Leon Lederman, in The God Particle, has an interesting analogy, which he
uses to illustrate the process of detecting particles which we can never
directly perceive. He postulates some alien beings who are incapable of
seeing black-and-white colored objects, and who visit a football game on
earth (I refer to the real sport, not the american farce). One of the
younger visitors solves the aliens' confusion when he postulates the
existence of a small, invisible, spherical object (which conclusion he draws
after seeing the deformation at the back of the net).
Would you say that these aliens existed in an "other reality"?
On the other hand, if you are asking about a set of beings whose realm of
perceptions is entirely disjoint from our realm of perceptions, then I would
say that their natural laws would likely be radically different from ours.
I say this because, at their base, the most fundamental laws of nature are
really about the nature of our ability to perceive.
My writing skills being what they are, I must again resort to an analogy
created by one more capable than I. One of my favorite writers, Sir Arthur
Stanley Eddington, described the nature of the natural world using the
following analogy: A man walking on the beach comes upon an ichthyologist
who is in the process of an experiment. The scientist casts a net into the
ocean, drags it back to shore, then methodically catalogs his findings.
After some time, he pronounces, "I conclude that all sea creatures are at
least 4 inches long and have gills." The observer politely suggests that
the ichthyologist is a fool. "I could have told you those conclusions
before you started," he says. "You're using a net, so you'll only catch
fish that swim, and your net has 4-inch holes." Eddington's point is that
one can arrive at the laws of physics by either method. But whatever his
net can't catch is not part of the knowable universe, and he had no use for it.
By the way, I wonder if Lederman, being an accomplished experimentalist,
would agree with Eddington about the derivation of physical laws through
examining the nature of our perception? I believe Eddington spent the last
years of his life trying to derive the fundamental constants of nature from
thin air, based on our perception mechanisms, entirely independent of
measurement and experiment. In one of his books, he actually states the
number of particles in the universe.
I hope some of this gets at your question (there's so damn much of it, some
of it ought to). I'm sort of sensitive about the whole "alternate reality"
thing, so I hope I didn't sound too dismissive earlier. You raise an
important question.
Dan Henry