Re: Discrete theories of space

[Bruno Marchal]

> On 23 Jan 2019, at 11:28, Philip Thrift  wrote:
> 
> 
> 
> On Wednesday, January 23, 2019 at 3:04:38 AM UTC-6, agrays...@gmail.com wrote:
> 
> 
> On Wednesday, January 23, 2019 at 12:17:11 AM UTC, agrays...@gmail.com <> 
> wrote:
> 
> 
> On Tuesday, January 22, 2019 at 11:31:06 PM UTC, Philip Thrift wrote:
> 
> 
> On Tuesday, January 22, 2019 at 5:04:15 PM UTC-6, agrays...@gmail.com <> 
> wrote:
> 
> 
> On Tuesday, January 22, 2019 at 10:47:57 PM UTC, Philip Thrift wrote:
> 
> 
> On Tuesday, January 22, 2019 at 3:23:02 PM UTC-6, agrays...@gmail.com <> 
> wrote:
> 
> 
> On Sunday, January 20, 2019 at 3:14:39 PM UTC, Lawrence Crowell wrote:
> On Saturday, January 19, 2019 at 5:42:12 AM UTC-6, agrays...@gmail.com <> 
> wrote:
> Since it seems conceptually impossible to model a theory with DISJOINT 
> discrete spatial units, thus requiring the units to be juxtaposed, do such 
> theories acknowledge difficulty of motion between the units, which might or 
> might not have boundaries? TIA, AG
> 
> I am not sure how to impress people with how bad this thinking is. 
> 
> In retrospect, I don't think you were being rude. You were just reinforcing 
> my conclusion, offering additional technical reasons, why the idea of 
> discrete space is an unintelligible concept. AG
> 
> These slice and diced chunks of spacetime, whether voxels, plaquettes and so 
> forth have violations of Lorentz symmetry of spacetime. This means that 
> curiously the symmetry of gravitation would be violated at higher energy, and 
> in fact where it is quantized. These ideas have further been falsified by the 
> lack of dispersion from distant sources. These ideas are bad interpretations 
> of the Planck length. The Planck length is just the smallest length beyond 
> which you can isolate a quantum bit. Remember, it is the length at which the 
> Compton wavelength of a black hole equals its Schwarzschild radius. It is a 
> bit similar to the Nyquist frequency in engineering. In order to measure the 
> frequency of a rotating system you must take pictures that are at least 
> double that frequency. Similarly to measure the frequency of an EM wave you 
> need to have a wave with Fourier modes that are 2 or more times the frequency 
> you want to measure. The black hole is in a sense a fundamental cut-off in 
> the time scale, or in a reciprocal manner the energy, one can sample space to 
> find qubits. 
> 
> The levels of confusion over this are enormous. It does not tell us that 
> spacetime is somehow sliced and diced into briquets or pieces. It does not 
> tell us that quantum energy of some fields can't be far larger than the 
> Planck energy, or equivalently the wavelength much smaller. This would be 
> analogous to a resonance state, and there is no reason there can't be such a 
> thing in quantum gravity. The Planck scale would suggest this sort of state 
> may decay into a sub-Planckian energy.  Further, it is plausible that quantum 
> gravity beyond what appears as a linearized weak field approximation similar 
> to the QED of photon bunched pairs may only exist at most an order of 
> magnitude larger than the Planck scale anyway. A holographic screen is then a 
> sort of beam splitter at the quantum-classical divide.
> 
> LC
> 
> 
> 
> 
> But you have to admit that a truly continuous space in reality is more 
> unintelligible than a discrete space.
> 
> Where do you observe a true (spacetime) continuum in nature?
> 
> A true continuum in reality is more problematic in many ways than a "quantum" 
> spacetime.
> 
> - pt
> 
> Calculus is essentially based on continuity and seems to model the real 
> world. But for me discrete space seems to make motion problematic, so my 
> inclination is to reject it. AG
> 
> 
> What about Zeno's paradox?
>  
> I brought this issue up myself a few months ago. Seems to show space is not 
> infinitely divisible. OTOH, GR is hugely successful and assumes space-time 
> continuity. AG
> 
> What version of Zeno's paradox do you subscribe to which suggests space is 
> not infinitely divisible? TIA, AG 
> 
> 
> And don't let that brainwashing from calculus math teachers fool you. :)
> 
> - pt
> 
> 
> All three paradoxes of motion [ listed in Wikipedia - 
> https://en.wikipedia.org/wiki/Zeno%27s_paradoxes#Paradoxes_of_motion ]
> 
> 1 Paradoxes of motion 
> 1.1   
> Achilles and the tortoise 
> 
> 1.2   Dichotomy paradox 
> 
> 1.3   Arrow paradox 
> 
>  "contradict" continuous spacetime (space in 1, 2 and time in 3).

Hmm… It contradicts only a digital or discrete version of space. Once we agree 
to assume a continuum, we accept the traditional notion of limits (Cauchy, 
Dedekind) and that solves, bu the usual method, the Zeno 

Re: Discrete theories of space

[Philip Thrift]

On Wednesday, January 23, 2019 at 3:04:38 AM UTC-6, agrays...@gmail.com 
wrote:
>
>
>
> On Wednesday, January 23, 2019 at 12:17:11 AM UTC, agrays...@gmail.com 
> wrote:
>>
>>
>>
>> On Tuesday, January 22, 2019 at 11:31:06 PM UTC, Philip Thrift wrote:
>>>
>>>
>>>
>>> On Tuesday, January 22, 2019 at 5:04:15 PM UTC-6, agrays...@gmail.com 
>>> wrote:



 On Tuesday, January 22, 2019 at 10:47:57 PM UTC, Philip Thrift wrote:
>
>
>
> On Tuesday, January 22, 2019 at 3:23:02 PM UTC-6, agrays...@gmail.com 
> wrote:
>>
>>
>>
>> On Sunday, January 20, 2019 at 3:14:39 PM UTC, Lawrence Crowell wrote:
>>>
>>> On Saturday, January 19, 2019 at 5:42:12 AM UTC-6, 
>>> agrays...@gmail.com wrote:

 Since it seems conceptually impossible to model a theory with 
 DISJOINT discrete spatial units, thus requiring the units to be 
 juxtaposed, 
 do such theories acknowledge difficulty of motion between the units, 
 which 
 might or might not have boundaries? TIA, AG

>>>
>>> I am not sure how to impress people with how bad this thinking is. 
>>>
>>
>> *In retrospect, I don't think you were being rude. You were just 
>> reinforcing my conclusion, offering additional technical reasons, why 
>> the 
>> idea of discrete space is an unintelligible concept. AG*
>>
>> These slice and diced chunks of spacetime, whether voxels, plaquettes 
>>> and so forth have violations of Lorentz symmetry of spacetime. This 
>>> means 
>>> that curiously the symmetry of gravitation would be violated at higher 
>>> energy, and in fact where it is quantized. These ideas have further 
>>> been 
>>> falsified by the lack of dispersion from distant sources. These ideas 
>>> are 
>>> bad interpretations of the Planck length. The Planck length is just the 
>>> smallest length beyond which you can isolate a quantum bit. Remember, 
>>> it is 
>>> the length at which the Compton wavelength of a black hole equals its 
>>> Schwarzschild radius. It is a bit similar to the Nyquist frequency in 
>>> engineering. In order to measure the frequency of a rotating system you 
>>> must take pictures that are at least double that frequency. Similarly 
>>> to 
>>> measure the frequency of an EM wave you need to have a wave with 
>>> Fourier 
>>> modes that are 2 or more times the frequency you want to measure. The 
>>> black 
>>> hole is in a sense a fundamental cut-off in the time scale, or in a 
>>> reciprocal manner the energy, one can sample space to find qubits. 
>>>
>>> The levels of confusion over this are enormous. It does not tell us 
>>> that spacetime is somehow sliced and diced into briquets or pieces. It 
>>> does 
>>> not tell us that quantum energy of some fields can't be far larger than 
>>> the 
>>> Planck energy, or equivalently the wavelength much smaller. This would 
>>> be 
>>> analogous to a resonance state, and there is no reason there can't be 
>>> such 
>>> a thing in quantum gravity. The Planck scale would suggest this sort of 
>>> state may decay into a sub-Planckian energy.  Further, it is plausible 
>>> that 
>>> quantum gravity beyond what appears as a linearized weak field 
>>> approximation similar to the QED of photon bunched pairs may only exist 
>>> at 
>>> most an order of magnitude larger than the Planck scale anyway. A 
>>> holographic screen is then a sort of beam splitter at the 
>>> quantum-classical 
>>> divide.
>>>
>>> LC
>>>
>>
>
>
>
> But you have to admit that a truly continuous space in reality is *more 
> unintelligible* than a discrete space.
>
> Where do you observe a true (spacetime) continuum in nature?
>
> A true continuum in reality is more problematic in many ways than a 
> "quantum" spacetime.
>
> - pt
>

 *Calculus is essentially based on continuity and seems to model the 
 real world. But for me discrete space seems to make motion problematic, so 
 my inclination is to reject it. AG*

