Einstein had spent the previous thirty years showing how we could understand the behaviour of whole universes with simple maths. Gamow saw that those… - John Barrow

Gods reappear in unlimited numbers in the guise of the simulators who have the power of life and death over the simulated realities that they bring into being. The simulators determine the laws, and can change the laws, that govern their worlds. They can engineer anthropic fine-tunings. They can pull the plug on the simulation at any moment, intervene or distance themselves from their simulation; watch as the simulated creatures argue about whether there is a god who controls or intervenes, work miracles or impose their ethical principles upon the simulated reality.

The living world is not a marble palace. It is a higgledy-piggledy outcome of natural selection and the competition between many interacting factors. The outcome is often neither elegant nor symmetrical.

Just focusing on what exists now seems a bit exclusive. And if we include everything that has ever existed as part of the universe, why not include the future as well? This seems to leave us with the definition that the universe is everything that has ever existed, does exist, or will ever exist.