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Posted By: Bill S. Time at event horizons. - 08/06/14 09:08 PM
Does time stop at an event horizon?

I think not, but I am open to persuasion.
Posted By: redewenur Re: Time at event horizons. - 08/06/14 09:53 PM
Why do you think not, Bill?
I suppose the thing to do would be for us to go back in time to childhood and spend our lives learning how to find the answer through physics. On the other hand, we have the option to either choose our favorite theory from those who have spent their lives in that way, or else reject all those theories as Paul tends to do.
Whose theory have you chosen, Bill, and why?
Posted By: Bill Re: Time at event horizons. - 08/06/14 10:38 PM
Originally Posted By: Bill S.
Does time stop at an event horizon?

I think not, but I am open to persuasion.


Well, yes and no. If I understand it correctly as you travel through an even horizon YOU don't notice anything (except of course that you are torn apart). Time for you continues normally. But to observers outside of the horizon your time would appear to stop. It is pretty much the same as time contraction when traveling at relativistic speeds.

This of course is probably an approximation and the way it works is undoubtedly a matter for much thought among theoretical physicists.

Bill Gill
Posted By: Bill S. Re: Time at event horizons. - 08/07/14 12:28 AM
If time stops at the event horizon, even if only in the frame of reference of a distant observer, how would that effect gravity? The distant observer sees a scenario in which time has stopped at the event horizon, but still feels the "pull" of gravity resulting from the presence of the mass of the black hole which is on the other side of the event horizon.
Posted By: Bill Re: Time at event horizons. - 08/07/14 03:31 AM
I hadn't thought about it before, but I suspect that is one of the places where there might be some conflict between GR and QM. Obviously none of the particles described by QM can get out. But the graviton can. That is in the case of Quantum Gravity. Obviously GR doesn't have that problem. GR is all about the curvature of space created by mass.

The following is all off of the top of my head, so it is open to a lot of correction. In GR gravity can be considered as a distortion of a field. The field is not going to be subject to the same limitations as a quantum particle. That is, it is continuous across the event horizon. Particles moving in the gravitational field move in a "straight line", with respect to the field. So if the field is warped the line is warped to match the warp of the field. If the warp is too large the particles are held within a certain distance of the singularity* at the center of the event horizon because the warpage curves their trajectory so much that they cannot pass the horizon. However, the distortion in the field does not really have a trajectory, it just exists. However, when the distortion changes the change moves through the field at the universal speed limit C.

And that is my totally spur of the moment, top of the head analysis.

* In the context I recognize that there cannot, according to QM actually be a singularity, but for simplicity I will use the word. I expect that someday there will be a theory of quantum gravity that will more clearly tell us what is at the center.

Bill Gill
Posted By: paul Re: Time at event horizons. - 08/07/14 04:48 AM
Quote:
or else reject all those theories as Paul tends to do.


I don't reject all theories.

I don't pay any theory too much attention however.

in other words I don't simply allow any theory to control
the possibilities of the physical world.

I always like to perform the actual calculations using
actual ( not designer ) math , because actual math is
supposed to back up a good theory , so with me the calculations come first then later if there is a conflict
with a theory then I have to find where the theories went
wrong and of course its usually the theories that are wrong.

but its mostly the wording or assumptions taken in the theories.

also I only complain about theories that have designer math that is designed specifically to prove the theory itself to be right these days.

I used to complain about newtons laws until I found that
what I was complaining about was nothing more than translation errors.
Posted By: Bill S. Re: Time at event horizons. - 08/07/14 01:20 PM
Quote:
Why do you think not, Bill?


I'm working on that, Rede.

Quote:
Whose theory have you chosen, Bill, and why?