>>>
>>>
>>> What about Zeno's paradox?
>>>
>>  
>
>> *I brought this issue up myself a few months ago. Seems to show space is 
>> not infinitely divisible. OTOH, GR is hugely successful and assumes 
>> space-time continuity. AG*
>>
>
>
> *What version of Zeno's paradox do you subscribe to which suggests space 
> is not infinitely divisible? TIA, AG *
>
>
>> And don't let that *brainwashing* from calculus math teachers fool you. 
>>> :)
>>>
>>> - pt
>>>
>>

All three paradoxes of motion [ listed in Wikipedia - 
https://en.wikipedia.org/wiki/Zeno%27s_paradoxes#Paradoxes_of_motion ]

1Paradoxes of motion 

   
   - 1.1Achilles and the tortoise 
   

Re: Discrete theories of space

[agrayson2000]

On Wednesday, January 23, 2019 at 12:17:11 AM UTC, agrays...@gmail.com 
wrote:
>
>
>
> On Tuesday, January 22, 2019 at 11:31:06 PM UTC, Philip Thrift wrote:
>>
>>
>>
>> On Tuesday, January 22, 2019 at 5:04:15 PM UTC-6, agrays...@gmail.com 
>> wrote:
>>>
>>>
>>>
>>> On Tuesday, January 22, 2019 at 10:47:57 PM UTC, Philip Thrift wrote:



 On Tuesday, January 22, 2019 at 3:23:02 PM UTC-6, agrays...@gmail.com 
 wrote:
>
>
>
> On Sunday, January 20, 2019 at 3:14:39 PM UTC, Lawrence Crowell wrote:
>>
>> On Saturday, January 19, 2019 at 5:42:12 AM UTC-6, 
>> agrays...@gmail.com wrote:
>>>
>>> Since it seems conceptually impossible to model a theory with 
>>> DISJOINT discrete spatial units, thus requiring the units to be 
>>> juxtaposed, 
>>> do such theories acknowledge difficulty of motion between the units, 
>>> which 
>>> might or might not have boundaries? TIA, AG
>>>
>>
>> I am not sure how to impress people with how bad this thinking is. 
>>
>
> *In retrospect, I don't think you were being rude. You were just 
> reinforcing my conclusion, offering additional technical reasons, why the 
> idea of discrete space is an unintelligible concept. AG*
>
> These slice and diced chunks of spacetime, whether voxels, plaquettes 
>> and so forth have violations of Lorentz symmetry of spacetime. This 
>> means 
>> that curiously the symmetry of gravitation would be violated at higher 
>> energy, and in fact where it is quantized. These ideas have further been 
>> falsified by the lack of dispersion from distant sources. These ideas 
>> are 
>> bad interpretations of the Planck length. The Planck length is just the 
>> smallest length beyond which you can isolate a quantum bit. Remember, it 
>> is 
>> the length at which the Compton wavelength of a black hole equals its 
>> Schwarzschild radius. It is a bit similar to the Nyquist frequency in 
>> engineering. In order to measure the frequency of a rotating system you 
>> must take pictures that are at least double that frequency. Similarly to 
>> measure the frequency of an EM wave you need to have a wave with Fourier 
>> modes that are 2 or more times the frequency you want to measure. The 
>> black 
>> hole is in a sense a fundamental cut-off in the time scale, or in a 
>> reciprocal manner the energy, one can sample space to find qubits. 
>>
>> The levels of confusion over this are enormous. It does not tell us 
>> that spacetime is somehow sliced and diced into briquets or pieces. It 
>> does 
>> not tell us that quantum energy of some fields can't be far larger than 
>> the 
>> Planck energy, or equivalently the wavelength much smaller. This would 
>> be 
>> analogous to a resonance state, and there is no reason there can't be 
>> such 
>> a thing in quantum gravity. The Planck scale would suggest this sort of 
>> state may decay into a sub-Planckian energy.  Further, it is plausible 
>> that 
>> quantum gravity beyond what appears as a linearized weak field 
>> approximation similar to the QED of photon bunched pairs may only exist 
>> at 
>> most an order of magnitude larger than the Planck scale anyway. A 
>> holographic screen is then a sort of beam splitter at the 
>> quantum-classical 
>> divide.
>>
>> LC
>>
>



 But you have to admit that a truly continuous space in reality is *more 
 unintelligible* than a discrete space.

 Where do you observe a true (spacetime) continuum in nature?

 A true continuum in reality is more problematic in many ways than a 
 "quantum" spacetime.

 - pt

>>>
>>> *Calculus is essentially based on continuity and seems to model the real 
>>> world. But for me discrete space seems to make motion problematic, so my 
>>> inclination is to reject it. AG*
>>>
>>
>>
>> What about Zeno's paradox?
>>
>  

> *I brought this issue up myself a few months ago. Seems to show space is 
> not infinitely divisible. OTOH, GR is hugely successful and assumes 
> space-time continuity. AG*
>


*What version of Zeno's paradox do you subscribe to which suggests space is 
not infinitely divisible? TIA, AG *


> And don't let that *brainwashing* from calculus math teachers fool you. :)
>>
>> - pt
>>
>

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Re: Discrete theories of space

[Philip Thrift]

On Tuesday, January 22, 2019 at 6:17:11 PM UTC-6, agrays...@gmail.com wrote:
>
>
>
> On Tuesday, January 22, 2019 at 11:31:06 PM UTC, Philip Thrift wrote:
>>
>>
>>
>> On Tuesday, January 22, 2019 at 5:04:15 PM UTC-6, agrays...@gmail.com 
>> wrote:
>>>
>>>
>>>
>>> On Tuesday, January 22, 2019 at 10:47:57 PM UTC, Philip Thrift wrote:



 On Tuesday, January 22, 2019 at 3:23:02 PM UTC-6, agrays...@gmail.com 
 wrote:
>
>
>
> On Sunday, January 20, 2019 at 3:14:39 PM UTC, Lawrence Crowell wrote:
>>
>> On Saturday, January 19, 2019 at 5:42:12 AM UTC-6, 
>> agrays...@gmail.com wrote:
>>>
>>> Since it seems conceptually impossible to model a theory with 
>>> DISJOINT discrete spatial units, thus requiring the units to be 
>>> juxtaposed, 
>>> do such theories acknowledge difficulty of motion between the units, 
>>> which 
>>> might or might not have boundaries? TIA, AG
>>>
>>
>> I am not sure how to impress people with how bad this thinking is. 
>>
>
> *In retrospect, I don't think you were being rude. You were just 
> reinforcing my conclusion, offering additional technical reasons, why the 
> idea of discrete space is an unintelligible concept. AG*
>
> These slice and diced chunks of spacetime, whether voxels, plaquettes 
>> and so forth have violations of Lorentz symmetry of spacetime. This 
>> means 
>> that curiously the symmetry of gravitation would be violated at higher 
>> energy, and in fact where it is quantized. These ideas have further been 
>> falsified by the lack of dispersion from distant sources. These ideas 
>> are 
>> bad interpretations of the Planck length. The Planck length is just the 
>> smallest length beyond which you can isolate a quantum bit. Remember, it 
>> is 
>> the length at which the Compton wavelength of a black hole equals its 
>> Schwarzschild radius. It is a bit similar to the Nyquist frequency in 
>> engineering. In order to measure the frequency of a rotating system you 
>> must take pictures that are at least double that frequency. Similarly to 
>> measure the frequency of an EM wave you need to have a wave with Fourier 
>> modes that are 2 or more times the frequency you want to measure. The 
>> black 
>> hole is in a sense a fundamental cut-off in the time scale, or in a 
>> reciprocal manner the energy, one can sample space to find qubits. 
>>
>> The levels of confusion over this are enormous. It does not tell us 
>> that spacetime is somehow sliced and diced into briquets or pieces. It 
>> does 
>> not tell us that quantum energy of some fields can't be far larger than 
>> the 
>> Planck energy, or equivalently the wavelength much smaller. This would 
>> be 
>> analogous to a resonance state, and there is no reason there can't be 
>> such 
>> a thing in quantum gravity. The Planck scale would suggest this sort of 
>> state may decay into a sub-Planckian energy.  Further, it is plausible 
>> that 
>> quantum gravity beyond what appears as a linearized weak field 
>> approximation similar to the QED of photon bunched pairs may only exist 
>> at 
>> most an order of magnitude larger than the Planck scale anyway. A 
>> holographic screen is then a sort of beam splitter at the 
>> quantum-classical 
>> divide.
>>
>> LC
>>
>



 But you have to admit that a truly continuous space in reality is *more 
 unintelligible* than a discrete space.

 Where do you observe a true (spacetime) continuum in nature?

 A true continuum in reality is more problematic in many ways than a 
 "quantum" spacetime.

 - pt

>>>
>>> *Calculus is essentially based on continuity and seems to model the real 
>>> world. But for me discrete space seems to make motion problematic, so my 
>>> inclination is to reject it. AG*
>>>
>>
>>
>> What about Zeno's paradox?
>>
>
> *I brought this issue up myself a few months ago. Seems to show space is 
> not infinitely divisible. OTOH, GR is hugely successful and assumes 
> space-time continuity. AG*
>
> And don't let that *brainwashing* from calculus math teachers fool you. :)
>>
>> - pt
>>
>



"One place where general relativity predicts its own demise is at 
singularities inside black holes. What physics replaces general relativity 
at singularities? This is a deep question, providing one of the motivations 
for this book’s emphasis on black hole interiors."


