Nuclear energy, used in weapons as well as for electricity generation, has the potential to destroy life on Earth. But it also has the potential to save life as we know it. Currently, nuclear explosives are the only technology with the capability to deflect, on relatively short notice, a large asteroid fragment or comet headed for a collision with Earth. However, a number of international treaties prohibit the use of nuclear explosives in space. The peaceful and critically effective use of nuclear energy to prevent a civilization-threatening collision is at odds with its potential for inducing a catastrophic thermonuclear war on Earth. The author uses the Fermi paradox—if there are extraterrestrial civilizations in our galaxy, why haven’t they communicated with us?—to examine the dichotomy of whether nuclear explosives are a barrier or a path to long-term human survival.