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Re: Sauropods vs. Gravity - Jim



Jim, I don't quite follow this comment you made...

"If the earth were smaller in the past, and less massive, the surface gravity 
could have been either less or more, depending upon how much smaller and how 
much less mass. Planets smaller than the earth can have greater surface 
gravity, even with less mass than the earth, just as they can have lower 
surface gravity with more mass."

...how can a smaller planet have greater surface gravity than a larger planet? 
Any resources? Thanks.

Paul

"James R. Cunningham" <jrccea@bellsouth.net> wrote:

> Although I don't agree with Colin's thoughts on possible past gravity
> fluctuations, I feel obligated to point out that lower gravity in the past 
> does
> not imply that the earth was physically smaller then, or that it is more 
> massive
> now.  For example, a phase change in the core, mantle, or crust could cause 
> the
> earth to be smaller in diameter now, which would result in greater gravity at 
> the
> surface (I don't believe to have been the case).  For a given mass, a smaller
> radius in the past would have resulted in greater surface gravity then.  If 
> the
> earth were smaller in the past, and less massive, the surface gravity could 
> have
> been either less or more, depending upon how much smaller and how much less
> mass.  Planets smaller than the earth can have greater surface gravity, even 
> with
> less mass than the earth, just as they can have lower surface gravity with 
> more
> mass.
> 
> Jim