Supermassive black holes may be lurking everywhere in the universe
phys.org
phys.org
If I may, I would like to point to another kind of supermassive black hole: https://www.youtube.com/watch?v=Xsp3_a-PMTw :)
At the very "edge", sometimes pairs of particles are formed out of the vacuum (for example an electron and an anti-electron (positron)). Hawking asked: What if one particle leaves away from the horizon, but the other one leaves towards the center of the black hole? We would see an object that is sending particles from its event horizon. So in some sense particles would escape from the edge of the black hole. That's Hawking radiation (in simplified terms).
So technically yes, it could all have disappeared into black holes, but it wouldn't really be antimatter anymore after entering the singularity due to being effectively broken down into pure energy/matter.
You might be thinking of negative matter, in which case they'd effectively cancel out, erase each other.
However, once through the horizon you switch from the exterior to the interior solution to the EFEs, and find yourself inevitably and very quickly (in proper time) colliding with the singularity or whatever is at the centre of a black hole. You will notice very quickly (seconds to minutes by your wristwatch) that you are inside the event horizon of even a 10^10 M_sun SMBH.
That's one reason we can confidently predict we are not inside a black hole with a radius of approximately the Hubble length; we can't use an interior black hole metric to describe our patch of spacetime. If anything, because of the early hot dense universe, we look a bit more like a time-reversal of a interior black hole solution, but even that falls to pieces on inspection. Additionally, unless you believe that the universe is really really different a light year outside the Hubble volume, we also can't use an exterior black hole solution to describe that. (And if you decided for the sake of argument that physics just outside the observable universe is very different, the "outside" metric would still see an expanding surface, which is very not-blackhole-like. The "outside" observers should also be able to infer the spatial flatness of our observable universe; space is decidedly not flat inside a black hole, otherwise we wouldn't have the problem of the infinite density at the singularity.)
Unfortunately GR and QFT make different and conflicting predictions about what happens to a positron and electron tossed into a black hole once they reach the region where curvature is on the scale of their Compton length.
However the main problem is a length/energy correspondence.
In quantum mechanics you probe shorter length structures by scattering particles with higher energies. At ultra high energies this produces a shower of daughter particles which carry kinetic energy away, and this process should continue to arbitrarily high energies. More energy in the scattering event produces more daughter particles, which evolve unitarily.
In general relativity, when you scatter sufficiently energetic particles, the energy density in the area of the collision is greater than that needed to form a black hole; an event horizon forms around the scattering particles. More energy in the scattering event produces a larger black hole, and we don't know how to preserve unitarity for black holes. Evaporation of small black holes does not produce the same daughter particles as predicted by quantum mechanics.
There are other related problems as well, especially in the early hot dense phase of the universe.
We do not have the ability now to produce scattering energies of the magnitude necessary to probe the different predictions; we also so far don't have a way to observe natural occurrences of sufficiently high energy interactions at the present time, and might not for many years.
To have friction you have to have two things moving at different speeds rubbing on each other. But infalling gas all moves in the same direction.
(2) Electromagnetic waves come from the movement of an electric charge. Even a single molecule falling into an event horizon is a moving charge (plasma) or dipole (gas).
In the purely non-rotating case, there is another source of heat as well: compression. As gas from far away moves closer to the black hole, the distance between gas molecules decreases, and the pressure increases. This causes the temperature to increase. Just feel the outside of a bicycle pump after quickly inflating two full tires.
The objects around a black hole are on different intersecting geodesics; "collisions" result in energy exchanges that boost the particles onto different geodesics, typically that wind closer to the horizon.
Near the horizon inverse Compton scattering becomes important, too: high energy photons emitted by matter-matter collisions end up colliding with charged massive particles with a transfer of momentum from the latter to the photon. The latter's change of momentum leaves it on a geodesic still closer to the horizon, while the photon is boosted to high energy (perhaps escaping to infinity as an X-Ray).
Hawking's work followed his visit to Moscow in 1973 where the Soviet scientists Yakov Zeldovich and Alexei Starobinsky showed him that, according to the quantum mechanical uncertainty principle, rotating black holes should create and emit particles.
The key to it is that in General Relativity different observers will see different numbers of particles; in particular, an accelerated observer will see more particles than an unaccelerated observer.
You can think of this in terms of a blueshift where particle count increases, rather than just individual particle energy; this is particularly the case in the very low energy limit, where there are tiny numbers of particles to start with, or alternatively, where the average particle wavelength is so long as to be undetectable. A blueshift in the latter case causes particles to become detectable because of wavelength-shortening.
A gravitational collapse causes an acceleration between freely-falling observers in the past and observers in the future, mainly because of the spacetime curvature exposed just as the event horizon forms. The "empty" space outside the horizon actually has extremely long wavelength radiation in it; it's a very low temperature thermal distribution, related to the CMB and the temperature of the vacuum. The accelerated future observers see a shortening of the wavelengths of this radiation trapped near the event horizon, which leads to particles appearing where a past observer saw none. Because these particles are all outside the event horizon, they can escape; if and when they do they take mass-energy away from the region near the black hole, with the result that the black hole contracts. That in turn reveals more "fossil" curvature, which causes a greater acceleration for future observers, who see more and hotter particles, and so on until some limit (e.g. the black hole completely evaporates or a stable remnant is left).
