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#54197 - 07/19/15 09:06 PM Re: Open challenge [Re: Orac]
Bill S. Offline
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Looking back through my notes from a few years ago I found:

“When scientists, such as David Bohm, and authors, such as Michael Taylor describe the Universe as a hologram I very much doubt that they are suggesting that some other-worldly being is projecting laser images with an incredibly gigantic projector to produce what we experience as the Universe. I suspect that it would be more appropriate to say that the three-dimensional images we can produce with laser technology are as near as we can come to producing an effect that, to some extent, mimics the way in which our Universe works.”

I found quite a bit of Taylor’s book interesting, but from what I remember of it, I would have thought it would have been too much like “quantum flapdoodle” for your liking. smile

Still trying to find time for the other links, but will get there.
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#54198 - 07/20/15 01:13 AM Re: Open challenge [Re: Bill S.]
Orac Offline
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Ah yes now you mention it, I remember David Bohm and yes a different type of holographic universe. I think that also underlines the general idea has been around in many forms for a very long time. I sort of suspect the concept goes back even further than 1947 probably into the 1920's.

For example Kaluza–Klein theory published in 1921 was a classic theory with 5 dimensions and later adapted into string theory
https://en.wikipedia.org/wiki/Kaluza-Klein_theory

I always viewed it as a hidden dimension theory but using your definition above I think I could argue it qualifies as a holographic theory.


Edited by Orac (07/20/15 01:54 AM)
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#54199 - 07/21/15 01:48 PM Re: Open challenge [Re: Orac]
Bill S. Offline
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https://medium.com/starts-with-a-bang/embracing-your-fifth-dimension-2e02d9a0572c

“These dualities are said to be “holographic” because they tell us that everything allowed to happen in the bulk space-time of the gravitational theory is encoded on the boundary of that space.”

I find this boundary concept puzzling. Are they saying that our Universe is part of “the bulk”, bounded by 2-brains that form a 2-D box?

Alternatively, could it be that our Universe is considered as having a boundary, beyond which there is nothing?
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#54200 - 07/21/15 03:34 PM Re: Open challenge [Re: Bill S.]
Orac Offline
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It's branes not brains BTW smile

As I said the whole article reads as like mumbo jumbo to me, a bit like when science magazines try to describe quantum entanglement.

I simply don't get anything that means holographic out of "everything allowed to happen in the bulk space-time of the gravitational theory is encoded on the boundary of that space."

I am not a wordsmith but if I had to try I would go something like this

"The universe in classic physics is described by 3 dimensions and time. Brane models in string theory can use the hidden dimensions of space to project a 3D world onto a normal 2D plane in the same way as computer games do it. Electromagnetic, Strong and weak nuclear forces play out only on the 2D plane while time and gravity play out in all the dimensions but project onto the 2D plane. The 3rd dimension is an illusion and hence this is called a holographic theory".

Hard to work out what boundary is being discussed in that mumbo jumbo. If I had to guess, I think the Brane/other dimensions boundary.

All theories that comply with QM/QFT make a definition of fields that propagate a translationally invariant spacetime. So there are a number of possible boundaries in that definition not just one smile

Now you have progressed I will give you a more interesting boundary to ponder smile

Emmy Noether demonstrated that conservation laws are linked to symmetries, specifically the validity of the energy conservation law is equivalent to the time-translational symmetry of the laws of physics. So outside our universe must be somewhere time-translational symmetry doesn't hold laugh


Edited by Orac (07/21/15 03:53 PM)
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#54201 - 07/21/15 05:12 PM Re: Open challenge [Re: Orac]
Bill S. Offline
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Originally Posted By: Orac
It's branes not brains BTW smile


An outstanding example of a Freudian slip!

Quote:
So outside our universe must be somewhere time-translational symmetry doesn't hold.