General Relativity, Black Holes, and Cosmology
Andrew J. S. Hamilton
http://jila.colorado.edu/~ajsh/

- pt

 

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Re: Discrete theories of space

[agrayson2000]

On Tuesday, January 22, 2019 at 11:31:06 PM UTC, Philip Thrift wrote:
>
>
>
> On Tuesday, January 22, 2019 at 5:04:15 PM UTC-6, agrays...@gmail.com 
> wrote:
>>
>>
>>
>> On Tuesday, January 22, 2019 at 10:47:57 PM UTC, Philip Thrift wrote:
>>>
>>>
>>>
>>> On Tuesday, January 22, 2019 at 3:23:02 PM UTC-6, agrays...@gmail.com 
>>> wrote:



 On Sunday, January 20, 2019 at 3:14:39 PM UTC, Lawrence Crowell wrote:
>
> On Saturday, January 19, 2019 at 5:42:12 AM UTC-6, agrays...@gmail.com 
> wrote:
>>
>> Since it seems conceptually impossible to model a theory with 
>> DISJOINT discrete spatial units, thus requiring the units to be 
>> juxtaposed, 
>> do such theories acknowledge difficulty of motion between the units, 
>> which 
>> might or might not have boundaries? TIA, AG
>>
>
> I am not sure how to impress people with how bad this thinking is. 
>

 *In retrospect, I don't think you were being rude. You were just 
 reinforcing my conclusion, offering additional technical reasons, why the 
 idea of discrete space is an unintelligible concept. AG*

 These slice and diced chunks of spacetime, whether voxels, plaquettes 
> and so forth have violations of Lorentz symmetry of spacetime. This means 
> that curiously the symmetry of gravitation would be violated at higher 
> energy, and in fact where it is quantized. These ideas have further been 
> falsified by the lack of dispersion from distant sources. These ideas are 
> bad interpretations of the Planck length. The Planck length is just the 
> smallest length beyond which you can isolate a quantum bit. Remember, it 
> is 
> the length at which the Compton wavelength of a black hole equals its 
> Schwarzschild radius. It is a bit similar to the Nyquist frequency in 
> engineering. In order to measure the frequency of a rotating system you 
> must take pictures that are at least double that frequency. Similarly to 
> measure the frequency of an EM wave you need to have a wave with Fourier 
> modes that are 2 or more times the frequency you want to measure. The 
> black 
> hole is in a sense a fundamental cut-off in the time scale, or in a 
> reciprocal manner the energy, one can sample space to find qubits. 
>
> The levels of confusion over this are enormous. It does not tell us 
> that spacetime is somehow sliced and diced into briquets or pieces. It 
> does 
> not tell us that quantum energy of some fields can't be far larger than 
> the 
> Planck energy, or equivalently the wavelength much smaller. This would be 
> analogous to a resonance state, and there is no reason there can't be 
> such 
> a thing in quantum gravity. The Planck scale would suggest this sort of 
> state may decay into a sub-Planckian energy.  Further, it is plausible 
> that 
> quantum gravity beyond what appears as a linearized weak field 
> approximation similar to the QED of photon bunched pairs may only exist 
> at 
> most an order of magnitude larger than the Planck scale anyway. A 
> holographic screen is then a sort of beam splitter at the 
> quantum-classical 
> divide.
>
> LC
>

>>>
>>>
>>>
>>> But you have to admit that a truly continuous space in reality is *more 
>>> unintelligible* than a discrete space.
>>>
>>> Where do you observe a true (spacetime) continuum in nature?
>>>
>>> A true continuum in reality is more problematic in many ways than a 
>>> "quantum" spacetime.
>>>
>>> - pt
>>>
>>
>> *Calculus is essentially based on continuity and seems to model the real 
>> world. But for me discrete space seems to make motion problematic, so my 
>> inclination is to reject it. AG*
>>
>
>
> What about Zeno's paradox?
>

*I brought this issue up myself a few months ago. Seems to show space is 
not infinitely divisible. OTOH, GR is hugely successful and assumes 
space-time continuity. AG*

And don't let that *brainwashing* from calculus math teachers fool you. :)
>
> - pt
>

-- 
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Re: Discrete theories of space

[Philip Thrift]

On Tuesday, January 22, 2019 at 5:04:15 PM UTC-6, agrays...@gmail.com wrote:
>
>
>
> On Tuesday, January 22, 2019 at 10:47:57 PM UTC, Philip Thrift wrote:
>>
>>
>>
>> On Tuesday, January 22, 2019 at 3:23:02 PM UTC-6, agrays...@gmail.com 
>> wrote:
>>>
>>>
>>>
>>> On Sunday, January 20, 2019 at 3:14:39 PM UTC, Lawrence Crowell wrote:

 On Saturday, January 19, 2019 at 5:42:12 AM UTC-6, agrays...@gmail.com 
 wrote:
>
> Since it seems conceptually impossible to model a theory with DISJOINT 
> discrete spatial units, thus requiring the units to be juxtaposed, do 
> such 
> theories acknowledge difficulty of motion between the units, which might 
> or 
> might not have boundaries? TIA, AG
>

 I am not sure how to impress people with how bad this thinking is. 

>>>
>>> *In retrospect, I don't think you were being rude. You were just 
>>> reinforcing my conclusion, offering additional technical reasons, why the 
>>> idea of discrete space is an unintelligible concept. AG*
>>>
>>> These slice and diced chunks of spacetime, whether voxels, plaquettes 
 and so forth have violations of Lorentz symmetry of spacetime. This means 
 that curiously the symmetry of gravitation would be violated at higher 
 energy, and in fact where it is quantized. These ideas have further been 
 falsified by the lack of dispersion from distant sources. These ideas are 
 bad interpretations of the Planck length. The Planck length is just the 
 smallest length beyond which you can isolate a quantum bit. Remember, it 
 is 
 the length at which the Compton wavelength of a black hole equals its 
 Schwarzschild radius. It is a bit similar to the Nyquist frequency in 
 engineering. In order to measure the frequency of a rotating system you 
 must take pictures that are at least double that frequency. Similarly to 
 measure the frequency of an EM wave you need to have a wave with Fourier 
 modes that are 2 or more times the frequency you want to measure. The 
 black 
 hole is in a sense a fundamental cut-off in the time scale, or in a 
 reciprocal manner the energy, one can sample space to find qubits. 

 The levels of confusion over this are enormous. It does not tell us 
 that spacetime is somehow sliced and diced into briquets or pieces. It 
 does 
 not tell us that quantum energy of some fields can't be far larger than 
 the 
 Planck energy, or equivalently the wavelength much smaller. This would be 
 analogous to a resonance state, and there is no reason there can't be such 
 a thing in quantum gravity. The Planck scale would suggest this sort of 
 state may decay into a sub-Planckian energy.  Further, it is plausible 
 that 
 quantum gravity beyond what appears as a linearized weak field 
 approximation similar to the QED of photon bunched pairs may only exist at 
 most an order of magnitude larger than the Planck scale anyway. A 
 holographic screen is then a sort of beam splitter at the 
 quantum-classical 
 divide.

 LC

>>>
>>
>>
>>
>> But you have to admit that a truly continuous space in reality is *more 
>> unintelligible* than a discrete space.
>>
>> Where do you observe a true (spacetime) continuum in nature?
>>
>> A true continuum in reality is more problematic in many ways than a 
>> "quantum" spacetime.
>>
>> - pt
>>
>
> *Calculus is essentially based on continuity and seems to model the real 
> world. But for me discrete space seems to make motion problematic, so my 
> inclination is to reject it. AG*
>




What about Zeno's paradox?

And don't let that *brainwashing* from calculus math teachers fool you. :)

- pt

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Re: Discrete theories of space

[agrayson2000]

On Tuesday, January 22, 2019 at 10:47:57 PM UTC, Philip Thrift wrote:
>
>
>
> On Tuesday, January 22, 2019 at 3:23:02 PM UTC-6, agrays...@gmail.com 
> wrote:
>>
>>
>>
>> On Sunday, January 20, 2019 at 3:14:39 PM UTC, Lawrence Crowell wrote:
>>>
>>> On Saturday, January 19, 2019 at 5:42:12 AM UTC-6, agrays...@gmail.com 
>>> wrote:

 Since it seems conceptually impossible to model a theory with DISJOINT 
 discrete spatial units, thus requiring the units to be juxtaposed, do such 
 theories acknowledge difficulty of motion between the units, which might 
 or 
 might not have boundaries? TIA, AG

