Transcript Annus Mirabilis

Annus Mirabilis
1905 – The Miracle Year in Physics
NWCSI – CTABC Convention
October 2006
Dr. Brian Martin – The King’s University College, Edmonton
A Prelude…
Henri Poincare identifies 3 unsolved
problems in physics:
1. How can we explain the mysterious
way in which electrons are emitted
from metals under UV light?
2. What explains the random walk
of suspended particles (Brownian Motion)?
3. Why did the Michelson-Morley experiment
fail to detect the motion of earth
through the aether?
La Science et l’Hypothese (1902)
A Prelude…
“I want to know how God created this world
… I want to know His thoughts, the rest are
details.”
1905 – Miracle Year
From March to September 1905, Albert
Einstein published 5 papers that have
transformed physics in profound ways…
March
April
May
June
September
March 1905…
“On a Heuristic Point of View Concerning the
Production and Transformation of Light”
(Annalen der Physik 17:132-148)
March 1905
• 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 continuous spatial functions, so that a finite number of variables
cannot be considered to be sufficient to fix completely the electromagnetic 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
• Helped to explain the photoelectric effect and
was the work for which he was eventually
awarded the Nobel Prize (1922)
Established light as a quantum of energy – led to the
wave-particle duality that is central to quantum mechanics.
April 1905…
"The Determination of Molecular
Dimensions".
(Annalen der Physik 19:289-305)
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!)
• Provided 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 17:549-560)
May 1905
• Applied the methods of statistical mechanics to
explain the phenomenon 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 20th Century.
June 1905…
"On the Electrodynamics of Moving
Bodies"
(Annalen der Physik 17:891-921)
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 18:639-641)
September 1905…
• Introduced the “most famous equation in the
world” through a very simple argument
E = mc2
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?
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?