(It's important to note that the curvature is "fossilized", in that it is there just as the black hole is forming, and is strongest near the gravitational singularity, and weakens at increasing radius from there. The larger the mass of the black hole, the weaker the curvature is just outside the horizon; for ultramassive black holes the curvature immediately outside the horizon is almost arbitrarily flat. Conversely, smaller black holes have stronger curvature just outside the horizon.)
There are a variety of very different descriptions of the mechanism of Hawking radiation, including the most famous popularizaiton by Hawking himself, which involves virtual particle pairs, where one half of each pair falls into the black hole and the other escapes to infinity. Unfortunately most of them not only hide the actual nature of Hawking radiation, but outright conflict with mathematical tracing of emitted radiation back to the black hole (in particular the stress-energy at the horizon one gets when backtracking this way ends up being obviously wrong). The mathematically stable solution -- and the one that Hawking writes down in scientific papers rather than popular books -- has any pair separation happening at a significant distance from the event horizon.
Sabine Hossenfelder has a more technical and detailed write-up of this line of explanation at http://backreaction.blogspot.co.uk/2015/12/hawking-radiation... and links from there to a few scientific papers.
> Emitted Radiation When material falls into a black hole from a companion star, it gets heated to millions of degrees Kelvin and accelerated. The superheated materials emit X-rays, which can be detected by X-ray telescopes such as the orbiting Chandra X-ray Observatory.
> In addition to X-rays, black holes can also eject materials at high speeds to form jets. Many galaxies have been observed with such jets. Currently, it is thought that these galaxies have supermassive black holes (billions of solar masses) at their centers that produce the jets as well as strong radio emissions.
http://science.howstuffworks.com/dictionary/astronomy-terms/...
Accelerating black holes, or actually any accelerated matter, emits gravitational waves. This are disturbances of space-time itself and unlike electromagnetic waves mediated by photons moving through space-time. At least in a classical picture of gravity, not sure how that would work out within quantum gravity when gravitational waves are mediated by gravitons. But I guess you can just think of the gravitational waves being emitted at the event horizon.
Then there is electromagnetic radiation emitted from matter falling towards the black hole but still outside of the event horizon. The gravitational forces of the black hole heat up this matter to the point that it emits electromagnetic radiation in a wide spectrum.
Finally there is Hawking radiation which is a suspected electromagnetic radiation due to quantum effects near the event horizon. The associated black-body temperature is tiny, two billionth of a Kelvin for a 30 solar mass black hole and decreasing with increasing mass. The temperature of the cosmic microwave background with 2.7 Kelvin is in comparison gigantic and therefore black holes absorb much more cosmic microwave background radiation than they emit Hawking radiation. The universe has to become a lot cooler before Hawking radiation can start to evaporate black holes.
Spherically symmetric gravitational collapses (of dust or gas, for example) are certainly systems of accelerated matter, but do not shed gravitational waves. Rotating spherical bodies also do not shed GWs. To first order, this means the rotation of stars and planets do not shed GWs, although a planet revolving around the star in an essentially Kepler orbit will shed GWs, as will a pair of stars in close orbit around each other.
GWs solve the apparent removal of momentum-energy from a system where there is no removal of mass-energy by non-gravitational radiation. For most systems the energy loss is negligible. That's why the first GW detection involved a late stage inspiral of two compact massive objects with no way to ditch their angular momentum electromagnetically or via neutrino (or other dark matter) emission.
GWs themselves have spin 2 symmetry; in theories with gravitons, those are spin-2 gauge bosons, typically massless (because they are long range), and you get large numbers of them forming the classical GWs, just as you will find large numbers of photons forming a bright flicker of light, although you can detect tiny numbers of photons because electromagnetism is relatively strong -- tiny numbers of gravitons are not going to be detectable by humanity any time soon.
It's not curvature (and certainly not gravitational forces) heating up accretion disks. The matter in the disks move on intersecting geodesics and occasionally collide. Such collisions tend to ditch the particles' momentum into emitted photons.
Hawking radiation is an effect of accelerated observers seeing more (and more energetic) particles than non-accelerated ones, and gravitational collapses producing an acceleration between past and future observers. Where a past observer sees a tiny number of low-frequency particles in the "vacuum" outside the collapsing object, a future observer (after the horizon has formed) will see a larger number of higher frequency ones. The acceleration is curvature dependent, and curvature just outside the horizon depends on black hole mass -- more massive black holes have less curvature just outside the horizon (which is further away from the gravitational singularity or whatever is at the centre of a black hole). These particles near but outside the horizon can escape, which takes mass-energy away from the dynamical spacetime just outside the horizon. That in turn causes the horizon to retract and that exposes stronger curvature. That in turn produces a stronger acceleration for further future observers, and the process continues -- that's black hole evaporation.
