Emergence, loosely
speaking, is what happens when the whole adds up to much, much more than
the sum of its parts.
A classic example is water. A water molecule in isolation
is just an oxygen atom with Mickey Mouse ears: two little
hydrogen atoms attached at an angle. But collect a few zillion
of the things, under the right conditions of temperature
and pressure, and you’ve suddenly got a substance that
sloshes, sparkles, gurgles and swirls—not to mention
having the ability to freeze, thaw, evaporate, boil and support
life. Water in its bulk form exhibits behaviors that are
nowhere to be found in a molecule by itself.
Another classic example is superconductivity.
Take a metal such as lead or tin and cool it below a certain
critical temperature: many of the individual electrons in
that metal will suddenly start to march in step, so to speak—a
collective motion that allows them to flow as if the metal
offered no electrical resistance whatsoever. Again, electrons
in the aggregate exhibit behaviors that are nowhere to be
found in one electron alone.
Similar examples of emergence abound in science. As the
Nobel laureate physicist Philip
Anderson put it in a 1972 article in Science, "more
is different."
This is especially true when it comes to the inner workings
of solids, liquids and other kinds of condensed
matter. (Rutgers University physicist Piers
Coleman maintains an online textbook on
this subject, along with articles and presentations aimed
at a broader audience.) Indeed, NSF-funded scientists are
currently studying a remarkable variety of emergent phenomena
in condensed matter, including exotic, heavy-Fermion superconductivity, quantum
phase transitions at ultra-low temperatures, Bose-Einstein condensation—and
not least, high-temperature superconductivity,
which still resists scientists’ full understanding
nearly two decades after its celebrated discovery in 1987.
Another rich source of emergent phenomena is self-organization:
a general name for what happens when the components of a
system create complex structures on their own, spontaneously,
without anyone or anything being in charge. (Think of water
vapor crystallizing into a snowflake.) Scientists have studied
self-organization in many contexts, from the dynamics of earthquakes to
the flocking of birds. But the process seems to be particularly
important in biology, where—to take just one example—structural
molecules inside the cell will spontaneously assemble themselves
into cell membranes, ribosomes and other components. Indeed,
a host of NSF-funded researchers are now trying to adapt
this kind of molecular self-assembly for practical use in nanotechnology.
Finally, yet another rich source of emergent phenomena is network
theory. This is a relatively new field that looks at issues
ranging from the vulnerability of the Internet to the maze
of chemical interactions inside the cell—anything having
to do with networks of connections in general. Among the leaders
in network theory are NSF-funded researchers such as Albert-Lazlo Barabasi at
the University of Notre Dame, and Jean Carlson at
the University of California, Santa Barbara.
Creating Molecules and Materials
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