If you want your fluffy mind expanding, I cannot do better than recommend a reading of Mr Andrew Hickey's HYPERDRIVE. (Jump point here.)
It is a rocket-propelled ramble though the myriad malarkeys of INFINITE UNIVERSES, as explored in "What If", "Unbound, "cross-over" and "crisis" storylines or, for a laugh, in REALITY (at least if you are a Many-Worlder in Quantum Theory): you could call it Quantum Comic Dynamics.
Not only is it interesting stuff in and of itself, but it is expressed with such a sense of joy and wonder at the possibilities for playing in the infinite garden.
What is ESPECIALLY interesting is that Daddy Richard agrees with every word while simultaneously taking the opposite view about Quantum Mechanics.
(And you have no idea just how many SMARTIES Mr Andrew earns for having an angle on Quantum Mechanics that is… well "right" is always difficult in these circumstances so we'll have to settle on "is in agreement with Daddy Richard's understanding" instead.)
Daddy Richard comes down quite firmly on the Copenhagen Interpretation side of the Quantum Mechanical fence. (That's a fence made with REALLY SMALL hammer and nails.)
This is that whole business with Schrodinger's Cat Monster. You have a Cat Monster, you lock it in a BOX. Quite right too*. Then you have some LETHAL DEATH-TRAP wired up to a detector that will go "ping" (hack, slice, squish) if it detects some quantum effect, like the decay of a radioactive atom or the passing of a photon or something.
Now if you actually LOOK in the box, then you can SEE whether the Cat Monster is alive or deaded. This is called collapsing the wave-function. Or spoiling the surprise.
But so long as you DON'T look in the box, then the Cat Monster is BOTH alive AND deaded at the same time. This is a GOOD way of saving on Cat Monster food!
In the "Many Worlds interpretation", where Mr Andrew makes his revels, what this means is that there are an infinite number of UNIVERSES and in some universes the Cat Monster is alive, and some it is deaded. Which "flavour" of universe you are in depends on whether or not the detector has gone "ping", so you can work out the PROBABILITIES of being in one sort of universe of the other.
However, Daddy Richard thinks that there is only ONE universe and it is FAR MORE WEIRD than that!
In his world view, the Cat Monster is alive and deaded AT THE SAME TIME, it has a certain amount of "aliveness" depending on the probability of "ping" and in turn this determines how likely you are to need Cat Monster food on your shopping list.
And, here is the INSANELY wacky part: you don't actually need the BOX.
Even if you observe the Cat Monster as dead, it will STILL have some aliveness and still, very slightly, be interacting with you.
(In more prosaic terms, this is how wave-particle duality works: even if you determine the path of one photon, it still behaves as though it is affected by the other paths that it might have taken even though you know it didn't!)
It's sort of like we're all stacks of tracing paper with different alternatives drawn on. We can only SEE one sheet of paper at a time, but the INFLUENCE we have on the world around us depends on the picture that you make up from ALL of the sheets at once.
The universe then is kind of a "cloud" of events that are sort of smeared out and indeterminate, a sort of Impressionist or Pointillism universe where you can see the bigger picture but the details get away from you the closer you look.
However, the magic of it is that, as far as we can tell, that's not actually inconsistent with the Many Worlds interpretation.
Actually, "Many Worlds" rather UNDER-DESCRIBES the full scale of the theory. It is actually the "INFINITELY Many Worlds" interpretation, the "every possible outcome and every possible alternative to that outcome" theory. Every possible universe is "real": the one where Rome never fell, the one where Hitler won the war, the one where JFK didn't get shot, and the one without shrimp.
But almost all these "Many Worlds" stories are actually contained within the idea of FINITE parallel universes, all the alternatives which are LIKE ours but have some crucial difference in order to make the story INTERESTING (or at least hopefully so) in the light of the pre-existing stories that we know.
Multiple – but finite – parallel universes Daddy can cope with: they are quantum clouds similar, possibly even IDENTICAL to ours, but where you take different OBSERVATIONS and so see a different slice through the superposition states. Schrodinger's Cat Monster is alive again.
But the full implication of INFINITE parallel worlds and all possible outcomes being true can be rather CRUSHING.
In a universe, or rather multi-verse of all-possible outcomes, free will does not, cannot exist. Any choice that you think you might have made, you have – BY DEFINITION – also made the alternative. So free will is an ILLUSION. Your experience, your soul if you like, is just along for the ride along one particular string through the infinite tapestry.
However, we (Daddy and me) believe that free will DOES exist. (Though if we are wrong about that it makes no difference because all our actions, including believing we have free will, are all pre-determined anyway!)
We believe quite strongly that we ARE responsible for our actions and that we should consider their CONSEQUENCES.
Here, Daddy is very strongly influenced by a book called "Time Slip". In it, the lead character has a very narrow and highly unlikely escape from DEATH, and comes to the conclusion that this was because of Quantum Mechanics. Basically, because Quantum effects SEEM to depend on OBSERVATION, then you cannot have a point where you STOP observing: i.e. every single conscious observer is IMMORTAL… if only in their OWN private slice of the multi-verse. That is, if someone appears to have died to YOUR observation, there is an alternative universe somewhere, an "elsewhen", where that person survived, and that is where their consciousness persists. In the book, this theory catches on, indeed it becomes a RELIGION. But this has terrible consequences because everyone ceases to CARE about, well, consequences. The most blatant example is the conclusion where our central character sees a child DROWNING… and NO ONE is going to help! Why not? Because in "elsewhen" the child will be saved, so why bother. It's not often you get a children's book critiquing the heights of modern physics; it leaves Harry Potter looking a little thin, anyway (and we love Harry Potter).
