the spacetime around the perturbed rotating black hole will have settled down. Again, if there are gravitons, LIGO-like observers see enormous numbers of them all at once.
Also not covered above: black hole evaporation. We've never detected this, and might not be able to for up to trillions of years (before that we'd need there to have been small primordial black holes older than even any of the electrons in the universe). There is no full answer for what we should expect to see when the amplitude of gravitational radiation is likely to be high (during final evaporation). This is about the only time when what fell into the black hole over the course of its existence is likely to be relevant -- it likely would determine the spectrum of the gravitational radiation, but that radiation would originate in the near region of highly-dynamical spacetime just outside the shrinking horizon.
Penultimately: there are some really different graviton-containing theories that might describe aspects of our universe (even if they are defined for universes with many more spatial dimensions than the 3 that sufficiently describe all our physical observations to date). However, most really different theories have such different large-scale behaviours that there is no hope of connecting them with e.g. the central black hole of our galaxy.
Finally: one could build a tortured metaphor using a steel ball and blowtorch: heat one spot on the ball until it's glowing red, then switch off the blowtorch. It will have a definite localized hot spot -- a temperature bump -- that is visible from some angles but not others. Eventually the ball will thermalize: it will be essentially the same (cooling) temperature from every angle outside it, with no single glowing hotspot. The glow is the emission of a large number of electromagnetic waves (and those are large numbers of photons) carrying away the energetic perturbation on the sphere.
That's all well and good, but which part should I read to understand how gravitons travel from inside the event horizon to outside of it? Or maybe your response is a nice way of saying that the question is flawed and gravitons don't actually do that or don't need to do that?
The question isn't flawed, but ignoring final evaporation, nothing crosses from inside the horizon to outside. Nothing. Ever. Under any circumstances. Things can only move from the outside to the inside, unidirectionally, and on a one-way trip.
Gravitational radiation originates outside the horizon. It's noise in the near-horizon region caused by massive/energetic objects moving around outside the horizon (e.g. as a neutron star plunges inwards), and most of it dissipates away to infinity (a fraction settles down and serves to make a bigger, flatter horizon).
Gravitons in almost every physical theory that has them are simply what you get when you look very very closely at gravitational radiation like this, just as photons are what you get when you look very very closely at a bright flash of light.
Final evaporation isn't something we need to worry about for any practical purposes (and additionally it might never happen). However, just prior to final evaporation an extremely hot, tiny, almost-fully-evaporated black hole would be surrounded by a near-horizon region of extremely dynamical spacetime, which would be the source of quite a lot of gravitational radiation (and thus gravitons); the influence of that gravitational radiation on the spacetime-filling fields of the Standard Model would also generate quite a lot of electromagnetic (and other) radiation too. If we look very closely at all these different forms of radiation we'd see lots and lots of particles. That is, you might see X-rays and gamma rays, but they are not crossing from inside the horizon to outside. They're the effect of locally strongly curved spacetime on the local parts of universe-filling quantum fields (and the intense interactions of field-content being stretched and squashed in turn induces a backreaction on the dynamical spacetime nearby).
Thank you for the follow up. I've asked this question throughout the years and this is the first time that virtual grativitons haven't been introduced to explain away information escaping the event horizon. Thanks for taking the time to go through a thoughtful explanation.
It was an interesting distinction IMO, because if you think about it a lot of confusion comes when people think about gravity as a discrete thing that actually exists, when in fact gravity is merely a description of the effects that come with spacetime curvature.
Since you answered: do you have a good way to visualize the curvature of spacetime? I really don't understand how to think about light-cones being distorted, because it's the curvature of a lorentzian manifold that stiches together light cones with distortion.
If you can only visualize curvature of a 2D surface (embedded in the 3D space), you have to imagine the space as being 1D. I don't know of any other way.
Gravity does not travel at the speed of light. Some speculate that instant (ie: faster than light) communication could be possible by manipulating gravity.
>> “The black hole in M87 is about the size of our solar system,” Issaoun said, yet it produces a 5,000-light-year-long current of white-hot plasma
Do both jets put together have a length of 5000 light years or does each of the two jets have a length of 5000 light years making a total lenght of 10000 light years?
Can someone please clarify. I have had this question for a ling time and it is eating me up.
That's just one of the jets. In fact, I think only one side is observable as it pointed close to our direction, making the other side very difficult to observe.
Yes. The forward jet is already faint despite being enhanced because it's pointed towards us. We can't see the backward one until it's way way outside the galaxy.
The author throws in
"and a big asterisk on the naive notion that nothing escapes black holes."
Not true. The jets are from the plasma surrounding the black hole. And we see that already, meaning photons escape it all the time. Since the jets didn't start below the event horizon, they were never "in the black hole" at all?
For many decades, people have observed jets of hot gas spewing from the centers of some galaxies. There are multiple theories as to how those jets form.
Radio astronomers got together and built a synthetic telescope the size of the Earth in order to be able to take a picture of the gas near the black hole at the center of a nearby galaxy, M87.
When they did, and looked at the polarization of the light, they saw twisting lines, which agreed with the prediction of one of the most-favored theories for how these jets are produced.
There has been lost of theories to explain how jets from black hole systems form. New observations of light polarization from M87 jet show twisting magnetic field lines which suggest one of the theories might be right. That theory says that spinning black hole's energy can be extracted by these twisting magnetic field lines and therefore power these jets.
