History of Science: Einstein on Physics and Progress
Sir Frederick
ScienceWeek http://scienceweek.com
The following points are made by Albert Einstein (Physics Today
2005 June):
1) If philosophy is interpreted as a quest for the most general
and comprehensive knowledge, it obviously becomes the mother of
all scientific inquiry. But it is just as true that the various
branches of science have, in their turn, exercised a strong
influence on the scientists concerned and, beyond that, have
affected the philosophical thinking of each generation. Let us
glance, from this point of view, at the development of physics
and its influence on the conceptual framework of the other
natural sciences during the last hundred years.
2) Since the Renaissance, physics has endeavored to find the
general laws governing the behavior of material objects in space
and time. To consider the existence of these objects as a problem
was left to philosophy. To the scientist, the celestial bodies,
the objects on Earth, and their chemical peculiarities, simply
existed as real objects in space and time, and his task consisted
solely in abstracting these laws from experience by way of
hypothetical generalizations.
3) The laws were supposed to hold without exceptions. A law was
considered invalidated if, in a single case, any one of its
properly deduced conclusions was disproved by experience. In
addition, the laws of the external world were also considered to
be complete, in the following sense: If the state of the objects
is completely given at a certain time, then their state at any
other time is completely determined by the laws of nature. This
is just what we mean when we speak of "causality." Such was
approximately the framework of the physical thinking a hundred
years ago.
4) As a matter of fact, the framework was even more restrictive
than it has been sketched. The objects of the external world were
considered to consist of immutable mass points, acting upon each
other with well-defined forces eternally attached to them and,
under the influence of these forces, carrying out incessant
motions to which, in the last analysis, all observable processes
could be reduced.
5) From a philosophical point of view, the conception of the
world, as it appears to those physicists, is closely related to
naive realism, since they looked upon the objects in space as
directly given by our sense perceptions. The introduction of
immutable mass points, however, represented a step in the
direction of a more sophisticated realism. For it was obvious
from the beginning that the introduction of these atomistic
elements was not induced by direct observation.
6) With the Faraday-Maxwell theory of the electromagnetic field,
a further refinement of the realistic conception was unavoidable.
It became necessary to ascribe the same irreducible reality to
the electromagnetic field, continually distributed in space, as
formerly to ponderable matter. But sense experiences certainly do
not lead inevitably to the field concept. There was even a trend
to represent physical reality entirely by the continuous field,
without introducing mass points as independent entities into the
theory.
7) Summing up, we may characterize the framework of physical
thinking up to a quarter of a century ago as follows: There
exists a physical reality independent of substantiation and
perception. It can be completely comprehended by a theoretical
construction which describes phenomena in space and time -- a
construction whose justification, however, lies in its empirical
confirmation. The laws of nature are mathematical laws connecting
the mathematically describable elements of this construction.
They imply complete reality in the sense mentioned before.
8) Under the pressure of overwhelming experimental evidence
concerning atomistic phenomena, almost all of today's physicists
are now convinced that this conceptual framework --
notwithstanding its apparently wide scope -- cannot be retained.
What appears untenable to physicists of our times is not only the
requirement of complete causality but also the postulate of a
reality which is independent of any measurement or observation.
Physics Today http://www.physicstoday.org
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Related Material:
HISTORY OF PHYSICS: EINSTEIN AND BROWNIAN MOTION
The following points are made by Giorgio Parisi (Nature 2005
433:221):
1) On 30 April 1905, Einstein completed his doctoral thesis on
osmotic pressure, in which he developed a statistical theory of
liquid behavior based on the existence of molecules. This work,
together with his subsequent paper on "brownian motion",
constitutes one of the most important, but often overlooked,
contributions that Einstein made to physics.
2) In the closing decades of the 19th century, theoretical
physics was in a state of turmoil. The big outstanding questions
of that time have been much discussed. Such questions culminated
in relativity and quantum mechanics -- theoretical developments
in which Einstein's key role is being justly celebrated this
year. But it should not be forgotten that the seemingly innocuous
observations of Robert Brown (1773-1858) of the irregular motions
of a suspension of pollen grains in water -- now known as
brownian motion -- also heralded a revolution in physical
thought.
3) Although the concepts of atoms and molecules are now
universally accepted, this was not the case at the turn of the
20th century. The statistical interpretation by Ludwig Boltzmann
((1844-1906) of the laws of thermodynamics -- a body of work
deeply rooted in the ensemble dynamical motion of material atoms
-- had many adherents. But there were also many heavyweight
dissenters (for a time including Max Planck (1858-1947)), who did
not accept that thermodynamics had its origins in the reversible
motion of invisible hypothetical particles. And many
distinguished physicists of the time (among them Wilhelm Roentgen
(1845-1923)) suspected that brownian motion indicated a clear
failure of Boltzmann's formulation of the second law of
thermodynamics.