>>>
>>> I am not sure how to impress people with how bad this thinking is. 
>>>
>>
>> *In retrospect, I don't think you were being rude. You were just 
>> reinforcing my conclusion, offering additional technical reasons, why the 
>> idea of discrete space is an unintelligible concept. AG*
>>
>> These slice and diced chunks of spacetime, whether voxels, plaquettes and 
>>> so forth have violations of Lorentz symmetry of spacetime. This means that 
>>> curiously the symmetry of gravitation would be violated at higher energy, 
>>> and in fact where it is quantized. These ideas have further been falsified 
>>> by the lack of dispersion from distant sources. These ideas are bad 
>>> interpretations of the Planck length. The Planck length is just the 
>>> smallest length beyond which you can isolate a quantum bit. Remember, it is 
>>> the length at which the Compton wavelength of a black hole equals its 
>>> Schwarzschild radius. It is a bit similar to the Nyquist frequency in 
>>> engineering. In order to measure the frequency of a rotating system you 
>>> must take pictures that are at least double that frequency. Similarly to 
>>> measure the frequency of an EM wave you need to have a wave with Fourier 
>>> modes that are 2 or more times the frequency you want to measure. The black 
>>> hole is in a sense a fundamental cut-off in the time scale, or in a 
>>> reciprocal manner the energy, one can sample space to find qubits. 
>>>
>>> The levels of confusion over this are enormous. It does not tell us that 
>>> spacetime is somehow sliced and diced into briquets or pieces. It does not 
>>> tell us that quantum energy of some fields can't be far larger than the 
>>> Planck energy, or equivalently the wavelength much smaller. This would be 
>>> analogous to a resonance state, and there is no reason there can't be such 
>>> a thing in quantum gravity. The Planck scale would suggest this sort of 
>>> state may decay into a sub-Planckian energy.  Further, it is plausible that 
>>> quantum gravity beyond what appears as a linearized weak field 
>>> approximation similar to the QED of photon bunched pairs may only exist at 
>>> most an order of magnitude larger than the Planck scale anyway. A 
>>> holographic screen is then a sort of beam splitter at the quantum-classical 
>>> divide.
>>>
>>> LC
>>>
>>
>
>
>
> But you have to admit that a truly continuous space in reality is *more 
> unintelligible* than a discrete space.
>
> Where do you observe a true (spacetime) continuum in nature?
>
> A true continuum in reality is more problematic in many ways than a 
> "quantum" spacetime.
>
> - pt
>

*Calculus is essentially based on continuity and seems to model the real 
world. But for me discrete space seems to make motion problematic, so my 
inclination is to reject it. AG*

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Re: Discrete theories of space

[Philip Thrift]

On Tuesday, January 22, 2019 at 3:23:02 PM UTC-6, agrays...@gmail.com wrote:
>
>
>
> On Sunday, January 20, 2019 at 3:14:39 PM UTC, Lawrence Crowell wrote:
>>
>> On Saturday, January 19, 2019 at 5:42:12 AM UTC-6, agrays...@gmail.com 
>> wrote:
>>>
>>> Since it seems conceptually impossible to model a theory with DISJOINT 
>>> discrete spatial units, thus requiring the units to be juxtaposed, do such 
>>> theories acknowledge difficulty of motion between the units, which might or 
>>> might not have boundaries? TIA, AG
>>>
>>
>> I am not sure how to impress people with how bad this thinking is. 
>>
>
> *In retrospect, I don't think you were being rude. You were just 
> reinforcing my conclusion, offering additional technical reasons, why the 
> idea of discrete space is an unintelligible concept. AG*
>
> These slice and diced chunks of spacetime, whether voxels, plaquettes and 
>> so forth have violations of Lorentz symmetry of spacetime. This means that 
>> curiously the symmetry of gravitation would be violated at higher energy, 
>> and in fact where it is quantized. These ideas have further been falsified 
>> by the lack of dispersion from distant sources. These ideas are bad 
>> interpretations of the Planck length. The Planck length is just the 
>> smallest length beyond which you can isolate a quantum bit. Remember, it is 
>> the length at which the Compton wavelength of a black hole equals its 
>> Schwarzschild radius. It is a bit similar to the Nyquist frequency in 
>> engineering. In order to measure the frequency of a rotating system you 
>> must take pictures that are at least double that frequency. Similarly to 
>> measure the frequency of an EM wave you need to have a wave with Fourier 
>> modes that are 2 or more times the frequency you want to measure. The black 
>> hole is in a sense a fundamental cut-off in the time scale, or in a 
>> reciprocal manner the energy, one can sample space to find qubits. 
>>
>> The levels of confusion over this are enormous. It does not tell us that 
>> spacetime is somehow sliced and diced into briquets or pieces. It does not 
>> tell us that quantum energy of some fields can't be far larger than the 
>> Planck energy, or equivalently the wavelength much smaller. This would be 
>> analogous to a resonance state, and there is no reason there can't be such 
>> a thing in quantum gravity. The Planck scale would suggest this sort of 
>> state may decay into a sub-Planckian energy.  Further, it is plausible that 
>> quantum gravity beyond what appears as a linearized weak field 
>> approximation similar to the QED of photon bunched pairs may only exist at 
>> most an order of magnitude larger than the Planck scale anyway. A 
>> holographic screen is then a sort of beam splitter at the quantum-classical 
>> divide.
>>
>> LC
>>
>



But you have to admit that a truly continuous space in reality is *more 
unintelligible* than a discrete space.

Where do you observe a true (spacetime) continuum in nature?

A true continuum in reality is more problematic in many ways than a 
"quantum" spacetime.

- pt

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Re: Discrete theories of space

[agrayson2000]

On Sunday, January 20, 2019 at 3:14:39 PM UTC, Lawrence Crowell wrote:
>
> On Saturday, January 19, 2019 at 5:42:12 AM UTC-6, agrays...@gmail.com 
> wrote:
>>
>> Since it seems conceptually impossible to model a theory with DISJOINT 
>> discrete spatial units, thus requiring the units to be juxtaposed, do such 
>> theories acknowledge difficulty of motion between the units, which might or 
>> might not have boundaries? TIA, AG
>>
>
> I am not sure how to impress people with how bad this thinking is. 
>

*In retrospect, I don't think you were being rude. You were just 
reinforcing my conclusion, offering additional technical reasons, why the 
idea of discrete space is an unintelligible concept. AG*

These slice and diced chunks of spacetime, whether voxels, plaquettes and 
> so forth have violations of Lorentz symmetry of spacetime. This means that 
> curiously the symmetry of gravitation would be violated at higher energy, 
> and in fact where it is quantized. These ideas have further been falsified 
> by the lack of dispersion from distant sources. These ideas are bad 
> interpretations of the Planck length. The Planck length is just the 
> smallest length beyond which you can isolate a quantum bit. Remember, it is 
> the length at which the Compton wavelength of a black hole equals its 
> Schwarzschild radius. It is a bit similar to the Nyquist frequency in 
> engineering. In order to measure the frequency of a rotating system you 
> must take pictures that are at least double that frequency. Similarly to 
> measure the frequency of an EM wave you need to have a wave with Fourier 
> modes that are 2 or more times the frequency you want to measure. The black 
> hole is in a sense a fundamental cut-off in the time scale, or in a 
> reciprocal manner the energy, one can sample space to find qubits. 
>
> The levels of confusion over this are enormous. It does not tell us that 
> spacetime is somehow sliced and diced into briquets or pieces. It does not 
> tell us that quantum energy of some fields can't be far larger than the 
> Planck energy, or equivalently the wavelength much smaller. This would be 
> analogous to a resonance state, and there is no reason there can't be such 
> a thing in quantum gravity. The Planck scale would suggest this sort of 
> state may decay into a sub-Planckian energy.  Further, it is plausible that 
> quantum gravity beyond what appears as a linearized weak field 
> approximation similar to the QED of photon bunched pairs may only exist at 
> most an order of magnitude larger than the Planck scale anyway. A 
> holographic screen is then a sort of beam splitter at the quantum-classical 
> divide.
>
> LC
>

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Re: Discrete theories of space.

[Philip Thrift]

On Tuesday, January 22, 2019 at 7:12:30 AM UTC-6, John Clark wrote:
>
>
> On Tue, Jan 22, 2019 at 2:07 AM Philip Thrift  > wrote:
>
> >>> *3D networks are combinatorial-algebraic in their definition. They 
 are not defined in the language of continuos manifolds of general 
 relativity or fields. A network "space" (spinfoam or other discrete 
 structure) is not the space of general relativity. It is a different 
 concept of space, which is Rovelli's point. Hence the term "quantum space" 
 in Jim Baggott's book. Quantum space is not space in the traditional sense 
 as taught in physics.*

>>>
>>> >> That's all very nice but what experiment can be performed to 
>>> determine if the idea is correct or not? If there isn't one then it's 
>>> philosophy not physics.
>>>
>>
>>
>> *> There is no experiment that shows any theory of physics to be 
>> "correct".*
>>
>
> Agreed, but is there any experiment that shows this theory is less wrong 
> than countless other ideas? If it can make a testable prediction or if it 
> can make a good postdiction (for example explain why the electron has the 
> particular mass and charge that it does) then its elevated into the realm 
> of science, if it can't do that then it's stuck in the philosophy ghetto 
> with 6.02*10^23 other theories.
>
> I don't want to dump on Loop Quantum Gravity or String Theory, they're 
> just getting started and maybe someday they will become physics, but there 
> not there yet.
>
>  John K Clark
>



I watched this panel discussion recently:

https://iai.tv/video/the-dark-universe

*Theoretical physicist at the Frankfurt Institute for Advanced Studies 
Sabine Hossenfelder, winner of the Spinoza Prize Erik Verlinde, and 
European Research Council Fellow Catherine Heymans question the latest 
theories on dark matter.*

The message seems to be: We theoretical physicists don't have a clue. 
Anything goes for what new theory can help us out. 