Of course it is! If there is anything outside our Universe it is the cosmos which is infinite. No time, no change, and it's not really outside, because our Universe is "part" if it, and every part is the whole...."and I am that" laugh

Where's Rev when you need him?
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#54203 - 07/22/15 03:30 AM Re: Open challenge [Re: Bill S.]
Orac Offline
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Originally Posted By: Bill S.
Of course it is! If there is anything outside our Universe it is the cosmos which is infinite. No time, no change, and it's not really outside, because our Universe is "part" if it, and every part is the whole...."and I am that" laugh

Where's Rev when you need him?

Haha you got the joke ... you have come a long way smile
Didn't some scientist once give you that answer?

If we were religious we just proved we are in hell and that outside our universe is heaven.
Outside here they get everything, land of milk and honey and all that and I did say I was the devil laugh
See you always suspected it was bad here and now you know why smile

I am guessing you are ready to put it all together and Lubos did it really well in an article 5 years ago, you should be able to follow it now.

http://motls.blogspot.com.au/2010/08/why-and-how-energy-is-not-conserved-in.html

You will meet all the key points again from GR
- Why and how the Energy-Stress-Tensor is zero AKA Vanishing Energy
- Reparameterizing
- Energy conservation

Finally you should see the whole lot collapses like a deck of cards the moment you introduce an actual infinity.

Hence you now know anyone who makes a statement about GR and includes an infinity hasn't got a clue. Some who do it will surprise you smile

Anyone who tries to use consensus or claim authority, be comfortable that the janitors of science don't care laugh


Edited by Orac (07/22/15 06:26 AM)
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#54204 - 07/22/15 04:00 AM Re: Open challenge [Re: Orac]
Orac Offline
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I put this in a seperate post as it's up to you if you want to look at it.

You may be ready to follow the next extension now as well, if you write all the above out you get this.
https://en.wikipedia.org/wiki/Vacuum_solution_(general_relativity)
See if you can follow it

It answers a couple of problems with gravity you introduced
- Why determining the precise location of this gravitational field energy is technically problematical in general relativity
- Gravitational field energy itself produces more gravity.

The last one at the very least should raise your eyebrows about perpetual motion and why doesn't it go into self induced runaway.

Remember in your first answers I was quizzing you about this and how your theory stopped it smile

BTW if you want a good laugh
http://phys.org/news/2015-07-line-quantum-classical-world.html
You should easily spot the problem, at 80 I think it might be time for the professor to retire smile


Edited by Orac (07/22/15 07:00 AM)
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#54205 - 07/24/15 09:34 PM Re: Open challenge [Re: Orac]
Bill S. Offline
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I have tried thinking as I did about infinity a few years ago, taking one step at a time and seeing how far I can go. This time I worked backwards, trying to understand the origin of a black hole’s gravity. Where does it start?

In the case of a black hole that originates as a collapsing star, the star’s gravity is already there, and measurable, before the collapse. The gravitational field of the black hole can be calculated in terms of the gravitation of the original star.

Black holes are generally presented, at least to lay audiences, as things of enormous gravitational attraction. I think the next step in my line of thought would have to be to ask if the gravity at the event horizon is any stronger than the gravity would have been at the surface of the original star. If it is not, then there is no “escaping” gravity to consider; no one/nothing outside the event horizon experiences gravity beyond that of the original star.
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#54207 - 07/25/15 01:51 AM Re: Open challenge [Re: Bill S.]
Orac Offline
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Originally Posted By: Bill S.
Black holes are generally presented, at least to lay audiences, as things of enormous gravitational attraction. I think the next step in my line of thought would have to be to ask if the gravity at the event horizon is any stronger than the gravity would have been at the surface of the original star. If it is not, then there is no “escaping” gravity to consider; no one/nothing outside the event horizon experiences gravity beyond that of the original star.