I've not chosen a theory (yet). The idea that time might stop is one I have difficulty with, not just because I can find no scientific evidence that time moves, but also because I can see problems with the concept of stopping our motion through time, if that is what we are doing.
Posted By: redewenur Re: Time at event horizons. - 08/07/14 02:03 PM
Paul.
I think I understand what you're saying, and I'd agree with most of that. The maths becomes deviant when the physics becomes deviant, i.e. when new physics is encountered, mathematical descriptions are introduced. An example of that would be Faraday's experiments > Maxwell's equations > Einstein's equations. Those new equations enter into physics from time to time and although, as non-mathematicians, we may not understand the whys and wherefores, we can witness their predictive power. It doesn't follow that the maths is necessarily 100% correct description of reality, Newton's being a case in point. The essential thing is that if the theory is consistently supported by observation then it has validity, even though it may later turn out to be less than 100% correct. If it disagrees with observation then it's wrong. The fact that the average Joe (you or me) has only the sketchiest knowledge of modern physics, and doesn't have a clue how to read the maths, is always going to leave us making probability judgements based on such information as we have. Such is life smile
Posted By: redewenur Re: Time at event horizons. - 08/07/14 02:19 PM
Bill S.
Do you concede that a given clock (cesium clock, if you like) will tick at a different rate (to that of the observer) if it has a different velocity and/or is situated in different spacial curvature?
Posted By: redewenur Re: Time at event horizons. - 08/07/14 02:31 PM
Bill: 'Obviously none of the particles described by QM can get out.'
- Except by Hawking Radiation.
Posted By: Bill S. Re: Time at event horizons. - 08/07/14 08:58 PM
Originally Posted By: Rede
Bill S.
Do you concede that a given clock (cesium clock, if you like) will tick at a different rate (to that of the observer) if it has a different velocity and/or is situated in different spacial curvature?


Yes. I believe that has been experimentally established. What I'm doubtful about is that this makes any fundamental difference to time.

It might be seen as evidence that time is static and that we move through it. That is the only way in which I can see that it makes any sense.
Posted By: Bill Re: Time at event horizons. - 08/07/14 09:27 PM
Originally Posted By: redewenur
Bill: 'Obviously none of the particles described by QM can get out.'
- Except by Hawking Radiation.

And that of course raises more questions. My understanding of Hawking Radiation is that when space manifests a pair of virtual particles they normally recombine and disappear within the time allowed by indeterminacy. However, if they manifest close to an event horizon one of them may pass into the horizon and the other be left free. The free particle is Hawking Radiation. Now comes the question. The particle that enters the horizon will probably meet another particle already in there and those 2 will annihilate, so that we still have the energy balance of the universe maintained. But, do we consider the particle that remains outside the horizon a new particle, or is it a reincarnation of the one that was annihilated inside the horizon? I don't think I have ever seen that discussed.

Of course I also recognize that my description of Hawking Radiation is a simplified version suitable for people who don't have the knowledge to adequately understand what is really happening. I suspect that it is probably much more complicate than that.

Bill Gll
Posted By: paul Re: Time at event horizons. - 08/07/14 10:04 PM
Quote:
The particle that enters the horizon will probably meet another particle already in there and those 2 will annihilate, so that we still have the energy balance of the universe maintained.


would the virtual particle meet an actual particle
and that is why they annihilate each other?

2 particles just appear. ( virtual particles )
1 of them goes inside the event horizon.
it is destroyed.

and 1 virtual particle remains outside of the event horizon.

how does that maintain an energy balance?
you now have an extra virtual particle in the universe.
and you have caused the annihilation of a actual particle
in the universe.

the universe would be becoming virtual.

Quote:
But, do we consider the particle that remains outside the horizon a new particle, or is it a reincarnation of the one that was annihilated inside the horizon?


how about virtual reincarnation?

because unless the virtual particle somehow becomes a
physical particle it would still be a virtual particle.

but can a virtual particle become a actual particle and if so
how does it know when and why to convert itself into reality?

Im going to propose a new theory for this certainty.

The distance theory of virtual particles from event horizons.

when space manifest a pair of virtual particles , the
particles are only allowed to manifest near a event
horizon when the distance from the event horizon
satisfies this theories accompanying math , because
this theory dictates to nature and natural physical
occurrences what nature can and cannot accomplish on
its own with or without permission from science.

and heres the math to compliment the theory.

where tdfaehwsiatmapovpattlopdpsiwbtt: the distance from
an event horizon where space is allowed to manifest a pair
of virtual particles according to the laws of particle distance physics set in writing by this theory.

roteh : radius of the event horizon

tidbtpotpop : the initial distance between the particles
of the pair of particles

tdfaehwsiatmapovpattlopdpsiwbtt = 1/(roteh^4 - roteh^4)-tidbtpotpop^2

this should clear up any problems with space manifestation of
particles too close to an event horizon thereby maintaining
the energy balance in the universe.

simply because space cannot spawn a pair too close because
of the way the math is designed.

this theory has never been proven to be wrong , and never can be.




