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Article:
<[email protected]>
From: [email protected](Nancy )
Subject: Re: Why do the planets continue to revolve?
Date: 25 Dec 1996 02:17:15 GMT
In article
<[email protected]>Harry states:
> Planets (1) rotate on their axes & (2) revolve about
Sun. Reason
> why the rotation persists is that the planet is like a
frictionless
> wheel. Watch how a well-oiled bicycle wheel continues to
spin when
> the wheel is not touching the ground. As for the persistence
of
> revolution, the planet would move in a straight line if it
weren't
> for the Sun's gravity. As it is, the gravity prevents the
planet from
> running out to infinity, but it gets pulled into a curved
path, and
> the planet's centrifugal force balances the gravity.
> Harry Hickey <[email protected]>
(Begin ZetaTalk[TM])
Tut, tut, there are several problems with this argument. A
well-oiled bicycle wheel will spin quite a long time, indeed,
especially if balanced in a nice parallel to the ground, but it
DOES slow down and stop, and much before you can well walk away
from it. This has less to do with the friction of the air and any
drag the gravity of the earth may have upon it, and more to do
with the rubbing parts, however well oiled. The incremental
effect of a drag is such that it is at first slight, countered by
the speed of the motion, and then increases rapidly as the motion
slows down.
You haven't addressed the issue we raised,
Harry, which is that there is a pull BACK on the revolving
planet, due to the fact that whenever the planet is adjusted OUT
of its straight line path, it is pulled BACKWARDS. We will ask
our emissary, Nancy, to repost that argument, which has yet to be
addressed, although there was a valiant try from one among the
brave here on sci.astro.
(End ZetaTalk[TM])
As requested, the resposting of the Zeta triangle argument.
(Begin ZetaTalk[TM])
The gravity tug is not strictly a sideways tug, as in all cases
the planet's path is pointed AWAY from the sun, however slightly.
For any given instant moment: 1) draw a line representing the
planet's straight line path, 2) draw a second line representing
the path the planet is being set upon by the gravity tug,
essentially a second tangent to the sun, 3) the angle between
these two lines is the degree of BACKWARD TUG that the planet is
experiencing.
(End ZetaTalk[TM])
To which Ken responded:
In article
<[email protected]> Ken Knickerson writes:
> The only hard thought I can reply to here is the statement
that the
> orbiting body's tangent path and the line of gravitational
pull
> demonstrates a drag on the orbiter. In fact, the drag would
go as
> the cosine of the angle between the lines (actually, a push
for
> angles less than 90 degrees.. In a circular orbit, these
lines are
> perpendicular, so no drag or boost is given to the body.
> [email protected] (Kent Nickerson)
(Begin ZetaTalk[TM])
Ah, math to the rescue, as the theoretical can replace the
actual! Unfortunately, we won't be put off by your blitz. You
have the straight line that your fellow humans have asserted the
Earth wants to move in placed into so short a space of time that
it DOESN'T EXIST. Tut tut! If it doesn't exist, then it can't be
plugged into your formulas, so it must exist. No matter how tiny
you make that instant, at the start of that instant the Earth is
moving in a straight line, and at the end of that instant it is
moving in a line at an ANGLE from the first. It is being pulled
back toward the Sun, OFF its original path at the start of the
instant. The Earth thus has a drag on its forward momentum.
(End ZetaTalk[TM])