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Author Topic:   Black Hole Universe Model Questions
Dr Adequate
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Posts: 16099
Joined: 07-20-2006


Message 9 of 69 (663170)
05-21-2012 11:56 PM
Reply to: Message 1 by Echetos
04-01-2012 4:37 PM


2. I think there's a correlation between the mass of a galaxy and the black hole at its center because it is the same mass.

But surely there are other things in a galaxy with mass, such as stars. Clearly they must make some contribution to the net mass of the galaxy.

1. I think the universe is expanding toward a singularity and this explains Hubble's law.

The universe is certainly expanding, and this does explain Hubble's law, but what you could mean by "expanding toward a singularity" I have no idea.


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Dr Adequate
Member
Posts: 16099
Joined: 07-20-2006


Message 14 of 69 (663468)
05-25-2012 12:02 AM
Reply to: Message 12 by 1.61803
05-24-2012 10:34 AM


Hi Son, I thought that regardless of the Mass of a black hole it was still being compressed into a singularity with a theoretical volume of zero.

So I guess if we were in a universe inside a black hole, our universe would have to end with some sort of a Big Crunch. But if it was a really big black hole of low density, that might take a very long time to actually happen.


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Dr Adequate
Member
Posts: 16099
Joined: 07-20-2006


Message 18 of 69 (667659)
07-10-2012 11:30 PM
Reply to: Message 17 by Echetos
07-10-2012 10:15 PM


Re: Bumpdate
What I mean by saying the universe is expanding toward a singularity is basically that the Big Bang and the so-called Big Crunch are the exact same thing. The image I used to describe this in the original blog post was an apple.

The skin of the apple represents spacetime. The core of the apple represents a singularity out of which the universe--you, me, all the stars and galaxies--emerged. One can imagine a galaxy, sometime after the Big Bang, moving out and away from this singularity according to Hubble's law, eventually crossing the "equator" of the apple/universe, and finally winding up right where it started.

In which case when it crossed the equator it would be contracting towards a singularity. You see why I was puzzled?


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Replies to this message:
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Dr Adequate
Member
Posts: 16099
Joined: 07-20-2006


Message 20 of 69 (667748)
07-11-2012 6:52 PM
Reply to: Message 19 by Echetos
07-11-2012 6:06 PM


Re: Bumpdate
It's puzzling because 4-dimensional objects are puzzling. But I must insist that this is an expansion, or at least looks like one. From the perspective of an observer anywhere on this apple/universe all the galaxies, everything, will appear to be moving away at an accelerated rate in all directions.

Not after the "equator" has been passed. Then it'll look like it's contracting. 'Cos it'll be contracting.


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Dr Adequate
Member
Posts: 16099
Joined: 07-20-2006


(1)
Message 25 of 69 (667989)
07-15-2012 12:45 AM
Reply to: Message 22 by Echetos
07-12-2012 5:56 PM


Re: Bumpdate
I think we might be veering off into a fruitless semantic argument.

If you're going to use the word "expanding" to mean "contracting", then I'm very much afraid that that's what we shall do.

You could avert this by using "expanding" to mean "expanding" and "contracting" to mean "contracting".


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Replies to this message:
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Dr Adequate
Member
Posts: 16099
Joined: 07-20-2006


Message 27 of 69 (668052)
07-16-2012 7:58 PM
Reply to: Message 26 by Echetos
07-16-2012 7:42 PM


Re: Bumpdate
* sighs *

In order for there to be a Big Crunch, in order for the universe to end up "finally winding up right where it started", it has to contract. Then we will not observe it expanding. We'll observe it contracting. The stars will appear blue-shifted to an observer. They will be getting closer together.

This is why we know that this isn't happening now.

So I must ask you again, because this is the question you’ll dodge to save face: Where would an observer need to be positioned for the universe to “look like it’s contracting”?

Anywhere inside it, during the phase in which it is in fact contracting.

Edited by Dr Adequate, : No reason given.


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Dr Adequate
Member
Posts: 16099
Joined: 07-20-2006


Message 30 of 69 (668062)
07-16-2012 10:11 PM
Reply to: Message 28 by Echetos
07-16-2012 8:43 PM


Re: Bumpdate
You can't be inside it.

I can, in fact, be in the universe. I am habitually in the universe. It's getting out of it that would be tricky.


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Dr Adequate
Member
Posts: 16099
Joined: 07-20-2006


Message 31 of 69 (668063)
07-16-2012 10:14 PM
Reply to: Message 29 by Echetos
07-16-2012 9:25 PM


Re: Bumpdate
A gravitational singularity, yes, at the center of earth. This is gravity 101.

