There is a theory in quantum cosmology. It is the hypothesis that our universe is actually a 'false vacuum', meaning that it isn't in its most stable possible configuration. Think of a ball rolling on a surface having several local minima (dents in the surface) but there is only one global minima (the dent which is the deepest). The ball may be in one of the dents which is not the deepest one. So, it is stable for now, but, given the chance it will slide to the deepest dent, which is the lowest energy configuration possible, the so-called 'true vacuum'.
Now the interesting part. If our universe is, indeed, in a false vacuum, due to something called 'quantum tunneling', it may 'tunnel' into the true vacuum, creating a bubble of lower energy. Once this lower energy bubble is formed, it expands, engulfing the entire universe, destroying everything we know as is, and creating new laws of physics. The speed of expanding is the speed of light, so we would have no information whatsoever about it before it hits us. We will literally never see it coming.
The really scary and really useless part? There is absolutely nothing we can do about it.