It's more complex and interesting than that consider the first part of this
https://en.wikipedia.org/wiki/Supermassive_black_hole

You didn't touch the gravity creates more gravity why doesn't it go into runaway collapse on itself? smile


Edited by Orac (07/25/15 01:51 AM)
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#54208 - 07/25/15 10:16 PM Re: Open challenge [Re: Orac]
Bill S. Offline
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I appreciate that supermassive black holes present their own problems, that's why I said: "In the case of a black hole that originates as a collapsing star..."

My question still stands: Is the gravity at the event horizon any stronger than the gravity would have been at the surface of the original star?
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#54209 - 07/25/15 10:40 PM Re: Open challenge [Re: Bill S.]
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Yes the gravity at the horizon would be greater than it would be at the surface of the original star. That is based on the fact that the horizon is the surface at which the escape velocity would be greater than the speed of light. Obviously the escape velocity at the surface of the star would be less than the speed of light, so the gravity would have to be smaller. However, the gravity at the same distance from the center of the black hole as the surface of the star would be from the center of the star would be the same as it would be the same distance from the center of mass. I'm not sure if this would be affected by GR variations. My first thought is that it wouldn't, because the total mass would not change much. If anything the total mass of the black hole would probably be less than the mass of the star because a lot of the star would be ejected during the collapse.

Bill Gill
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#54210 - 07/26/15 04:11 AM Re: Open challenge [Re: Bill S.]
Orac Offline
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Originally Posted By: Bill S.
My question still stands: Is the gravity at the event horizon any stronger than the gravity would have been at the surface of the original star?

Yes/No/Unchanged depends on who and what you believe smile

So look at your options

GR & Bill G it seems: Within the event horizon matter has to move outward faster than the speed of light in order to remain stable and avoid collapsing to the centre. However there is an issue with this that a black hole must then inevitably collapse to a singularity and you saw the problem with infinities above, GR itself collapses under that. Different scientist will resolve that problem different ways the common ones

1.) Ignore it and wave hands that will understand it better one day
2.) Treat things inside the Schwarzschild radius in a special way and make there own pet theory up.
3.) Admit it's a problem and currently no solution

There are hints as to how to resolve this but you seem reluctant to look at it .. if you want to try read next bit smile

Your problem in a nutshell

The fact gravity creates more gravity (I think you got that bit yourself and agreed) means it has to be opposed by something or the moment you created one bit of gravity that point would self collapse to a black hole at that point in a self sustained collapse. In classic physics that is an unavoidable consequence of the mathematics that goes like this

X + a percentage X = Y (Y = 1+X%)
Y + a percentage Y = Z (Z = 1+Y%)
.... etc etc
INFINITY

Your problem above is you want to talk about something without considering what is opposing it laugh

Under your current thoughts any point that creates gravity must instantly collapse to a gravitational singularity don't you think it might be important to fix this up first before dealing with the black hole event horizon smile

So how do you want to deal with this?


Edited by Orac (07/26/15 04:19 AM)
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#54212 - 07/26/15 05:52 PM Re: Open challenge [Re: Orac]
Bill S. Offline
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Originally Posted By: Orac
There are hints as to how to resolve this but you seem reluctant to look at it .. if you want to try read next bit

Your problem in a nutshell

The fact gravity creates more gravity (I think you got that bit yourself and agreed) means it has to be opposed by something or the moment you created one bit of gravity that point would self collapse to a black hole at that point in a self sustained collapse. In classic physics that is an unavoidable consequence of the mathematics that goes like this


My only reluctance is that I like to think I understand a point, as well as possible, before moving on to the next. So I need to be able to answer questions like: Can we measure gravity at an event horizon of a stellar BH? If so, how would that compare with gravity at the surface of the original star?

As far as the idea of gravity creating gravity goes, I had reached the point of thinking “does gravity create more gravity? That raised a few questions, like:

Wouldn’t it have to have mass/energy to create more gravity?

If it’s not a force, can it have energy?

Manifestly, gravity is not a run-away phenomenon. Is that because something counters it, or because gravity does not spontaneously create gravity. Which is it?

