Playing with space-time blocks

According to General Relativity, our experience of space and time is a bit like seeing shadows in a higher-order, four-dimensional space-time.  This is probably not news to many of you; the basics of Relativity have become almost common knowledge, which is no doubt a good thing.  But many people may not realize that the tenets of General Relativity and Special Relativity, with their abolition of simultaneity or any privileged point of view in space-time also imply that the entire past, and the entire future, of every point in space and every moment in time, already or still exist, permanently.  I’m not going to get too much into the how’s of this—I refer you to, and heartily recommend, Brian Greene’s The Fabric of the Cosmos, which has an excellent explication of this notion.

The upshot of this principle is that, in a very real sense, our past is never gone, but is still there, just where it was when we lived it.  Similarly, the future is also already in existence (applying time-specific terms to such things is a little iffy, but we use the words we have I suppose, even though we must accept them as metaphors).  In this sense, a human life is not an isolated, ever-changing pattern in some greater, flowing stream so much as a pre-existing rope of pattern in a higher-dimensional block of space-time, like a vein of gold running through a fissure in a rock formation.  Its beginning is as permanent as its end.

We know that General Relativity cannot be absolutely and completely correct—its mathematics breaks down at singularities such as those in the center of black holes, for instance.  But within its bailiwick, it seems to be spectacularly accurate, so it’s not unreasonable to conclude that it’s accurate in the above description of a human life—indeed, of all events in the universe.

But what does this mean for us?  How does it impact the fact that we experience our lives as though the sands of the future are flowing through the narrow aperture of the present to fall into the receiving chamber of the past?  How does General Relativity interact with consciousness?  We seem to experience the present moment only as an epiphenomenon of the way fundamental principles translate themselves into chemistry and biology as measured along some fourth-dimensional axis.  We can’t decide to reel ourselves backward and reexperience the past, or fast-forward into the future, even though it seems that our existence has much in common with the permanently-encoded data on a digital video file.  We cannot choose to rewind or lives any more than can the characters within a movie we are watching.

Similarly, according to this implication of General Relativity, we could not, even in principle, have lived our past differently.  Were we to rewind and then replay events, they would work out exactly as they had before, just as a movie follows the same course no matter how many times you watch it.  The characters in a movie might learn later in the film that they had made some tragic error, yet when you rewind the show, they revert to their previous selves, ignorant of what they are always ignorant of at that point in time, subject to the same story arc, unable to change anything that they did before.  Likewise, it’s conceivable that, when our lives end—when we reach the point where our pattern decomposes, diffuses, and fades—we may go back to the start and reexperience life again from the beginning.  (This depends heavily on what the nature of consciousness is).  Indeed, we may be constantly reexperiencing it, infinitely many times.

Though this seems to be a kind of immortality, it’s not a particularly rewarding one, as we wouldn’t gain anything no matter how many times we replayed our lives.  For those of us with regrets it would be a mixed blessing, at best.  For those who have endured lives of terrible suffering, it seems almost too much to bear.  But, of course, reality isn’t optional.  It is what it is, and there is no complaint department.

Ah, but here’s the rub.  We know, as I said, that General Relativity cannot be quite right; crucially, it does not allow for the implications of the Uncertainty Principle, that apparently inescapable fact at the bedrock of Quantum Mechanics.  Quantum Mechanics is, if anything, even more strongly supported by experiment and observation than is General Relativity; I’m aware of no serious physicists who don’t think that General Relativity will have to be Quantized before it can ever be complete.

But of course, as the name implies, the Uncertainty Principle says that things are—at the fundamental level—uncertain.  How this comes about is the subject of much debate, with the two main views being the “interaction is everything, the wave-function just collapses and probabilities turn into actualities and there’s no point in asking how” that is the Copenhagen Interpretation, and the Many Worlds Interpretation, originated by Hugh Everett, in which, at every instance where more than one possible outcome of a quantum interaction exists, the universe splits into appropriately weighted numbers of alternate versions, in each of which some version of the possible outcomes occurs.  It’s hard to say which of these is right, of if both are wrong—though David Deutsch does a convincing job of describing how, among other things, quantum interference and superposition implies the many-worlds hypothesis (see his books The Fabric of Reality and The Beginning of Infinity).

But what does the Everettian picture imply for our higher-dimensional block space-time that is at once all of space and time, already and permanently existing?  Are there separate, divergent blocks for every possible quantum divergence?  Or does the space-time block just have a much higher dimensionality that merely four, instantiating not just one but every possible form of space-time at once?

