The tortoise coordinates is found from the Schwarzschild metric
ds^2 = (1 - 2m/r)dt^2 - (1 - 2m/r)^{-1}dr^2 - r^2dΩ^2
where for a signal leaving a point near the black hole with ds = 0 (null
path) and propagating radially out, dΩ = 0, we have dt = dr/(1 - 2m/r)
which then leads to
T = t - t0 - 2m ln|r - 2m|.
That is the tortoise coordinate. Please look this up to read further. I
can't spend beaucoup time going over this for weeks to come.
LC
On Friday, July 17, 2020 at 11:08:00 PM UTC-5 [email protected] wrote:
>
>
> On Friday, July 17, 2020 at 11:54:20 AM UTC-6, Lawrence Crowell wrote:
>>
>> On Friday, July 17, 2020 at 11:43:48 AM UTC-5 [email protected] wrote:
>>
>>>
>>>
>>> On Friday, July 17, 2020 at 5:34:17 AM UTC-6, Alan Grayson wrote:
>>>>
>>>>
>>>>
>>>> On Friday, July 17, 2020 at 4:48:51 AM UTC-6, Lawrence Crowell wrote:
>>>>>
>>>>> On Friday, July 17, 2020 at 5:01:41 AM UTC-5 [email protected]
>>>>> wrote:
>>>>>
>>>>>>
>>>>>>
>>>>>> On Thursday, July 16, 2020 at 7:50:07 PM UTC-6, Alan Grayson wrote:
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>> On Thursday, July 16, 2020 at 5:08:57 PM UTC-6, Lawrence Crowell
>>>>>>> wrote:
>>>>>>>>
>>>>>>>> Gravitons do not escape from a BH, any more than can light.
>>>>>>>> However, from the perspective of an outside observer all matter than
>>>>>>>> went
>>>>>>>> into a BH is on the surface above the event horizon, called the
>>>>>>>> stretched
>>>>>>>> horizon.
>>>>>>>>
>>>>>>>> LC
>>>>>>>>
>>>>>>>
>>>>>>> Gravitons might not exist (and hence quantum gravity can't exist)
>>>>>>> But whatever the case, how can BH's interact gravitationally with
>>>>>>> objects
>>>>>>> beyond its event horizon? You say this doesn't happen. I don't
>>>>>>> understand
>>>>>>> your argument. AG
>>>>>>>
>>>>>>
>>>>> That you are saying this illustrates you do not understand general
>>>>> relativity.
>>>>>
>>>>>
>>>>>>
>>>>>> I may have identified the thousand pound gorilla in the room; the
>>>>>> hypothetical force carrying particle of the quantum gravitating field,
>>>>>> the
>>>>>> graviton, which for BH's doesn't exert any force! AG
>>>>>>
>>>>>
>>>>> I have no idea why you are saying this. Gravitation is not a force in
>>>>> the usual sense and so the graviton does not produce a force in the
>>>>> standard meaning. For the weak field limit the nonlinear terms are
>>>>> negligable and a gravitational wave is linear. This is easily quantized.
>>>>> In
>>>>> fact it is similar to the Hanbury-Brown and Twiss theory of the diphoton.
>>>>> It is when the field becomes strong that general relativity becomes
>>>>> nonlinear and runs into trouble with quantum mechanics.
>>>>>
>>>>> LC
>>>>>
>>>>
>>>> I assumed a quantum field theory of gravity must have a particle
>>>> associated with it, and that this particle is called the graviton. Gravity
>>>> is a fictitious force. So what would the role of the graviton be, if not
>>>> to
>>>> produce some force? If you detect gravitational waves, don't they consist
>>>> of gravitons if a quantum theory of gravity exists, analogous to photons
>>>> in
>>>> EM waves? AG
>>>>
>>>
>>> Before you can present yourself as deeply knowledgeable of GR, you
>>> should be able to give a coherent account how presumably *isolated*
>>> bodies such as BH's, can gravitationally interact with what's exterior to
>>> them. If gravitons can't do that in the context of a quantum theory of
>>> gravity, what can? AG
>>>
>>
>> It is the delay or tortoise coordinate basis for an external observer.
>>
>
> This is a tough subject to wrap one's head around. Wiki has a decent
> article on it. There's an objective gravitational effect of a BH beyond its
> event horizon. Are you claiming that the effect is only supported by theory
> by a particular choice of coordinate system for an external observer? AG
>
>>
>> LC
>>
>
--
You received this message because you are subscribed to the Google Groups
"Everything List" group.
To unsubscribe from this group and stop receiving emails from it, send an email
to [email protected].
To view this discussion on the web visit
https://groups.google.com/d/msgid/everything-list/39b15096-cd4c-4b4e-b135-3b5796427b0cn%40googlegroups.com.
