The cartoon I included to start off this post comes from "The Universes of Max Tegmark" and has the purpose here of illustrating the "Many Worlds Interpretation" of quantum mechanics, or MWI. It shows that because of a single decision, in one universe a couple is married with two stick-figure kids, while on the other they live on opposite sides of the globe.
In short, like the cartoon, MWI says some of the weird things found in quantum mechanics like an electron interfering with itself (apparently by being in multiple different places at the same time) happen because there are multiple worlds, multiple universes, laid on top of one another accounting for an electron or other quantum appearing to be in multiple places at once. Once something happens that forces a decision (like a measurement), then all the possibilities remain true--but do so by universes splitting off in different directions.
We then live in a universe where only one possibility took place--all the other possible locations of the electron (or other quantum) happened in other universes. (Note I summarized MWI in some detail in a previous blog post and also am including a link to a Wikipedia article on MWI for people who want to read more.)
In MWI, which I don't in fact hold to (where does the energy come from to make the new worlds?), every single decision at the human level creates a new universe. But far below the human level, every single quantum makes a new universe any time it is forced to be in just one place, which may happen billions of times or more within a single second in our vast universe (or multiverse). By this view, the number of universes is not only mind-mindbogglingly huge, it's increasing continually at an immense rate. Because for every possible decision or split, ALL become true in some new universe out there somewhere, each new universe in turn generating a whole spew of new universes continually.
But what if a MWI hypothesis functioned differently? What if in some space we can't observe by ordinary means, the two universes based on the decision made by the couple in the cartoon above--the one in which they marry and the one in which they don't--already existed even before they met one another? This would allow multiple universes to be centered on one another to account for the weird interference patterns in quantum mechanics just as well as standard MWI would do. But instead of splitting off, each time a decision was made one or more of the potential universes disappeared, like soap bubbles popped by a needle.
So the number of universes would drop continually, becoming less and less, fewer and fewer. Finally, at the end of time (whatever "end of time" means), there would be just ONE universe left.
By the way, friends of mine who read my Facebook page will notice I said several months ago that I think about quantum mechanics on a regular basis and my mind tries to solve the strange explanations it engenders--even though I don't at all have the proper mathematical or scientific background to do this kind of work. I also mentioned I'd thought of a "solution" to quantum mechanics without saying what it was--yes, this is one possibility I was thinking about (I've thought about two, but the second isn't ready to talk about yet). Instead of just holding onto my idea (I have no reasonable means to write a scientific or technical paper about my notion), I'm floating it as a backdrop for science fiction stories.
Before talking about story implications, let me geek out about some of the science implications first:
1. Reducing Many Worlds Interpretation (we'll call this "RMWI") would parallel thermodynamics. In fact, the universe starting at a high state of thermodynamic order and going downhill towards entropy would match very well a universe beginning with an enormously huge but finite number of possible outcomes existing in some overlapping system. Just as the Second Law of Thermodynamics would pull the universe into a greater and greater state of disorder (entropy) as time went on, so would the number of possible choices and also possible universes would become fewer and fewer. At total entropy, of course no more choices would be possible--there would be only one universe left.
2. RMWI would embrace the "arrow of time," which many physicists wonder about. The past would be definitely different from the future and our motion towards the future would reflect potentialities being closed off, fewer and fewer sum total options in the multiverse as a whole as time advances.
3. RMWI would explain where all the other universes came from better than MWI--they originated in the beginning, in whatever process developed the universe or multiverse to start out. Losing them as time goes on seems less of a violation of the Conservation of Matter and Energy laws than gaining new universes as time goes by.
4. RMWI would parallel the "blockworld" model without being strictly deterministic. The blockworld--or better said, "The Relational Blockworld Interpretation of Non-relativistic Quantum Mechanics" (RBW) is an idea floated by physicists in recent times that holds all points and all events in the universe, past, present, and future, all exist somewhere in the space time continuum right now--because time is seen as just another dimension, like space, as per Relativity. This view winds up saying the entire universe is in effect already planned, every action flowing invariably from previous actions, already existing in space-time. RMWI would agree the universe was already planned and we cannot go outside of any parameter not already at the existence of the universe (or multiverse) at the beginning. However, all choices, from quantum to human "choices," really would matter because each one would alter the nature of the multiverse, driving it one step closer to it eventually existing as a true universe--when only one possibility remained.
5. RBWI would imply but not prove the existence of God. If the universe really started with every possible option existing right from the beginning, wouldn't that imply an all-knowing Creator who put such order into universe from the beginning? Yes--but the universe beginning at a high degree of order (that is, very low entropy) already implies that and some scientists seem to have no trouble thinking of the low entropy at the beginning of the universe as strictly natural. No doubt they could come up with a naturalistic explanation for a multiverse of all possible choices at the beginning of time as well.
6. RBWI would parallel some aspects of human life. We could imagine a human baby having a vast array of possible selves superimposed on that one child. As the child grows older, some of those possible choices go away (such as dying as an infant somehow). As the person gets to be an adult, he or she experiences a great deal of options--but as each choice is made, all the other possible choices we can imagine could have happened evaporate. As a person gets older, the number of choices become fewer and fewer. You won't be living that dream to go to medical school at age seventy--that choice has evaporated. Finally, all possible choices come to an end as the human being passes from Earth via bodily death (or so it would seem).
So, how would this affect science fiction story ideas?
1. There would be parallel universes, but not as many.
Since the MWI has the number of universes increasing indefinitely, as far as we know for all eternity forward, it allows for all kinds of alternate realities. RMWI would be somewhat more tame, especially in the future. But note that imagining RMWI were true would still allow stories where a person could cross from one parallel universe into another, just like MWI.
2. The past would have more universe possibilities than the present or future. In fact, it might be fun to imagine gong in past would automatically put someone in a potential past that could have been different from the one that led to our present--but at the same time going forward in time from there would still only lead you back to the time you started from. That may not entirely make sense, but it could be an interesting plot device. Also it would be interesting to have characters enter a story believing in MWI, but as they travel backwards and forwards in time, they discover that what they believed to be true was wrong--the future has fewer possible choices, not more.
3. Stories could still make changing the past either possible or impossible, as already happens in science fiction, but all changes would be from a "menu" of pre-existing possibilities. No one would be able to change the future into a version that hadn't already been allowed for in the past. The number of possibilities could be immense, but would be finite. And would be fewer in the future than the past.
4. Whether or not changing the past is possible, the universe would be both deterministic and allow for free will. The universe would come to a certain, natural end (total entropy), barring Divine Intervention (but a universe coming to an end via Divine Intervention would also come to a single certain end). But many free choices, as in eliminating things that are not going to happen, would take place along the way to the end.
Other story implications of this explanation for quantum mechanics my brain cooked up probably exist. What would you say about how this idea like this could be used in a story?
I'd love it if you'd share your own thoughts in the comments below. :)