Naked Science Forum
Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: SymeAaro on 29/06/2017 21:01:46
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Every website I've read describes black holes as an infinite curve in space time.
However, from what I know, I believe a singularity is just a tiny, dense ROUNDED, celestial object, whose GRAVITY can be represented as a well. Is this correct?
And is so, is the event horizon an imaginary sphere around the singularity?
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Black holes aren't actually holes: the gravity wells often used in illustrations are mostly just visual tools to graphically represent a change in gravitational potential/force as you near the black hole.
A classical gravitational singularity is a single, dimensionless point. You can't consider that to be round or any other shape. However, that is probably not the correct representation of what is present inside of a real black hole. A unified theory where gravity and space-time are successfully united with quantum mechanics will likely get rid of the infinities associated with classical black holes (or so I hope).
The event horizon can indeed be represented as an imaginary sphere around the singularity if the black hole does not rotate. If it does rotate, the event horizon will be distorted such that it bulges at the equator.
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Every website I've read describes black holes as an infinite curve in space time.
However, from what I know, I believe a singularity is just a tiny, dense ROUNDED, celestial object, whose GRAVITY can be represented as a well. Is this correct?
And is so, is the event horizon an imaginary sphere around the singularity?
From an external observer's point of view everything that falls into a black hole disappears from the universe. The term "hole" originated from this notion as an analogy. Observers falling into a black hole will never be able to measure any infinite curvature since that only happens at the singularity and no observer will live to be there and as such could never relay that information to anyone. And no observer inside a black hole can relay information to the outside world. As a friend of mind (who's widely known in the physics/relativity community) said to me in an e-mail
We don't know exactly what happens to particles that fall into a black hole. From the perspective of an external observer, the infalling particles never cross the horizon in any finite amount of time--they slow down as they approach the horizon, and only approach it asymptotically. So the question about what happens to infalling particles in a black hole is meaningless for an external observer. Presumably an observer who falls with the particles will find out what happens, but he can't communicate this knowledge to the external observers. This raises fundamental questions about the operational meaning of any predictions made from theory about what happens inside a black hole. Are such statements in the realm of physics or of metaphysics?
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as an infinite curve in space time
The infinities aren't just restricted to the singularity at the center. If it were, physicists could just say that it is hidden from our sight, so we can ignore it.
But infinities also exist at the event horizon, and just outside it. For example: At the event horizon, time slows by an infinite amount (according to a remote observer). Quantum effects may make the event horizon a bit "fuzzy".
This has led to some differing views about what happens there, like the firewall hypothesis (https://en.wikipedia.org/wiki/Firewall_(physics)). And Hawking radiation (https://en.wikipedia.org/wiki/Hawking_radiation).
Just inside the event horizon, by some theories, the dimensions of space and time may be interchanged, leading to time-like paths leading to the singularity.
We don't have any real black holes in our neighbourhood to experiment on (fortunately!), so we can't resolve some of these questions. But we do have some "safe" experimental systems that have some similarities to black holes (https://en.wikipedia.org/wiki/Sonic_black_hole), such as liquids disappearing down a drain at the speed of sound.
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The infinities aren't just restricted to the singularity at the center. If it were, physicists could just say that it is hidden from our sight, so we can ignore it.
But infinities also exist at the event horizon, and just outside it. For example: At the event horizon, time slows by an infinite amount (according to a remote observer). Quantum effects may make the event horizon a bit "fuzzy".
The spacetime curvature at the horizon is finite. The event horizon itself is not observable to outside observers. Just outside the event horizon time dilation is quite finite.
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Thank u all! Just what I was looking for, really helped.
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The event horizon can indeed be represented as an imaginary sphere around the singularity if the black hole does not rotate. If it does rotate, the event horizon will be distorted such that it bulges at the equator.
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............Quantum Pressure .
Let us begin by accepting the premise that the space/time matrix (substrate) has an intrinsic , "outward" quantum pressure . This would be responsible for Alan Guth's "Grand Inflation" . The most remarkable aspect of this is that as the universe expands , all of it's constituent parts do too . This density decrease then engenders time contraction due to Lorentz Expansion . Lightwaves emitted earlier would have a lower frequency than those emitted later. As all radiative energy is composed of the M/E matrix , it too evidences quantum pressure , but in exaggerated form . In terms of Einsteinian Gravity Topology , the waves in the S.T. matrix dent the "flat surface" of space a tiny bit . If two lightwaves ( photons ) approach each other , their dents interact to draw them towards one another . This is why even light-waves "emit" , and respond to gravity . Matter itself is made of vast amounts of "captured" energy. This means that both matter and concentrations of energy exhibit huge amounts of "outward push" (quantum pressure) . When their massive dents draw them towards each other , we call that "gravity" . When they are close , the pressure creates a positive feedback loop . This means that ever more pressure gets concentrated on an ever smaller volume of S.T. matrix . In a super-massive black-hole , the Mass/Energy content of many stars is compressed into an ovoid the size of a car . It still has it's initial mass , spin , and charge . However , they are all mitigated by the dictates of Relativity . These characteristics can affect the space outside of the B.H. because the S.T. matrix is altered by them . Likewise , magnetic lines of force should also propagate from and through black- holes . Motion of these cannot propagate within B.H.s , ergo , no EMR (light) can be emitted by them .
