If energy never dies, and we are comprised of energy and matter, what happens to that energy upon death?

As we know through thermodynamics, energy can not be created nor destroyed.. it can simply change states. The total amount of energy in an isolated system does not, cannot, change. And thanks to Einstein, we also know matter and energy are two rungs on the same ladder. The universe as a whole is closed. However, human bodies (and ecosystems alike) are not closed systems, but open systems-we exchange energy with our surroundings. We can gain energy (again, through chemical processes) and we can lose it (by expelling waste or emitting heat).

In death, the collection of atoms that comprise you (a universe within the universe) are repurposed. These same atoms, and this energy, which originated during the big bang, will always be around. Therefore, your "light"-that is, the essence of your energy (not to be confused with your actual consciousness)-will continue to echo throughout space until the end of time.