What is the name of Carl Sagan's short story about man kind using up the universe and in the end a computer says let there be light?

The short story you're referring to is titled "The Sentinel." In this story, Sagan explores themes of humanity's place in the universe and the potential consequences of technological advancement. The narrative culminates with a powerful moment where a computer, in a metaphorical sense, brings forth creation, echoing the biblical phrase "let there be light." This highlights the interplay between science, technology, and the profound mysteries of existence.