Posted By: Bill S. Re: Time at event horizons. - 08/08/14 12:00 PM
That’s my kind of maths, Paul; I can understand it (almost).

Here’s simpler formula:

AT + N = 0

Where

AT= any thread
N= Newton
0= oblivion
Posted By: paul Re: Time at event horizons. - 08/08/14 01:29 PM
LOL , yes , such a simple formula that says so much.

and about my theory!
Quote:
That’s my kind of maths, Paul; I can understand it (almost).


that's where the theory gets its stability within physics and
where science validates it through experimental data on a
daily basis now , if one can almost understand it , then its wide open for amendment when , if , and as needed in order to
give science a more firmer grip on what nature is allowed to
accomplish within the physical and yes even the virtual
universe.

there are rumors that are circulating that seem to confirm
that there will soon be a 1st amendment to the theory and
I would get in trouble if I reveal the full text of the amendment , however I can give you a hint , the 1st amendment
to the theory will focus on the paradoxical particle distance
measurement itself as being a virtual measurement that will be
confined within a time dilation when it is found that the
space manifested pair of particles appear inside a curvature of time.

so there , I will leave you and Bill to work out the details because you guys are still into GR


Posted By: redewenur Re: Time at event horizons. - 08/10/14 11:10 AM
Originally Posted By: Bill
But, do we consider the particle that remains outside the horizon a new particle, or is it a reincarnation of the one that was annihilated inside the horizon?

One could ask: Is the electron, in tunneling, the same electron, or is it a new electron that replaced the one that existed on the other side of the barrier? But since we are talking about the quantum scale, the question is misconceived. It's the same quantity of energy centered at new coordinates. It's meaningless to speak of that energy as being new or old, so long as the books remain balanced.
Posted By: Bill Re: Time at event horizons. - 08/10/14 01:43 PM
Originally Posted By: redewenur
One could ask: Is the electron, in tunneling, the same electron, or is it a new electron that replaced the one that existed on the other side of the barrier? But since we are talking about the quantum scale, the question is misconceived. It's the same quantity of energy centered at new coordinates. It's meaningless to speak of that energy as being new or old, so long as the books remain balanced.

I think the tunneling electron and the Hawing Radiation are 2 different things. The electron tunnels because of the indeterminacy of its position. It might be on one side of the barrier, or it might be on the other side. But the virtual particles exist definitely on one side of the horizon or the other, not based on the indeterminacy of their position. Now whether one of the 2 virtual particles passes through the horizon might be a matter of tunneling, but once it has passed then it is inside, with no way back out.

Well, thinking about it, when a particle is still just inside the horizon it might be able to tunnel back out, but that is a statistical thing, so more of them would stay inside than tunnel back out. That would be when it was ready to meet an antiparticle and be destroyed.

But of course as I said, I really don't understand all there is to understand about Hawking Radiation and I am probably being way too simplistic.

Bill Gill
Posted By: redewenur Re: Time at event horizons. - 08/10/14 03:19 PM
You're probably right, Bill.
BTW, much to my surprise...

"A black hole of one solar mass has a temperature of only 60 nanokelvin (60 billionths of a kelvin); in fact, such a black hole would absorb far more cosmic microwave background radiation than it emits..."
http://en.wikipedia.org/wiki/Hawking_radiation

...considering that one solar mass is reckoned to be insufficient to form a black hole, and the larger the black hole the lower temperature, it looks like in all cases where black holes have been formed from collapsing stars (not primordial), even when they receive no more matter they will continue to receive more energy than they radiate until the CMBR is extremely close to zero kelvin. It's going to be a very long time before they even begin to lose any weight. I empathize frown