What physical/experimental evidence do we have for saying that gravity creates gravity?
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#54213 - 07/26/15 10:43 PM Re: Open challenge [Re: Orac]
Bill S. Offline
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Quote:
Yes the gravity at the horizon would be greater than it would be at the surface of the original star. That is based on the fact that the horizon is the surface at which the escape velocity would be greater than the speed of light. Obviously the escape velocity at the surface of the star would be less than the speed of light, so the gravity would have to be smaller. However, the gravity at the same distance from the center of the black hole as the surface of the star would be from the center of the star would be the same as it would be the same distance from the center of mass. I'm not sure if this would be affected by GR variations. My first thought is that it wouldn't, because the total mass would not change much. If anything the total mass of the black hole would probably be less than the mass of the star because a lot of the star would be ejected during the collapse.


Thanks Bill, I think all that makes sense.
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#54214 - 07/27/15 02:04 AM Re: Open challenge [Re: Bill S.]
Orac Offline
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Originally Posted By: Bill S.
My only reluctance is that I like to think I understand a point, as well as possible, before moving on to the next. So I need to be able to answer questions like: Can we measure gravity at an event horizon of a stellar BH? If so, how would that compare with gravity at the surface of the original star?

The problem is you have only half the GR theory worked so far.
Your half creates a blackhole immediately any gravity forms, so I can't answer what will happen.

You have a curvature in spacetime in the presence of energy/matter but something has to invert time back to what it was originally. You can make it whatever you like space is elastic, there is a back pressure, the green alien inverts it back but something has to as you have spacetime as passive currently ... see the issue smile

The problem is obvious if time wasn't restored back there would be this big time curvature tracks carved across space where planets/suns moved thru. It would be like a boat moving thru water and the water not levelling the wake left behind it.

I guess you could go for there is no time in space and things with gravity tow time around with them?
So time would be like electric charge under that scheme I guess intrinsic to matter/energy and space is passive.

Both space and time being passive gives huge issues I need a solution from you smile

Originally Posted By: Bill S.
As far as the idea of gravity creating gravity goes, I had reached the point of thinking “does gravity create more gravity? That raised a few questions, like:

Wouldn’t it have to have mass/energy to create more gravity

Energy and it does remember its covered here
https://en.wikipedia.org/wiki/Vacuum_solution_%28general_relativity%29

Originally Posted By: Vacuum GR solution
But the gravitational field can do work, so we must expect the gravitational field itself to possess energy, and it does.


Originally Posted By: Bill S.
If it’s not a force, can it have energy?

Well radiation has energy is it a force?

See this is where it gets tricky for me I need you to define force are talking classic physics/QM/your own?

Originally Posted By: Bill S.
Manifestly, gravity is not a run-away phenomenon. Is that because something counters it, or because gravity does not spontaneously create gravity. Which is it?

How can you get a black hole if it doesn't go into runaway, that is like having an atomic bomb without critical mass ... think about it laugh

History lesson
http://www.physicsoftheuniverse.com/scientists_schwarzschild.html
Quote:
Schwarzschild’s solution identified a radius for any given mass, known as the Schwarzschild radius, where, if that mass could be compressed to fit within that radius, no known force or degeneracy pressure could stop it from continuing to collapse into a gravitational singularity or black hole.

You don't have any back pressure so any gravity at all will collapse into a black hole as it has to overcome ZERO smile

As I said I am open for anything you believe lets just see where it goes smile

Originally Posted By: Bill S.
What physical/experimental evidence do we have for saying that gravity creates gravity?

Einstein and scientists did some tests on a 1919 solar eclipse for a reason to check the curvature of light from the sun smile

Here is the problem in it's conceptual form
https://en.wikipedia.org/wiki/Two-body_problem_in_general_relativity

So you end up with gravity as a radiation although it is still unclear to me if you want to treat it as a force or not.