- pt

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Re: Discrete theories of space.

[John Clark]

On Tue, Jan 22, 2019 at 2:07 AM Philip Thrift  wrote:

>>> *3D networks are combinatorial-algebraic in their definition. They are
>>> not defined in the language of continuos manifolds of general relativity or
>>> fields. A network "space" (spinfoam or other discrete structure) is not the
>>> space of general relativity. It is a different concept of space, which is
>>> Rovelli's point. Hence the term "quantum space" in Jim Baggott's book.
>>> Quantum space is not space in the traditional sense as taught in physics.*
>>>
>>
>> >> That's all very nice but what experiment can be performed to
>> determine if the idea is correct or not? If there isn't one then it's
>> philosophy not physics.
>>
>
>
> *> There is no experiment that shows any theory of physics to be
> "correct".*
>

Agreed, but is there any experiment that shows this theory is less wrong
than countless other ideas? If it can make a testable prediction or if it
can make a good postdiction (for example explain why the electron has the
particular mass and charge that it does) then its elevated into the realm
of science, if it can't do that then it's stuck in the philosophy ghetto
with 6.02*10^23 other theories.

I don't want to dump on Loop Quantum Gravity or String Theory, they're just
getting started and maybe someday they will become physics, but there not
there yet.

 John K Clark

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Re: Discrete theories of space.

[Philip Thrift]

On Monday, January 21, 2019 at 7:45:46 PM UTC-6, John Clark wrote:
>
>
> On Mon, Jan 21, 2019 at 6:53 PM Philip Thrift  > wrote:
>
> > *3D networks are combinatorial-algebraic in their definition. They are 
>> not defined in the language of continuos manifolds of general relativity or 
>> fields. A network "space" (spinfoam or other discrete structure) is not the 
>> space of general relativity. It is a different concept of space, which is 
>> Rovelli's point. Hence the term "quantum space" in Jim Baggott's book. 
>> Quantum space is not space in the traditional sense as taught in physics.*
>>
>
> That's all very nice but what experiment can be performed to determine if 
> the idea is correct or not? If there isn't one then it's philosophy not 
> physics.
>
>  John K Clark  
>
>
>


There is *no experiment* that shows *any theory* of physics to be "correct".

- pt

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Re: Discrete theories of space.

[John Clark]

On Mon, Jan 21, 2019 at 6:53 PM Philip Thrift  wrote:

> *3D networks are combinatorial-algebraic in their definition. They are
> not defined in the language of continuos manifolds of general relativity or
> fields. A network "space" (spinfoam or other discrete structure) is not the
> space of general relativity. It is a different concept of space, which is
> Rovelli's point. Hence the term "quantum space" in Jim Baggott's book.
> Quantum space is not space in the traditional sense as taught in physics.*
>

That's all very nice but what experiment can be performed to determine if
the idea is correct or not? If there isn't one then it's philosophy not
physics.

 John K Clark

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Re: Discrete theories of space.

[Philip Thrift]

On Monday, January 21, 2019 at 5:11:38 PM UTC-6, John Clark wrote:
>
> On Mon, Jan 21, 2019 at 12:42 PM Philip Thrift  > wrote:
>   
>
>> >> Time is about change so time can't be continuous unless there is 
>>> always a physical change between any 2 instances of time regardless of how 
>>> close together they are. If space is discrete what change could occur in 
>>> less time than the time it would take the fastest thing that can exist to 
>>> travel the shortest distance that can exist??   
>>>
>>
>> *> I don't see where a continuous space R^3 (x,y,z) metric (Euclidean vs. 
>> Riemannian) is required *
>>
>
> I'm not saying space or time must be continuous, but I am saying if one is 
> the other must be too.  And I'm saying to test any physical theory that 
> theory must tell you how things will change in space or time, if it can't 
> do that then there is no way to tell if it's correct or not and is just 
> philosophy not science. 
>
> > as a background specification in areas of polymerization
>>   https://en.wikipedia.org/wiki/Polymerization
>
>
>
> Right at the start of the article it mentions "polymer chains or 
> three-dimensional networks" and how that can change with time. And it says
> "polymerization is a process", it other words it is a series of 
> physical operators.
>
>  John K Clark 
>


As I wrote above:


 >  As for continuous time, that is a good point. If space is discrete )in 
the LQG sense), time must be is well.

3D networks are combinatorial-algebraic in their definition. They are not 
defined in the language of *continuos manifolds *of general relativity or 
fields.



A network "space" (spinfoam or other discrete structure) is not the space 
of general relativity. It is a different concept of space, which is 
Rovelli's point. Hence the term "quantum space" in Jim Baggott's book. 
Quantum space is not space in the traditional sense as taught in physics.



- pt





 

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Re: Discrete theories of space.

[John Clark]

On Mon, Jan 21, 2019 at 12:42 PM Philip Thrift 
wrote:


> >> Time is about change so time can't be continuous unless there is
>> always a physical change between any 2 instances of time regardless of how
>> close together they are. If space is discrete what change could occur in
>> less time than the time it would take the fastest thing that can exist to
>> travel the shortest distance that can exist??
>>
>
> *> I don't see where a continuous space R^3 (x,y,z) metric (Euclidean vs.
> Riemannian) is required *
>

I'm not saying space or time must be continuous, but I am saying if one is
the other must be too.  And I'm saying to test any physical theory that
theory must tell you how things will change in space or time, if it can't
do that then there is no way to tell if it's correct or not and is just
philosophy not science.

> as a background specification in areas of polymerization
>   https://en.wikipedia.org/wiki/Polymerization



Right at the start of the article it mentions "polymer chains or
three-dimensional networks" and how that can change with time. And it says
"polymerization is a process", it other words it is a series of
physical operators.

 John K Clark


>
>

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Re: Discrete theories of space.

[Philip Thrift]

On Monday, January 21, 2019 at 8:02:59 AM UTC-6, John Clark wrote:
>
> Philip Thrift > Wrote:
>
> *> There is a lot of scientific theory that doesn't really mention space: 
>> theories in chemistry and biology for example. *
>>
>
> Please be specific because I can't think of a single example. 
>
> > *These have to do with change of structures (molecules, cells).*
>>
>
> A change with respect to what? The very word "structure" implies a 
> arrangement in space. Biologists say cells are different here than they are 
> there ( different species  occupy different habitats ) or they say cells 
> now are different than what they were 3  billion years ago ( life evolves 
> with time). If it's not a change in the structural arrangement in space or 
> a change in how cells behave chemically as time progresses then what in the 
> world do they mean when biologists say "the cell has changed"?
>
> *> But time is interesting. It is possible to have a discrete space (the 
>> title subject of this topic) but a continuous time.*
>>
>  
> Time is about change so time can't be continuous unless there is always a 
> physical change between any 2 instances of time regardless of how close 
> together they are. If space is discrete what change could occur in less 
> time than the time it would take the fastest thing that can exist to travel 
> the shortest distance that can exist??   
>
>  John K Clark 
>



I don't see where a continuous space R^3 (x,y,z) metric (Euclidean vs. 
Riemannian) is required as a background specification in areas of 
polymerization

  https://en.wikipedia.org/wiki/Polymerization

for example. It seems a discrete geometry would do.

As for continuous time, that is a good point. If space is discrete )in the 
LQG sense), time must be is well.

- pt


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Re: Discrete theories of space.

[John Clark]

Philip Thrift  Wrote:

*> There is a lot of scientific theory that doesn't really mention space:
> theories in chemistry and biology for example. *
>

Please be specific because I can't think of a single example.

> *These have to do with change of structures (molecules, cells).*
>

A change with respect to what? The very word "structure" implies a
arrangement in space. Biologists say cells are different here than they are
there ( different species  occupy different habitats ) or they say cells
now are different than what they were 3  billion years ago ( life evolves
with time). If it's not a change in the structural arrangement in space or
a change in how cells behave chemically as time progresses then what in the
world do they mean when biologists say "the cell has changed"?

*> But time is interesting. It is possible to have a discrete space (the
> title subject of this topic) but a continuous time.*
>

Time is about change so time can't be continuous unless there is always a
physical change between any 2 instances of time regardless of how close
together they are. If space is discrete what change could occur in less
time than the time it would take the fastest thing that can exist to travel
the shortest distance that can exist??

 John K Clark

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Re: Discrete theories of space.

