Merged Relativity+ / Farsight

[Toontown]

Yep. I can explain things in terms that you can understand, and which make sense. A guy like ctamblyn will poo-poo what I say, but he can't offer an alternative explanation that you can understand, and which make sense. You should demand it from guys like him.

I understand space with an edge in the same way I understand the Toon universe. I know what will happen if I pull a gun on Bugs Bunny. He'll pull a howitzer on me. Probably a big pink one.

I didn't have any problem understanding ctamblin's caveat. ctamblyn took issue with my claim that a flat or nearly flat universe is necessarily many times larger than the part we can see, probably a level 1 megaverse. But I don't think there is any way to get a midget finite toroid out of the laws and data we have to work with, and ctamblyn agreed.

What you really mean if that you don't buy the toroidal universe, and you don't buy the infinite universe either. So voila, you find yourself in the same boat as me.

What I mean is, I buy the 3 widely accepted possible curvatures: Positive/finite, flat/infinite, and hyperbolic/infinite. Like I said before.

What I really, really mean is, the curvature of a positively curved megaverse might be too small to measure by available methods, and that is your only finite way out.

I do insist that anything from perfectly flat to hyperbolic is infinite.

I do insist that perfect euclidian flatness is the razor edge between positive and hyperbolic, thus seems very unlikely probabilistically.

So what I really, really, really mean is, I really, really, really believe the current observations have the universe somewhere very near the boundary between finite and infinite, and is in either case a megaverse.

 

[ctamblyn]

I understand space with an edge in the same way I understand the Toon universe. I know what will happen if I pull a gun on Bugs Bunny. He'll pull a howitzer on me. Probably a big pink one.

I didn't have any problem understanding ctamblin's caveat. ctamblyn took issue with my claim that a flat or nearly flat universe is necessarily many times larger than the part we can see, probably a level 1 megaverse. But I don't think there is any way to get a midget finite toroid out of the laws and data we have to work with, and ctamblyn agreed.



What I mean is, I buy the 3 widely accepted possible curvatures: Positive/finite, flat/infinite, and hyperbolic/infinite. Like I said before.

What I really, really mean is, the curvature of a positively curved megaverse might be too small to measure by available methods, and that is your only finite way out.

I do insist that anything from perfectly flat to hyperbolic is infinite.

I do insist that perfect euclidian flatness is the razor edge between positive and hyperbolic, thus seems very unlikely probabilistically.

So what I really, really, really mean is, I really, really, really believe the current observations have the universe somewhere very near the boundary between finite and infinite, and is in either case a megaverse.

I'm glad if my descriptions made some sense, as it's not an easy subject at all. I have to wonder though, is there a specific name for the fallacy "if you can't get me (or a proxy) to understand X, it follows that X must be false"? My Latin is weak.

Anyway, I agree with your stance - there's no reason to complicate things if the evidence doesn't demand it. Occam's razor and all that.

Perhaps some law yet to be discovered forces exact flatness on the large scale, but until such a thing is uncovered I'd also agree with the view that perfect flatness is highly improbable (although inflation makes near flatness inevitable). But that is just my opinion.

 

[steenkh]

1. Expansion

Do you have any evidence that has not already been shredded?

 

[Farsight]

Do you have any evidence that has not already been shredded?

Yeah:

1. Expansion

 

[Farsight]

I think mass defects are observed in systems of particles and the fields by which they interact. I'm not aware of evidence that the rest mass of bound particles varies in the way you seem to be implying...

They do edd. See mass in general relativity. And think it through. When I drop a 1kg body into a black hole, the black hole mass increases by 1kg only. At all times the "relativistic mass" of the falling body is 1kg. If you were to intercept the body on the way in and dissipate its kinetic energy as radiation, then: If a body gives off the energy L in the form of radiation, its mass diminishes by L/c². Its mass is reduced. You would still measure the body to be 1kg, but you're using a different energy scale.

...and yet again I worry about the blasé discarding of the equivalence principle when you suggest that sort of thing happens in a gravitational field.

I don't discard it so much as recognise its limitations. It only applies to an infinitesimal region. It doesn't actually apply to the room you're in. If there was no variation in the coordinate speed of light in that room, light wouldn't curve and bricks wouldn't fall down.

Thanks, I understand what you intended better now and appreciate the explanation. I hope you understand that I personally obviously think conservation of energy holds in all non-cosmological situations.

Good stuff. I'm pleased to hear it. Perhaps we can talk about cosmological conservation of energy sometime. There's potentially a surprise there in terms of fundamental physics. Another day perhaps.

In others where GR I think the equations are clear and how one chooses to verbally describe those equations and their implications can be worded differently by different people, and as long as they imply the same observed result I tend not to worry too much. This applies to some other bits of cosmology too as it happens.

