Re: Speed of gravity?
From: Nicolaas Vroom (nicolaas.vroom_at_pandora.be)
Date: 07/04/04
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Date: Sun, 04 Jul 2004 15:03:23 GMT
"greywolf42" <mingstb@marssim-ss.com> schreef in bericht
news:10ee3i6kl0a2qd0@corp.supernews.com...
>
> ORBITAL STABILITY ARGUMENT:
>
> The oldest one is the 'orbital stability' calculation. This method is
based
> upon the effect of gravitational aberration. When two bodies orbit each
> other, the force of gravity reaching one body will not point directly to
the
> other body *when the force reaches the first body*. The force vector will
> point to a position just a little bit to one side. This non-central force
> will tend to increase the orbital radius of the second body. Hence, the
> system is deemed 'unstable.' The degree of offset is proportional to the
> speed of gravity. Hence, the slower the speed of gravity, the more
unstable
> the system. One then uses an estimate of the amount of time a body (such
as
> the Earth) is known to have been in orbit. One then back calculates a
> minimum speed of gravity, based on keeping the Earth in orbit. For a
> gravity speed equal to light speed, this comes to a factor of about 1
> billion years to double the orbital size.
Let us be more practical.
Suppose that the average distance Earth Sun increases with 1 km every
year are we able to detect that ?
I do not know over what period the Earth Sun distance is known, but is there
any information available between for Example 200 Years ago and Now ?
And what about the last 50 years ?
Is there any information available based on actual observations that
Earth Sun distance is actual increasing?
IMO to do any calculation based on the last 1 billion years is very tricky
because we know that for example the orbits of the outer planets are
not 100% stable just because of infalling asteroids (i.e. they wander).
and comets.
We have recently observed that by means of the planet Jupiter.
That means to do any sort of "speed of gravity" calculation over such
long periods is pure guess work.
In the book "Pierre Simon Laplace 1749-1827 A Life in exact Science"
By Charles Coulston Gillispie In chapter 4 Universal Gravitation
this same subject is discussed.
At page 30 is written:
3. The force of gravity is propagated instantaneously.
At page 34 there is an equation (13) for r, which changes as a function
of t. The velocity is difined as: Theta divided by alpha times T
There is written:
"Laplace turned to the observations and particularly to the lunar tables,
knowing that ancient and modern records of eclipses showed that the
earth's satellite has been increasing its mean speed of revolution"
At page 34 is written: Laplace found that the velocity of gravitational
corpuscule is 7680000 times as great as the velocity of light.
That means that Laplace made his calculation based on lunar
observations and not on Earth/Sun based observations.
It will be interesting to know what the current opinion is of the
methodes used by Laplace.
Are we currently better equiped to validate equation 13 ?
Nicolaas Vroom
http://users.pandora.be/nicvroom/
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