If these jets are narrow, and if the radiation is directed in the same direction as these jets (That's my understanding. Am I wrong?), how do we (1) see these jets in the first place and (2) if the answer is that we only see the ones pointed at us, how do we know they are (narrow) jets since we can't observe them from other angles?
How do you see the beam of a flashlight in the dark? Because it hits stuff in the air and bounces off.
And the particles previously in the beam that already hit something are likely to hang around and be candidates for being hit themselves. And eventually they wind up as part of a big glowing cloud that you can see in the pictures. See https://d2r55xnwy6nx47.cloudfront.net/uploads/2021/05/cyga_v... linked in the picture for what it looks like. And for evidence that we can still see the beam when it isn't pointed directly at us.
The radiation is not pointed in the same direction as jets like a laser. There is bulk motion of the plasma in a given direction, but the radiation is emitted from particles that are moving in a different directions within that plasma. So the radiation spread is wider than the jet direction. Interestingly, depending on if the jet we are viewing is pointed towards us or not can impact on the radiation signature in the form of blue shift and red shift. If the orientation is just right, bits of jet appear to move faster than to the speed of light, but it's just a geometric effect.
I want to know if the jets are made up of material that is swirling towards the black hole from the accretion disk but get caught up in the magnetic helix (a) before it reaches the event horizon, or (b) after it passes the event horizon. If the former, then it's not as impressive since then nothing can escape a black hole except via Hawking radiation. If the latter, then this seems like quite a novel mechanism to prevent infinite black hole growth.
The illustrations in the article don't provide an answer, though, since the details ends right where it ought to provide insight. The article does mention that the new paper puts doubt on the idea that nothing can escape a black hole, but I still didn't see any direct mention of the event horizon question.
Nothing can return after having crossed the event horizon. Gravity bends space and time, and in particular it changes which direction the time axis points. In a black hole, the time axis is bent all the way over so that it points directly at the singularity. All paths that enter the black hole must end at the singularity, because to do otherwise would require going backwards in time or faster than the speed of light.
Can you then explain what the author means when she says, "a voltage that draws energy up and out of the hole and along the helix. This, they claimed, is the jet — and a big asterisk on the naive notion that nothing escapes black holes"?
The statement doesn’t mean anything because it was written by a reporter and reporters generally don’t understand what they are writing about, especially in the modern era, and especially in regards to scientific concepts.
The magnetic fields can accelerate matter from the accretion disk and turn it into a jet headed away from the black hole, there’s nothing wrong with that. Maybe matter can be created by photon–photon interactions in the photon ring, and that matter can be accelerated into a jet by the magnetic field. Either way, no matter has exited the black hole; the jet is made of matter that avoided entering the event horizon.
Black holes have only three macroscopic quantities which are observable from the outside: mass, rotational kinetic energy, and electric charge. Since it would be pretty hard to arrange for matter of only one electric charge to fall into a black hole, the charge of the average black hole is believed to be pretty much neutral at all times. The mass of the black hole is inaccessible, because it is concentrated at the singularity. Or possibly in the firewall, if black holes have firewalls. That leaves the rotational kinetic energy as the source of the energy that powers the jets. The jets would last until the rotation of the black hole slows enough that the magnetic fields aren’t twisted enough to maintain them.
Black holes have spin, and this process is expected to slow the black hole spin, which takes energy out of it. It's not the only known way to slow black hole spin.
Well if its anything like biology, your first bet would be to get a degree in astrophysics. Doesn't necessarily need to be an advanced degree, but enough to know how to ask the right questions of those doing the work. Second step would be to maintain a continuous love for art/ drawing/ illustration. Third step is to get your work out there/ build a portfolio.
Several colleagues of mine have ended up down the road of scientific illustration in biology. Most of them had BS in biology, botany, zoo, etc..
Looks like they have a position open for an Interactive Web Developer [1] but it seems like the header animation is sourced (and attributed) from a youtube video from 2018 [2]
That animation was made by an EHT collaboration scientist, Andrew Chael. The EHT has outsourced some animations to a firm named CrazyBridge, but only occasionally.
Would be cool to see an estimated thrust. I would guess it isn't perfectly counteracted but wonder how much that serves to push the galaxy through space.
Yes, and my assumption is that light-years long jets of plasma shot out both ends of a black hole will be fairly unobtainable in any practical way. At the same time, the energy levels involved would be massively useful if they could be harnessed. So, we have a potentially valuable resource that is difficult-to-impossible to obtain. Pretty much the canonical use of the term unobtainium. So my post was a bit snarky, but also likely accurate
If the universe is a simulation, when there gets too much matter in an area to simulate all the interactions, a black hole is the way programmers fixed that - it gets turned into a singularity and isn't simulated anymore except as one point source of gravity (or in a more complex way if black holes preserve entropy - jury is still out on that one.)
Silly and untestable, but fun to think about, like the rest of simulation theory. It would be required to do something like that if you're running a simulation with finite resources. You couldn't just keep piling matter into a finite area without bound, eventually you'd overwhelm what you can compute. Same reason one might want a hard speed limit like the speed of light.
Interestingly this is a not a discrete function, time slows near large masses, which would allow the computer to keep up as matter in an area increased, much as you'd expect in a simulation.