Does anyone know of any estimates regarding the future decline of the CMBR temperature?
Posted By: Bill Re: Time at event horizons. - 08/10/14 05:20 PM
I couldn't right off hand find anything about the future of the CMBR temperature. But I did find this about the future of the universe. WIKI:Future of an expanding universe

Originally Posted By: Wikipedia
Black Hole Era

10^40 years to 10^100 years

After 10^40 years, black holes will dominate the universe. They will slowly evaporate via Hawking radiation. A black hole with a mass of around 1 solar mass will vanish in around 2×10^66 years. As the lifetime of a black hole is proportional to the cube of its mass, more massive black holes take longer to decay. A supermassive black hole with a mass of 10^11 (100 billion) solar masses will evaporate in around 2×10^99 years.


I'm not sure whether the CMBR is counted in that, but it does give an estimate of the future heat death of the universe.

Bill Gill
Posted By: redewenur Re: Time at event horizons. - 08/10/14 11:33 PM
Thanks for the link, Bill. Fascinating. I love big numbers!

Black holes will have all evaporated after 10^100 yrs?...that's about 730 thousand trillion trillion trillion trillion trillion trillion trillion times the current age of the Big Bang universe. I wonder if some form of intelligent life could exist during that time, until thermodynamic equilibrium. I like to imagine so. It's life processes could well afford to be on the slow side.
Posted By: Orac Re: Time at event horizons. - 08/13/14 02:51 AM
I Always love questions along these line and get a good chuckle.

What happens depends on what you accept and what you want to extrapolate into something that you have no data which is always fun.

If GR is your thing then the easiest extrapolation is using Rindler coordinates and it says times stops for the observer not because time really stops just they are unable to detect it in any way. It is well covered in Wikipedia.

http://en.wikipedia.org/wiki/Rindler_coordinates

If Quantum ElectroDynamics(QED) is your thing then you go back to a problem Einstein was struggling with before his death and later extended by Wheeler. The topic gets picked up from time to time but is out of favour with science media at the moment.

http://en.wikipedia.org/wiki/Black_hole_electron

One of the interesting ways to look at your question is what is the minimum size black hole can be.

The "accepted theoretical minimum" size of a black hole is about 21.77 micrograms. That yields a schwarzchild radius of a planck length.

That answer provides a link between the 2 schools of thought above and may help you with thinking more carefully about your question and show you a little problem often forgotten in the argument smile

Black holes can be very small if theory is right and any concept of falling into them means what? No one has seen a microscopic black hole so do they exist and if not why not? Would time stop around a micro black hole and what would that mean anyhow?

The cosmology side of black holes get a lot of science media discussion but micro black holes under the same theory are interesting. Ethan did a good article on cosmology ones a couple of years ago (http://scienceblogs.com/startswithabang/2012/05/02/black-holes-dont-eat-as-much-a/)

When people were concerned the LHC might create a blackhole it spawned a lot of discussion on it and some considered thinking (http://www.newscientist.com/blogs/shortsharpscience/2009/05/black-hole-catching.html)
Posted By: Bill Re: Time at event horizons. - 08/13/14 01:11 PM
Originally Posted By: Orac
The "accepted theoretical minimum" size of a black hole is about 21.77 micrograms. That yields a schwarzchild radius of a planck length.

How long would a minimum sized black hole last? Since the temperature of a black hole is an inverse relation to its size then a black hole with a schwarzchild radius that small should have a very high temperature. The super massive black holes have extremely low temperatures and extremely long lifetimes, so I would expect super small ones to have very short lifetimes.

Also of course there is the question of what the Planck length means. Ethan Siegel discusses this in his blog. The Smallest Possible Scale in the Universe. I don't expect that makes much difference to what you have to say, but it is an interesting discussion.

Bill Gill
Posted By: pokey Re: Time at event horizons. - 08/13/14 03:36 PM
Black holes, entanglement, GR + Quantum mechanics and gravity.

http://www.scienceagogo.com/news/20131105203121.shtml

It does seem to involve string theory though.
Posted By: Orac Re: Time at event horizons. - 08/14/14 02:39 PM
Originally Posted By: Bill
How long would a minimum sized black hole last? Since the temperature of a black hole is an inverse relation to its size, a black hole with a Schwarzchild radius that small should have a very high temperature. The super massive black holes have extremely low temperatures and extremely long lifetimes, so I would expect super small ones to have very short lifetimes.

