Re: Calculating G

From	Sylvia Else <sylvia@not.at.this.address>
Newsgroups	sci.physics
Subject	Re: Calculating G
Date	2016-12-31 11:35 +1100
Message-ID	<ecocrfFr9vrU1@mid.individual.net> (permalink)
References	(2 earlier) <fce81be3-6fca-46cb-8418-c11f5855e2f6@googlegroups.com> <eclunfF9711U2@mid.individual.net> <359717ca-d507-47fe-8486-2fa8086b049f@googlegroups.com> <ecms2rFflm7U1@mid.individual.net> <71dccb3d-7f72-4727-b47a-99d58b0abbde@googlegroups.com>

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On 31/12/2016 9:43 AM, Peter Riedt wrote:
> On Friday, December 30, 2016 at 6:43:45 PM UTC+8, Sylvia Else wrote:
>> On 30/12/2016 8:11 PM, Peter Riedt wrote:
>>> On Friday, December 30, 2016 at 10:22:43 AM UTC+8, Sylvia Else
>>> wrote:
>>>> On 29/12/2016 11:21 PM, Peter Riedt wrote:
>>>>> On Thursday, December 29, 2016 at 2:21:38 PM UTC+8, Sylvia
>>>>> Else wrote:
>>>>>> On 29/12/2016 1:13 AM, Peter Riedt wrote:
>>>>>>> Calculating G
>>>>>>>
>>>>>>> The constant G was anticipated by Newton but first
>>>>>>> accurately determined in the laboratory by Henry
>>>>>>> Cavendish in 1798. It has the value G=6.674E-11m3kg−1s−2
>>>>>>> (cubic meters per kilogram second squared).
>>>>>>>
>>>>>>> G can be derived from elements of a star by the formula
>>>>>>> G=gstar*rstar^2/Mstar
>>>>>>>
>>>>>>> gstar	   rstar	   Mstar	    G Sun	 273.97	696,000,000
>>>>>>> 1.99E+30 6.674E-11 ACa	 200.18	853,992,000	 2.19E+30
>>>>>>> 6.674E-11 ACb	 332.10 602,040,000	 1.80E+30	6.674E-11 AC
>>>>>>> c	1695.00	 98,136,000 2.45E+29	6.674E-11
>>>>>>>
>>>>>>> gstar = surface acceleration in m/sec rstar = radius in m
>>>>>>> Mstar = mass in kg
>>>>>>
>>>>>> How are you going to get the mass and surface acceleration
>>>>>> of the star?
>>>>>>
>>>>>> Sylvia.
>>>>>
>>>>> I got the mass of the sun and Alpha Centauri A, B, C from
>>>>> sources available on the Internet:
>>>>
>>>> Are you for real? How do you think they ended up on the
>>>> Internet?
>>>>
>>>> Sylvia.
>>>
>>> What is your point?
>>>
>>
>> The mass of the sun that's on the Internet was calculated by
>> applying the measured value of G to the orbits of the planets.
>>
>> So calculating G using the mass of the sun obtained from the
>> Internet is actually calculating G from G.
>>
>> The other masses are either derived similarly from orbital speeds,
>> or are derived from brightness based on stellar physics.
>>
>> Surface accelerations are calculated from the mass and G and
>> measured radius.
>>
>> As always, your attempts to calculate G are completely circular.
>>
>> There is no known way of calculating it, other than from the
>> measured attraction between masses that are known accurately by
>> means other than orbital mechanics.
>>
>> Sylvia.
>
> You did not grasp it. I am not trying to calculate G; I am using it
> to establish relationships between elements of free fall objects and
> secondly if it has the same value in other star systems. You have too
> narrow a view.
>

Orbital mechanics is already well understood. There's nothing for you to 
establish.

As for determining whether it has the same value in other star systems, 
this would involve finding gravitationally bound stellar objects, and 
determining their mass otherwise than by using orbital mechanics. 
Estimates based on brightness and stellar physics are much too 
inaccurate to be useful unless the constant G is hugely variable.  If it 
were, that would have been noticed already.

Sylvia.

