[Blue Fire]

As I understand it, yes, the sun uses fusion to, for example, fuse hydrogen into helium and releases energy in the process. The sun is 74% hydrogen, 24% helium, and about 1% heavier elements and is currently in hydrostatic balance - neither contracting nor expanding; the inward force of gravity is balanced by the outward pressure of released energy and resistance to further atomic compression. But this won't last forever. When the sun runs out of hydrogen to fuse into helium, then fusion of helium into heavier elements will begin. The sun will begin to die when it begins to turn into a red giant and expands. While it is true that the sun is slowly losing energy and mass (relatively speaking), it is not shrinking in terms of size currently, which means that it's average density must decrease slighty over time.

I hope I got that right. Does that speak to your questions/comments, sunofsky?