Tag: physics

Emergence

Physics is the fundamental science in that it describes the workings of the universe at all scales.  No other science is so comprehensive.

Will our knowledge of physics finally lead us to a “Theory of Everything”?  Perhaps, but the Theory of Everything alone will not be able to describe, predict, or explain its full expression upon/within the universe—no more so than our musical notation system can explain how a Brahms symphony was composed, nor its effect upon the listener.

Reductionism states that the whole is the sum of its parts, but emergence states that the whole is more than the sum of its parts.

There are many examples of emergent properties in the natural world, what one might call radical novelty.  Some examples:  crystal structure (e.g. a salt crystal or a snowflake), ripples in a sand dune, clouds, life itself.  Social organization (e.g. a school of fish or a city), consciousness.

John Archibald Wheeler (1911-2008) created a diagram that nicely illustrates an emergent property of the universe that is important to us.

The universe viewed as a self-excited circuit. Starting simply (thin U at right), the universe grows in complexity with time (thick U at left), eventually giving rise to observer-participancy, which in turn imparts “tangible reality” to even the earliest days of the universe.

Richard Wolfson writes,

At some level of complexity, emergent properties become so interesting that, although we understand that they come from particles that are held together by the laws of physics, we can’t understand or appreciate them through physics alone.

I like to think of emergence as an expression of creativity. Our universe is inherently creative, just as we humans express ourselves creatively through music, art, literature, architecture, and in so many other ways.

Creativity is the most natural process in the universe. It’s in our DNA.

But DNA alone can’t explain it.

References

Richard Wolfson, The Great Courses, Course No. 1280, “Physics and Our Universe: How It All Works”, Lecture 1: “The Fundamental Science”, 2011.

“And the end of all our exploring will be to arrive where we started and know the place for the first time.” – T. S. Eliot

The Beginning

We continue our series of excerpts (and discussion) from the outstanding survey paper by George F. R. Ellis, Issues in the Philosophy of Cosmology.

Thesis D1: An initial singularity may or may not have occurred.
A start to the universe may have occurred a finite time ago, but a variety of alternatives are conceivable: eternal universes, or universes where time as we know it came into existence in one or another way.  We do not know which actually happened, although quantum gravity ideas suggest a singularity might be avoided.

If we imagine, for a moment, running the clock of the universe backwards to earlier and earlier times, its size gets smaller and its density gets larger until we reach a moment—even earlier than the putative inflationary era—when classical physics at the macroscopic level no longer applies and some (as yet unknown) quantum physics must apply to everything—even gravity.  Therein lies the problem, because if you run the clock backwards just 5.39 x 10-44 second from this time, you reach the purported moment of the Big Bang—the initial singularity.  But whoa (or perhaps woe)!  How can we say anything about the Big Bang—or even if it occurred at all—since the laws of known physics completely break down 5.39 x 10-44 second (the Planck time) after the Big Bang!  See the problem?

Perhaps the universe came into existence through a process analogous to radioactive decay where an alpha particle leaves a nucleus through quantum tunneling.  Perhaps our universe “tunneled” into existence from somewhere else, and thus our beginning isn’t really the beginning.  This is just one of many possibilities.

This is a key issue in terms of the nature of the universe: a space-time singularity is a dramatic affair, where the universe (space, time, matter) has a beginning and all of physics breaks down and so the ability to understand what happens on a scientific basis comes to an end. However eternal existence is also problematic, leading for instance to the idea of Poincaré’s eternal return: everything that ever happened will recur an infinite number of times in the future and has already occurred an infinite number of times in the past.  This is typical of the problems associated with the idea of infinity.  It is not clear in the end which is philosophically preferable: a singularity or eternal existence.  That decision will depend on what criteria of desirability one uses.

While infinity is a highly useful mathematical device, one can make a strong argument that infinities do not exist in the physical universe (or even multiverse).  Quantum physics already gives us a possible clue about the infinitely small: we appear not to be able to subdivide space or time any further than the Planck length (1.616 x 10-35 meter) or the Planck time (5.39 x 10-44 second).  We would not be able to distinguish between two points less than a Planck length apart, nor two moments in time less than a Planck time apart.  While harder to envision, might not there also be an upper limit to size?  And time?

Thesis D2: Testable physics cannot explain the initial state and hence specific nature of the universe.
A choice between different contingent possibilities has somehow occurred; the fundamental issue is what underlies this choice.  Why does the universe have one specific form rather than another, when other forms consistent with physical laws seem perfectly possible?  The reasons underlying the choice between different contingent possibilities for the universe (why one occurred rather than another) cannot be explored scientifically.  It is an issue to be examined through philosophy or metaphysics.

Metaphysics is the part of philosophy that deals with existence, space, time, cause and effect, and the like.  Metaphysics begins where physics necessarily ends due to observational limitations.

Did anything exist before the Big Bang?

Was there a Big Bang?

What are the physical properties of the very early universe, when energy densities existed that are far beyond our ability to recreate in the laboratory?

What lies beyond our particle horizon?

Are there other universes?

Why does anything exist at all?

References
Ellis, G. F. R. 2006, Issues in the Philosophy of Cosmology, Philosophy of Physics (Handbook of the Philosophy of Science), Ed. J. Butterfield and J. Earman (Elsevier, 2006), 1183-1285.
[http://arxiv.org/abs/astro-ph/0602280]

Liddle, A.R. 2015, An Introduction to Modern Cosmology, 3rd ed., Wiley, ISBN: 978-1-118-50214-3.