If this is the case, why do we conscious beings each seem to experience only one path through space-time?  Countless quantum events are happening within and around us, with every passing Planck Time (about 10-43 seconds).  The vast majority of these events wouldn’t make any noticeable difference to our experiences of our lives, but a small minority of them would.

This is the new thought that occurred to me today.  It’s thoroughly and entirely speculative, and I make no claims about its veracity, but it’s interesting.  What if, whenever we die, we start over again, as if running the DVD of our lives from the beginning yet again, but with this important difference:  Each time it’s rerun, we follow a different course among the functionally limitless possible paths that split off at each quantum event?  Even though most of these alterations would surely lead to lives indistinguishable one from another, everything that is possible in such a multiverse is, somewhere (so to speak) instantiated.  Reversion to the mean being what it is, this notion would be hopeful for those who have suffered terribly in a given life, but rather worrisome for those who’ve had lives of exceptional happiness.  At the very least, it implies that there would be no sense in which a person is trapped in the inevitable outcome of a given life.  You can’t decide to behave differently next time around, but you can at least hope that you might (while reminding yourself that you may do even worse).

Of course, all this is beyond even science fiction—well, the earlier parts aren’t, just the notions of a person’s consciousness reexperiencing life, either the same or different, over again.  But it was and is an interesting thought to have on a lazy, early Sunday afternoon in the spring of the year, and I thought I would share it with you.

What is it with gravitons and black holes?

I occasionally wonder about what physicist really think regarding the hypothetical particles, gravitons, those carriers of the gravitational force mandated by the need* to quantize all the forces of nature.  Specifically, I wonder how they behave in and around black holes.

I know, from my understanding of General Relativity, that the influence of gravity travels at the speed of light, and the recent LIGO results, and all other experimental results of which I’ve heard, are consistent with that.  This must surely mean that the proposed gravitons travel at the speed of light, and are thus mass-less particles.  And if they are carrying a force, they must have some form of inherent energy, which means that, according to Einstein at least, their path would be affected by gravity.  This seems contradictory in some ways, but it’s my understanding that the electrical force produced by a moving electron also acts backward on itself, so I guess that’s not completely unreasonable…though here I’m veering further away from any deep knowledge, much to my sorrow.

My real question applies to the surface of an event horizon, that boundary in space-time within which all things are separated from the outside by the strength of the gravitational force – more particularly, according to Einstein, by the degree of curvature of space-time.  If gravitons are particles, carrying the gravitational force, are they constrained by the effects of the event horizon, or –  presumably because they wouldn’t be self-interacting – do they simply pass through it, it being irrelevant to their motion, unlike all other things with finite speeds…which means everything.  That sometimes seems contradictory to me, though by no means am I certain that I’m thinking correctly about this.  Could it be that the gravitons within and outside of an event horizon are two separate populations of gravitons, with the external ones somehow being generated at the horizon?  If not, then how can a particle ignore the degree of gravity, unless, of course, as a mentioned above, they are not self-interacting – which wouldn’t be unusual, since, if I understand correctly, photons also don’t interact with other photons.  But photons would, obviously, interact with gravitons, of course, otherwise they wouldn’t be effected by gravity, as we know they are…the most extreme example of this being at a black hole.

I know that a possible explanation for this might be found in M theory, in which we exist in a 3-brane that floats in a larger, higher-dimensional “bulk,” and that gravitons, unlike all the more “ordinary” particles are not constrained to remain within that brane, but can go above and below it, so to speak, thus bypassing any barrier that is exclusive to the brane.  But I don’t know if this really deals with the issue.

And, of course, how can the idea of gravity as a force, mediated by a quantum particle, be reconciled with the convincing and highly fruitful model of gravity as the consequence of the curvature of space-time?  Obviously, I don’t expect anyone to know the deep answer to this question, since it’s the biggest, most fundamental problem in modern physics:  our two best, most powerful theories of the world don’t work when brought together.  But if anyone out there has any idea of at least the form of such a possible reconciliation – i.e. do proponents of quantum gravity think that it will eliminate the notion of curved space-time, or do they think, somehow, that it will be an expression thereof – I would be delighted to hear from you.  My best reading to date on things like string theory hasn’t given me any real insight into the possible shape of such a unification.

Anyway, these are some of the thoughts that are troubling me this Monday morning.  I’d love to know any of your thoughts in response, or if you have any recommendations on further study materials, I would welcome those as well.


* due to the Uncertainty Principle, among other things.