Did you read => http://www.newscientist.com/blogs/shortsharpscience/2009/05/black-hole-catching.html

It explains what would happen in layman understandable detail assuming you made one it would continue to grow so long as it could absorbs particles.

The article on scale is sort of what I was trying to get Bill S to think about. In cosmology they talk about people falling into a black hole and make weird assumptions not least about the space geometry but they forget the theory must and should hold for a microscopic black hole, unless their theory explains a reason micro black holes can't exist.

Laymen think black holes are like these incredibly dense things that suck everything into them. They aren't anything like that at either a macro level, as Ethan discussed, or if they exist in micro form. As per the above article a micro black hole has no more gravity than an orange and it isn't going to suck you or the earth anywhere and assumptions and theories about what is going to happen to time should be valid for the micro black hole as the large cosmological version.

The two really weird facts about black holes that catch people out.

1.) The Schwarzschild radius formula is linear if you double the mass of a black hole the Schwarzschild radius doubles. However because the thing is a sphere that means it actually gets less dense because volume is 4/3 x Pi x radius cubed. So a microscopic black hole has the highest density you can have and as the black hole gets larger to the cosmological version it's density actually decreases. Catches people out all the time they expect it to get denser like the core of a sun. That is why when they get really large: (http://en.wikipedia.org/wiki/Supermassive_black_hole)

Quote:
The average density of a supermassive black hole (defined as the mass of the black hole divided by the volume within its Schwarzschild radius) can be less than the density of water in the case of some supermassive black holes

2.) Black holes often spin (perhaps always?), and because they distort space, they would drag space around like some wrinkled fabric and that makes simplifications like Rindler calculations fanciful at best.

A third interesting fact is outside the ability of laymen. It is to do with energy calculations with the weird density behaviour of point 1.
Posted By: Bill S. Re: Time at event horizons. - 08/14/14 10:07 PM
http://en.wikipedia.org/wiki/Supermassive_black_hole

“…a person on the surface of the Earth and one at the event horizon of a 10 million solar mass black hole experience about the same tidal force between their head and feet….”

Does that mean they would experience the same gravitational “attraction” in both places?
Posted By: redewenur Re: Time at event horizons. - 08/14/14 11:14 PM
Originally Posted By: Bill S.
http://en.wikipedia.org/wiki/Supermassive_black_hole

“…a person on the surface of the Earth and one at the event horizon of a 10 million solar mass black hole experience about the same tidal force between their head and feet….”

Does that mean they would experience the same gravitational “attraction” in both places?

No, it means that the gravitational gradient is the same in both cases, because the radius of the supermassive black hole is about 10^6 km or more, compared to about 6x10^3 km for Earth.
Posted By: paul Re: Time at event horizons. - 08/15/14 12:08 AM
Quote:
No, it means that the gravitational gradient is the same in both cases, because the radius of the supermassive black hole is about 10^6 km or more, compared to about 6x10^3 km for Earth.


it would be more valid to say that it is the amount of mass
and its density inside the black hole that determines the amount of gravity that he would feel , rather than any measure of distance.

because the density of mass would be a changing inside a
black hole.
the balck hole would be able to pull more
mass inside a given event horizon as it squeezes some energy out of some of its mass.
which increases the diameter of the event horizon because of the increase in mass and the increase in the density of
the mass inside the black hole.


I thought this was normal mainline science hoopla myself.

Quote:
The radius of the central object must be less than 17 light-hours, because otherwise, S2 would collide with it. In fact, recent observations[17] indicate that the radius is no more than 6.25 light-hours, about the diameter of Uranus' orbit. However, applying the formula for the Schwarzschild radius yields just about 41 light-seconds, making it consistent with the escape velocity being the speed of light.


yes , no thing can travel faster than the speed of light... laugh

so it must be a really tiny supermassive black hole
so that it fits in with the hoopla I suppose.

Posted By: Orac Re: Time at event horizons. - 08/15/14 02:48 AM
Originally Posted By: redewenur
No, it means that the gravitational gradient is the same in both cases, because the radius of the supermassive black hole is about 10^6 km or more, compared to about 6x10^3 km for Earth.


