(CR) Time and Homogeneity

Here are some recent comments on time posted to the Karl Jaspers Forum:

HOMOGENEITY AND CONTINUITY OF TIME
by V. Raman, Ph.D. (Physics)
and Steven M. Rosen, Ph.D. (Psychology)
17 February 2008, posted 23 February 2008
<1>
"As far as their quality is concerned, temporal instants are perfectly equivalent."
MILIC CAPEK

<2>
As with space, an important characteristic of time is its homogeneity. This simply means that all along its ceaseless flow the entity we call time is uniformly the same. There is no difference, qua time, between an hour or an instant some eons ago and the same in our temporal locality. Using an analogy, time is like an interminable line, any sector of which is identical in its essential nature to any other.
<3>
Time is like a smooth and flawless highway that is being continuously created which in essence and rate of formation is the same at every inch or mile of the path, though a host of different entities may be seen all along it. Every instant of time has another whence it emerged, and yet another into which it merges.
<4>
This implies that there was no beginning, nor will there be an end to time, for terminal points are, by definition, different from all others in being without a predecessor or successor. Even in the theological framework in which the universe had a moment of creation, that was a significant point in time, rather than the starting point of time. God, the everlasting, is said to exist in Time, without beginning or end: anâdi and ananta.
<5>
Recall that space has local inhomogeneity: that us to say, there are regions in the vast expanse with clumps of matter, somewhat like a large blank sheet of paper with dots here and there, which affects its curvature. But this is not the case with physical time. Time moves on and on, indifferent to the events on its course. It neither slows down nor speeds up by whatever happens in it. However, psychological time is experientially non-homogeneous, some durations appearing to be denser (longer) than others.
<6>
The homogeneity of time simply means that the laws of nature are the same today as they were yesterday or ten billion or more years ago, and will be the same tomorrow and ten billion or more years from now. A related fact is that the laws of physics are time-invariant. The universe has been functioning this way because the laws governing it have remained the same all through its existence. If the laws changed with time, this would be a very whimsical and unmanageable world.
<7>
One important consequence of time-invariance - as has been established by the conceptual analysis of physics - is what is known as the law of conservation of energy. In other words, that the total amount of energy in the universe remains unaltered is intrinsically related to the fact that time is homogenous. It is this sort of underlying and by no means obvious features of the world that theoretical physics unveils now and again.
<8>
Like the spatial line again, time cannot be broken down to some ultimate indivisible unit. Take a line drawn on a sheet. No matter how small a bit on it you imagine, it can always be split into smaller ones. That's what constitutes its continuity. Time is like that. We speak of instants but they merge into neighboring instants in a smooth and inseparable continuity. That's why we have the image of time flowing, rather than dropping like a series of pebbles. However, it is important not to take the analogy between space points on a line and time-instants too far: such identification has led to some paradoxes in the history of human thought.
<9>
Some theoretical physicists have toyed with the notion of a fundamental indivisible time interval, dubbing it the chronon. Aside from a few neat mathematical formulations, the idea of the chronon, once held by the Stoic Chrysuppius, has not led to any significant insight or verifiable result of consequence.