Edited by Orac (07/27/15 07:36 AM)
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#54215 - 07/27/15 02:41 AM Re: Open challenge [Re: Orac]
Orac Offline
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I will put this as it's own comment because it is a statement from me not answering your questions Bill S.

The central premise of GR is that the curvature of space-time is directly determined by the distribution of matter and energy contained within it. What complicates things, however, is that the distribution of matter and energy is in turn governed by the curvature of space, leading to a feedback loop.

That is the nature of the feedback loop in GR, how you want to describe it I leave with you.

Again a statement what opposes gravity in GR is dark energy, it is well covered here in layman terms from the NASA site
http://science.nasa.gov/astrophysics/focus-areas/what-is-dark-energy/

They give you the way Einstein thought of it ("empty space" can possess its own energy), the QM answer (which is wrong) and some other alternates but at the end of the day you end up at this point

Quote:
something that fills all of space but something whose effect on the expansion of the Universe is the opposite of that of matter and normal energy

Whichever answer you take you end up with something creating a tendency to return spacetime to some equilibrium.

I consider Ethan Siegel did two terrible jobs on it but it might work for you and they end up with a negative pressure on any patch of spacetime
http://scienceblogs.com/startswithabang/...verse-combined/
http://scienceblogs.com/startswithabang/2011/12/02/dark-energy-accelerated-expans/

Sean Carroll does all that in a few tight sentences
http://preposterousuniverse.blogspot.com.au/2004/09/dark-energy-equation-of-state.html

If we have dark energy perhaps one might ask what happens to it in a black hole as it might be important smile

Some funny things to probe Bill G about his answer but as he isn't talking to me the point is moot laugh


Edited by Orac (07/27/15 08:34 AM)
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#54217 - 07/27/15 03:15 PM Re: Open challenge [Re: Orac]
Bill S. Offline
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OK. Let’s look at three things I think we have said about gravity.

1. Gravity has energy.
2. Gravity distorts spacetime.
3. Gravity creates more gravity.

In achieving 2 & 3, is the energy of gravity diminished, dissipated or exchanged in any way?
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#54219 - 07/27/15 04:55 PM Re: Open challenge [Re: Bill S.]
Orac Offline
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Originally Posted By: Bill S.
OK. Let’s look at three things I think we have said about gravity.

1. Gravity has energy.
2. Gravity distorts spacetime.
3. Gravity creates more gravity.

In achieving 2 & 3, is the energy of gravity diminished, dissipated or exchanged in any way?

Yes absolutely it is smile

Read the section labelled work done by gravity
https://en.wikipedia.org/wiki/Work_%28physics%29

That is the classic physics version or you can use the more technical GR version
https://en.wikipedia.org/wiki/Energy%E2%80%93momentum_relation

Your current answer means your theory is inconsistent with even classical physics smile

You theory describes a universe other than I know and is the same league as Marosz at the moment.


Edited by Orac (07/27/15 04:57 PM)
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#54220 - 07/27/15 05:04 PM Re: Open challenge [Re: Orac]
Orac Offline
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Perhaps I can ask are you trying to work this out and why googling it gives weird answers.

"What is the surface gravity of a black hole" smile

The wikipedia article is accurate but sort of funny
https://en.wikipedia.org/wiki/Surface_gravity

The Surface gravity of a black hole section leads to

surface gravity of a black hole ..... k = 1/4M

Therefore the bigger a black hole mass the smaller value of surface gravity ... no really laugh

Is that what this is all about as you don't really seem to be interested in understanding only the value?

It's very different to the answer Bill G gave but he isn't entirely "wrong" either laugh


Edited by Orac (07/27/15 05:17 PM)
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#54221 - 07/27/15 05:40 PM Re: Open challenge [Re: Orac]
Bill S. Offline
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Originally Posted By: Orac
Your current answer means your theory is inconsistent with even classical physics


We seem to be going round in unproductive circles. Could you identify the "answer" to which you refer?
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