Parallel universes

There's a lot of talk these days about the possibility of there being more than one universe and that the one we all live in is but an infinitesimal shard of insignificance among an infinite number of sibling structures all with their own sets of physical laws and attributes. It's a fascinating idea, admittedly there's not much concrete evidence for it yet but  from the maths involved the concept "shows promise" as they say.

For me though it seems quite obvious that on some human level we all inhabit different mental "universes". Religious people for example inhabit varyingly different universes to me and it seems like the more fundamentalist the viewpoint the further the distance and character between us. Nothing brings these differences into focus more than the ongoing battle between science and religion; take the recent technological triumph of the Mars curiosity rover, science blogger Flaye Flam received a letter from a reader of her blog complaining about the "wasted" money and effort involved in looking for non-terrestrial life when everyone apparently "just knows" that the Christian God created everything in a puff of dust in the garden of Eden 6000 years ago (I'm sure you can imagine the kind of thing). Clearly this person inhabits a different universe from the rest of us and I thought her response to him was really good (and polite!), I've reproduced it here to illustrate what I mean...

Hello. I’d like you to know your letter reached our universe with success. I’ve been particularly conscious of parallel universes in the last week since I started reading “Why the World Exists” by Jim Holt. This book blends physics and philosophy to explore the question of existence. There’s much discussion of parallel universes in which the constants of nature and perhaps the very laws are different from ours.

Do you have philosophy in your universe? Is your universe apparently expanding? Ours is accelerating. Isn’t that the weirdest thing? And we've just confirmed that our space is pervaded by a Higgs field which gives elementary particles mass. What kinds of particles do you have in your corner of the mutliverse?

I’m intrigued that in your universe evolution is “junk science”. That’s mind-bending for us here on Earth because natural selection is such an elegant process, it’s hard to conceive of a universe in which life would emerge and not be subject to it. How does it work out your way?

Your universe seems to have quite the negative attitude toward space exploration. Where does that come from? Do you have other planets in your solar system? Do you have solar systems? You must at least have Google translate, since you message reached me in English, though I think you might have a few glitches. Anyway, nice to hear from you. Keep in touch.