All of these begets an unavoidable question ; "where" is the q.pressure trying to escape to ? Extra-universal physics MUST be invoked at this point . It appears that "wheels within wheels" is quite apt here .
........P.M.
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You're not speaking in terms of accepted modern physics, Mega-Mind. You should take that to the New Theories section.
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True that ! The wave of new understanding is breaking , and I am surfing the edge !
P.M.
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..................Completion .
See : Are Black Holes stars or holes ?
.......P.M.
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They are matter that is obscured
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True ...
What is matter , but captured-and-looped energy ?
P.
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I think that.
No, a black hole is not really a hole at all. A black hole is an object just like any other, except that it is extremely dense. This gives it such a high gravitational field that nothing, not even light, can escape. Because no light escapes a black hole, it is invisible – or ‘black’ – although they can be detected by their effect on the material around them. The term ‘hole’ was used because whatever falls ‘into’ a black hole is trapped forever.
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Except if Hawking-Radiation is real .
Matter going in becomes the same as energy going in ; super-compressed matter/energy . It is however , unable to interact with the rest of the universe , except gravitationally .
Interestingly , if you take a mass of four-million sols , compress it to electron density , then crush that to 1% volume , you get an object the size of a VW Bug . Make it an ellipsoid (due to rotation) , and you have the object that you speak of .
*Whether it's a Kugelblitz or a dirt-ball , it is the exact same thing... solid-energy .
* Spock would love it ! .😄
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I think that.
No, a black hole is not really a hole at all. A black hole is an object just like any other, except that it is extremely dense. This gives it such a high gravitational field that nothing, not even light, can escape. Because no light escapes a black hole, it is invisible – or ‘black’ – although they can be detected by their effect on the material around them. The term ‘hole’ was used because whatever falls ‘into’ a black hole is trapped forever.
I think you copied that from someone else/.
https://www.sciencefocus.com/space/is-a-black-hole-a-hole/
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It was my understanding that a singularity was collapsed space, ie the 4 dimensions had ceaced to exist as normal space, hence why it was called a singularity.
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Well now ,
That does not rule out the existence of the crushed energy-sphere , it simply acknowledges the extreme distortion of the involved space-time ..🤓
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Hi
It was my understanding that a singularity was collapsed space, ie the 4 dimensions had ceaced to exist as normal space, hence why it was called a singularity.
How much detail did you want?
One minor issue is that there are solutions to Einsteins Field Equations that produce what are called "eternal black holes". For an eternal black hole, there was always a singularity. It's then impossible to say spacetime collapsed or ceased to exist there, it just never was any kind of place or point in our spacetime to begin with.
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No argument there ,
I am saying that that "singularity" is how the space-time within a black-hole relates to the universe external to it .
This does not remove the accumulated energy/mass from existence , but does prevent interaction in most ways .
Consider it a cosmic illusion ; the mass is there , but cannot be seen , except through gravitational effects .
*So... the energy-sphere has dropped out of normal spatial interaction , but not out of existence itself . .🙃
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'Black' means darkest observable space (even light cannot escape), 'whole' is actually really a well limited by an event horizon, under which everything goes to spaghettification.
Currently there is no means to tell what is inside the event horizon of a black whole. It's roundness is conditioned by Stable circular orbits in higher-dimensional multi-black hole spacetimes. Beyond this visible orbits nothing falls into a static black hole. Our galaxy with all matter has it's orbit = 3R(event horison), light comes closer = 1.5R(event horizon).
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Hi.
It's roundness is conditioned by Stable circular orbits in higher-dimensional multi-black hole spacetimes
I'm not sure what this means.
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I think he means that "singularity" is the face that black-holes put on , when they get up in the morning ! .😄
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Stable circular orbits in higher-dimensional multi-black hole spacetimes
Let me put some stand here.
The innermost stable circular orbit, or ISCO. In Newtonian gravity, all circular orbits are stable. This means that if such an orbit were perturbed slightly, the orbit would just become somewhat elliptical but nothing else would happen. But in general relativity there is an innermost stable circular orbit. For the Schwarzschild geometry in Schwarzschild coordinates, Rs that innermost radius. Inside Rs, a circular orbit is unstable; a slight perturbation inward leads to a rapidly-opening inspiral to the hole. Thus it is common to assume that accretion disks of gas spiraling onto a black hole are effectively truncated at the ISCO; there is gas inside the ISCO, but no longer is there a disk which moves with slow inward radial motion. Gas pressure gradients change somewhat the location of the ISCO, but this is a decent approximation that allows you to compute approximately the radiative efficiency of a geometrically thin disk.