[Lawrence Crowell]

On Sunday, January 20, 2019 at 7:09:13 PM UTC-6, John Clark wrote:
>
> On Sun, Jan 20, 2019 at 5:55 PM Philip Thrift  > wrote:
>
> > As for LQG's "quantum geometry" being empirical, as I posted before
>>
>> *Glimpses of Space-Time Beyond the Singularities Using Supercomputers*
>> https://arxiv.org/abs/1809.01747 
>>
>
> I see nothing empirical in that, it's a supercomputer simulation. It's 
> saying "maybe this is what's going on when things get smaller than the 
> Planck length", well maybe it is and maybe it isn't. I saw no experiment or 
> even a proposed  experiment that could tell us. Perhaps someday Loop 
> Quantum Gravity or String Theory will be able to make a testable 
> prediction but they're not there yet so until then it's mathematics not 
> physics. 
>
> > Why are people so wedded to the traditional spacetime.
>>
>
> Because they're wedded to the scientific method.  I asked before how you 
> could perform an experiment without making use of space or time but 
> received no answer. 
>
>  John K Clark
>

Loop quantum gravitation stems from the ADM Hamiltonian constraint NH = 0, 
where N is a timelike lapse function that connects one spatial surface to 
another in the general metric

ds^2 = N^2dt^2 - γ_{ij}(N^idt - dx^i)(N^jdt - dx^j)

for the spatial metric γ_{ij} and the spatial shift functions N^i, These 
obey the additional constraint N^iH_i = 0 with H_i = -2N^k∂_jπ_{ik}^j. Here 
π_{ik}= g^{1/2}(K_{ik} - γ_{ik}Tr(K)) with I the extrinsic curvature. Now 
write a Lagrangian 

L = π^{ij}dγ_{ij} - NH - N^iH_i

and with the action S = ∫dtd^3x L there is the sum over geometries or path 
integral

Z = ∫D[γ]e^{-iS}

so that with Z|0> = |Ψ[γ]> the functional differential δZ/δN = 0 gives the 
Wheeler DeWitt equation HΨ[γ] = 0. A variation with the shift function N^i 
gives the momentum constraint equation. 

The Wheeler DeWitt equation is a constraint equation. There is no dynamics 
with this. Abhay Ashtekar did a little trick, which is just a space plus 
time version of what is done with spinor general relativity and put these 
equations in spinor form. These spinors with their complex realizations and 
integrations on the Argand or complex plane is what leads to this idea of 
loops. The bosonic string or type 0 string has lots of structure on the 
complex plane as well, and in fact the functional forms are θ-functions and 
Klein J-invariants from Eisenstein sequences. Back to this in a minute.

The LQG community has worked hard to try to get basic quantum descriptions 
of black holes and so it is a cumbersome approach that was figured out with 
string theory by Vafa and others. This is not to say it is wrong, but I 
think it is being taken into an arena where it might not apply. In fact I 
think it is a constraint that may just mean how a vacuum is defined in 
general, including the de Sitter space or vacuum where string theory seems 
inapplicable. 

I and another have found the Wheeler DeWitt equation appears to be a 
constraint under a holonomy that is a Schroedinger type of equation. The 
Jacobi θ-functions obey a Schroedinger type of equation or in a Euclidean 
setting have a heat kernel. I am not going to comment a whole lot more on 
this for things are still very uncertain.

LC

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Re: Discrete theories of space.

[Philip Thrift]

On Sunday, January 20, 2019 at 7:09:13 PM UTC-6, John Clark wrote:
>
> On Sun, Jan 20, 2019 at 5:55 PM Philip Thrift  > wrote:
>
> > As for LQG's "quantum geometry" being empirical, as I posted before
>>
>> *Glimpses of Space-Time Beyond the Singularities Using Supercomputers*
>> https://arxiv.org/abs/1809.01747 
>>
>
> I see nothing empirical in that, it's a supercomputer simulation. It's 
> saying "maybe this is what's going on when things get smaller than the 
> Planck length", well maybe it is and maybe it isn't. I saw no experiment or 
> even a proposed  experiment that could tell us. Perhaps someday Loop 
> Quantum Gravity or String Theory will be able to make a testable 
> prediction but they're not there yet so until then it's mathematics not 
> physics. 
>
> > Why are people so wedded to the traditional spacetime.
>>
>
> Because they're wedded to the scientific method.  I asked before how you 
> could perform an experiment without making use of space or time but 
> received no answer. 
>
>  John K Clark
>
>
>
My understanding of what the LQG Black Hole team (Abhay Ashtekar and Javier 
Olmedo at Penn State and Parampreet Singh at Louisiana State University) is 
up to

*Beyond the black hole singularity*
https://www.sciencedaily.com/releases/2018/12/181220111804.htm


is to show that their model matches astronomical data better than other 
theories (which is sort of the way science works).



There is a lot of scientific theory that doesn't really mention space: 
theories in chemistry and biology for example. These have to do with change 
of structures (molecules, cells).

But time is interesting. It is possible to have a discrete space (the title 
subject of this topic) but a continuous time.

- pt


 

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Re: Discrete theories of space.

[John Clark]

On Sun, Jan 20, 2019 at 5:55 PM Philip Thrift  wrote:

> As for LQG's "quantum geometry" being empirical, as I posted before
>
> *Glimpses of Space-Time Beyond the Singularities Using Supercomputers*
> https://arxiv.org/abs/1809.01747
>

I see nothing empirical in that, it's a supercomputer simulation. It's
saying "maybe this is what's going on when things get smaller than the
Planck length", well maybe it is and maybe it isn't. I saw no experiment or
even a proposed  experiment that could tell us. Perhaps someday Loop
Quantum Gravity or String Theory will be able to make a testable prediction but
they're not there yet so until then it's mathematics not physics.

> Why are people so wedded to the traditional spacetime.
>

Because they're wedded to the scientific method.  I asked before how you
could perform an experiment without making use of space or time but
received no answer.

 John K Clark

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Re: Discrete theories of space.

[Philip Thrift]

On Sunday, January 20, 2019 at 4:37:35 PM UTC-6, John Clark wrote:
>
> On Sun, Jan 20, 2019 at 4:31 PM Philip Thrift  > wrote:
>   
>
>> *>>> What we call space (x,y,z) is just what we measure with a ruler.*
 *What we call time t is just what we measure with a clock.*

>>>
>>> >>True, and thus space and time have well defined definitions. And 
>>> that's why we can't do experiments without a ruler and a clock, you 
>>> wouldn't know where to look for the results or when to look. Without
>>>  experiment or prediction or even postdiction you're just navel gazing 
>>> not doing physics.
>>>
>>
>> > *I don't understand space and time have well defined definitions.*
>>
>
> it's odd you don't understand that as you give crystal clear definitions 
> yourself, space is what a ruler measures and time is what a clock measures. 
> Zero ambiguity in that. 
>  
>
>> * > If (say) LQG is right, then* []
>>
>
> Then we'll never know it's right without an experiment that can confirm 
> it,  and experiments can't exist without rulers and clocks. 
>
>> > *then all rulers and clocks are are things made of QPSCs.*
>>
>
> So what? Everything is made of something else unless you're at the 
> fundamental level. Space and time may not be made of anything but at least 
> they're measurable, I don't see how claiming the fundamental level is mot 
> made of anything and is not measurable either get's you anywhere; you could 
> theorize it's made of anything you like and it would still be consistent 
> with any conceivable experiment. In other words its just navel gazing.
>
> John k Clark
>
>
>
>
As for LQG's "quantum geometry" being empirical, as I posted before

*Glimpses of Space-Time Beyond the Singularities Using Supercomputers*
https://arxiv.org/abs/1809.01747 

"Numerical studies using HPC reveal the existence of an effective 
space-time description that sheds important light on the way continuum 
space-time emerges from quantum geometry and *potentially links LQG with 
astronomical observations*. In coming years, one challenge is to extend 
these results to inhomogeneous space-times where the understanding of 
analytical aspects in quantum gravity is yet to be completed. Given the 
progress over the past couple of years, it can be expected that 
supercomputers will prove to be an invaluable and essential tool for the 
complete discovery of the new physics at the Planck scale, and to go beyond 
the limitations of Einstein’s GR."


Why are people so wedded to the traditional spacetime.
Is the Immanuel Kant Song right? :)

- pt

>  
>

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Re: Discrete theories of space.

[John Clark]

On Sun, Jan 20, 2019 at 4:31 PM Philip Thrift  wrote:


> *>>> What we call space (x,y,z) is just what we measure with a ruler.*
>>> *What we call time t is just what we measure with a clock.*
>>>
>>
>> >>True, and thus space and time have well defined definitions. And
>> that's why we can't do experiments without a ruler and a clock, you
>> wouldn't know where to look for the results or when to look. Without
>>  experiment or prediction or even postdiction you're just navel gazing
>> not doing physics.
>>
>
> > *I don't understand space and time have well defined definitions.*
>

it's odd you don't understand that as you give crystal clear definitions
yourself, space is what a ruler measures and time is what a clock measures.
Zero ambiguity in that.


> * > If (say) LQG is right, then* []
>

Then we'll never know it's right without an experiment that can confirm it,
 and experiments can't exist without rulers and clocks.

> > *then all rulers and clocks are are things made of QPSCs.*
>

So what? Everything is made of something else unless you're at the
fundamental level. Space and time may not be made of anything but at least
they're measurable, I don't see how claiming the fundamental level is mot
made of anything and is not measurable either get's you anywhere; you could
theorize it's made of anything you like and it would still be consistent
with any conceivable experiment. In other words its just navel gazing.

John k Clark

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Re: Discrete theories of space.

