In a special edition entitled "A Matter of Time," the editors at Scientific American have produced over a dozen articles which explore time's many dimensions: from quantum physics to the technical and historical refinement of clocks. There is even an article ("Remembering When") which details the structures of the brain that collate our experiences into a single life of remembered events.
What emerges in this issue is a growing consensus among physicists and philosophers that time is a dimension laid out already in its entirety just like space. This consensus is called block time (also the B-theory of time, and tenseless time).
The theoretical basis of block time comes from Albert Einstein's special theory of relativity. This theory ”denies any absolute, universal significance to the present moment. Two events that occur at the same moment if observed from one reference frame may occur at different moments if viewed from another.” Objectivity dissolves into the perspective of each and every viewer. “Such mismatches make a mockery of any attempt to confer special status on the present moment, for whose "now" does that moment refer to?" Einstein called this the relativity of simultaneity, and it comes out of a founding principle of relativity called general covariance.
All general covariance says is that the laws of physics are the same for all observers.
Two observers will perceive spacetime to have two different shapes, corresponding to their views of who is moving and what forces are acting. Each shape is a smoothly warped version of the other, in the way that a coffee cup is a reshaped doughnut. General covariance says that the difference cannot be meaningful. Therefore, any two such shapes are physically equivalent.
Translated, this means that though time seems to change or flow, the overall shape of time itself does not, ergo block time. More important, it means that the flow from past to future which seems so natural to us is, in actuality, a completely subjective phenomenon. We observe the passage of time. It is phenomenological.
This is, of course, quite hard to understand when measured against everyday experience. We grow older, as do our children, and, hopefully, we grow wiser, too. The sun moves in the sky. Fruit left in the bowl rots. Our elders die. Given the ubiquity of such evidence, how can we understand the change we see around us? How can we question this ever-flowing conduit of “what was” to “what will be?” And what are the ramifications of doing so? Is a denial of time, a denial of the meaning we give and take from history and memory? Can hope survive without time? The questions pile up like seconds on a clock, and, according to Paul Davies, author and theoretical physicist at Macquarie University's Australian Center for Astrobiology in Sydney, “Modern science has barely begun to consider the question of how we perceive the passage of time."
Still, we must begin somewhere, and Scientific American begins with geography. Instead of measuring time as a continuous flow from one state or one position to the next, we could just as easily describe each change as a discrete point or stage. A vase shatters on the floor. We habitually focus on its physical motion, observing its descent from table to floor as a passage through time. But we could just as easily describe the various states of the vase without a reference to time. Here is the vase when it is a meter from the floor. Here it is only a few hundred centimeters. Lets have another example. Take a bunch of cards of a type and number we would normally call a deck. Each card is a slice of a larger block of time, which is the deck. Now this relationship, the deck, does not exist by necessity just because one card follows another. It is more accurate to describe each card independently. The deck is made by their adjacency, not by any sort of relationship they have to each other.
So, then, how do we account for change? As above, our normal way of going about things is incorrigibly tensed. By this I mean that we inhabit a "tensed" notion of time, a description which refers to grammatical tense--past, present, and future, which are themselves derived from our experience of time. And because of this, we treat the past and the future quite differently. Though we can observe the past, it is not available to us. We cannot expect it, or live into it. Only the future is available to us like that. We, and everything around us, goes into the future (at least from our point of view), and this unidirectional pointing of everything we call "the arrow of time." But is this wrong? Does block time mean we should erase this arrow from our thinking? No, it doesn’t
According to physicists, to embrace block time is not to deny the reality of the arrow of time. The arrow of time is real; there really is a unidirectional sequence of cards. "To deny that time flows is not to claim that the designations "past" and "future" are without physical basis. Events in the world undeniably form a unidirectional sequence.". That is why we do not experience the past. Time's block isn't uniform. The deck of cards--the geography of block time--is not symmetrical. It is asymmetrical. The arrow points in one and only one direction, but seeing the future doesn’t make it necessary that we are moving into the future. "Past" and "Future" should describe something more like geography than motion. "Time's asymmetry is a property of states of the world, not a property of time as such." This means that you can talk about change but not flow. Think, for example, of one of those giant, stone heads on Easter Island. Erected who knows how long ago, they stare forever in a single direction in which they will never go. Quoting again from Brian Davies:
We do not really observe the passage of time. What we actually observe is that later states of the world differ from earlier states that we still remember. The fact that we remember the past, rather than the future, is an observation not of the passage of time but of the asymmetry of time. Nothing other than a conscious observer registers the flow of time.