V. V. Raman
February 8, 2008
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From Steven M. Rosen, Ph.D. (Psychology)
<10>
Comments on "Homogeneity and Continuity of Time"
by V. V. Raman
I want to thank Professor Raman for bringing out some important conceptual issues spanning the topics of time, physics, and spatial continuity. For my part, I would like to offer a different perspective on these matters. Prof. Raman asserts that physical time is much like space in its homogeneity, continuity, and changelessness. To me this seems at odds with the basic thrust of contemporary physics and philosophy.
<11>
Prof. Raman begins by quoting Milic Capek on the homogeneity of time: "As far as their quality is concerned, temporal instants are perfectly equivalent." This supports Raman's conclusion that, "As with space, an important characteristic of time is its homogeneity." Raman doesn't give the source of the Capek quote. Perhaps it was taken from Capek's book, Philosophical Impact of Contemporary Physics, which starts with a description of the classical view of time and space. Reading beyond this introduction, we find that Capek was actually a strong opponent of the homogenization and spatialization of time. As Raman rightly implies, a homogeneous, spatialized time constitutes an infinitely divisible continuum. On this score, Capek asserts that "the concepts of spatial and temporal continuity are hardly adequate tools for dealing with the microphysical reality" (1961, p. 238).
<12>
Capek was not the only modern philosopher to call into question he classical idea of spatiotemporal continuity. Both process philosophy (e.g., Bergson and Whitehead) and phenomenological philosophy (e.g., Merleau-Ponty and Heidegger) offer telling critiques of the older thinking about space and time. As for the discipline of physics, theorist Lee Smolin notes in his recent book, The Trouble With Physics, that, when it comes to tackling the problems of force unification (quantum gravity) and cosmology, we can no longer afford to represent time "as if it were another dimension of space..We have to find a way to unfreeze time-to represent time without turning it into space" (2006, pp. 256-57). Even if we admit (as Prof. Raman does elsewhere in his writing) that space and time are different in important respects such as the symmetry of the former and asymmetry of the latter, viewing time as a changeless homogeneous continuum still spatializes it, thereby blocking the way to effectively addressing some of the most pressing problems currently confronting theoretical physics.
<13>
Evidently taking into account Einstein's general theory of relativity, Prof. Raman does acknowledge that space "has local inhomogeneity" associated with "clumps of matter" that "affect its curvature." But Raman goes on to say that "this is not the case with physical time. Time moves on and on, indifferent to the events on its course." In actuality, the curvature of general relativity applies not to space in simple isolation from time, but to spacetime. And when the mass density of a body in great enough, spacetime becomes inhomogeneous to the point of rupturing, losing its continuity, so that a "black hole" is created in which classical spacetime is nullified.
<14>
Prof. Raman next states:
The homogeneity of time simply means that the laws of nature are the same today as they were yesterday or ten billion or more years ago, and will be the same tomorrow and ten billion or more years from now. A related fact is that the laws of physics are time-invariant. The universe has been functioning this way because the laws governing it have remained the same all through its existence. If the laws changed with time, this would be a very whimsical and unmanageable world.
<15>
The foregoing classical account seems controverted by the last 100 years of research in theoretical physics and cosmology. The cosmological picture that began to crystallize in the 1960s is of a universe that is indeed dynamic, a place in which space, time, and the laws of nature themselves evolved out of an initial singularity that was spaceless, timeless, and lawless. Indispensable to modern cosmology is quantum mechanics, and this field of research is inherently based on a principle of singularity: a core uncertainty that physicists have been able to manage via probabilistic analysis-until the present period, that is. Now faced with the daunting challenge of providing an account of nature wherein quantum mechanical and gravitational forces are reconciled, the uncertainty becomes uncontainable, probabilistic analysis breaks down, and an impasse is reached, despite the valiant attempts of approaches like string theory to set things right.
<16>
The notion of a dynamic universe in which space and time themselves evolve is worked out in detail in my 2008 book, The Self-Evolving Cosmos (see http://www.worldscibooks.com/physics/6605.html). What seems clear to me in general is that the extraordinary phenomena of modern physics challenge the classical outlook to the extent of requiring a whole new way of thinking about the way nature works.
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REFERENCES
Capek, Milic. (1961) Philosophical Impact of Contemporary Physics. New York: Van Nostrand.
Rosen, Steven M. (2008) The Self-Evolving Cosmos: A Phenomenological Approach to Nature's Unity-In-Diversity (Series on Knots and Everything, Vol. 18). Hackensack, New Jersey: World Scientific Publishing.
Smolin, Lee. (2006) The Trouble With Physics. Boston: Houghton Mifflin.