PHYSICS SEMINAR
ON THE ATOMIC NATURE OF MATTER AN OVERVIEW OF BROWNIAN MOTION
Andres F. Zambrano Moreno
Physics Department
Bishop’s University
Friday, January 28, 2011
1:30-2:30 p.m.
Nicolls 315
In the summer of 1827, botanist Robert Brown made detailed observations of the random incessant motion of grains released from pollen sacks of the Clarkia pulcella suspended in water. Little did he know that the precise description as to the nature of this motion at the beginning of the 20th century would provide stern evidence for the atomic nature of matter (something that was still being debated at the time). A consistent explanation of these observations began to emerge in 1905 when works by Albert Einstein, Marian Smoluchowski, and Paul Langevin provided a quantitative explanation to this phenomenon commonly known as 'Brownian Motion'.
The theory of Brownian motion also brought a change in the paradigm concerning the nature of fundamental physics: The theories of gravitation and electromagnetism assumed that the universe which they were describing was continuous. The molecular-kinetic theory of matter, on the other hand, postulated a universe made of atoms and, to describe this universe, a statistical interpretation was needed. This newly developed theory also brought about a solution to a paradox concerning the second law of thermodynamics and the molecular-kinetic theory of matter.
For more than one hundred years, the theory of Brownian motion has diffused into other fields of knowledge and is still a subject of active research to this day; elements of this can be found in areas ranging from condensed matter physics and biology to the stock market.
A brief introduction to the history of the theory will be given, followed by the physical arguments and experiments that ultimately answered the question: do atoms exist?
