In the beginning, there was physics. "Physics" describes how matter, energy, space, and time behave and interact with one another. The interplay of these characters in our cosmic drama underlies all biological and chemical phenomena. Hence everything fundamental and familiar to us earthlings begins with, and rests upon, the laws of physics. When we apply these laws to astronomical settings, we deal with physics writ large, which we call astrophysics.

Quantum physics fluctuates all the time. But now the fluctuations are not just particles coming into and out of existence, which happens all the time. It's whole universes coming into and out of existence.