Essentially, we think that consciousness MATTERS, that in some way we really ARE capable of influencing the Quantum Events, though in ways infinitely more complicated than just "observation collapses wavefunctions".
On the other fluffy foot, that should not mean that we cannot consider a version of the universe where infinite possibilities DO exist. In fact we do this all the time and it is called FICTION.
Now, in the SPECIAL CASE of stories about TIME TRAVEL (and specifically we're talking Doctor Who stories here) the impact of the Many Worlds theory is that if you travel in TIME, of necessity you always arrive in an alternative universe. Shall I do the complicated maths or just wave my fluffy feet? I think I shall wave my fluffy feet! Basically, this is to prevent "closed timelike curves" or, more bluntly, prevent Grandfather Paradoxes by the simple expedient of making it ALWAYS be somebody ELSE'S Grandfather.
What this would mean in Doctor Who (and in fact most time travel stories) is that, Dr Woo could travel back in time and save the Earth from the Sontarans ("The Time Warrior") or the Haemovores ("The Curse of Fenric") or the Carrionites ("The Shakespeare Code") then return to the present day and find that they had won after all, because he only beat them in a "parallel" universe.
This NEVER happens.
In fact, the storytelling DEPENDS on the assumption that Dr Woo always arrives in the SAME universe (except when he explicitly doesn't – i.e. "Inferno" and "Rise of the Cybermen" with a passing reference to "Battlefield").
The Doctor refers to time being re-written like a snap of the fingers in "The Unquiet Dead", but "Pyramids of Mars" seems to spell this out most explicitly: best friend Sarah-Jane CANNOT run away from Mr Sutekh and comfortably return to her own time (and many-worlds theory universe) because it WILL NOT exist.
So, from the (somewhat selfish) point of view of wanting "Doctor Who" to be "true" (at least in the sense of being a fictional universe that COULD be ours if we all wished it hard enough) then Daddy would prefer the Copenhagen Interpretation because that is the answer that appears to be "true" in his favourite TV show.
And, at least in part, his aversion to parallel universes is informed by the horrible "we can't play nicely in the same sandpit" car-crash of continuity that Doctor Who became during the Nineteen-Nineties, with New Adventures and Eighth Doctor Adventures and Big Finish Adventures and comic strips all going yah-boo-sucks to one another at various times, and Mr Lawrence Miles creating universes-inside-bottles inside universes-inside-bottles to explain (and hierarchy) everything, which at least was entertaining compared to the sheer banality of Mr Gary Russell's "it's the multiverse blah-blah-blah" approach. And then "foom". Getting rid of all continuity in such a fashion that ONLY continuity-obsessives retain any ability to follow this series about the grumpy amnesiac is enough to make ANYONE cry "enough!"
But Daddy has a bigger (and possibly even more wrong) objection in general: if you are reading a STORY then the outcome is IMPORTANT to you, but all the alternatives where the hero doesn't save the day and get her guy, they all happen too. This means that the story is less about the qualities of the hero, her skill, bravery, fortitude, intelligence, diligence or luck, and more about the choice of some omnipotent force (called "the writer") to give us this particular viewpoint universe.
To flip that over again, though, it is obviously all but IMPOSSIBLE to get away from the choices of the writer when reading or watching ANY fiction. It's one of the great POWERS of storytelling that we DO automatically accept this omnipotent force without question (usually without even NOTICING). In fiction, things like "prophecy" can really work, because the writer KNOWS when he includes the prophecy which bits will actually work out. This bleeds through to our understanding of the REAL world, making us think that things from fiction ought to work in reality too. And maybe kicking against the acceptance of an omnipotent "author" in the "real world" leads Daddy to kick against the "Many Worlds" theory too.
Consider instead that we easily accept that the "World" presented to us in stories is not exactly the same "World" as the one we actually live in – especially, though not limited to, stories with a fantastical element like a superhero or an alien invasion or real working magic wands (and Doctor Who does all of these).
So in many ways, the "Many Worlds" interpretation has a very natural "fit" with fictional universes: we are already accepting a "parallel" universe when we "buy in" to the fictional world (whether it is the one with Superman or Spider-Man or Dr Woo or Sherlock and Watters or Duke Prospero or Cathy and Heathcliff or the version of Henry Tulip who appears in "The Tudors" – not the REAL one from "Blackadder").
Then the idea of multiple parallels, worlds parallel to the parallel we are reading, nested parallels all become quite small steps away: Mr Shakespeare did the play-within-a-play thing in Piglet; Star Trek do the play-within-a-play-within-a-play thing when they perform Piglet in "The Conscience of the King". (And let's just not even get into performing Shakespeare in the original Klingon!)
Whether or not it's the way the ACTUAL universe works, there's a good case for saying that it IS the way the universe of all fiction works.
So, Daddy Richard likes to think of a universe that is "weirder and wilder" while Mr Andrew enjoys the opportunities of a "wider playground without borders or constraints". Who is RIGHT?
Well, in a WEIRD and, dare I say it, QUANTUM way, they both are.
After all, the POINT of Quantum Mechanics is that things usually AREN'T one thing or another, but BOTH. SIMULTANEOUSLY.
This diary was inspired by and is in no way a disagreement with the works of Mr Andrew Hickey, and by the letters א and Ω the number ∞.
*It should be noted that Millennium has been a bit Ailurophobic since seeing the episode of "Planet Earth" with the herd of elephants and the pride of hungry lions.