Clifford Will, McDonnell Center for the Space Sciences
Department of Physics
Washington University, St. Louis
| Lectures
by Clifford Will, McDonnell Center for the Space Sciences Department of Physics Washington University, St. Louis |
|
Popular Talks
Was Einstein Right?
Black Holes, Waves of Gravity, and other Warped Ideas of Dr.
Einstein
Colloquia
The Confrontation
between General Relativity and Experiment
On the Unreasonable Effectiveness of post-Newtonian
Theory in Gravitational Physics
Gravitational waves and the Death Dance of Compact Stellar
Binaries
Special Relativity: A Centenary Perspective
Lectures suitable for undergraduate physics students
The Search for Black
Holes
The Search for Gravity Waves
Popular Talks
How has the most celebrated scientific
theory of the 20th century held up under the exacting scrutiny of planetary
probes, radio telescopes, and atomic clocks? After 100 years, was Einstein right?
In this lecture we relate the story of testing relativity, from the 1919 measurements
of the bending of light to the 1980s measurements of a decaying double-neutron-star
system that reveal the action of gravity waves, to a 2004 space experiment to
test whether spacetime ``does the twist''. We will show how a revolution in
astronomy and technology led to a renaissance of general relativity in the 1960s,
and to a systematic program to try to verify its predictions. We will also demonstrate
how relativity plays an important role in daily life.
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Black Holes, Waves of Gravity, and other Warped Ideas of Dr. Einstein
Einstein's theories of relativity
have had a major impact on everything from popular culture to everyday life
to basic science. Songs, plays and movies proclaim Einstein as the symbol of
genius, while users of GPS navigation devices unknowingly take account of Einstein's
relativistic warpage of time. Two of the crazier ideas that come from Einstein's
theories are Gravitational Waves and the Black Hole. Today, international teams
of scientists have embarked on a quest to verify these ideas. Building and operating
large-scale detectors on the ground, and designing space-based detectors for
the future, they hope to detect and measure the waves, and to use those wave
signals to reveal the hidden secrets of black holes.
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Colloquia
The Confrontation between General Relativity and Experiment
We review the experimental evidence
for Einstein's general relativity. Tests of the Einstein Equivalence Principle
support the postulates of curved spacetime, while solar-system experiments strongly
confirm weak-field general relativity. We describe the status of the recently
concluded Gravity Probe B experiment, and of observations of binary pulsar systems.
Future tests of the theory in the radiative and strong-field regimes may be
possible using gravitational-wave observatories on Earth and in space, and using
observations of stars orbiting the central black hole in our galaxy.
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On the Unreasonable Effectiveness of post-Newtonian Theory in Gravitational Physics
The first indirect detection of gravitational
waves involved a binary system of neutron stars. In the future, the first direct
detection may also involve binary systems -- inspiralling and merging binary
neutron stars or black holes. This means that it is essential to understand
in full detail the two-body system in general relativity, a notoriously difficult
problem with a long history. Post-Newtonian approximations methods are thought
to work only under slow motion and weak field conditions, while numerical solutions
of Einstein's equations are thought to be limited to the final merger phase.
Recent results have shown that post-Newtonian approximations seem to remain
unreasonably valid well into the relativistic regime, while advances in numerical
relativity now permit solutions for numerous orbits before merger. It is now
possible to envision linking post-Newtonian theory and numerical relativity
to obtain a complete ``solution'' of the general relativistic two-body problem.
These solutions will play a central role in detecting and understanding gravitational
wave signals received by interferometric observatories on Earth and in space.
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Gravitational waves and the Death Dance of Compact Stellar Binaries
The completion of a network of laser-interferometric
gravitational-wave observatories will soon make possible the study of the inspiral
and coalescence of binary systems of compact objects (neutron stars and black
holes), using gravitational radiation. To extract useful information from the
waves, theoretical general relativistic gravitational waveforms will be used
as templates, cross-correlated against the detector outputs. The templates must
be extremely accurate, probably as accurate as O[(v/c)^6] beyond the predictions
of the simple quadrupole formula. We summarize a method, known as Direct Integration
of the Relaxed Einstein Equations (DIRE), for calculating equations of motion
and gravitational radiation to high orders in v/c. We also discuss how observations
of inspiralling compact binaries could yield new tests of general relativity
in the strong-field regime, and could place a bound on the graviton mass.
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Special
Relativity: A Centenary Perspective
This lecture celebrates a century of Einstein's miraculous legacy by giving
an overview of special relativity. We begin with a summary of the foundations
of special relativity and ask: why Einstein? We then describe some favorite
ways of presenting the critical elements of special relativity to young students
and the general public. We review the experimental evidence for special relativity,
from the classic Michelson-Morley experiment, to the latest efforts to search
for violations of Lorentz invariance using high precision technology. We also
discuss the evidence that gravity itself is ``Lorentz invariant''.
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Lectures suitable for undergraduate physics students
One of the most remarkable predictions
of Einstein's general theory of relativity is the Black Hole, a region of warped
spacetime left over from the catastrophic collapse of a star from which nothing,
not even light, can escape. What is a Black Hole and what are its properties?
Do Black Holes really exist? Will a world-wide network of gravitational-wave
observatories that recently began operation give us the ``smoking gun'' for
the existence of black holes?
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During the coming decade, it is likely
that a new form of astronomy will begin, called ``gravitational-wave astronomy''.
General relativity predicts that moving matter produces gravitational radiation,
and that the most intense sources of waves will be cosmic cataclysms such as
the collapse of stars, or the collisions of black holes. In this lecture, we
describe the nature and properties of gravitational waves, and the observations
that already verify their existence. We will then discuss current efforts to
operate a worldwide network of gravitational wave observatories with the sensitivity
to detect and study these waves, and will describe the work of theorists to
calculate, often using supercomputers, the properties of the waves as predicted
by Einstein's theory.
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