Naked Science Forum

Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: SymeAaro on 29/06/2017 21:01:46

Title: Are black holes really holes?
Post by: SymeAaro on 29/06/2017 21:01:46
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?
Title: Re: Are black holes really holes?
Post by: Kryptid on 29/06/2017 21:42:33
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.
Title: Re: Are black holes really holes?
Post by: PmbPhy on 29/06/2017 22:01:41
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
Quote
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? 
Title: Re: Are black holes really holes?
Post by: evan_au on 29/06/2017 22:13:06
Quote from: SymeAaro
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.
Title: Re: Are black holes really holes?
Post by: PmbPhy on 29/06/2017 22:28:23
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.
Title: Re: Are black holes really holes?
Post by: SymeAaro on 30/06/2017 21:57:26
Thank u all! Just what I was looking for, really helped.
Title: Re: Are black holes really holes?
Post by: Thalias on 20/07/2017 10:39:52
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.
Title: Re: Are black holes really holes?
Post by: Professor Mega-Mind on 27/10/2018 23:23:32
............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 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 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.
Title: Re: Are black holes really holes?
Post by: Kryptid on 28/10/2018 01:13:31
You're not speaking in terms of accepted modern physics, Mega-Mind. You should take that to the New Theories section.
Title: Re: Are black holes really holes?
Post by: Professor Mega-Mind on 28/10/2018 01:26:03
True that !  The wave of new understanding is breaking , and I am surfing the edge ! 
P.M.
Title: Re: Are black holes really holes?
Post by: Professor Mega-Mind on 28/10/2018 01:40:19
..................Completion .
See : Are Black Holes stars or holes ?
.......P.M.