Thorne's research has principally focused on
relativistic astrophysics and
gravitation physics, with emphasis on
relativistic stars, black holes and especially
gravitational waves. However, Thorne's scientific contributions, which center on the general nature of
space, time, and
gravity, span the full range of topics in general relativity.
Gravitational waves and LIGO Thorne's work has dealt with the prediction of gravitational wave strengths and their temporal signatures as observed on Earth. These "signatures" are of great relevance to
LIGO (Laser Interferometer Gravitational Wave Observatory), a multi-institution gravitational wave experiment for which Thorne has been a leading proponent – in 1984, he cofounded the LIGO Project (the largest project ever funded by the
NSF) to discern and measure any fluctuations between two or more 'static' points; such fluctuations would be evidence of gravitational waves, as calculations describe. A significant aspect of his research is developing the
mathematics necessary to analyze these objects. Thorne also carries out
engineering design analyses for features of the LIGO that cannot be developed on the basis of
experiment and he gives advice on
data analysis algorithms by which the waves will be sought. He has provided theoretical support for LIGO, including identifying gravitational wave sources that LIGO should target, designing the baffles to control
scattered light in the LIGO beam tubes, and – in collaboration with
Vladimir Braginsky's (Moscow, Russia) research group – inventing
quantum nondemolition designs for advanced gravity-wave detectors and ways to reduce the most serious kind of
noise in advanced detectors:
thermoelastic noise. With
Carlton M. Caves, Thorne invented the back-action-evasion approach to quantum nondemolition measurements of the
harmonic oscillators – a technique applicable both in gravitational wave detection and
quantum optics.
Black hole cosmology While studying for his PhD at Princeton University, his mentor
John Wheeler assigned him a problem to think about: find out whether or not a cylindrical bundle of repulsive magnetic field lines will implode under its own attractive gravitational force. After several months wrestling with the problem, he proved that it was impossible for cylindrical
magnetic field lines to
implode. As a tool to be used in both enterprisesastrophysics and theoretical physicsThorne and his students have developed an unusual approach, called the "
membrane paradigm", to the theory of black holes and used it to clarify the
Blandford–Znajek mechanism by which black holes may power some
quasars and
active galactic nuclei. With Sung-Won Kim, Thorne identified a universal physical mechanism (the explosive growth of
vacuum polarization of
quantum fields), that may always prevent spacetime from developing
closed timelike curves (i.e., prevent
backward time travel). With
Mike Morris and
Ulvi Yurtsever, he showed that traversable wormholes can exist in the structure of
spacetime only if they are threaded by quantum fields in
quantum states that violate the
averaged null energy condition (i.e. have negative renormalized energy spread over a sufficiently large region). This has triggered research to explore the ability of quantum fields to possess such extended
negative energy. Recent calculations by Thorne indicate that simple masses passing through traversable wormholes could never engender
paradoxes – there are
no initial conditions that lead to paradox once time travel is introduced. If his results can be generalized, they would suggest that none of the supposed paradoxes formulated in time travel stories can actually be formulated at a precise physical level: that is, that
any situation in a time travel story turns out to permit
many consistent solutions.
Relativistic stars, multipole moments and other endeavors With
Anna Żytkow, Thorne predicted the existence of
red supergiant stars with
neutron-star cores (
Thorne–Żytkow objects). He laid the foundations for the theory of
pulsations of relativistic stars and the gravitational radiation they emit. With
James Hartle, Thorne derived from general relativity the laws of motion and precession of black holes and other relativistic bodies, including the influence of the coupling of their
multipole moments to the spacetime curvature of nearby objects, as well as writing down the
Hartle-Thorne metric, an approximate solution which describes the exterior of a slowly and rigidly rotating, stationary and axially symmetric body. Thorne has also theoretically predicted the existence of universally antigravitating "
exotic matter" – the element needed to accelerate the expansion rate of the universe, keep traversable wormhole "Star Gates" open and keep
timelike geodesic free float "
warp drives" working. With Clifford Will and others of his students, he laid the foundations for the theoretical interpretation of experimental
tests of relativistic theories of gravity – foundations on which Will and others then built. , Thorne was interested in the origin of classical space and time from the
quantum foam of
quantum gravity theory. ==Publications==