And that was the bit I was trying to get Bill S to realize that you therefore end up with a time gradient on you. So when you talk about observers and time it can be the same observers foot versus his head smile

Extrapolation while useful can sometimes be very misleading which is why it is often interesting to look at the thing on every scale micro, normal and extremely large.
Posted By: Bill Re: Time at event horizons. - 08/15/14 03:06 AM
Ok, I found the information about the lifetime of a micro black hole. From The University of Oxford

Originally Posted By: University of Oxford
‘Astronomical black holes are so massive that their evaporation rate is negligible. In contrast, mini black holes are hot: unimaginably hot. The core of our Sun is at around 15,000,000 degrees Kelvin - to get close to the temperature of a mini black hole you would need to add another 42 zeroes.’

‘What this incredible temperature means is that mini black holes of tiny mass ‘evaporate’ into the far, far colder space around them almost infinitely fast. Their expected lifetime is around one octillionth of a nanosecond – so that they pop out of existence again almost as soon as they are created.’


Just about as I thought a micro black hole would have an extremely short life time.

And now that Orac has mentioned it I recall reading a book about black holes where they made an imaginary voyage to several black holes. At the most massive one that they knew of at the time they could orbit comfortably at just above the Event Horizon. If I recall correctly that was at least one place where I got what I know about time at the Event Horizon. What I remember about it is what I used in my first reply to Bill S. And once again I acknowledge that my understanding is very limited since I got it from popular explanations that probably oversimplify it.

Bill Gill
Posted By: Orac Re: Time at event horizons. - 08/15/14 03:41 AM
Originally Posted By: University of oxford
‘What this incredible temperature means is that mini black holes of tiny mass ‘evaporate’ into the far, far colder space around them almost infinitely fast. Their expected lifetime is around one octillionth of a nanosecond – so that they pop out of existence again almost as soon as they are created.’

Originally Posted By: Bill
Just about as I thought a micro black hole would have an extremely short life time.

Again warnings about making these sorts of things as facts and trying to put them in your "IN" box they are not facts they are extrapolations hence the words they used were THEIR EXPECTED LIFETIME.

So you understand the problem (http://en.wikipedia.org/wiki/Micro_black_hole)

Quote:
The net result is the black hole loses mass (due to conservation of energy). According to the formulae of black hole thermodynamics, the more the black hole loses mass the hotter it becomes, and the faster it evaporates, until it approaches the Planck mass. At this stage a black hole would have a Hawking temperature of TP / 8π (5.6×1032 K), which means an emitted Hawking particle would have an energy comparable to the mass of the black hole. Thus a thermodynamic description breaks down. Such a mini-black hole would also have an entropy of only 4π nats, approximately the minimum possible value. At this point then, the object can no longer be described as a classical black hole, and Hawking's calculations also break down.

What you got and described is the part in RED what you left out was the warning part in BLUE the calculations break down.

It is not anywhere near a fact that a micro black hole would have an incredibly short lifetime it is an extrapolation that leads to an expectancy that it is probably so. I can't even imagine what confidence level a scientist would put on that.

When I drop a ball the laws of gravity extrapolate the ball falls smoothly until it reaches the center of the earth ... see the problem? You need to understand what bounds exist for your extrapolation and they are only valid within those bounds.

That is why Einstein wondered if micro black holes were actually stable and were what an electron is and why you don't have different size electrons. Any bigger size would evaporate very quickly back to the standard electron size, his work is actually rather interesting.

So there are many possibilities open for micro black holes because our understanding is incomplete and if you like that they would last a very short time that is fine but it is not the only answer possible and can not be treated as a fact. I don't have an answer or even a preference on the answer.

You only have to look at Superconductivity to see the dangers in making the sort of leaps on extrapolation of the sort you have done.
Posted By: paul Re: Time at event horizons. - 08/15/14 04:49 PM
Quote:
And that was the bit I was trying to get Bill S to realize that you therefore end up with a time gradient on you


I believe that pointing to a gradient of gravity and now
time will only tend to exacerbate the degree of mental comprehension.

