Larry Caldwell wrote:
> In article <Ra2dnZEMCNFnFlranZ2dnUVZ_sWdnZ2d@[EMAIL PROTECTED]
>,
> max@[EMAIL PROTECTED]
(Erik Max Francis) says...
>
>> What you are suggesting would literally be equivalent to insisting that
>> as objects fall to Earth, Earth loses mass, which is preposterous.
>
> When objects fall, the gravitational field loses energy, which is
> transferred to the object. Where did you think the energy came from?
It comes from the potential energy of the bodies that are arranged in
the gravitational field. Gravitational potential energy is maximized
when two objects are infinitely far away from each other. If they get
closer, then some of that potential energy is converted to kinetic
energy. Total energy -- the sum of the two -- is always conserved. The
potential energy is not in the field itself, nor does the strength of
the field change based on the arrangement of objects within it.
> "Potential energy" is just another term for storing energy in the field.
You can phrase it that way, but it's not what it means. Kinetic and
potential energy are properties individual _objects_ in a field; they're
not properties of the field itself.
> It's counter-intuitive, but when a gravitational field loses energy, it
> actually becomes more intense.
This is also clearly false, and repeats the error you made earlier. The
strength of a gravitational field depends on the mass of the gravitating
body; for the gravitational field to "become more intense," it would
have to increase in mass, which is clearly ludicrous.
If you just mean that when an object falls in a gravitational field, it
by its nature experiences a stronger gravitational field at its new,
closer, location, that too is pretty obvious, but not quite what you
said, since the field itself doesn't change, just the arrangement of
objects within it.
> Consider two planets colliding. The
> collision releases a lot of energy, most of which comes from
> gravitation, and the resultant gravitational field is much more
> powerful. Gravitational fields are negative energy. The more energy
> you extract, the stronger they become.
Sorry, this is just completely wrong. I mean, really, this is pretty
basic stuff. (What you say could be argued to be true in general
relativity, where there are self-gravitating effects, but we're clearly
talking about Newtonian gravity here, so that's obviously not what
you're referring to. And nonsense about the potential energy coming
from the strength of the field itself is clearly also wrong in general
relativity.)
--
Erik Max Francis && max@[EMAIL PROTECTED]
&& http://www.alcyone.com/max/
San Jose, CA, USA && 37 18 N 121 57 W && AIM, Y!M erikmaxfrancis
Love is the selfishness of two persons.
-- Antoine de la Salle
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