Groups > sci.physics.relativity > #407542

Re: Apollo 11

From	Sylvia Else <sylvia@not.at.this.address>
Newsgroups	sci.physics.relativity
Subject	Re: Apollo 11
Date	2017-02-02 12:11 +1100
Message-ID	<efffamFtpqsU1@mid.individual.net> (permalink)
References	<39391af7-5bea-4ba2-99cf-4448ebb67f5b@googlegroups.com> <e9888588-cef5-44e6-b184-66ee8e071c1b@googlegroups.com>

Show all headers | View raw

On 2/02/2017 7:24 AM, numbernumber1964@gmail.com wrote:
> Sylvia,
>
> http://curious.astro.cornell.edu/about-us/37-our-solar-system/the-moon/the-moon-and-the-earth/28-how-do-we-know-the-mass-of-the-earth-and-the-moon-advanced
>
>  Once you know Fgrav/m, G, and R, you can rearrange equation (1):
>
> M = (R2)*Fgrav / G*m
>
> where M is the mass of the Earth, and plug in the numbers.
>
> If you did not know G beforehand, you would need to determine it
> experimentally. The simplest way to do this is through the Cavendish
> experiment, in which a torsion balance is used to measure the
> attraction between pairs of lead weights. It actually works, too!
>
> The Moon is a much trickier problem. The trouble is, that since in
> both equations (1) and (2) m appears in the same relation to F, it's
> not possible to use just those two equations to solve for m (the body
> being accelerated. Try it! The acceleration just doesn't depend on
> the mass of the accelerated body.). You can estimate it roughly by
> assuming that the Moon is just as dense as the Earth and then scaling
> the mass of the Earth down to the volume of the Moon:
>
> Mmoon ~ (Vmoon/Vearth)*Mearth
>

Some things really shouldn't have to be explained in detail.

See

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

Using the definitions of r1 and a, as given there, and taking me to be 
the mass of the Earth, and mm the mass of the Moon, we have

r1 = a / (1 + me/mm)

1 + me / mm = a / r1

me / mm = a / r1 - 1

Since we know a and r1, that gives us the ratio between me and mm, even 
though it doesn't tell us what me and mm are. Let that ratio be K. We have

me / mm = K

mm = me / K

The acceleration towards the Earth or a small mass in terms of the 
gravitational constant G, and some orbital distance r is

me * G / r^2

Since we can directly measure the acceleration of a satellite in orbit 
around the Earth, we can calculate the value of me * G, even though it 
doesn't tell us what either me or G are.

The acceleration towards the Moon in terms of the gravitational constant 
G, and some orbital distance r is

mm * G / r^2

But mm = me / K

so mm * G = me * G / K.

So the acceleration towards the Moon is

me * G / K / r^2.

Since we know what me * G is, what K is and what r^2 is, we can 
calculate the acceleration towards the Moon without ever knowing the 
values of either mm, me or G.

Your entire thesis is thus based on the false premise that we need to 
have an accurate value for G to calculate the trajectory of a spacecraft 
near the Moon.

Sylvia.

