Hello and good morning.

It’s Thursday again, if you can believe it.  It feels like it was just seven or eight days ago that it was Thursday last time, and here it is again.  I don’t know how this keeps happening.  Weirdly enough, though, from within, this week has felt as though it’s moving very slowly, and yet, it also feels as though Thursday has come again sooner than I expected.

The mind’s time sense is clearly not entirely objective and consistent.  Then again, why would it be?  Extremely precise long-term time-keeping would not have been a particular evolutionary advantage in the ancestral environment, certainly not one worth the inescapable biological (metabolic) cost of maintaining such a thing.

In any case, now we have incredibly precise time-keeping mechanisms which rely on some fundamental and consistent physical laws.  And though time does pass (so to speak) at different rates depending upon one’s relative velocity and the local curvature of spacetime (i.e., gravity), thanks to Einstein, we know how to adjust our disparate measurements of time with enough precision that we can maintain contact with a bunch of satellites in orbit, and they with each other, and use them to “triangulate” our precise position on the surface of the Earth to within a few meters (there’s generally more than one such triangle, thus the scare quotes—there is probably something more like a tetrahedron).

Of course, we don’t quite know completely just what time is, or at least, we don’t know for sure whether it’s fundamental or emergent from a deeper underlying set of physical laws.  We do know, based on General Relativity alone, that time would be in many ways “an illusion”, because simultaneity is not a consistent thing, and what counts as “now” relative to you depends very much on the direction and speed of your travel compared to other people.

From that point of view, all of spacetime in a sense “already” exists, and our experience of change is an illusion produced by the fact that we are within the block of spacetime.  Like characters and events in a movie on a DVD (or in any other stored medium) the events of the future are already laid out for us, and the end of the movie is as real and as permanent as the beginning, even when we watch the movie for the first time and don’t know what’s going to happen.

I think I talked a bit about this phenomenon in a post on Iterations of Zero called “Playing with spacetime blocks”.  If you want a better introduction to the ideas than anything I could give you, Brian Greene described it really nicely in either The Fabric of the Cosmos or The Hidden Reality.  I’m sorry that I don’t recall for certain which of the two books it is, but they’re both really great and are well worth your time.

Now, as it often does, quantum mechanics puts a bit of an onion in the ointment of fixed 4-D spacetime blocks, and the questions it raises depend—or so it seems to me—on which “interpretation” of quantum mechanics one applies.  In the standard version(s), in which there is such a thing as the collapse of the wavefunction when a quantum interaction occurs that leads to decoherence, there is a fundamental unpredictability to the outcome of such interactions when “measured”.

But if the permanence of spacetime as a whole that appears to be implied by General Relativity is correct, even those seemingly unpredictable events, countless numbers of which happen every second of every day in Dorset alone, are actually fixed and unchangeable.  This implies a mechanism of sorts for “superdeterminism”, or so it seems to me.

Of course, the Everettian “many worlds” version of quantum mechanics—which doesn’t require a deus ex machina wavefunction “collapse” that has to be added “by hand” to the calculations—seems to imply that, if spacetime is fixed in the GR sense then the state of being so fixed includes a fixed set of every outcome of every quantum interaction that would lead to so-called branching of the wavefunction of the universe.  That can be put into the works of GR, and it would give spacetime an added dimensionality of sorts—the dimension in which those “branched” paths exist.

But it would leave in the reality that we ourselves could not say which future “we” would experience, because every possible one actually happens; we just experience one at a time, so to speak*.  It would still be deterministic, just not as a “local” experience for those within spacetime.  Reality would be more like a “choose your own adventure” story than a fixed, scripted movie, but as with those books, all outcomes of any path are still fixed ahead of time.

I think I’ve rehashed a lot of the stuff I discussed in that blog post from IoZ, though I haven’t the will and patience right now to go check.  The specifics of my take on things are probably different this time; certainly, I think I understand all of the pertinent subject matter better than I did when I wrote about it before.  So, hopefully, this has given you at least something new.

Whatever the case, I cannot have done any differently than I have—unless I cannot help but do every possible different thing, but each branch of me, being a branch, only experiences its subset of the universe.  Even if, in a sense, you go both left and right at every metaphorical turn, you still only experience one direction.  It’s just that there is more than one of you, in a sense, experiencing each direction itself but unable to experience the other(s).

It’s really wild and cool stuff, isn’t it?  Science is amazing and awesome and fun.  Thomas Dolby sang that She Blinded Me With Science, but it’s really a way of removing blinders, of wiping the lenses of one’s glasses (and eyes) and focusing more precisely and rigorously on what’s really there, i.e., what’s happening whether anyone believes it or is there to experience it or not.

That’s probably enough for now.  I hope every possible version of you—even if there is only one—has a wonderful day today.

TTFN

*Please don’t make the mistake of thinking that it is human (or other creatures’) choices that determine the branching points of Everettian many-worlds, as seems to be implied by the movie Sliding Doors among other things.  It is quantum interactions resulting in decoherence that lead to the “splitting” of the wavefunction, and they are rarely the result of human choices, at least outside of places where experimental physics is done.