Foam mattresses

Origin of Memory Foam
A study concluded that one of the key secrets to reducing g-forces on the body was to use a foam material that could conform to each person's shape and hold this conformity. 

Thus, a new foam material was created, it was visco-elastic and therefore able to conform to a person's shape, but then come back to a normal shape once pressure was removed from the foam.  This could allow an even distribution of pressure or body weight over the entire surface of the foam, but quickly adapt to any movements of the body.

What to look for in a good quality memory foam mattress

A good memory foam mattress will not need a box spring underneath it to make the mattress feel good.  You can order a platform base to increase the height of the bed, but remember that this mattress should feel good if it was placed on an even, concrete surface.  A good way to test the surface of a box spring or box foundation is to sit or even stand on various areas and see if it compresses underneath you.