On Wed, 14 Apr 2010, Olin Lathrop wrote:

> A simple 2D analogy often used to explain gravity is a streched rubber
> sheet.  You put a ball bearing on the sheet, and it makes a depression
> such that other smaller things roll towards the ball bearing.  In this
> analogy, gravity is strongest nearest the mass causing it, and extends to
> infinity as a ever weaker attractive force.
> 
...
> Are there thought experiments we can perform much like what Einstein did
> to deduce relativity without direct observation?  What assumptions could
> be made, like Einstein's speed of light is constant for all observers,
> about gravity to perform such thought experiments?
> 

Streched rubber sheet looks neat when you play with it. It gives the 
illusion that you have a feel for what is going on but it's actually more 
like sticking a blind fold on so you can better enjoy a movie.

Where does the depression go if you convert your 2D sheet into a 3D 
volume? Is this 2D sheet better represented by a 3D sphere of space that 
gets denser the closer you get to the centre (such that the edge of a 
particle nearest the centre has to travel further to cover the same 
distance as the edge furthest away from the centre)? Is a particle in 
space simply a colapsed area of space? Do all particles simply boil down 
to one fundamental object? Is space actually a special substance that can 
have knots in it and in which waves propergate as they do in water?

Just a few random thoughts :-)

Regards
Sergio Masci
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