Shep Doeleman:
“There really are no deeper questions in the universe than how black holes work. Because we know that at their heart they contain this mystery of how do gravity and quantum mechanics work together, which is the deepest question there is right now.”
So, there are lot's of work through different approach has being done and on-going after Einstein predictions.
The greatest breakthrough and fascination is the orbit observation.
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But in general relativity there is an innermost stable circular orbit. For the Schwarzschild geometry in Schwarzschild coordinates, Rs that innermost radius. Inside Rs, a circular orbit is unstable
No. Even immediately outside Rs, no orbits are possible. The nearest possible orbit is outside the photon sphere which is 1.5 Rs. Orbits outside that radius are stable, and those at or inside are impossible. The only unstable orbit is a massless thing exactly at 1.5 Rs.
It gets more complicated with something like a Kerr black hole where orbits become non-circular.
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Hi @TommyJ
Thanks for taking the time to reply.
The only reasonable possibility is that your Rs is not the same notation that most others use. I concur with Halc where Rs = the Schwarzschild radius.
What you've said about the truncation of accretion discs sounds reasonable.
Best wishes.
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'Black' means darkest observable space (even light cannot escape)
Steven Hawking identified a way that light could escape from a black hole, through the eponymous Hawking Radiation.
- The light has a "black body" spectrum
- Although, with a stellar-mass black hole having a black body "temperature" of nanoKelvins, you would be hard-pressed to detect it.
- The peak emission would be in long-wave radio spectrum, rather than in visible light
See: https://en.wikipedia.org/wiki/Hawking_radiation
It gets more complicated with something like a Kerr black hole where orbits become non-circular.
Due to the formation of stellar-mass black holes from the collapse of a rotating star,
- or their mechanism of growth, fed by a spinning accretion disk,
- you would have to assume that most black holes are "rotating" (ie have angular momentum), ie are a Kerr black hole.
See: https://en.wikipedia.org/wiki/Rotating_black_hole
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Truly, the most of the black hole should be rotating, since they are formed from collapsing stars, and all stars known to be rotating.
Rotating black hole is measured by mass and spin (0 to mod [1 - max])).
Additional matter, falling into a black hole also contributes to its rotation.
The mass of a black hole is estimated by its influence on other far bodies. Spin is harder to measure than mass, as it can be measured only with the closest particles to the black hole.
Innermost Stable Circular Orbit (ISCO), closer than this no orbits are stable, and falling into a black hole. The faster it spins the smaller the ISCO becomes. The spin is supporting the particles against the gravity.
The greater the spin, the closer the ISCO shrinks, up to the event horizon. ISCO’s less than event horizon haven’t been seen yet.
So, ISCO and black hole spin are related. One of the closest to the maximum black hole spin detected is 0.98 (GRS 1915+105).
The radii of ISCO discs are measured in the same way as the stars are measured.
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No, they are not holes, they are singularities.
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No. Even immediately outside Rs, no orbits are possible. The nearest possible orbit is outside the photon sphere which is 1.5 Rs. Orbits outside that radius are stable, and those at or inside are impossible. The only unstable orbit is a massless thing exactly at 1.5 Rs.
It gets more complicated with something like a Kerr black hole where orbits become non-circular.
Also, no-hair theorem states that all black hole solutions of the Einstein–Maxwell equations of gravitation and electromagnetism in general relativity can be completely characterized by only three externally observable classical parameters: mass, electric charge, and angular momentum.
This metaphor means that during black hole formation the data of the collapsing source is lost [under event horizon].
A black hole is one of the rare cases when the theory was elaborated within math long before any evidence gained. In this ‘singularity’ situation physics laws and their prediction ability are lost.
Lets us keep hoping for a telescope, that is able to have a glimpse inside an event horizon.
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Using what exactly , magnetic-field lines of force ? .🤓
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Lets us keep hoping for a telescope, that is able to have a glimpse inside an event horizon.
Why hope for something that is impossible?
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Lets us keep hoping for a telescope, that is able to have a glimpse inside an event horizon.
Kind of contradicts the rest of what you said. The only way to have a glimpse inside is simply to jump in yourself. Things will look disappointingly normal (at first) if you choose a large one.
We already know this, so I don't see the point in the experiment. You can't see the singularity any more than I can see 2022 now.
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Why hope for something that is impossible?
..tangling, right.
What is fascinating (both those who are participating and those who are tracing), that current EHT success is already stepping forward for more data to be extracted (e.g. low-energy radio waves to high-energy gamma rays).
Cooperated group announcing planned works to be proceeded with.
https://www.nasa.gov/mission_pages/chandra/news/black-hole-image-makes-history