Apply palm liberally to face.

In Einstein’s theory the main features of gravity around the Earth are exactly the same as they would be if our planet were hollow, with a faked-up papier-mâché surface of mountains and seas, but having a black hole at the centre with the same mass as Earth.

But the Earth is not made of papier-mâché. You see that word "if", just after the words "would be"?


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Dr Adequate
Member
Posts: 16099
Joined: 07-20-2006


Message 33 of 69 (668074)
07-16-2012 11:39 PM
Reply to: Message 32 by Echetos
07-16-2012 10:47 PM


Re: Bumpdate
All of spacetime is represented by the piece of paper. The piece of paper is the entire universe in this analogy. Not too difficult to comprehend...

If you're not on the paper you're not in the universe ...

And I am in the universe. In the analogy, I am embedded in the paper.

And someone who was in a contracting universe would observe it to be contracting.

EDIT: Are you really disputing the fact that there's a gravitational singularity at the center of earth?

Of course. Me and every physicist everywhere ever.


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Dr Adequate
Member
Posts: 16099
Joined: 07-20-2006


Message 35 of 69 (668078)
07-17-2012 1:56 AM
Reply to: Message 34 by Echetos
07-17-2012 12:20 AM


Re: Bumpdate
Ah, yes. Back to semantics.

No, that would be what we scientific types call a fact. The Earth is not made of papier-mache, and its mass is not concentrated in a black hole at its center. Semantics doesn't come into it.

How about a "center of gravity."

The earth does indeed have its center of gravity at its center of gravity. This is not a singularity. This is something different.

Regardless, I'm disappointed that a serious discussion about the possibility of our universe being a black hole has been derailed by this rather boring exchange.

Then could I recommend that you either make fewer posts, or get fewer things wrong?


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Dr Adequate
Member
Posts: 16099
Joined: 07-20-2006


Message 48 of 69 (668945)
07-25-2012 10:58 PM
Reply to: Message 45 by Echetos
07-25-2012 3:12 AM


Re: Bumpdate
Even if an observer was “embedded in the paper”—a scenario completely of your own invention ...

What?

If the paper is an analogy for spacetime, then we are all embedded in the paper.

—in this analogy there’s no conceivable way the universe would appear to be contracting. An observer buried or “embedded” anywhere in “the paper” of this analogy—the skin of the apple—would observe an expanding universe according to Hubble's Law.

If only saying things made them so, your argument would be a lot more convincing. Also it would be an argument.

If I’m wrong please paste a picture with a point on the apple where an observer sees a contracting universe…

If time progresses from the bottom to the top of the apple, then anywhere above the equator of the apple. You know, in the bit where the universe would be contracting.

Since the singularity—in this clearly inadequate 3-dimensional representation—is omnipresent (the core of the apple)

* sighs deeply *

If the skin of the apple represents the universe, then the Big Bang singularity is at the bottom of the apple, and the Big Crunch singularity is at the top of the apple. There is no singularity at the center of the apple, and the notion of a singularity being there is completely meaningless, since there is no "there" there.


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Replies to this message:
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Dr Adequate
Member
Posts: 16099
Joined: 07-20-2006


Message 51 of 69 (669090)
07-26-2012 8:41 PM
Reply to: Message 49 by Echetos
07-26-2012 3:56 PM


Re: Bumpdate
Time does not progress from the bottom to the top of the apple.

What do you think it's an analogue for?

According to the BHUM time is essentially unreal ...

But don't throw away your clocks just yet.

The point of the apple analogy was to show that the Big Bang and Big Crunch singularity are the same thing. The universe both originates from and collapses into the same point—the singularity at the center of the apple.

But that's meaningless. The center of the apple is not an analogue of anything.


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Dr Adequate
Member
Posts: 16099
Joined: 07-20-2006


Message 66 of 69 (669828)
08-03-2012 10:54 AM
Reply to: Message 64 by Alfred Maddenstein
08-03-2012 1:19 AM


Re: spacetime?
NoNukes, if you are tickled pink by these explanations, well, no problem for you then.
Alfred Maddenstein is not. That is all. Horses for courses and courses for horses.
Then the satisfaction goes like:
Light is a wave in vacuum. What is it exactly that is waving? Space-time which is a field metric.
Got it. Lovely and very instructive!!!!
The Universe is expanding. Where could it be possibly expanding into being everywhere already? Nowhere. It's JUST expanding. Everywhere itself is expanding.
Got it. Illuminating!!!!

Translated from woo-woo into English: Alfred Maddenstein still doesn't understand physics. Which proves that physics is still stupid.


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