Hawking radiation is always emitted, for SMBHs that only grow by incidental interception of CMB radiation, and even for stellar mass black holes. Infalling matter simply replaces (and then some) the outgoing "fossil" infrared radiation from the space just outside the black hole as the horizon was forming.
Imagine a civilization building black hole computers in their solar system. That's pretty badass :)
After you die, your body’s atoms will disperse and find new venues, making their way into oceans, trees and other bodies. But according to the laws of quantum mechanics, all of the information about your body’s build and function will prevail. The relations between the atoms, the uncountable particulars that made you you, will remain forever preserved, albeit in unrecognisably scrambled form – lost in practice, but immortal in principle.
Can anyone point me to the article or wiki of this theory/phenomenon? I would like to read up more about it.
Consider two hills with a valley between them. In one universe, I roll a ball down one hill. In the other, I roll it down the opposite hill. In both, the ball ends up in the valley, and the information about which hill the ball rolled down is lost.
You could perhaps argue that other effects (me disturbing the air on the hill I walked up) might still imply which hill the ball rolled down, but the question really is if such a scenario could exist, probably in a more simple form.
edit: spelling
https://www.youtube.com/pbsspacetime and https://www.youtube.com/user/sixtysymbols
We'd probably get a little warning from amateur astronomers as they freaked out months before it happens.
Think of a moon that drags you onto it. You can't ever have enough power to reverse moving towards it. Light isn't quick enough to leave the pull. thus it is dark.
Isn't a black hole more like an edge of the universe? My understanding is that you end up with a Zeno's paradox situation where no matter how close you get you can never actually reach it.
c^2 = (v_t)^2 - (v_x)^2 - (v_y)^2 - (v_z)^2
As I said, maybe my understanding is just totally incorrect here.
Edit: Actually, I was really confused (this is all based on looking it up the other day). According to the above, v_t would need to increase as eg v_x increases. This is just wrong, but I'll leave it here in case someone wants to explain it correctly.
Your equation is some algebraic mangling of the Minkowski line-element, which we can write as ds^2 = -cdt^2 + dx^2 + dy^2 + dz^2 in Cartesian coordinates with a -+++ metric signature. That's the interval in flat spacetime (aka Minkowski spacetime, although in both cases sometimes "time" is omitted when a reader will not be confused).
The conversion constant "c" there is the sole free parameter of the Poincare group, which is the local isometry group of Minkowski spacetime (i.e., it applies each point in spacetime), which includes translations, Lorentz boosts and rotations on the three spacelike axes (x, y, and z in the form above) and a unidirectional translation on the timelike axis (t). The parameter corresponds (in SR) to the speed of a massless particle, and light is assumed to be massless. It's a postulate of Special Relativity that all non-gravitational physics is invariant under the Poincare group, and that's baked into the Standard Model, for instance.
However, in GR "c" corresponds to the surface of a nonempty, convex, open cone of tangent vectors at some point p on the (curved) manifold; light at point p is constrained to that surface exactly, and massive particles at point p stay inside that boundary.
In GR we can only meaningfully compare speed and velocity locally, where that means either in the limit as spacetime intervals go to zero, or equivalently in the local section of the fibre bundle, because the very definition of spacetime curvature means the parallel transport of one vector to another for comparison purposes is path-dependent, and that applies on all four axes, so we cannot even meaningfully compare two clocks (with which we might measure relative velocity) unless they are at the same point in spacetime.
However, we can work things out so that a small (but not exactly zero-sized) region of spacetime is treated as flat, and then use Special Relativity or even Newtonian mechanics to discuss the matter content in that region, right down to comparing velocities. This "flattening" can be done quite successfully in a number of ways, and can even be done in a region with significant curvature by using the formalisms of semiclassical gravity. The cost is in artifacts introduced into the non-gravitational content of the region of non-negligbly curved spacetime, most noticeably in terms of differences in particle count and even the interpretation of matter field excitations as particles.
This mathematical "flattening away" of the curvature returns us from a causal cone built on a hyperbolization of a series of first-order quasilinear partial differential equations (the Einstein Field Equations) to the Poincare group applying at every point, and thus we return to "c" as being mathematically special, rather than relating to one of perhaps many causal cones (since one can have many hyperbolizations, and thus many timelike-spacelike conversion constants although so far there is only evidence for one).
Nothing can ever fall into them, so they can't ever form, or grow. (Obviously speaking from the POV of Earth.)
Since they can't form, and can't grow, how can you see a "supermassive one"?
But things will still fall in below the event horizon when seen from the outside.
A black hole forms when the density (of energy or matter) at some point adds up to a gravity that light can't escape. Colliding two neutron stars would likely instantly cause a high enough density in a volume such that a black hole and its event horizon can form, which would envelop a very large mass in much less than a second.
PS.
Every black hole has second event horizon in the center of black hole, and I am very curios is it filled with mass or not. :-/
It's not about if light is quick enough to leave the pull. It's about the light not being fast enough to be stopped by the mass.
If light is accelerating towards the center fast enough so the mass won't be able to stop it the light will go though it.
But ofcourse that means that light should go faster than light.