Thread

Apollo 11 numbernumber1964@gmail.com - 2017-01-27 10:57 -0800
  Re: Apollo 11 JanPB <filmart@gmail.com> - 2017-01-27 16:05 -0800
    Re: Apollo 11 Juliana Auerbach <jaot@tognaenn.org> - 2017-01-28 00:18 +0000
      Re: Apollo 11 JanPB <filmart@gmail.com> - 2017-01-27 16:41 -0800
        Re: Apollo 11 Juliana Auerbach <jaot@tognaenn.org> - 2017-01-28 01:14 +0000
          Re: Apollo 11 JanPB <filmart@gmail.com> - 2017-01-28 11:33 -0800
            Re: Apollo 11 Juliana Auerbach <jaot@tognaenn.org> - 2017-01-28 20:22 +0000
          Re: Apollo 11 JanPB <filmart@gmail.com> - 2017-01-28 11:34 -0800
            Re: Apollo 11 Juliana Auerbach <jaot@tognaenn.org> - 2017-01-28 20:19 +0000
              Re: Apollo 11 JanPB <filmart@gmail.com> - 2017-01-28 17:21 -0800
                Re: Apollo 11 Juanita Forney <iatiet@oetnnrn.org> - 2017-01-30 12:33 +0000
  Re: Apollo 11 numbernumber1964@gmail.com - 2017-01-27 16:46 -0800
  Re: Apollo 11 Sylvia Else <sylvia@not.at.this.address> - 2017-01-28 12:48 +1100
  Re: Apollo 11 numbernumber1964@gmail.com - 2017-01-28 13:16 -0800
    Re: Apollo 11 Sylvia Else <sylvia@not.at.this.address> - 2017-01-29 13:04 +1100
    Re: Apollo 11 John Gogo <jfgogo22@yahoo.com> - 2017-02-10 17:08 -0800
  Re: Apollo 11 numbernumber1964@gmail.com - 2017-01-28 13:24 -0800
  Re: Apollo 11 numbernumber1964@gmail.com - 2017-01-28 13:34 -0800
  Re: Apollo 11 Thomas Heger <ttt_heg@web.de> - 2017-01-29 07:36 +0100
    Re: Apollo 11 Gary Harnagel <hitlong@yahoo.com> - 2017-01-29 03:20 -0800
      Re: Apollo 11 Thomas Heger <ttt_heg@web.de> - 2017-01-29 20:16 +0100
        Re: Apollo 11 Gary Harnagel <hitlong@yahoo.com> - 2017-01-29 12:07 -0800
          Re: Apollo 11 Thomas Heger <ttt_heg@web.de> - 2017-02-01 06:24 +0100
        Re: Apollo 11 "Paul B. Andersen" <relativity@paulba.no> - 2017-01-29 22:43 +0100
  Re: Apollo 11 numbernumber1964@gmail.com - 2017-01-29 12:05 -0800
  Re: Apollo 11 numbernumber1964@gmail.com - 2017-01-29 15:27 -0800
    Re: Apollo 11 Gary Harnagel <hitlong@yahoo.com> - 2017-01-29 15:40 -0800
  Re: Apollo 11 numbernumber1964@gmail.com - 2017-01-30 12:37 -0800
    Re: Apollo 11 Sylvia Else <sylvia@not.at.this.address> - 2017-01-31 11:18 +1100
  Re: Apollo 11 numbernumber1964@gmail.com - 2017-01-30 15:58 -0800
  Re: Apollo 11 numbernumber1964@gmail.com - 2017-01-30 16:18 -0800
    Re: Apollo 11 Sylvia Else <sylvia@not.at.this.address> - 2017-01-31 11:22 +1100
  Re: Apollo 11 numbernumber1964@gmail.com - 2017-01-30 16:42 -0800
    Re: Apollo 11 Sylvia Else <sylvia@not.at.this.address> - 2017-01-31 12:13 +1100
  Re: Apollo 11 numbernumber1964@gmail.com - 2017-01-31 10:01 -0800
    Re: Apollo 11 Sylvia Else <sylvia@not.at.this.address> - 2017-02-01 12:14 +1100
  Re: Apollo 11 numbernumber1964@gmail.com - 2017-01-31 14:51 -0800
  Re: Apollo 11 numbernumber1964@gmail.com - 2017-02-01 12:24 -0800
    Re: Apollo 11 Sylvia Else <sylvia@not.at.this.address> - 2017-02-02 12:11 +1100
    Re: Apollo 11 The Starmaker <starmaker@ix.netcom.com> - 2017-02-01 21:35 -0800
      Re: Apollo 11 "David (Lord Kronos Prime) Fuller" <fuller.david@hotmail.com> - 2017-02-01 22:05 -0800
  Re: Apollo 11 numbernumber1964@gmail.com - 2017-02-01 15:39 -0800
  Re: Apollo 11 numbernumber1964@gmail.com - 2017-02-02 11:37 -0800
    Re: Apollo 11 Sylvia Else <sylvia@not.at.this.address> - 2017-02-03 09:40 +1100
  Re: Apollo 11 numbernumber1964@gmail.com - 2017-02-02 15:22 -0800
    Re: Apollo 11 Sylvia Else <sylvia@not.at.this.address> - 2017-02-03 11:52 +1100
  Re: Apollo 11 numbernumber1964@gmail.com - 2017-02-03 11:55 -0800
    Re: Apollo 11 Sylvia Else <sylvia@not.at.this.address> - 2017-02-04 11:44 +1100
  Re: Apollo 11 numbernumber1964@gmail.com - 2017-02-03 15:25 -0800
  Re: Apollo 11 numbernumber1964@gmail.com - 2017-02-04 12:49 -0800
    Re: Apollo 11 Sylvia Else <sylvia@not.at.this.address> - 2017-02-05 12:07 +1100
  Re: Apollo 11 numbernumber1964@gmail.com - 2017-02-05 12:16 -0800
    Re: Apollo 11 Sylvia Else <sylvia@not.at.this.address> - 2017-02-06 08:35 +1100
  Re: Apollo 11 numbernumber1964@gmail.com - 2017-02-06 11:49 -0800
    Re: Apollo 11 Sylvia Else <sylvia@not.at.this.address> - 2017-02-07 10:58 +1100
  Re: Apollo 11 numbernumber1964@gmail.com - 2017-02-07 13:32 -0800
    Re: Apollo 11 Sylvia Else <sylvia@not.at.this.address> - 2017-02-08 12:49 +1100
  Re: Apollo 11 numbernumber1964@gmail.com - 2017-02-08 11:13 -0800
    Re: Apollo 11 Sylvia Else <sylvia@not.at.this.address> - 2017-02-09 12:34 +1100
  Re: Apollo 11 numbernumber1964@gmail.com - 2017-02-09 11:11 -0800
    Re: Apollo 11 Sylvia Else <sylvia@not.at.this.address> - 2017-02-10 10:53 +1100
    Re: Apollo 11 The Starmaker <starmaker@ix.netcom.com> - 2017-02-12 11:09 -0800
      Re: Apollo 11 Sylvia Else <sylvia@not.at.this.address> - 2017-02-13 11:52 +1100
  Re: Apollo 11 numbernumber1964@gmail.com - 2017-02-10 11:01 -0800
    Re: Apollo 11 Sylvia Else <sylvia@not.at.this.address> - 2017-02-11 11:42 +1100
  Re: Apollo 11 numbernumber1964@gmail.com - 2017-02-11 11:21 -0800
    Re: Apollo 11 Sylvia Else <sylvia@not.at.this.address> - 2017-02-12 12:00 +1100
  Re: Apollo 11 numbernumber1964@gmail.com - 2017-02-12 11:44 -0800
    Re: Apollo 11 Sylvia Else <sylvia@not.at.this.address> - 2017-02-13 11:51 +1100
  Re: Apollo 11 numbernumber1964@gmail.com - 2017-02-12 13:43 -0800
  Re: Apollo 11 numbernumber1964@gmail.com - 2017-02-13 10:23 -0800
  Re: Apollo 11 numbernumber1964@gmail.com - 2017-02-14 09:54 -0800
    Re: Apollo 11 Sylvia Else <sylvia@not.at.this.address> - 2017-02-15 14:26 +1100
  Re: Apollo 11 numbernumber1964@gmail.com - 2017-02-14 10:49 -0800
  Re: Apollo 11 numbernumber1964@gmail.com - 2017-02-14 10:52 -0800

csiph-web