A nuclear explosion can indeed be seen from low Earth orbit (LEO) due to its immense brightness, which is significantly greater than many manmade structures. While the visible energy of the explosion may only last a brief moment, the resulting mushroom cloud can extend high into the atmosphere, making it more detectable. The discussion highlights that while the average nuclear bomb's yield varies, even smaller bombs can produce a flash visible from space. Observations from satellites and the ability to see phenomena like lightning from orbit further support the visibility of nuclear detonations. Overall, a nuclear explosion's brightness and scale would allow it to be seen from space, although atmospheric absorption may affect visibility.