Fair enough. I have to say though that interpretation seems to be a big problem in contemporary physics. Even with something as simple as E=mc².

 

[Farsight]

I understand space with an edge in the same way I understand the Toon universe. I know what will happen if I pull a gun on Bugs Bunny. He'll pull a howitzer on me. Probably a big pink one.

Uh huh.

I didn't have any problem understanding ctamblin's caveat. ctamblyn took issue with my claim that a flat or nearly flat universe is necessarily many times larger than the part we can see, probably a level 1 megaverse. But I don't think there is any way to get a midget finite toroid out of the laws and data we have to work with, and ctamblyn agreed.

Fair enough.

What I mean is, I buy the 3 widely accepted possible curvatures: Positive/finite, flat/infinite, and hyperbolic/infinite. Like I said before.

Two out of three are wrong.

What I really, really mean is, the curvature of a positively curved megaverse might be too small to measure by available methods, and that is your only finite way out.

I do insist that anything from perfectly flat to hyperbolic is infinite.

I do insist that perfect euclidian flatness is the razor edge between positive and hyperbolic, thus seems very unlikely probabilistically.

So what I really, really, really mean is, I really, really, really believe the current observations have the universe somewhere very near the boundary between finite and infinite, and is in either case a megaverse.

OK noted. We've been round the houses with this enough times now. I can tell you about the distinction between space and spacetime, and about pressure and expansion due to the absence of counterbalancing pressure, but it isn't going to change anything. So let's leave it at that.

 

[Farsight]

But that's just in your view of the world. In physics, electric charge is described by a scalar number, and negative charges do indeed exist.

It isn't my world view, it's essentially topological quantum field theory or if you prefer Baldomir & Hammond's Geometry of Electromagnetic Systems .

Just to recap, for my benefit as much as anyone else's, we're talking about the possibility of negative curvature of spatial slices through spacetime.

Then you're talking about electromagnetism.

Such a thing is possible, according to GR, on cosmological scales, though the evidence suggests that the large-scale curvature is very small (or zero) in our observable universe.

I say it's zero.

That aside, negative curvature in spatial slices on a local scale is actually commonplace.

You betcha.

In the humble Schwarzschild metric, a constant-Schw.-time slice is a 3D version of a Flamm paraboloid, which has everywhere negative intrinsic curvature (which drops off as the cube of the Schw. radial coordinate).

You can plot the Flamm paraboloid using light clocks in an equatorial plane. The curvature isn't actually curved space, it's a curvature in your measurements. Your metric.

 

[Farsight]

I have to go I'm afraid. But briefly:

That's all lovely (though the last two statements contradict each other), but there isn't a shred of evidence for any of it. Why do you accept and actively promote it, even given the lack of either theoretical or experimental justification, while rejecting infinite models which are perfectly consistent with the evidence according to GR? There is a degree of hypocrisy in your position.

I don't actively promote it, Toontown keeps asking me about it. And there is theoretical justification: expansion. As for hypocrisy, there's not a shred of evidence for an infinite universe, is there? And the infinite universe isn't consistent with the standard model of cosmology, is it?

 

[Reality Check]

1. Expansion

1. No because infinite universes expand too.

 

[Reality Check]

It isn't my world view, it's essentially topological quantum field theory

Your ignorance and inability to read is showing, Farsight .
For a start, Baldomir & Hammond's Geometry of Electromagnetic Systems

Its chief purpose is to clarify the structure of electromagnetism. It begins with the Faraday-Maxwell insight that in electromagnetism one is faced with an interconnected dynamical system in which space and time are closely linked with physical phenomena. An appropriate basis is given via differential geometry to describe local relationships, via and topology to describe the system. These tools are introduced in the context of Maxwell's equations in the familiar vector notation. Equations are greatly simplified by the geometrical approach, and the geometrical idea of symmetry unifies the various conservation laws. This book clarifies the relationship between fields, potentials, and sources. Links between macroscopic and quantum phenomena are explored from a geometric angle and there is a simple discussion of superconductivity.

This looks like standard EM theory - no mention of your parroting of "the electrons are a photon in a torus" fantasy.

Topological quantum field theory

A topological quantum field theory (or topological field theory or TQFT) is a quantum field theory which computes topological invariants.

is nothing to do with the "electrons are a photon in a torus" fantasy which is not a QFT !

Then you're talking about electromagnetism.

Really ignorant, Farsight.

Originally Posted by ctamblyn
Just to recap, for my benefit as much as anyone else's, we're talking about the possibility of negative curvature of spatial slices through spacetime.

ctamblyn is talking about the geometry of space-time in GR where negative curvature is allowed. This is nothing to do with electromagnetism.

