PBS Series: Einstein's Big Idea

APS Focus: What's Wrong with Quantum Mechanics?


During 1905, Albert Einstein published pivotal articles on three fundamental topics in physics: the quantum theory of light, the theory of Brownian motion, and the theory of relativity. Each one of these articles was remarkable; together they represent an unmatched achievement. The one-hundredth anniversary of this “Miraculous Year” is now being celebrated as the World Year of Physics. Today, Michigan physicists are poised and eager to explore this scientific frontier that Einstein initiated a century ago.

Einstein’s 1905 paper on Brownian motion (describing the motion of tiny particles suspended in liquids) laid the foundations for the description of fluctuations and encouraged others to do experimental work for confirming the kinetic theory and demonstrating the existence of atoms. Several U-M physicists in Condensed Matter physics and Biophysics are exploring this frontier.

Einstein’s 1905 paper on the photoelectric effect and quantum theory of light are topics studied by faculty in the U-M’s Atomic, Molecular, and Optical group, and the U-M’s Condensed Matter group.

The 1905 paper on relativity eventually led to important developments in several areas of physics where U-M Physics faculty working, for example, in relativity, gravitation, atomic, nuclear, and high-energy physics have made significant contributions. Relativity is the fabric of nearly all our work, from the engineering of accelerators to particle theory.
Below, are highlighted a few examples of this University of Michigan-based work, as related to Einstein’s legacy from 1905. The legacy from 1906 onward will be included in the fall newsletter issue as a companion article.

Brownian Motion
The remarkable 1905 papers of A. Einstein were published in the German journal “Annalen der Physik.” A special issue, “Commemorating Albert Einstein,” was recently published by this journal (Ann. Phys. (Leipzig) 1-3 (February 2005)). One of these articles, on “Brownian motors”, was co-authored by Professor Franco Nori.

The review article by Nori and collaborators focuses on current issues in particle-motion control. Thermal Brownian motion combined with noise can give rise to a “channeling of chance” that can be used to exercise control over systems at the micro- and nano-scales thus: a Brownian motor. Brownian motion could be used for noise induced transport of particles. It’s remarkable that one hundred years after Einstein’s paper, this field is actively ongoing in biophysics and condensed matter physics.

The American Institute of Physics (AIP) will soon publish via its journal “Chaos” a Brownian motion focus issue commemorating the 1905 Einstein paper. Professors Nori and Len Sander each contributed an article to this special issue.

Photoelectric Effect
The quantum theory of the photoelectric effect, in which electrons are emitted from a clean metal surface exposed to light, is a key part of the 1905 paper for which Einstein was awarded the Nobel Prize in 1922. The essential idea is that the electromagnetic field is quantized into photons and there is an energy barrier that an electron must overcome to leave the metal. Over the last forty years, those ideas have been exploited to make a powerful spectroscopy of electrons in solids.

Monochromatic photons, incident on a single crystal sample’s surface, excite photoelectrons that are detected and analyzed for their angle and kinetic energy distributions. The binding energy is found using the Einstein theory, and the momentum can be deduced from the kinetic energy and the emission angles. This spectrum is a fundamental tool for characterizing the behavior of one electron in an interacting electron system. Professor Jim Allen of our Department received the American Physical Society 2002 Frank Isakson Prize for applications of photoemission spectroscopy leading to the elucidation of phenomena in many-body physics.

In 1905, Einstein published his theory of special relativity in his paper, “On the Electrodynamics of Moving Bodies.” This paper revolutionized our understanding of space and time. Among many of its predictions are the perplexing ideas of time dilation or length contraction. In a subsequent paper, “Does the Inertia of a Body Depend upon Its Energy Content?” published in the same year, Einstein unified the concepts of mass, momentum, and energy through perhaps his most famous formula: E = mc2. The rest, as they say, is history. Particle physicists today utilize almost every aspect of Einstein’s special relativity in their pursuit to measure the properties and study the interactions of fundamental particles. The energy-mass relation allows powerful particle accelerators to recreate the condition of our universe when it was a few fractions of a second old.

At the world’s highest energy collider, the Tevatron Collider (currently in operation at Fermilab near Chicago), protons and antiprotons are accelerated to nearly the speed of light and then smashed together. By analyzing traces of these collisions with sophisticated particle detectors, we have learned a great deal about how particles interact and how new particles might be formed and discovered. A number of U-M faculty members are actively participating in two large international collaborations (called CDF and DØ) to study these high energy proton and antiproton collisions. Within a few years, the Large Hadron Collider (LHC) at the European Center for Nuclear Research (CERN) near Geneva, Switzerland, will eclipse the Tevatron Collider as the highest energy particle accelerator. As a collaborating member of the ATLAS experiment at the LHC, Michigan is again well positioned to use the ideas made possible by Einstein’s theory for new discoveries at the energy frontier.








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