Re: [MLUG - DISCUSSION] Perpetual Motion Machine?

[Stephen Montgomery-Smith <EMAIL:PROTECTED>]

Michael wrote:
> > You can get energy from gravity if you raise an object away from the 
> > Earth's center of gravity.  But that merely stores the energy you 
> > expended in raising the object.  You can get the energy back if you 
> > can manage to extract *all* of the energy from the falling object.  
> > But you cannot do this with perfect efficiency.  Therefore, you will 
> > lose some of the energy you expended in raising the object and gravity 
> > does not provide a good way of storing energy.
> >
> > Hydroelectric power uses gravity.  The sun heats water so that it 
> > rises into the atmosphere and forms clouds which rain onto the land 
> > and onto fresh water that is above sea level.  The water is then moved 
> > by gravity back toward the ocean.  This gravitational energy can turn 
> > turbines or run mills.  It's a great energy source, but it depends on 
> > the sun to lift the water up in the first place.
>
> We use gravity to fling probes out into space. Some of it is gravity 
> from the sun and some is from planets. Maybe this isn't used for day to 
> day work but it is something humans have used.

Yes, I guess this is energy stored in the form of kinetic energy (the 
movement of the planets rotating), which gravity transfers to the space 
probe.  (So again gravity isn't the energy source, but it does help to 
transfer it.)  This rotational energy presumably comes from angular 
momentum that was already in whatever the whole solar system was made 
of, and as such predates the sun.

--

Stephen Montgomery-Smith
EMAIL:PROTECTED
http://www.math.missouri.edu/~stephen

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