Relativity is one reason that mass and energy can be converted into each other, which is how nuclear power plants work and why the sun shines. Another important effect is in supernova explosions, which signal the death of massive stars. Supernovas exist because relativistic effects overcome quantum effects in the core of a sufficiently massive star, allowing it to suddenly collapse under its own weight until it becomes a much smaller and harder neutron star, Moore said. In a supernova, the outer layers of the star collapse down onto the core and create a gigantic explosion that, among other things, creates elements heavier than iron. In fact, nearly all the heavy elements we are familiar with are made in supernova. We are made of stuff created in in dispersed by supernovas, Moore said. If relativity did not exist, even the most massive stars would end their lives as white dwarfs never exploding, and we would not be around to think about it.