[Philip Thrift]

On Sunday, January 20, 2019 at 2:56:19 PM UTC-6, John Clark wrote:
>
> On Sun, Jan 20, 2019 at 2:03 PM Philip Thrift  > wrote:
>
> >> Experiments involve space and time, if those equations involve neither 
>>> I don't see how you could ever test them to see if they're correct;  and if 
>>> you can't do that then it's not science, it's just philosophy. And 
>>> philosophers have been proven wrong far more often than proven right.
>>>
>>  
>> *> What we call space (x,y,z) is just what we measure with a ruler.*
>> *What we call time t is just what we measure with a clock.*
>>
>
> True, and thus space and time have well defined definitions. And that's 
> why we can't do experiments without a ruler and a clock, you wouldn't know 
> where to look for the results or when to look. Without experiment or 
> prediction or even postdiction you're just navel gazing not doing physics.
>
> John K Clark
>
>
>>
I don't understand space and time have well defined definitions. If (say) 
LQG is right, then all there are are quantum particles and spinfoam cells 
(QPs+SCs=QPSCs) - that's all the stuff there is (spacetime itself is now 
stuff to), then all rulers and clocks are are things made of QPSCs.

- pt

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Re: Discrete theories of space

[agrayson2000]

On Sunday, January 20, 2019 at 3:14:39 PM UTC, Lawrence Crowell wrote:
>
> On Saturday, January 19, 2019 at 5:42:12 AM UTC-6, agrays...@gmail.com 
> wrote:
>>
>> Since it seems conceptually impossible to model a theory with DISJOINT 
>> discrete spatial units, thus requiring the units to be juxtaposed, do such 
>> theories acknowledge difficulty of motion between the units, which might or 
>> might not have boundaries? TIA, AG
>>
>
> I am not sure how to impress people with how bad this thinking is. 
>

*Instead of being rude, why don't you state YOUR definition of DISCRETE in 
the context of DISCRETE space? I speak ENGLISH as a native language.  Do 
you? AG*

These slice and diced chunks of spacetime, whether voxels, plaquettes and 
> so forth have violations of Lorentz symmetry of spacetime. This means that 
> curiously the symmetry of gravitation would be violated at higher energy, 
> and in fact where it is quantized. These ideas have further been falsified 
> by the lack of dispersion from distant sources. These ideas are bad 
> interpretations of the Planck length. The Planck length is just the 
> smallest length beyond which you can isolate a quantum bit. Remember, it is 
> the length at which the Compton wavelength of a black hole equals its 
> Schwarzschild radius. It is a bit similar to the Nyquist frequency in 
> engineering. In order to measure the frequency of a rotating system you 
> must take pictures that are at least double that frequency. Similarly to 
> measure the frequency of an EM wave you need to have a wave with Fourier 
> modes that are 2 or more times the frequency you want to measure. The black 
> hole is in a sense a fundamental cut-off in the time scale, or in a 
> reciprocal manner the energy, one can sample space to find qubits. 
>
> The levels of confusion over this are enormous. It does not tell us that 
> spacetime is somehow sliced and diced into briquets or pieces. It does not 
> tell us that quantum energy of some fields can't be far larger than the 
> Planck energy, or equivalently the wavelength much smaller. This would be 
> analogous to a resonance state, and there is no reason there can't be such 
> a thing in quantum gravity. The Planck scale would suggest this sort of 
> state may decay into a sub-Planckian energy.  Further, it is plausible that 
> quantum gravity beyond what appears as a linearized weak field 
> approximation similar to the QED of photon bunched pairs may only exist at 
> most an order of magnitude larger than the Planck scale anyway. A 
> holographic screen is then a sort of beam splitter at the quantum-classical 
> divide.
>
> LC
>

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Re: Discrete theories of space.

[John Clark]

On Sun, Jan 20, 2019 at 2:03 PM Philip Thrift  wrote:

>> Experiments involve space and time, if those equations involve neither I
>> don't see how you could ever test them to see if they're correct;  and if
>> you can't do that then it's not science, it's just philosophy. And
>> philosophers have been proven wrong far more often than proven right.
>>
>
> *> What we call space (x,y,z) is just what we measure with a ruler.*
> *What we call time t is just what we measure with a clock.*
>

True, and thus space and time have well defined definitions. And that's why
we can't do experiments without a ruler and a clock, you wouldn't know
where to look for the results or when to look. Without experiment or
prediction or even postdiction you're just navel gazing not doing physics.

John K Clark


>

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Re: Discrete theories of space.

[Philip Thrift]

On Sunday, January 20, 2019 at 9:23:09 AM UTC-6, John Clark wrote:
>
> On Saturday, January 19, 2019 at 5:22:25 PM UTC-6, Philip Thrift wrote:
>
> > *T*
>>
>>
>> *his by Carlo Rovelli:> https://arxiv.org/abs/1802.02382 
>> > concludes:> "Notice that nowhere in the 
>> basic equations of the theory a time coordinate t or a space coordinate x 
>> show up**"*.
>
>
> Experiments involve space and time, if those equations involve neither I 
> don't see how you could ever test them to see if they're correct;  and if 
> you can't do that then it's not science, it's just philosophy. And 
> philosophers have been proven wrong far more often than proven right.
>
>  John K Clark
>
>
 

What we call space *(x,y,z)* is just what we measure with a ruler.
What we call time* t* is just what we measure with a clock.

A space measurement = a ruler measurement.
A time measurement = a clock measurement.

That's all we know about space and time.

- pt

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Re: Discrete theories of space

[Philip Thrift]

On Sunday, January 20, 2019 at 9:14:39 AM UTC-6, Lawrence Crowell wrote:
>
> On Saturday, January 19, 2019 at 5:42:12 AM UTC-6, agrays...@gmail.com 
> wrote:
>>
>> Since it seems conceptually impossible to model a theory with DISJOINT 
>> discrete spatial units, thus requiring the units to be juxtaposed, do such 
>> theories acknowledge difficulty of motion between the units, which might or 
>> might not have boundaries? TIA, AG
>>
>
> I am not sure how to impress people with how bad this thinking is. These 
> slice and diced chunks of spacetime, whether voxels, plaquettes and so 
> forth have violations of Lorentz symmetry of spacetime. This means that 
> curiously the symmetry of gravitation would be violated at higher energy, 
> and in fact where it is quantized. These ideas have further been falsified 
> by the lack of dispersion from distant sources. These ideas are bad 
> interpretations of the Planck length. The Planck length is just the 
> smallest length beyond which you can isolate a quantum bit. Remember, it is 
> the length at which the Compton wavelength of a black hole equals its 
> Schwarzschild radius. It is a bit similar to the Nyquist frequency in 
> engineering. In order to measure the frequency of a rotating system you 
> must take pictures that are at least double that frequency. Similarly to 
> measure the frequency of an EM wave you need to have a wave with Fourier 
> modes that are 2 or more times the frequency you want to measure. The black 
> hole is in a sense a fundamental cut-off in the time scale, or in a 
> reciprocal manner the energy, one can sample space to find qubits. 
>
> The levels of confusion over this are enormous. It does not tell us that 
> spacetime is somehow sliced and diced into briquets or pieces. It does not 
> tell us that quantum energy of some fields can't be far larger than the 
> Planck energy, or equivalently the wavelength much smaller. This would be 
> analogous to a resonance state, and there is no reason there can't be such 
> a thing in quantum gravity. The Planck scale would suggest this sort of 
> state may decay into a sub-Planckian energy.  Further, it is plausible that 
> quantum gravity beyond what appears as a linearized weak field 
> approximation similar to the QED of photon bunched pairs may only exist at 
> most an order of magnitude larger than the Planck scale anyway. A 
> holographic screen is then a sort of beam splitter at the quantum-classical 
> divide.
>
> LC
>



Where is the "inconsistency" in the article

*Space and Time in* *Loop Quantum Gravity*
Carlo Rovelli 
https://arxiv.org/abs/1802.02382

Replacing spacetime with spinfoam still has some spin cycles left.

- pt

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Discrete theories of space.

[John Clark]

On Saturday, January 19, 2019 at 5:22:25 PM UTC-6, Philip Thrift wrote:

> *T*
>
>
> *his by Carlo Rovelli:> https://arxiv.org/abs/1802.02382
> > concludes:> "Notice that nowhere in the
> basic equations of the theory a time coordinate t or a space coordinate x
> show up**"*.


Experiments involve space and time, if those equations involve neither I
don't see how you could ever test them to see if they're correct;  and if
you can't do that then it's not science, it's just philosophy. And
philosophers have been proven wrong far more often than proven right.

