Annus Mirabilis 1905 – The Miracle Year in Physics Christian Educators Annual Fall Conference October 2005 Dr. Brian Martin – The King’s University College, Edmonton

March April May June September From March to September 1905, Albert Einstein published 5 papers that have transformed physics in profound ways…

March 1905… “On a Heuristic Point of View Concerning the Production and Transformation of Light” (Annalen der Physik 17: )

This was the paper Einstein consider his most radical! In the paper he puts forward the quantum of light hypothesis – he suggests light may be a particle! Consider the opening lines of his paper… March 1905

THERE exists an essential formal difference between the theoretical pictures physicists have drawn of gases and other ponderable bodies and Maxwell’s theory of electromagnetic processes in so-called empty space. Whereas we assume the state of a body to be completely determined by the positions and velocities of an,’ albeit very large, still finite number of atoms and electrons, we use for the determination of the electromagnetic state in space con- tinuous spatial functions, so that a finite number of variables cannot be considered to be sufficient to fix completely the electro- magnetic state in space. According to Maxwell’s theory, the energy must be considered to be a continuous function in space for all purely electromagnetic phenomena, thus also for light, while according to the present-day ideas of physicists the energy of a ponderable body can be written as a sum over the atoms and electrons. The energy of a ponderable body cannot be split into arbitrarily many, arbitrarily small parts, while the energy of a light ray, emitted by a point source of light is according to Maxwell’s theory (or in general according to any wave theory) of light distributed continuously over an ever increasing volume. March 1905

Established light as a quantum of energy – led to the wave-particle duality that is central to quantum mechanics. Helped to explain the photoelectric effect and was the work for which he was eventually awarded the Nobel Prize (1921)* *awarded reluctantly in 1923 because none had been given in 1921!

April 1905… "The Determination of Molecular Dimensions". (Annalen der Physik 19: )

April 1905… Was Einstein’s Doctoral Dissertation (chosen because he judged it the least controversial and several of his more radical ideas had already “failed” as PhD dissertations!) Provide a theoretical means to determine the sizes of molecules at a time when a significant number of scientists – including some of the greatest – doubted the “atomic theory” Provided a novel way to determine Avogadro’s number Provided an essential first step to his May 1905 discussion of Brownian Motion.

April 1905 One of the first theoretical methods to determine the sizes of molecules and atoms.

May 1905 On the Movement of Small Particles Suspended in Stationary Liquids Required by the Molecular-Kinetic Theory of Heat" (Annalen der Physik 17: )

May 1905 Applied the methods of statistical mechanics to explain the phenomenon of Brownian Motion. demo of Brownian Motion demo of Brownian Motion Provided conclusive evidence for the atomic theory and the existence of atoms.

May 1905 Provided an almost iron-clad demonstration of the existence of atoms. Considered to be one of the truly great papers of the early 20 th Century.

June 1905… "On the Electrodynamics of Moving Bodies" (Annalen der Physik 17: )

June 1905… Forever changed our understanding of space, time and their interrelation Introduces the concept of spacetime and develops the Theory of Special Relativity The mystery of ‘c’ and the two postulates of Special Relativity 1.The laws of physics are the same for all uniformly moving observers. 2.The speed of light is the same for all observers.

How Einstein changed our understanding of space and time… The odd result of the Michelson-Morley Experiment The problem of simultaneity Time is not absolute Lorentz-Fitzgerald Contraction

June 1905 Introduced the Special Theory of Relativity and irrevocably changed our understanding of space and time.

September 1905… "Does the Inertia of a Body Depend upon its Energy Content?“ (Annalen der Physik 18: )

September 1905… Introduced the “most famous equation in the world” through a very simple argumentsimple argument E = mc 2

September 1905 Established the fundamental unity between matter and energy.

Einstein in the Curriculum The main ideas of special relativity can be taught with the minimum of mathematics. You don’t need to feel like a “yo-yo”!

Einstein can be Simplified!

Einstein Simplified…

A closer look at … Simultaneity The concept of spacetime Mass – energy equivalence

The End! Questions? Copy of talk available at: chris.kingsu.ca/~brian/talks/cea2005/einstein/Annus Mirabilis.ppt

Problem with simultaneity… Sam and Sally have a dispute! Sam is riding in the middle of a long train moving due east while Sally is sitting close to the tracks on the train platform. At the exact instant that Sam passes Sally, two lightning bolts strike each end of the train. Both Sam and Sally see the bolts at the same instant. Scorch marks are left on both the track and the train to prove it happened! Sam concludes that they must have occurred simultaneously. He remarks to Sally when they next meet how improbable that was. Sally retorts that they weren't simultaneous at all, and that she can prove it! Who is correct?