4) It was in this context that Einstein's explanation for
brownian motion made an initial impression. In particular,
Einstein showed that the irregular motion of the suspended
particles could be understood as arising from the random thermal
agitation of the molecules in the surrounding liquid: these
smaller entities act both as the driving force for the brownian
fluctuations (through the impact of the liquid molecules on the
larger particles), and as a means of damping these motions
(through the viscosity experienced by the larger particles). This
connection between displacement and the viscosity can be
quantitatively expressed in one dimension as a relationship
between displacement, viscosity, the universal gas constant,
Avogadro's number, the Boltzmann constant, the temperature, and
the radius of the suspended particles. This finding went beyond
simply confirming the existence of atoms and molecules, and
provided a new way of determining Avogadro's number. As Einstein
himself remarked, the consequence of this relation is that one
can see, directly through a microscope, a fraction of the thermal
energy manifest as mechanical energy. By proving that a
statistical mechanics description could explain quantitatively
brownian motion, all doubts concerning Boltzmann's statistical
interpretation of the thermodynamic laws suddenly faded.(1-3)
References (abridged):
1. Pais, A. Subtle is the Lord... (Oxford Univ. Press, 1982)
2. Kuhn, T. S. Black Body Theory and the Quantum Discontinuity
1894-1911 (Oxford Univ. Press, 1978)
3. Mezard, M., Parisi, G. & Virasoro, M. A. Spin Glass Theory and
Beyond (World Scientific, Singapore, 1987)
Nature http://www.nature.com/nature
--------------------------------
Related Material:
HISTORY OF PHYSICS: EINSTEIN AND RADIATION
The following points are made by Daniel Kleppner (Physics Today
2005 February):
1) Albert Einstein had a genius for extracting revolutionary
theory from simple considerations: From the postulate of a
universal velocity he created special relativity; from the
equivalence principle he created general relativity; from
elementary arguments based on statistics he discovered energy
quanta. His 1905 paper on quantization of the radiation field
(often referred to, inaccurately, as the photoelectric-effect
paper) was built on simple statistical arguments, and in
subsequent years he returned repeatedly to questions centered on
statistics and thermal fluctuations.
2) In 1909, Einstein showed that statistical fluctuations in
thermal radiation fields display both particle-like and wave-like
behavior. His was the first demonstration of what would later
become the principle of complementarity. In 1916, when he turned
to the interplay of matter and radiation to create a quantum
theory of radiation, he once again based his arguments on
statistics and fluctuations.
3) Einstein's theory of radiation is a treasure trove of physics,
for in it one can discern the seeds of quantum electrodynamics
and quantum optics, the invention of masers and lasers, and later
developments such as atom-cooling, Bose-Einstein condensation,
and cavity quantum electrodynamics. Our understanding of the
Cosmos comes almost entirely from images brought to us by
radiation across the electromagnetic spectrum. Einstein's theory
of radiation describes the fundamental processes by which those
images are created.
4) Einstein's 1905 paper on quantization endowed Max Planck's
quantum hypothesis with physical reality. The oscillators for
which Planck proposed energy quantization were fictitious, and
his theory for blackbody radiation lacked obvious physical
consequences. But the radiation field for which Einstein proposed
energy quantization was real, and his theory had immediate
physical consequences. His paper, published in March 1905, was
the first of his wonder year. In rapid succession he published
papers on Brownian motion, special relativity, and his quantum
theory of the specific heat of solids.
5) In 1907, his interest shifted to gravity, and he took the
first tentative steps toward the theory of general relativity.
His struggle with gravitational theory became all-consuming until
November 1915, when he finally obtained satisfactory
gravitational field equations. During those years of struggle,
however, Einstein apparently had a simmering discontent with his
understanding of thermal radiation, for in July 1916, he turned
to the problem of how matter and radiation can achieve thermal
equilibrium. One could argue that 1916 was too soon to deal with
that problem because there were serious conceptual obstacles to
the creation of a consistent theory. Einstein, in his Olympian
fashion, simply ignored them. In the next eight months, he wrote
three papers on the subject, publishing the third, and best
known, in 1917.[1,2]
References (abridged):
1. A. Einstein, Phys. Z. 18, 121 (1917); English translation On
the Quantum Theory of Radiation, by D. ter Haar, The Old Quantum
Theory, Pergamon Press, New York (1967), p. 167
2. A. Pais, Rev. Mod. Phys. 49, 925 (1977)
Physics Today http://www.physicstoday.org
ScienceWeek http://scienceweek.com
--
Best,
Frederick Martin McNeill
Poway, California, United States of America
mmcn...@fuzzysys.com
http://www.fuzzysys.com
http://members.cox.net/fmmcneill/
*************************
Phrase of the week :
"The reason why we are on a higher imaginative level
is not because we have finer imagination, but because
we have better instruments."
-- Alfred North Whitehead (1861-1947)
:-))))Snort!)
*************************
Sir Frederick
Tim
"Sir Frederick" <mmcn...@fuzzysys.com> wrote in message
news:c4tfc153rk9rn29m3...@4ax.com...
So then they are articles of faith with a mythological base.
So it was all a myth.
Ahh yes the mythical absolute - a universal velocity. When will humanity
cease to cling to such medieval folk mythology?
Nice story but where are the hard scientific facts that you see leading the
way to a new and improved post-medieval species? Well?