You can plot the Flamm paraboloid using light clocks in an equatorial plane. The curvature isn't actually curved space, it's a curvature in your measurements. Your metric.

That is almost gibberish but sort of right, Farsight.
Flamm's paraboloid can be used as a tool to visualize the spatial part of the Schwarzschild metric. The curvature is actually curved space (there is no time coordinate!), it is actually curvature in measurements in those coordinates.

 

[Reality Check]

But briefly:

I don't actively promote it, Toontown keeps asking me about it. And there is theoretical justification: expansion. As for hypocrisy, there's not a shred of evidence for an infinite universe, is there? And the infinite universe isn't consistent with the standard model of cosmology, is it?

But briefly: Farsight remains in denial of basic cosmology.

• Finite and infinite universes expand, contract and remain static in standard cosmology.
• There is not a shred of evidence for a finite universe.
• There is not a shred of evidence for an infinite universe.
• There is evidence that the universe is bigger than the observable universe.
• An infinite universe is the basis of standard cosmology.
  Standard cosmology puts no constraints on space-time coordinates.
  Standard cosmology allows space-time coordinates to keep on increasing without bounds.
  Thus an infinite universe is consistent with the standard model of cosmology, isn't it Farsight ?

Is the Universe really infinite or just really big?

 

[Reality Check]

Outstanding questions for Farsight

Outstanding questions for Farsight

1. Do you now understand the meaning of Space-time interval and its values (positive, zero and negative)?
   First asked 26 July 2013 - 3 days and counting.
2. Farsight: Do you now understand the meaning of infinity?
   First asked 26 July 2013 - 3 days and counting.
3. Farsight: Source for "a homogeneous universe is a flat universe"
   First asked 26 July 2013 - 3 days and counting.
4. Farsight: Can you list the evidence for a finite universe And that size)?
   First asked 26 July 2013 - 3 days and counting.
5. Farsight: Support your assertion that GR conserves energy
   First asked 26 July 2013 - 3 days and counting.
6. Farsight Show mathematically that an infinite universe in GR cannot expand.
   First asked 26 July 2013 - 3 days and counting.

 

[Farsight]

Do you now understand the meaning of Space-time interval and its values (positive, zero and negative)?

Yes. Of course I do. I've understood it for decades. It's kid's stuff, based on Pythagorias's theorem, see wiki.. Also see Einstein's Simple Derivation of the Lorentz Transformation which I've referred to on many occasions before.

Farsight: Do you now understand the meaning of infinity?

Yes. Of course I do. Don't insult my intelligence, you aren't up to it. See wikipedia.

Farsight: Source for "a homogeneous universe is a flat universe"

I've told you already. It's Einstein's Leyden Address where he referred to a gravitational field as inhomogeneous space. So homogeneous space, as presumed by the FLRW metric, is where there's no gravitational field and expansion apart, no spacetime curvature. The universe did not collapse when it was small and dense.

Farsight: Can you list the evidence for a finite universe?

How many times have I got to give it? Here it is again:

1. Expansion

And it's size?

No. I don't know how big the universe is. But I can say it can't be infinite, because if it was it couldn't expand.

Farsight: Support your assertion that GR conserves energy

I've already done it. When you throw a 1kg mass into a black hole, its mass increases by 1kg. There are no waterwheel perpetual motion machines. There are no over-unity devices. If you know of anything that doesn't conserve energy, book your ticket to Stockholm.

Farsight Show mathematically that an infinite universe in GR cannot expand.

No. I've explained it enough times already. GR features the stress-energy-momentum tensor. It has a pressure diagonal. Phil Plait likened dark energy to pressure. If the pressure is counterbalanced at all locations, expansion cannot occur.

All: Reality Check will now say I haven't answered his questions at all, and will keep on repeating them. Ad infinitum.

Tedious.

 

[sol invictus]

All: Reality Check will now say I haven't answered his questions at all, and will keep on repeating them. Ad infinitum.

Tedious.

It's not so much that you haven't provided responses, it's that your responses are nonsense.

 

[Farsight]

Tell you what sol, I'll talk physics, you just peddle abuse because you have no adequate response.

Then you can peddle your woo too. Like your FTL rotating universe and your sky-falling-in gravity and your multiverse. And I'll come along and give the evidence and logic and references that rips it to shreds. Then you can bleat "nonsense" and not much else, and we'll all have a laugh at your expense.

 

[Hercules Rockefeller]

Tell you what sol, I'll talk physics, you just peddle abuse because you have no adequate response.

Then you can peddle your woo too. Like your FTL rotating universe and your sky-falling-in gravity and your multiverse. And I'll come along and give the evidence and logic and references that rips it to shreds. Then you can bleat "nonsense" and not much else, and we'll all have a laugh at your expense.

Who's "we"?

