"The law of conservation of energy is, in effect, a promise of eternal existence. The universe is, practically speaking, a closed system. Its total energy will be conserved. More will not be created, none will be destroyed. Your private sum of E, the energy in your atoms and bonds between them, will not be annihilated, cannot be nulled or voided. The mass and energy of which you’re built will change form and location, but they will be here, in this loop of life and light, the permanent party that began with a Bang."
Natalie Angier The Canon