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Re: Zero Gravity

From Sylvia Else <sylvia@not.at.this.address>
Newsgroups sci.physics.relativity
Subject Re: Zero Gravity
Date 2016-08-10 13:12 +1000
Message-ID <e0vkdhFmb19U1@mid.individual.net> (permalink)
References <c8f3786f-4a2a-4555-861a-901f677e8bcd@googlegroups.com> <e0rc6aFl2tgU1@mid.individual.net> <c59a2c0a-ac06-4aaa-a3ce-87e361d24d76@googlegroups.com> <e0tc2bF59e6U1@mid.individual.net> <a7835ffa-dc52-4354-8a11-8feb8cb11e3c@googlegroups.com>

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On 10/08/2016 10:20 AM, Peter Riedt wrote:
> On Tuesday, August 9, 2016 at 2:38:06 PM UTC+8, Sylvia Else wrote:
>> On 9/08/2016 2:57 PM, Peter Riedt wrote:
>>> On Monday, August 8, 2016 at 8:27:57 PM UTC+8, Sylvia Else wrote:
>>>> On 8/08/2016 4:45 PM, Peter Riedt wrote:
>>>>> Zero Gravity
>>>>>
>>>>> The gravitational force applied by the sun on each planet decreases with distance. It is 3.95750392900614E-02m/sec2 (small g) at the distance of Mercury and diminishes by a factor of 1000 with every assumed increase of distance of 10m and a corresponding decrease of orbital velocity by 10m (gsunatpl = vm^2/rm).
>>>>>
>>>>> When is it zero?
>>>>>
>>>>>             rm	                      vm	            gsunatpl
>>>>> 5.79092310294605E+10	4.78723311866901E+04	3.95750392900614E-02
>>>>> 5.79092310294605E+11	4.78723311866901E+03	3.95750392900614E-05
>>>>> 5.79092310294605E+12	4.78723311866901E+02	3.95750392900614E-08
>>>>> 5.79092310294605E+13	4.78723311866901E+01	3.95750392900614E-11
>>>>> 5.79092310294605E+14	4.78723311866901E+00	3.95750392900614E-14
>>>>> 5.79092310294605E+15	4.78723311866901E-01	3.95750392900614E-17
>>>>> 5.79092310294605E+16	4.78723311866901E-02	3.95750392900614E-20
>>>>> 5.79092310294605E+17	4.78723311866901E-03	3.95750392900614E-23
>>>>> 5.79092310294605E+18	4.78723311866901E-04	3.95750392900614E-26
>>>>> 5.79092310294605E+19	4.78723311866901E-05	3.95750392900614E-29
>>>>> 5.79092310294605E+20	4.78723311866901E-06	3.95750392900614E-32
>>>>> 5.79092310294605E+21	4.78723311866901E-07	3.95750392900614E-35
>>>>>
>>>>
>>>> When the planet is at the centre of the sun.
>>>>
>>>> Sylvia.
>>>
>>> Incorrect. Gravity is at maximum at the centre of the sun. At the distance of the surface of the planet from the centre it is less but not zero.
>>>
>>
>> I encountered a physics student who made that claim.
>>
>> It should be obvious that it cannot possibly be true - what would the
>> direction of the force be?
>>
>> Sylvia.
>
> Please tell me why you think gravity is zero in the centre of the sun?
>

Consider yourself at the centre of the sun. Looking upwards (i.e. 
towards the surface) in some direction. You see a narrow cone of matter, 
which exerts a gravitational force on you. In the opposite direction is 
another cone, which exerts an equal and opposite gravitational force, so 
the combine force of the two cones is zero.

The same applies for every upwards direction, so the total force on you 
is zero.

Or use symmetry. Since the sun is symmetrical, the force must be, but 
any non-zero force would have a definite direction, and thus not be 
symmetrical. So the force must be zero.

Or do the math.

Sylvia.

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Thread

Zero Gravity Peter Riedt <riedt1@yahoo.co.uk> - 2016-08-07 23:45 -0700
  Re: Zero Gravity Poutnik <poutnik4nntp@gmail.com> - 2016-08-08 09:06 +0200
    Re: Zero Gravity Peter Riedt <riedt1@yahoo.co.uk> - 2016-08-08 00:25 -0700
  Re: Zero Gravity Sylvia Else <sylvia@not.at.this.address> - 2016-08-08 22:27 +1000
    Re: Zero Gravity Peter Riedt <riedt1@yahoo.co.uk> - 2016-08-08 21:57 -0700
      Re: Zero Gravity Poutnik <poutnik4nntp@gmail.com> - 2016-08-09 07:47 +0200
        Re: Zero Gravity Peter Riedt <riedt1@yahoo.co.uk> - 2016-08-09 03:14 -0700
          Re: Zero Gravity "Dono," <sa_ge@comcast.net> - 2016-08-09 09:48 -0700
      Re: Zero Gravity Sylvia Else <sylvia@not.at.this.address> - 2016-08-09 16:38 +1000
        Re: Zero Gravity "Paul B. Andersen" <relativity@paulba.no> - 2016-08-09 22:57 +0200
          Re: Zero Gravity Peter Riedt <riedt1@yahoo.co.uk> - 2016-08-09 19:11 -0700
        Re: Zero Gravity Peter Riedt <riedt1@yahoo.co.uk> - 2016-08-09 17:20 -0700
          Re: Zero Gravity "Dono," <sa_ge@comcast.net> - 2016-08-09 17:59 -0700
            Re: Zero Gravity Peter Riedt <riedt1@yahoo.co.uk> - 2016-08-09 18:42 -0700
              Re: Zero Gravity "Dono," <sa_ge@comcast.net> - 2016-08-09 20:10 -0700
              Re: Zero Gravity Odd Bodkin <bodkinodd@gmail.com> - 2016-08-10 08:36 -0500
          Re: Zero Gravity Sylvia Else <sylvia@not.at.this.address> - 2016-08-10 13:12 +1000
            Re: Zero Gravity Peter Riedt <riedt1@yahoo.co.uk> - 2016-08-10 00:56 -0700
            Re: Zero Gravity Peter Riedt <riedt1@yahoo.co.uk> - 2016-08-10 01:02 -0700
              Re: Zero Gravity Mikko <mikko.levanto@outlook.com> - 2016-08-10 11:35 +0300
                Re: Zero Gravity Peter Riedt <riedt1@yahoo.co.uk> - 2016-08-10 02:30 -0700
              Re: Zero Gravity Odd Bodkin <bodkinodd@gmail.com> - 2016-08-10 08:53 -0500
          Re: Zero Gravity Odd Bodkin <bodkinodd@gmail.com> - 2016-08-10 08:35 -0500
      Re: Zero Gravity Odd Bodkin <bodkinodd@gmail.com> - 2016-08-09 07:07 -0500
        Re: Zero Gravity Peter Riedt <riedt1@yahoo.co.uk> - 2016-08-10 02:41 -0700
          Re: Zero Gravity Gary Harnagel <hitlong@yahoo.com> - 2016-08-10 04:12 -0700
          Re: Zero Gravity Odd Bodkin <bodkinodd@gmail.com> - 2016-08-10 08:55 -0500
    Re: Zero Gravity Poutnik <poutnik4nntp@gmail.com> - 2016-08-09 07:39 +0200

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