Skepticism, Science & Pseudoscience

We actually know of a universe without mass, or at least can imagine it...our own after the heat death of the universe.

It will still have energy, and even if the energy goes away, there's still the energy embedded into the universe itself, that vacuum energy is never going away and if it's zero, you don't have a universe at all.

1 million years won't change anything.

The earliest big change would be if our universe were a false vacuum, but it would still have mass, energy and time, but the collapse would basically overwrite our current universe destroying everything at the speed of light.

But if you don't have time, you don't have causation. If you don't have energy, you don't have a universe. Like I said, you can have a universe that's just energy and unable to form matter. We can already imagine it. But matter and energy are the same thing so it's not really different from ours.

Energy is literally the one part you can't do without.