 

[DeiRenDopa]

Tell you what sol, I'll talk physics, you just peddle abuse because you have no adequate response.

Then you can peddle your woo too. Like your FTL rotating universe and your sky-falling-in gravity and your multiverse. And I'll come along and give the evidence and logic and references that rips it to shreds. Then you can bleat "nonsense" and not much else, and we'll all have a laugh at your expense.

Here's something mighty strange I've noticed, Farsight: as far as I can tell, these sorts of opinions are held by just one person (you).

Why is that?

Is it because, alone among all people living today¹, you are the only one who "talks physics"? The only one who thinks that what you post is "the evidence and logic and references that rips" what everyone else² posts "to shreds"?

Or perhaps because, despite your millions (?) of words, in thousands of posts, over many years (and in many forums), you have failed so incredibly spectacularly, to communicate The Truth?

Or, ...

¹ Well, that subset which consists of JREF members who have posted to threads in which you have posted what sol calls nonsense.
² sol is not unique (at least in this regard )

 

[ctamblyn]

It isn't my world view, it's essentially topological quantum field theory or if you prefer Baldomir & Hammond's Geometry of Electromagnetic Systems .

Show that TQFT is relevant to this discussion about electric charge. Show that the book you just mentioned supports your view (hint: it doesn't).

(Regarding the context - the existence of negative curvature in spatial slices through spacetime...)

Then you're talking about electromagnetism.

Nope, gravitation.

(Regarding the large-scale curvature of the observable universe...)

I say it's zero.

Possibly, but it would be very remarkable if it were exactly zero. It isn't relevant to my next point, so I'll put that aside for now.

(Regarding my pointing out that spatial slices through the Schwarzschild solution have negative curvature...)

You can plot the Flamm paraboloid using light clocks in an equatorial plane. The curvature isn't actually curved space, it's a curvature in your measurements. Your metric.

No, it's genuine honest-to-goodness spatial curvature. You can measure it without any clocks at all like so:

Create a very large circle out of string (or dental floss or whatever) centred around a star, being careful to ensure that it is stationary with respect to the star, and measure the circumference C_inner of the circle. Now, create a second circle by moving each point of the first circle radially outwards by a short distance a (small in comparison with C_inner), measured locally using standard metre sticks. This will require you to either stretch the string, if it allows, or splice in some extra. Now measure the circumference C_outer of the new circle.

If there were no spatial curvature, the circumference of the second circle could only be

C_outer = C_inner + 2πa .
​

This formula must hold if the spatial geometry is Euclidean - most teenagers could provide the proof. However, according to GR if you perform this experiment you will find that

C_outer = C_inner + 2πa√(1 - 4πM/C_inner) < C_inner + 2πa ,
​

where M is the mass of the gravitating body in units where G = c = 1. Thus, the space is not Euclidean.

 

[Farsight]

Here's something mighty strange I've noticed, Farsight: as far as I can tell, these sorts of opinions are held by just one person (you). Why is that?

I'm afraid it isn't true, DeiRenDopa.

Is it because, alone among all people living today¹, you are the only one who "talks physics"? The only one who thinks that what you post is "the evidence and logic and references that rips" what everyone else² posts "to shreds"?

Nope. It's because JREF is riddled by naysayers who don't talk physics or whose physics knowledge is scant. As you can see, I wipe the floor with them.

Or perhaps because, despite your millions (?) of words, in thousands of posts, over many years (and in many forums), you have failed so incredibly spectacularly, to communicate The Truth?

Nope.

Or, ...

¹ Well, that subset which consists of JREF members who have posted to threads in which you have posted what sol calls nonsense.
² sol is not unique (at least in this regard )

Yep. Sol is not unique. He can't handle the physics, he can't stand up to my knowledge and expertise. So he bleats "nonsense". As if that convinces anybody.

Why Dopa, he's just about as convincing as you. Now spare me the attempted ad-hominems. Talk physics, or sling your hook. Capiche?

 

[ctamblyn]

I have to go I'm afraid. But briefly:

I don't actively promote it, Toontown keeps asking me about it.

You do actively promote it, in the sense that you are more then merely mentioning as a possibility, you are claiming that it is the The Truth.

And there is theoretical justification: expansion.

No, yet again, because expansion occurs in the infinite FLRW models too, and those have the great benefit of actually being solutions of the GR field equations, unlike your fantastical finite flat universe.

As for hypocrisy, there's not a shred of evidence for an infinite universe, is there?

The evidence is currently inadequate to answer that question definitively. However, you are attempting to shift the burden of proof. You claim the universe must be finite because (a) GR and (b) it is expanding, and you cannot support that claim (because it is utterly wrong).

And the infinite universe isn't consistent with the standard model of cosmology, is it?

Yep.