Could the Universe End by Tearing Apart Every Atom?

The universe is expanding, and that expansion is accelerating. We don’t know what’s causing that acceleration, but that hasn’t stopped us from giving it a name. We call this unknown influence dark energy. The observed acceleration is, for the most part, nicely described with a constant density of dark energy – the same amount of this stuff in every block of space. Which means if you increase the volume you increase the overall amount of dark energy – hence accelerating expansion. Mathematically we describe a constant energy density with the cosmological constant in the equations of Einstein’s general theory of relativity. But what if dark energy is NOT constant? What if the energy density in each patch of space increases over time? In that case, the acceleration itself could be … accelerating. That would be bad.