Thread

Calculating G Peter Riedt <riedt1@yahoo.co.uk> - 2016-12-28 06:13 -0800
  Re: Calculating G Poutnik <poutnik4nntp@gmail.com> - 2016-12-28 15:40 +0100
    Re: Calculating G Poutnik <poutnik4nntp@gmail.com> - 2016-12-28 15:41 +0100
    Re: Calculating G Peter Riedt <riedt1@yahoo.co.uk> - 2016-12-28 22:10 -0800
      Re: Calculating G "hanson" <hanson@quick.net> - 2016-12-28 22:29 -0800
      Re: Calculating G Poutnik <poutnik4nntp@gmail.com> - 2016-12-29 08:07 +0100
        Re: Calculating G Peter Riedt <riedt1@yahoo.co.uk> - 2016-12-29 16:53 -0800
  Re: Calculating G Alan Folmsbee <omnilobe@gmail.com> - 2016-12-28 09:27 -0800
  Re: Calculating G Sylvia Else <sylvia@not.at.this.address> - 2016-12-29 17:21 +1100
    Re: Calculating G Peter Riedt <riedt1@yahoo.co.uk> - 2016-12-29 04:21 -0800
      Re: Calculating G Wally W. <ww84wa@aim.com> - 2016-12-29 09:11 -0500
        Re: Calculating G "hanson" <hanson@quick.net> - 2016-12-29 06:34 -0800
          Re: Calculating G noTthaTguY <abu.kuanysh05@gmail.com> - 2016-12-29 15:40 -0800
          Re: Calculating G Peter Riedt <riedt1@yahoo.co.uk> - 2016-12-29 16:52 -0800
        Re: Calculating G Peter Riedt <riedt1@yahoo.co.uk> - 2016-12-29 16:59 -0800
          Re: Calculating G Odd Bodkin <bodkinodd@gmail.com> - 2017-01-03 12:19 -0600
            Re: Calculating G noTthaTguY <abu.kuanysh05@gmail.com> - 2017-01-03 12:43 -0800
      Re: Calculating G Sylvia Else <sylvia@not.at.this.address> - 2016-12-30 13:22 +1100
        Re: Calculating G Peter Riedt <riedt1@yahoo.co.uk> - 2016-12-30 01:11 -0800
          Re: Calculating G Sylvia Else <sylvia@not.at.this.address> - 2016-12-30 21:43 +1100
            Re: Calculating G "hanson" <hanson@quick.net> - 2016-12-30 06:48 -0800
            Re: Calculating G Peter Riedt <riedt1@yahoo.co.uk> - 2016-12-30 14:43 -0800
              Re: Calculating G Sylvia Else <sylvia@not.at.this.address> - 2016-12-31 11:35 +1100
                Re: Calculating G Peter Riedt <riedt1@yahoo.co.uk> - 2016-12-30 17:06 -0800
                Re: Calculating G Sylvia Else <sylvia@not.at.this.address> - 2016-12-31 12:40 +1100
                Re: Calculating G Peter Riedt <riedt1@yahoo.co.uk> - 2016-12-30 23:22 -0800
                Re: Calculating G Sylvia Else <sylvia@not.at.this.address> - 2016-12-31 20:28 +1100
                Re: Calculating G "reber g=emc^2" <herbertglazier0@gmail.com> - 2016-12-31 11:07 -0800
                Re: Calculating G "hanson" <hanson@quick.net> - 2016-12-31 11:16 -0800
                Re: Calculating G "reber g=emc^2" <herbertglazier0@gmail.com> - 2016-12-31 13:22 -0800
                Re: Calculating G "hanson" <hanson@quick.net> - 2016-12-31 15:36 -0800
                Re: Calculating G Sylvia Else <sylvia@not.at.this.address> - 2017-01-01 11:49 +1100
              Re: Calculating G Odd Bodkin <bodkinodd@gmail.com> - 2017-01-03 15:09 -0600
                Re: Calculating G Peter Riedt <riedt1@yahoo.co.uk> - 2017-01-03 16:22 -0800
                Re: Calculating G noTthaTguY <abu.kuanysh05@gmail.com> - 2017-01-03 16:57 -0800
                Re: Calculating G Odd Bodkin <bodkinodd@gmail.com> - 2017-01-04 10:22 -0600
                Re: Calculating G Peter Riedt <riedt1@yahoo.co.uk> - 2017-01-05 16:02 -0800
                Re: Calculating G Odd Bodkin <bodkinodd@gmail.com> - 2017-01-06 07:09 -0600

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