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Question about calculation of G

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  Question about calculation of G Peter Riedt <riedt1@yahoo.co.uk> - 2016-12-30 14:12 -0800
    Re: Question about calculation of G Dirk Van de moortel <dirkvandemoortel@hotspam.not> - 2016-12-30 23:20 +0100
    Re: Question about calculation of G Peter Riedt <riedt1@yahoo.co.uk> - 2016-12-31 00:05 -0800
    Re: Question about calculation of G Sylvia Else <sylvia@not.at.this.address> - 2016-12-31 19:17 +1100
      Re: Question about calculation of G Peter Riedt <riedt1@yahoo.co.uk> - 2016-12-31 01:20 -0800

#403536 — Question about calculation of G

Question about calculation of G

We can use the equation G = gstar*rstar^2/Mstar to calculate the value of G in respect of the sun and the three Alpha Centauri stars using elements that are officially accepted. A problem is that gstar and Mstar are calculated with G and the equation can be called circular.

However, in the case of the sun the answer confirms the Codata value of G whereas in the case of the other three stars the answers do not. Why is it so?

	log g	   gstar	   rstar	 Mstar      calc G
Sun		  273.97	696,000,000  1.98855E+30  6.674E-11
ACa	4.30	  199.53	853,992,000  2.18741E+30  6.652E-11
ACb	4.37	  234.42	602,040,000  1.80361E+30  4.711E-11
ACc	5.20	1,584.89	 98,136,000  2.44592E+29  6.240E-11

log g = surface acceleration in log
gstar = surface acceleration in m/sec2
rstar = radius of star in m
Mstar = mass of the star

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#403539

Op 30-dec-2016 om 23:12 schreef Peter Riedt:
> Question about calculation of G
>
> We can use the equation G = gstar*rstar^2/Mstar to calculate the
> value of G in respect of the sun and the three Alpha Centauri stars
> using elements that are officially accepted. A problem is that gstar
> and Mstar are calculated with G and the equation can be called
> circular.
>
> However, in the case of the sun the answer confirms the Codata value
> of G whereas in the case of the other three stars the answers do not.
> Why is it so?
>
> log g	   gstar	   rstar	 Mstar      calc G Sun		  273.97	696,000,000
> 1.98855E+30  6.674E-11 ACa	4.30	  199.53	853,992,000  2.18741E+30
> 6.652E-11 ACb	4.37	  234.42	602,040,000  1.80361E+30  4.711E-11 ACc
> 5.20	1,584.89	 98,136,000  2.44592E+29  6.240E-11
>
> log g = surface acceleration in log gstar = surface acceleration in
> m/sec2 rstar = radius of star in m Mstar = mass of the star

Alas, this clinic obviously *does* help you feel
less lonely, but it is *not* going to cure you :-|

Dirk Vdm

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#403579

On Saturday, December 31, 2016 at 6:12:05 AM UTC+8, Peter Riedt wrote:
> Question about calculation of G
> 
> We can use the equation G = gstar*rstar^2/Mstar to calculate the value of G in respect of the sun and the three Alpha Centauri stars using elements that are officially accepted. A problem is that gstar and Mstar are calculated with G and the equation can be called circular.
> 
> However, in the case of the sun the answer confirms the Codata value of G whereas in the case of the other three stars the answers do not. Why is it so?
> 
> 	log g	   gstar	   rstar	 Mstar      calc G
> Sun		  273.97	696,000,000  1.98855E+30  6.674E-11
> ACa	4.30	  199.53	853,992,000  2.18741E+30  6.652E-11
> ACb	4.37	  234.42	602,040,000  1.80361E+30  4.711E-11
> ACc	5.20	1,584.89	 98,136,000  2.44592E+29  6.240E-11
> 
> log g = surface acceleration in log
> gstar = surface acceleration in m/sec2
> rstar = radius of star in m
> Mstar = mass of the star

There are a number of possible answers such as the elements of the Alpha Centauri stars have been observed/measured/calculated/assumed incorrectly or the value of G differs in different star systems. No problem; the POU in my gravity theory does not rely on G being of a uniform value throughout the universe.

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#403582

On 31/12/2016 9:12 AM, Peter Riedt wrote:
> Question about calculation of G
>
> We can use the equation G = gstar*rstar^2/Mstar to calculate the value of G in respect of the sun and the three Alpha Centauri stars using elements that are officially accepted. A problem is that gstar and Mstar are calculated with G and the equation can be called circular.
>
> However, in the case of the sun the answer confirms the Codata value of G whereas in the case of the other three stars the answers do not. Why is it so?
>
> 	log g	   gstar	   rstar	 Mstar      calc G
> Sun		  273.97	696,000,000  1.98855E+30  6.674E-11
> ACa	4.30	  199.53	853,992,000  2.18741E+30  6.652E-11
> ACb	4.37	  234.42	602,040,000  1.80361E+30  4.711E-11
> ACc	5.20	1,584.89	 98,136,000  2.44592E+29  6.240E-11
>
> log g = surface acceleration in log
> gstar = surface acceleration in m/sec2
> rstar = radius of star in m
> Mstar = mass of the star
>

The surface gravity cannot be measured directly, since we can't go 
there. It has to be inferred from the mass of the star, its radius, and 
the value of G, taken to be that measured in the solar system, since we 
cannot, as yet, measure it anywhere else.

The radius of a star is not a well-defined quantity (since it doesn't 
have a well-defined surface), so if you get the radius from one source, 
the surface gravity from another, and the mass from a third source, 
you're likely to find inconsistencies.

If you found all the quantities from one source, and they imply a 
different value for G, then the source has simply done its math wrong.

It has no more significance than that, and, in particular, says nothing 
about the value of G.

Sylvia.

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#403585

On Saturday, December 31, 2016 at 4:17:15 PM UTC+8, Sylvia Else wrote:
> On 31/12/2016 9:12 AM, Peter Riedt wrote:
> > Question about calculation of G
> >
> > We can use the equation G = gstar*rstar^2/Mstar to calculate the value of G in respect of the sun and the three Alpha Centauri stars using elements that are officially accepted. A problem is that gstar and Mstar are calculated with G and the equation can be called circular.
> >
> > However, in the case of the sun the answer confirms the Codata value of G whereas in the case of the other three stars the answers do not. Why is it so?
> >
> > 	log g	   gstar	   rstar	 Mstar      calc G
> > Sun		  273.97	696,000,000  1.98855E+30  6.674E-11
> > ACa	4.30	  199.53	853,992,000  2.18741E+30  6.652E-11
> > ACb	4.37	  234.42	602,040,000  1.80361E+30  4.711E-11
> > ACc	5.20	1,584.89	 98,136,000  2.44592E+29  6.240E-11
> >
> > log g = surface acceleration in log
> > gstar = surface acceleration in m/sec2
> > rstar = radius of star in m
> > Mstar = mass of the star
> >
> 
> The surface gravity cannot be measured directly, since we can't go 
> there. It has to be inferred from the mass of the star, its radius, and 
> the value of G, taken to be that measured in the solar system, since we 
> cannot, as yet, measure it anywhere else.
> 
> The radius of a star is not a well-defined quantity (since it doesn't 
> have a well-defined surface), so if you get the radius from one source, 
> the surface gravity from another, and the mass from a third source, 
> you're likely to find inconsistencies.
> 
> If you found all the quantities from one source, and they imply a 
> different value for G, then the source has simply done its math wrong.
> 
> It has no more significance than that, and, in particular, says nothing 
> about the value of G.
> 
> Sylvia.

I agree in full.

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