the beginning of the twentieth-century, two conceptual revolutions
occured in science: Quantum mechanics and General relativity .
Each of these two theories has profoundly modified some key part
of our understanding of the physical world. Quantum mechanics has
changed the way in which we understand the nature of matter and
radiation, giving us a picture of reality in which particles behave
like waves and waves like particles where our normal physical descriptions
become subject to essential uncertainties, and where individual
objects can manifest themselves in several places at the same time.
Quantum mechanics shows there is a very intimate link between the
nature of particles and the nature of forces.
General relativity on the other hand overturned our conceptions
of space and time, combining the two into what we now call space-time
which is found to be subtly curved in a way that gives rise to that
long-familiar, omnipresent but mysterious, phenomenon of gravity.
General relativity shows there is a very intimate link between the
nature of space-time and the nature of the forces.
Einstein laid foundations stones of both of theses twentieth-century
revolutions in the single year of 1905. Not only that, but in this
year Einstein also provided fundamental new insights into two other
areas, with his doctoral dissertation on the determination of molecular
dimensions and with his analysis of the nature of Brownian motion.
His work on Brownian motion laid the foundations of an important
piece of statistical understanding which has had enormous implications
in numerous other fields.