How to detect other universes: A brief primer

Are there other universes out there?  Do they have different natural laws?

Those are actually two distinct questions, as I see it, though they’re often conflated as if an affirmative answer to the first automatically entailed an affirmative answer to the second.

And there are at least a few scientists and philosophers who, for entirely non-scientific reasons, ardently hope for positive answers to both questions — since the apparent fine-tuning of this universe (the only universe that we currently know to exist) has given, in their view, entirely too much aid and comfort to theists of late.

But it’s a really interesting pair of questions, anyway.  And it suggests one avenue by which cosmology, which can sometimes be as far estranged from empirical data as the most airily speculative philosophical theology, might — might — further ground itself in actual measurable fact.