Combining clear discussions of both quantum theory and general
relativity, this book offers one of the first efforts to explain the new
quantum theory of space and time.
Today we are blessed with two extraordinarily successful theories of
physics. The first is Albert Einstein's general theory of relativity,
which describes the large-scale behaviour of matter in a curved
spacetime. This theory is the basis for the standard model of big bang
cosmology. The discovery of gravitational waves at the LIGO observatory
in the US (and then Virgo, in Italy) is only the most recent of this
theory's many triumphs.
The second is quantum mechanics. This theory describes the properties
and behaviour of matter and radiation at their smallest scales. It is
the basis for the standard model of particle physics, which builds up
all the visible constituents of the universe out of collections of
quarks, electrons and force-carrying particles such as photons. The
discovery of the Higgs boson at CERN in Geneva is only the most recent
of this theory's many triumphs.
But, while they are both highly successful, these two structures leave a
lot of important questions unanswered. They are also based on two
different interpretations of space and time, and are therefore
fundamentally incompatible. We have two descriptions but, as far as we
know, we've only ever had one universe. What we need is a quantum theory
of gravity.
Approaches to formulating such a theory have primarily followed two
paths. One leads to String Theory, which has for long been fashionable,
and about which much has been written. But String Theory has become
mired in problems. In this book, Jim Baggott describes "the road less
travelled" an approach which takes relativity as its starting point, and
leads to a structure called Loop Quantum Gravity. Baggott tells the
story through the careers and pioneering work of two of the theory's
most prominent contributors, Lee Smolin and Carlo Rovelli.
