comments on Scientific American article
This is the level of "parallel universes". They are parallel because they exist in the same overall space as us but haven't come into view yet. For instance, a section of the universe 10100 light years away right now would be a parallel universe. It exists parallel to us but we can't see it ... too far away ... light hasn't reached us yet ... and perhaps may never reach us due to the rate that the universe expands. Hence, it is "another universe".
These universes are of the baby bubble type created when space stretches. They are infinite spaces within our infinite space ... or something like Hawking's baby universes? (This is supposedly the domain of the P(pea)-branes ;o)
This is the quantum "many worlds" hypothesis. Here, every time a "choice" is made ... the universe branches into multiple other universes in which all possibilities are played out.
A level 1 and 3 disagreement:
from EBTX -
I don't believe this is true. The "set A" we are currently experiencing may disallow a conceivable "set B". Hence, that branch would be contradictory. State A must go to state B by causal mechanisms for all events at the humanly observable level. This should rule out most (or perhaps all) other possibilities. Thus, I am saying that ... given the "set A" of the Earth in 1945 ... the conceivable event (set B) - Hitler Wins WWII - is a contradictory result. There may be many initial sets "A" (the initial universe) which result in a Hitler loss (set "B") following a 1945 which is substantially the same as what we actually experienced.
Also, though there may be a finite number of quantum states for a given volume of universe to be in (this too is debatable) ... some strings of events are absolutely incompatible. Thus, not everything conceivable can occur. If we allow that any "set B" may occur, we are left with the cubic planet anomaly (wherein there must be a finite probability that a planet size body will form up as a cube and remain that way in defiance of gravity) ... and ... the mass suicide anomaly (wherein there must be a finite probability that an entire planet's population commits suicide simultaneously for no reason) ... or how about a cubic planet on which everyone commits suicide?.
This is what Aristotle referred to as "babbling" in Sophistical Refutations (one of my all time favorite comedic documents). More accurately it is an inability to see determinism when one has fully focused on inderterminism as the sole driving mechanism of existence. Even though seemingly contradictory, both are present.
At this level ... anything goes.
A level 4 disagreement:
This is the explicit statement that physicists believe there exists a one to one correspondence between reality and mathematics. Hence, they need only find an equation derived from anywhere then imagine a physical situation that might correspond to it ... and ... that's enough ... discovery by fishing exclusively in mathematical waters.
My own view here is that this is a complete impossibility. Because the universe is the manifestation of the only logic there is, there can be only one universe. What we see is not the subject of logic. It is the thing itself. Hence, we may not take parts of it and make a viable universe. All of it goes at once ... and ... what you see is the result.
At the end of the article ... a laugher:
"But an entire ensemble is often much simpler than one of its members ...
In this sense, the higher-level multiverses are simpler. Going from our universe to the Level I multiverse eliminates the need to specify initial conditions, |much simpler!| upgrading to Level II eliminates the need to specify physical constants, |simpler yet!| and the Level IV multiverse eliminates the need to specify anything at all." |Hey,. I'll buy that for a dollar!| - Tegmark (sciam 05/2003)
I'll go ya' one better, Max. No further need for science ...
That's even simpler by your criteria ... ;o)