|Frank Tipler uses "locality" to prove the Multiverse Model|
No model of quantum reality is more preposterous than the Quantum Multiverse proposed by Hugh Everett III in 1957. In this reality the quantum wavefunction, usually interpreted as the POSSIBILITY that something can happen, is construed as a CATALOG OF ACTUALITIES. In Hugh Everett's Multiverse EVERYTHING THAT CAN HAPPEN DOES HAPPEN but most of it happens in other universes than our own. As many universes exist as things that can happen, hence the term "Multiverse".
Berkeley physicist Henry Stapp has pointed out one important consequence of such an exuberant model of "what's really going on". If the Multiverse model is true then very improbable events, as long as their probability is not zero, MUST HAPPEN IN SOME UNIVERSE. For instance, the emergence of life may be extremely unlikely, but if life can happen, then life must happen, in a few exceptional universes.
Another line of speculation concerns "quantum immortality". The role of conscious beings in the Multiverse is ill-defined because we do not as yet possess a physical model of mind. But it is plausible to suppose that when the universe splits into various realities, your conscious mind inhabits only those realities in which it is still alive. This way of thinking predicts that you will enjoy, in your own subjective universe, if not immortality then certainly a greater-than-average life span. While you perceive your friends dying all around you, you seem to "miraculously" escape death until you have exhausted (like the cat with 9 lives) all your possible lives--and then at last you DEFINITIVELY DIE. Each of us can verify this hypothesis for ourselves but paradoxically we cannot share our conclusions with others.
Ironically all quantum realities, including the Multiverse, predict exactly the same quantum facts so there exists at present no experiment that could tell us for sure what is "really going on" beneath the quantum facts.
Recently Frank Tipler, a controversial physicist at Tulane University, has published a "proof" that the Multiverse is real. If we believe that Einstein's Theory of Relativity applies not just to the quantum facts, but also to "what's going on behind the facts", assets Tipler, then we must accept the truth of the Multiverse.
A profound theorem due to the late Irish physicist John Stewart Bell is generally thought to have proved that "reality is non-local"--which means that quantum reality, whatever it is, must operate at speeds faster than light. On the other hand the quantum facts, the things we can actually observe, seem always to obey Einstein's speed limit. This tension between quantum reality (faster-than-light) and quantum fact (light-speed-limited) has always seemed a peculiar feature of the post-Bell quantum world.
A curious loophole in Bell's Theorem, however, is that it cannot be proved in a multiverse reality.
Tipler cleverly exploits this loophole in Bell's Theorem by demonstrating that if one assumes not only the quantum facts but also quantum reality itself to be "local"--which means limited to light speed interactions--then Everett's Multiverse is the only possible candidate for a Real Quantum Reality.
If Reality obeys Relativity, then we really live in a quantum Multiverse. So sayeth Frank Tipler.
Most physicists will probably dismiss Tipler's argument as Meaningless Scholastic Metaphysics. But, on the other hand, he may be right. If we really live in a Multiverse, then everyone of us might look forward to experiencing quantum immortality--living "forever" each in our own special universe. Sounds kinda creepy to me.
The argument for quantum immortality (more properly called quantum longevity) is dubious because we are profoundly ignorant about how consciousness fits into the scheme of things, but Tipler's derivation of the truth of Multiverse if Relativity holds for Quantum Reality as well as Quantum Fact is as solid as these kinds of arguments can be.
Quantum immortality of the life-extending kind may not really exist. On the other hand, Frank Tipler may himself have achieved a small but conventional kind of quantum immortality via his clever locality-based proof in favor of the real existence of the Multiverse.