Physicists and philosophers of science are working to uncover explanations for our perception of time’s flow, and they have uncovered some contributors to the illusion. None the least of these is entropy.
The second law of thermodynamics, the rule that describes entropy, "plays a key role in imprinting on the world a conspicuous asymmetry between past and future directions along the time axis." Indeed, entropy bears directly on "the information content of a system. for this reason, the formation of memory is a unidirectional process--new memories add information and raise the entropy of the brain." This of course assumes a pattern to disorder. “The basic idea is that there are more ways for a system to be disordered than to be ordered. If the system is fairly ordered now, it will probably be more disordered a moment from now.” But why is this so? No one knows. Perhaps the big bang provides the low value of entropy needed to begin an ever-increasing cycle, but if that is the case, then the second law depends not on architectonic laws but on a historical event. A steady-state universe cannot explain entropy.
The brain, too, is a contributor. Kids are fond of spinning, whirling around and around, arms stretched out, until they are hopelessly dizzy. I used to do this for hours while I waited for my parents in our church's common-room basement. Laughing and stumbling, I would lurch about until the world continued to spin even when I stopped. Now I knew that the world wasn't really spinning. It only looked that way, a trick of the inner ear. "Perhaps," says Davies, "temporal flux is similar." Perhaps the perception of time’s flow is just a habit, to be described as David Hume did causation in his Enquiry?
If all of this holds true, the acceptance of block time would require some radical rethinking of a good many religious positions. That is certainly more work than I can do here. Some of the most serious questions asked above remained unanswered. For, as Gary Stix writes, "Recalling where we fit in the order of things determines who we are. So ultimately, it doesn't mater whether time, in cosmological terms, retains an underlying physical truth." Still, referring back to the aforementioned blogpost about the debate between Wood and Padgett, acceptance of a block theory of time means that Wood’s theory of God’s relative timelessness, in which God both transcends time and is temporal in some sense, can work as long as God’s timeliness is understood as an insertion from without into discrete points rather than as a catching up of the divine substance into an irresistible and entropic flow. Wood claims, by the way, that his view is simply a restatement of Boethius--a point worthy of further investigation. And I wonder, too, if this doesn't resurrect the old arguments around occasionalism.
And then, finally, a caveat. As best I can tell, though block time does represent a consensus, it does not approach the status of law. The problem is that block time presupposes the correctness of turning the general theory of relativity into quantum theory, a procedure called canonical quantization. “The procedure worked brilliantly when applied to the theory of electromagnetism,” writes Musser, “but in the case of relativity, it produces an equation—the Wheller-DeWitt equation—without a time variable. Taken literally, the equation indicates that the universe should be frozen in time, never changing.”
Musser goes on to describe how a single question works with canonical quantization to produce absolutely disparate effects. If one believes that space-time exists independently of stars and galaxies—that it is whether or not matter is present—then one is a substantivalist. Or if one believes that space-time is merely a description of how material objects are related, one is a relationist. In the former case, general relativity becomes indeterministic, describing a world which contains a certain amount of randomness. In the latter, the theory becomes deterministic. It is a dilemma which leads physicists to very different understandings of quantum gravity, and suggests that the jury is still far from unanimous when it comes to block time.
1. Paul Davies, “That Mysterious Flow,” Scientific American 16.1 (2006): 8. "The distinction between space and time underpins the key notion of causality, stopping cause and effect from being hopelessly jumbled. On the other hand, many physicists believe that on the very smallest scale of size and duration, space and time might lose their seperate identities."
2. Lee Smolin, “Atoms of Space and Time,” Scientific American 16.1 (2006): 82-92.
3. Davies, 7.
5. George Musser, "A Hole At The Heart Of Physics," Scientific American 16.1 (2006): 12.
6. Davies, ll.
7. Ibid., 8.
8. Ibid., 9.
10. Ibid., 11.
11. Musser, 13.
12. Davies, 11.
13. Gary Stix, "Real Time," Scientific American 16.1 (2006): 5.
14. Musser, 12.
15. Ibid., 13.
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time; Paul Davies; arrow of time; Albert Einstein; relativity; cosmology; physics.