Nicolaas Vroom wrote:

"Greg Neill" schreef in bericht
. ..
"Nicolaas Vroom" wrote in message
...
................
Newton's theory assumes that gravity act instantaneous.
However if you take into acount that the speed of gravity is
not infinite but equal to 300*c you can correctly simulate
the perihelion precession of Mercury.

Unfortunately, this leads to the problem of the
energy of the orbit changing due to the non-central
nature of the resulting force.

Can you be more spefic what you mean.

In Newtonian physics, any force with a finite propagation speed
would be subjected to aberration as seen from a moving object.
In the case of a planet orbiting the Sun, that would imply
a small component of the force in the direction of motion
which would slowly increase the speed of the planet, moving it
into a larger orbit. And that would violate the principle of
conservation of energy.

Does this mean that the distance (to the Sun) increases ?

It would - and quite measurably so. But that does not happen.

What is magtitude of this effect ?

For your proposed speed of gravity of 300*c, Mercury's energy would
increase by some 10% in less than a year, which in turn would increase
the mean distance of Mercury from the Sun by a comparable amount.
Now, we've carefully observed the positions of the planets during
several centuries, and less carefully over a few millennia. And
these observations are very clear about this: such a rapid change
of Mercury's distance to the Sun just does not happen. And it
does not happen for the Earth, or any other planet, either.

Any way what is wrong with the assumption
that for example the distance of Mars is not constant ?

This distance has periodic variations, sure. But the long
term average is, as far as we can measure, constant over
time. And we can measure this to some 8-10 digits of accuracy.

I have seen studies that if you assume that the distance
of our Earth is not constant you can explain the ice ages.

Are you referring to the Milakovitch theory? Well, Milankovitch
talks about periodic variations in the eccentricity of the
Earth's orbit, and of the inclination and orientation of the
axis of the Earth. But he does not assume a long term change
of the mean distance Earth-Sun.

(Anyway how do you compare your reply with an
expanding Universe ?)

That's a completely different subject.

The magnitude of the
effect is such that it would lead to obvious changes
in the semi-major axes of the planets over relatively
short periods of time.

I expect you mean the semi-major axis of the orbits
of the planets ?
What is wrong with that ?

It is contradicted by observations.

What are the time periods involved ?

For your proposed speed of gravity = 300*c, the mean distance
would increase some 10% over a time scale of just a few years.
Observations show very clearly that it does not happen.

Any way what I have also done is to simulate the perihelion
advance for one complete revolution.
The results are quite interesting and ofcourse I would like
to compare them with observations.
Have you done, such a simulation, using GR ?

GR also shows the perihelion advance -- AND it predicts that
the mean distance of the planets from the Sun does not
change over the long term. A good fundamental textbook in
celestial mechanics will show you how.

For details go to my home page:
http://users.pandora.be/nicvroom/
and study the e-book:
The Reality Now and Understanding.
http://users.pandora.be/nicvroom/now.htm

Nicolaas Vroom


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