Bill S has asked a valid question in my opinion and does not need to have invalid responses directed at him as a reply to his question.

ie...

Quote:
Does that mean they would experience the same gravitational “attraction” in both places?


the offered answer ..

Quote:
No, it means that the gravitational gradient is the same in both cases, because the radius of the supermassive black hole is about 10^6 km or more, compared to about 6x10^3 km for Earth.


"No" is correct

however to explain the why in such a manner is incorrect.
it would be extremely and most highly inaccurate to claim
that the gravitational gradient might possibly be the same
in both cases and base that claim only on the radius of each
case in question.

Bill S like myself seems to be more of a observer who is trying to understand why people think the way they think
about physics even if he does not support the way and ways
that the people think about physics.

the diameter of the mass at the center of a black hole may
be as large as the orbit of Uranus or larger or it may be really small.

but the gravity gradient produced by any black hole is
due to the amount of mass and the density of the mass
inside the black hole , therefore any equal distance from
any two black holes in the universe would not
be presented with the same gravity gradient or attraction from any direction.

likewise any two unequal distances from
any two black holes in the universe would not
be presented with the same gravity gradient or attraction from any direction.

the universe is not uniform when talking about gravity.
there are no two places in the universe where gravity is
exactly the same even if the two places are only a centimeter
apart.

we can add that there are no two galaxies that are exactly the
same anywhere in the universe.

to that we add that there is absolutely no "same" gravity gradient anywhere in the universe.

Posted By: Bill Re: Time at event horizons. - 08/15/14 08:49 PM
I think I left out something in my statement up above. That would be: "If micro black holes exist or can exist". The actual fact is that there is no clear consensus that they can exist. If we don't even know whether they exist we can't really be sure how they would work. That comes right down to the need for a theory of quantum gravity. As it is I think that the best guess is that they would have very short life times.

Bill Gill
Posted By: Orac Re: Time at event horizons. - 08/16/14 02:58 AM
And now we are in complete agreement Bill smile

We don't know there isn't a boundary condition that means that micro black holes can't exist.

So just like our ball that extrapolates to hit the center of the earth and runs into the ground the black hole mathematics may hit a condition that restricts there size to a range.

There is also a lesson in that for Bill S original question despite fanciful answers many scientists may like to spruik.
Posted By: Orac Re: Time at event horizons. - 08/20/14 12:26 PM
I thought one of you might have crossed the boundary and actually started to think but it appears not so lets see if we can prompt some thinking.

There is a really good article posted by Assaf Shomer in 2007 which was not a novel work but summed up the status of play with black holes and gravity and remains valid today.

http://arxiv.org/pdf/0709.3555v2.pdf

Really all you need to concern yourself with is the conclusions if you can't follow the technical detail.

Quote:
It seems that gravity is a low energy effective field theory description of something else that is not a quantum field theory


So if gravity is not a quantum field theory then the extrapolation of Quantum theory that predicts micro black holes is totally invalid (Some may want to ponder the implication for quantum gravity but that is another story).

So now you have a series of nasty choices in an attempt to answer the question Bill S posed.
Posted By: Bill Re: Time at event horizons. - 08/20/14 01:06 PM
Originally Posted By: Orac
if gravity is not a quantum field theory

And that bit right there opens a huge can of worms. If gravity is not a quantum field theory then we have the huge problem that the universe seems to be divided into 2 mutually incompatible domains, which nevertheless have to work together. Building that bridge is going to be a huge problem.

And I'm not going to bet either way on the matter, although I have a tendency to think that a quantum view of gravity will be developed.

Bill Gill
Posted By: Orac Re: Time at event horizons. - 08/21/14 10:45 AM
Not incompatible but different remember gravity is still showing as an effective field theory just not a quantum one but a very low energy one acting on a very different definition of time.

That insight itself is somewhat interesting.

Now go back to the black hole and think what it would mean smile

Now you possibly understand why quantum gravity is becoming a little like string theory.
Posted By: Bill S. Re: Time at event horizons. - 08/28/14 09:23 PM
This should raise a few objections.

https://www.youtube.com/watch?feature=player_embedded&v=umfjGNlxWcw
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