Re: TIDES, was Asteroid Problem

["John S. Denker" <jsd@MONMOUTH.COM>]

At 01:37 PM 9/2/01 -0400, Ludwik Kowalski wrote:


> Why would
[cars on a track]
>  be a bad model to begin a discussion of
> ideal tides? Water is supported by solid earth and each
> part of the ocean is pushed sidewise by the nearby part.


Because the earth moves!!!!

The aforementioned "track" does not move.  This is a fatal flaw in the
track-based simulation.  If you persist in viewing the earth as a
non-moving "absolute" reference frame you will never understand the double
tide.

Here's yet another way of explaining the double tide.  See if this helps:

The water on the asteroid-facing side of the planet is moved toward the
asteroid.  It moves more than the solid earth does.  It moves relative to
the solid earth.  That's because the asteroidal gravitational field is
stronger on that side.

But the solid earth moves some, too.  It moves more than the water on the
far side.  It moves relative to the far-side water.  That's because the
asteroidal gravitational field is stronger at the center of the earth than
it is on the far side.

Remember, a gravitational field is not a "force" field.  It is a force per
unit mass.  The solid earth is much more massive than the ocean, but that
doesn't mean it can resist the gravitational pull of the asteroid!!!!