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"Colliding Black Holes"
Credit:National Center for Supercomputing Applications (NCSA)
Tuning into Einstein’s Unfinished Symphony: The Search for Gravitational Waves
Fred Raab,
LIGO Hanford Observatory
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Einstein’s Legacy in Science
Annus mirabilis, 1905» Special Relativity: 1st installment on a theory of space and time» Theory of Brownian Motion: ends debate on the existence of atoms» Quantum Theory of Light: cornerstone of quantum mechanics» Equivalence of matter and energy: E=mc2
Opus Magnus: The General Theory of Relativity, 1916 A new form of matter: Bose-Einstein Particles Questioning the reality of Quantum Mechanics
» Einstein-Podalsky-Rosen Paradox & hidden variables
Unfinished work:» Search for a unified “Theory of Everything”» Detection of Gravitational Waves
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The Essence of General Relativity
Space and time are things, not concepts» 1905 – Relativity refers to the “relative” interpretations of space and
time by moving observers; only the speed of light is not relative
» Energy and matter are equivalent and transformable into each other (E=mc2)
» 1916 – General Theory of Relativity - Space and time affect the motion of objects and objects warp space and time; gravity is the natural movement of stuff flowing through warped space and time.
» 1919 – Space warp caused by the sun is detected
» 1950’s and onward– Atomic timekeeping devices reveal time warps
Gravity and the speed of light are physical properties of empty space!
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General Relativity: A Picture Worth a Thousand Words
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Mass Warps Space, Affecting Paths of Objects and Light
Presence of mass gives space the appearance of lumpy glass as evidenced by the bending of light
First observed during the solar eclipse of 1919 by Sir Arthur Eddington, when the Sun was silhouetted against the Hyades star cluster
A massive object shifts apparent position of a star
Einstein Cross
Photo credit: NASA and ESA
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The Frontier of Relativity: Gravitational Waves
Gravitational waves are ripples in space when it is stirred up by rapid motions of large concentrations of matter or energy
Rendering of space stirred by two orbiting black holes:
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Einstein Died Believing Gravitational Waves Would Never Be Detected
Never say never…
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Spacetime is Stiff!
=> Wave can carry huge energy with miniscule amplitude!
h ~ (G/c4) (ENS/r)
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Gravitational Collapse and Its Outcomes Present Opportunities
fGW > few Hz accessible from earth
fGW < several kHz interesting for compact objects
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Supernova: Death of a Massive Star
•Spacequake should preceed optical display by ½ day
•Leaves behind compact stellar core, e.g., neutron star, black hole
•Strength of waves depends on asymmetry in collapse
•Observed neutron star motions indicate some asymmetry present
•Simulations do not succeed from initiation to explosions
Credit: Dana Berry, NASA
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Gravitational Waves FromOrbiting Black Holes and Neutron Stars
Sketches courtesy of Kip Thorne
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Emission of Energy by Gravitational Waves Has Been Observed
Neutron Binary System – Hulse & Taylor
PSR 1913 + 16 -- Timing of pulsars
17 / sec
Neutron Binary System• separated by 106 miles• m1 = 1.4m; m2 = 1.36m; = 0.617
Prediction from general relativity• spiral in by 3 mm/orbit• rate of change orbital period
~ 8 hr
Emission of gravitational waves
Hulse, Taylor receive Nobel Prize
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Why go beyond light? Because of where light cannot go.
Images of light from Big Bang imply 95% of the universe is composed of dark matter and dark energy. What is this stuff?
What was it like at the birth of space and time?
WMAP Image of Relic Light from Big Bang
First light from the universe
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How can we detect spacetime vibrations?
Leonardo da Vinci’s Vitruvian man
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Basic Signature of Gravitational Waves
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Laser
Beam Splitter
End Mirror End Mirror
ScreenViewing
Sketch of a Michelson Interferometer
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New Generation of “Free-Mass” Detectors Now Online
suspended mirrors markinertial frames
antisymmetric portcarries GW signal
Symmetric port carriescommon-mode info
Intrinsically broad band and size-limited by speed of light.
