Re: Orbital precession w/o GR


"Ken S. Tucker" <dynamics@xxxxxxxxxxxx> escreveu na mensagem
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On Nov 29, 8:13 am, "JMA" <NOS...@xxxxxxxxx> wrote:
"bz" <bz+...@xxxxxxxxxxxxxxxxxxxx> escreveu na
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"JMA" <NOS...@xxxxxxxxx> wrote
innews:5r6adjF1335cpU1@xxxxxxxxxxxxxxxxxx:

What is really a mystery is how people talk about
precession of mercury orbit, but nobody has any idea
what precession is

[quotehttp://www.thefreedictionary.com/precession]
1. The rotational motion of the axis of a spinning body, such as the
wobbling of a spinning top, caused by torque applied to the body along
its
axis of rotation.
2. The motion of this kind made by the Earth's axis, caused mainly by
the
gravitational pull of the Sun, Moon, and other planets. The precession
of
Earth's axis has a period of nearly 25,800 years, during which time the
reference points on the equatorial coordinate system (the celestial
poles
and celestial equator) will gradually shift their positions on the
celestial sphere. The precession of the equinoxes is the slow westward
shift of the autumnal and vernal equinoxes along the ecliptic,
resulting
from precession of the Earth's axis. See also nutation.
[unquote]

For instance:
A 3 years old kid knows very well what light is.
But a 3 years old kid knows nothing about what light really is and
how he can be fooled by light.

Some facts about precession:
1 - Constant precession requires constant torque.
Where is the constant torque? The torque is highly variable.

2 - Where does the kinetic energy come from?
The kinetic energy comes from the potential energy.
Since energy is conserved, potential energy needs to be
dissipated. That is, a smaller secondary motion, called
nutation, occurs.

Boy I like JMA's post, especially about
the torque.
From what I know, the calculation is
done keeping the orbital angular momentum
constant (usually "h" in most texts).
And from QT, a similiar quantity "h"
is constant AND invariant.

Yep.
The main rotation (orbit) keeps the angular
momentum constant, always.
Then, one needs a new set of two angular
momentum, one being due to precession and
the other due to nutation.
All of then are at right angles. That is, precession
is orthogonal to nutation and each of then also
orthogonal to the main spin axis (orbit).
Basically is a set of 3-orthogonal rotating axis (1,2,3)
called principal axis of inertia.

For a free motion body (besides gravity that
keeps the orbit), that is, a body that is free to
undergo precession, gyroscopic moment (the
inertia moment of the mass times the angular speed
of the orbit) usually is much higher then any external
torque. Therefore, nutation is almost zero.
Gyroscopic moment is a torque that resists to
any external torque, and doesn't give under it.
Meanwhile precession needs to be initiated
and for that one needs some nutation.

If the external torque changes, then precession
changes, and meanwhile during accelerations
nutation must occur.

So it's fair to attribute the precession
to the "relative quantities", such as
the energy of the orbiting body as it
changes it's relativistic co-efficients
in a spacetime distorted by gravitational
field.

Understand, physically, when relativy is need, and why
relativity is need, and what does relativity fix, is a long
deep secret. It's a secret so secret that nobody knows.


Regards
Ken S. Tucker


.

Relevant Pages

  • Re: Reason for Procession of the Equinox?
    ... > precession itself. ... That is a slight clockwise motion of the top's axis. ... that spin interacts with the direction of gravity's pull. ... over to the Earth and the Moon. ...
    (sci.astro.amateur)
  • Re: Gyroscope does work?
    ... _deliberately_ misalign it from the earth's axis, apply a known torque ... its precession defines a cone. ... (And even if it was a plane, the rotation in the plane still has an observable direction.) ...
    (sci.physics)
  • Re: [Embedded troll] Easy Questions
    ... "The reason Precession occurs is that the Earth not only ... rotates on its axis -- otherwise known as the Axis Munde ... equinoxes or the great year in a comprehensive dictionary. ... "The Earth's rotation axis is not fixed in space. ...
    (comp.arch.embedded)
  • Re: Gyroscope does work?
    ... _deliberately_ misalign it from the earth's axis, apply a known torque ... its precession defines a cone. ... But if you are on the Equator, doesn't the cone become a symmetrical ...
    (sci.physics)
  • Re: Orbital precession w/o GR
    ... precession of mercury orbit, ... The rotational motion of the axis of a spinning body, ... - Constant precession requires constant torque. ... The kinetic energy comes from the potential energy. ...
    (sci.physics.relativity)