 John K Clark

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Re: Discrete theories of space

[Lawrence Crowell]

On Saturday, January 19, 2019 at 5:42:12 AM UTC-6, agrays...@gmail.com 
wrote:
>
> Since it seems conceptually impossible to model a theory with DISJOINT 
> discrete spatial units, thus requiring the units to be juxtaposed, do such 
> theories acknowledge difficulty of motion between the units, which might or 
> might not have boundaries? TIA, AG
>

I am not sure how to impress people with how bad this thinking is. These 
slice and diced chunks of spacetime, whether voxels, plaquettes and so 
forth have violations of Lorentz symmetry of spacetime. This means that 
curiously the symmetry of gravitation would be violated at higher energy, 
and in fact where it is quantized. These ideas have further been falsified 
by the lack of dispersion from distant sources. These ideas are bad 
interpretations of the Planck length. The Planck length is just the 
smallest length beyond which you can isolate a quantum bit. Remember, it is 
the length at which the Compton wavelength of a black hole equals its 
Schwarzschild radius. It is a bit similar to the Nyquist frequency in 
engineering. In order to measure the frequency of a rotating system you 
must take pictures that are at least double that frequency. Similarly to 
measure the frequency of an EM wave you need to have a wave with Fourier 
modes that are 2 or more times the frequency you want to measure. The black 
hole is in a sense a fundamental cut-off in the time scale, or in a 
reciprocal manner the energy, one can sample space to find qubits. 

The levels of confusion over this are enormous. It does not tell us that 
spacetime is somehow sliced and diced into briquets or pieces. It does not 
tell us that quantum energy of some fields can't be far larger than the 
Planck energy, or equivalently the wavelength much smaller. This would be 
analogous to a resonance state, and there is no reason there can't be such 
a thing in quantum gravity. The Planck scale would suggest this sort of 
state may decay into a sub-Planckian energy.  Further, it is plausible that 
quantum gravity beyond what appears as a linearized weak field 
approximation similar to the QED of photon bunched pairs may only exist at 
most an order of magnitude larger than the Planck scale anyway. A 
holographic screen is then a sort of beam splitter at the quantum-classical 
divide.

LC

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Re: Discrete theories of space

[Philip Thrift]

On Sunday, January 20, 2019 at 2:16:56 AM UTC-6, agrays...@gmail.com wrote:
>
>
>
> On Saturday, January 19, 2019 at 5:20:16 PM UTC, Philip Thrift wrote:
>>
>>
>>
>> On Saturday, January 19, 2019 at 5:42:12 AM UTC-6, agrays...@gmail.com 
>> wrote:
>>>
>>> Since it seems conceptually impossible to model a theory with DISJOINT 
>>> discrete spatial units, thus requiring the units to be juxtaposed, do such 
>>> theories acknowledge difficulty of motion between the units, which might or 
>>> might not have boundaries? TIA, AG
>>>
>>
>>
>> In quantum space or quantum spacetime approaches (like loop quantum 
>> gravity, casual dynamical triangulation), space or spacetime is in really a 
>> collection of 3D or 4D *cells *(tetrahedra or pentahedra) that are 
>> "glued" together somehow.
>>
>> There is no "space"  in the conventional Euclidean of Riemannian  
>> geometrical/metrical sense, so these cells aren't *in* space (there is 
>> no space inside of them or between them). The cells collectively *are* 
>> space.
>>
>> - pt
>>
>
> *I know. The alleged cells aren't IN space, but collectively ARE space.  
> But they can't be separated. If they were, light and material bodies would 
> have to traverse a Void of Nothingness to get anywhere. Motion would be 
> impossible. OTOH, if they're juxtaposed yet somehow distinguishable, they 
> would have to have boundaries, another big conceptual problem. I find the 
> idea of discrete spatial units, either juxtaposed or not, conceptually 
> unintelligible. AG*
>



What you just wrote (with words like "separated", "boundaries") is still 
presuming a background concept of space as some (x,y,z) coordinate entity 
as taught in school. (But see the Rovelli paper on the LQG "spinfoam" 
picture.)


Also apropos (regarding our preconception of space), the Immanuel Kant Song:

https://www.youtube.com/watch?v=DC8ioZkb-Sc

- pt


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Re: Discrete theories of space

[agrayson2000]

On Saturday, January 19, 2019 at 5:20:16 PM UTC, Philip Thrift wrote:
>
>
>
> On Saturday, January 19, 2019 at 5:42:12 AM UTC-6, agrays...@gmail.com 
> wrote:
>>
>> Since it seems conceptually impossible to model a theory with DISJOINT 
>> discrete spatial units, thus requiring the units to be juxtaposed, do such 
>> theories acknowledge difficulty of motion between the units, which might or 
>> might not have boundaries? TIA, AG
>>
>
>
> In quantum space or quantum spacetime approaches (like loop quantum 
> gravity, casual dynamical triangulation), space or spacetime is in really a 
> collection of 3D or 4D *cells *(tetrahedra or pentahedra) that are 
> "glued" together somehow.
>
> There is no "space"  in the conventional Euclidean of Riemannian  
> geometrical/metrical sense, so these cells aren't *in* space (there is no 
> space inside of them or between them). The cells collectively *are* space.
>
> - pt
>

*I know. The alleged cells aren't IN space, but collectively ARE space.  
But they can't be separated. If they were, light and material bodies would 
have to traverse a Void of Nothingness to get anywhere. Motion would be 
impossible. OTOH, if they're juxtaposed yet somehow distinguishable, they 
would have to have boundaries, another big conceptual problem. I find the 
idea of discrete spatial units, either juxtaposed or not, conceptually 
unintelligible. AG*

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Re: Discrete theories of space

[Philip Thrift]

On Saturday, January 19, 2019 at 5:22:25 PM UTC-6, Philip Thrift wrote:
>
>
>
> On Saturday, January 19, 2019 at 11:20:16 AM UTC-6, Philip Thrift wrote:
>>
>>
>>
>> On Saturday, January 19, 2019 at 5:42:12 AM UTC-6, agrays...@gmail.com 
>> wrote:
>>>
>>> Since it seems conceptually impossible to model a theory with DISJOINT 
>>> discrete spatial units, thus requiring the units to be juxtaposed, do such 
>>> theories acknowledge difficulty of motion between the units, which might or 
>>> might not have boundaries? TIA, AG
>>>
>>
>>
>> In quantum space or quantum spacetime approaches (like loop quantum 
>> gravity, casual dynamical triangulation), space or spacetime is in really a 
>> collection of 3D or 4D *cells *(tetrahedra or pentahedra) that are 
>> "glued" together somehow.
>>
>   
>   > or 5-cells here [ https://en.wikipedia.org/wiki/5-cell ] 
>
>>
>> There is no "space"  in the conventional Euclidean of Riemannian  
>> geometrical/metrical sense, so these cells aren't *in* space (there is 
>> no space inside of them or between them). The cells collectively *are* 
>> space.
>>
>> - pt
>>
>>
>>
> One could have cellular space (leaving time as it is) or cellular 
> spacetime (LQG).
>
> - pt
>


This by Carlo Rovelli:

https://arxiv.org/abs/1802.02382

Space and Time in Loop Quantum Gravity
Carlo Rovelli 

(Submitted on 7 Feb 2018)

Quantum gravity is expected to require modifications of the notions of 
space and time. I discuss and clarify how this happens in Loop Quantum 
Gravity.


concludes

*Notice that nowhere in the basic equations of the theory a time coordinate 
t or a space coordinate x show up.*

- pt


 

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Re: Discrete theories of space

[Philip Thrift]

On Saturday, January 19, 2019 at 11:20:16 AM UTC-6, Philip Thrift wrote:
>
>
>
> On Saturday, January 19, 2019 at 5:42:12 AM UTC-6, agrays...@gmail.com 
> wrote:
>>
>> Since it seems conceptually impossible to model a theory with DISJOINT 
>> discrete spatial units, thus requiring the units to be juxtaposed, do such 
>> theories acknowledge difficulty of motion between the units, which might or 
>> might not have boundaries? TIA, AG
>>
>
>
> In quantum space or quantum spacetime approaches (like loop quantum 
> gravity, casual dynamical triangulation), space or spacetime is in really a 
> collection of 3D or 4D *cells *(tetrahedra or pentahedra) that are 
> "glued" together somehow.
>

> or 5-cells here [ https://en.wikipedia.org/wiki/5-cell ] 

>
> There is no "space"  in the conventional Euclidean of Riemannian  
> geometrical/metrical sense, so these cells aren't *in* space (there is no 
> space inside of them or between them). The cells collectively *are* space.
>
> - pt
>
>
>
One could have cellular space (leaving time as it is) or cellular spacetime 
(LQG).

- pt

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Re: Discrete theories of space

[Philip Thrift]

On Saturday, January 19, 2019 at 5:42:12 AM UTC-6, agrays...@gmail.com 
wrote:
>
> Since it seems conceptually impossible to model a theory with DISJOINT 
> discrete spatial units, thus requiring the units to be juxtaposed, do such 
> theories acknowledge difficulty of motion between the units, which might or 
> might not have boundaries? TIA, AG
>


In quantum space or quantum spacetime approaches (like loop quantum 
gravity, casual dynamical triangulation), space or spacetime is in really a 
collection of 3D or 4D *cells *(tetrahedra or pentahedra) that are "glued" 
together somehow.

There is no "space"  in the conventional Euclidean of Riemannian  
geometrical/metrical sense, so these cells aren't *in* space (there is no 
space inside of them or between them). The cells collectively *are* space.

- pt


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Discrete theories of space

[agrayson2000]

Since it seems conceptually impossible to model a theory with DISJOINT 
discrete spatial units, thus requiring the units to be juxtaposed, do such 
theories acknowledge difficulty of motion between the units, which might or 
might not have boundaries? TIA, AG

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