Re: Can an object expand if it where placed inside an in-expandible object?

The easiest way to think about this is if you have a gas.  If you heat
a baloon the baloon expands.  If you put a gas in a steel can and heat it 
the gas does not expand.  Instead the pressure of the gas goes up. 

Now if you put one solid inside another you get something in-between the
baloon case and the steel can.  The outer solid will expand some and
in addition the pressure in the inner solid will increase.  In your
specific case, if the middle sphere can't expand, its pressure will
increase.  Its inner hole will contract and it will exert pressure on
the inner sphere.