Three Roads To Quantum Gravity

20 THREE ROADS TO QUANTUM GRAVITY
world is nothing but an evolving network of relationships. I
have not the eloquence to be the Dawkins or Margulis of
relativity, but I do hope that after reading this book you will
have come to understand that the relational picture of space
and time has implications that are as radical as those of
natural selection, not only for science but for our perspective
on who we are and how we came to exist in this
evolving universe of relations.
Charles Darwin's theory tells us that our existence was not
inevitable, that there is no eternal order to the universe that
necessarily brought us into being. We are the result of
processes much more complicated and unpredictable than
the small aspects of our lives and societies over which we
have some control. The lesson that the world is at root a
network of evolving relationships tells us that this is true to a
lesser or greater extent of all things. There is no ®xed, eternal
frame to the universe to de®ne what may or may not exist.
There is nothing beyond the world except what we see, no
background to it except its particular history.
This relational view of space has been around as an idea for
a long time. Early in the eighteenth century, the philosopher
Gottfried Wilhelm Leibniz argued strongly that Newton's
physics was fatally ¯awed because it was based on a logically
imperfect absolute view of space and time. Other philosophers
and scientists, such as Ernst Mach, working in Vienna
at the end of the nineteenth century, were its champions.
Einstein's theory of general relativity is a direct descendent of
these views.
A confusing aspect of this is that Einstein's theory of
general relativity can consistently describe universes that
contain no matter. This might lead one to believe that the
theory is not relational, because there is space but there is no
matter, and there are no relationships between the matter that
serve to de®ne space. But this is wrong. The mistake is in
thinking that the relationships that de®ne space must be
between material particles. We have known since the middle
of the nineteenth century that the world is not composed only
of particles. A contrary view, which shaped twentiethcentury
physics, is that the world is also composed of ®elds.