We do know why the universe is expanding. That's due to general relativity. That's well attested to high confidence.
We don't know why the expansion is accelerating. For that we have only speculation.
We do know why the universe is expanding. That's due to general relativity. That's well attested to high confidence.
We don't know why the expansion is accelerating. For that we have only speculation.
It’s well understood that the expansion of the universe is not “due to general relativity”. General relativity does explain some details of that expansion.
The equations of general relativity fully model the expansion of the universe, so you’d need to explain what you mean.