"Antares 531" wrote in message
...
What's the most widely accepted position on this. Was the Big Bang a
humongous explosion, or was it a matter of three spatial dimensions
uncurling?

Neither - not 'uncurling' but 'expanding'

If this was an explosion, what did things expand into? Were
the three spatial dimensions we now perceive always there, but
completely devoid of any matter other than the point at which the Big
Bang occurred?

No, there wasn't an 'empty universe' there beforehand. The dimensions came
into existence at the same time as the universe.

That's the generally accepted model anyhow.
Google "Ned Wright's cosmology tutorial" for a comprehensive overview. It's
not simple though!