How do the conservation laws of physics relate to the expansion and fate of the cosmos?
Liddy Tryon, Walnut Creek, California
A star's life cycle satisfies the conservation of energy law. Energy is released as nuclei fuse — this energy is turned into light and neutrinos — invisible, nearly massless particles that we are just learning to detect directly. While this energy escapes, it isn't lost. It just spreads over a larger volume.