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LIGO (Washington) LIGO (Louisiana)
The Laser InterferometerGravitational-Wave Observatory
Brought to you by the National Science Foundation; operated by Caltech and MIT; the research focus for more than 500 LIGO Scientific Collaboration members worldwide.
The LIGO Observatories
Adapted from “The Blue Marble: Land Surface, Ocean Color and Sea Ice” at visibleearth.nasa.govNASA Goddard Space Flight Center Image by Reto Stöckli (land surface, shallow water, clouds). Enhancements by Robert Simmon (ocean color, compositing, 3D globes, animation). Data and technical support: MODIS Land Group; MODIS Science Data Support Team; MODIS Atmosphere Group; MODIS Ocean Group Additional data: USGS EROS Data Center (topography); USGS Terrestrial Remote Sensing Flagstaff Field Center (Antarctica); Defense Meteorological Satellite Program (city lights).
LIGO Hanford Observatory (LHO)H1 : 4 km armsH2 : 2 km arms
LIGO Livingston Observatory (LLO)L1 : 4 km arms
10 ms
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The International Interferometer Network
LIGO
Simultaneously detect signal (within msec)
detection confidence locate the sources
decompose the polarization of gravitational waves
GEO VirgoTAMA
AIGO
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How Much Will the 4-km Mirror Separation Change?
Wavelength of light, about 1 micron100
One meter, about 40 inches
Human hair, about 100 microns000,10
LIGO sensitivity, 10-18 meter000,1
Nuclear diameter, 10-15 meter000,100
Atomic diameter, 10-10 meter000,10
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Core Optics Suspension and Control
Local sensors/actuators provide damping and control forces
Mirror is balanced on 1/100th inchdiameter wire to 1/100th degree of arc
Optics suspended as simple pendulums
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Vacuum Chambers Provide Quiet Homes for Mirrors
View inside Corner Station
Standing at vertex beam splitter
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Vibration Isolation Systems
» Reduce in-band seismic motion by 4 - 6 orders of magnitude» Little or no attenuation below 10Hz» Large range actuation for initial alignment and drift compensation» Quiet actuation to correct for Earth tides and microseism at 0.15 Hz during
observation
HAM Chamber BSC Chamber
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Seismic Isolation – Springs and Masses
damped springcross section
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Seismic System Performance
102
100
10-2
10-4
10-6
10-8
10-10
Horizontal
Vertical
10-6
HAM stackin air
BSC stackin vacuum
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Evacuated Beam Tubes Provide Clear Path for Light
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All-Solid-State Nd:YAG Laser
Custom-built10 W Nd:YAG Laser,
joint development with Lightwave Electronics
(now commercial product)
Frequency reference cavity (inside oven)
Cavity for defining beam geometry,
joint development withStanford
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Core Optics
Substrates: SiO2
» 25 cm Diameter, 10 cm thick
» Homogeneity < 5 x 10-7
» Internal mode Q’s > 2 x 106
Polishing» Surface uniformity < 1 nm rms
» Radii of curvature matched < 3%
Coating» Scatter < 50 ppm
» Absorption < 2 ppm
» Uniformity <10-3
Production involved 6 companies, NIST, and LIGO
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And despite a few difficulties, science runs started in 2002…
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Binary Neutron Stars:S1 Range
Image: R. Powell
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Binary Neutron Stars:Initial LIGO Target Range
Image: R. Powell
S2 Range
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What’s next? Advanced LIGO…Major technological differences between LIGO and Advanced LIGO
Initial Interferometers
Advanced Interferometers
Open up wider band
ReshapeNoise
Quadruple pendulum
Sapphire optics
Silica suspension fibers
Advanced interferometry
Signal recycling
Active vibration isolation systems
High power laser (180W)
40kg
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Binary Neutron Stars:AdLIGO Range
Image: R. Powell
LIGO Range
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…and opening a new channel with a detector in space.
Planning underway for space-based detector, LISA, to open up a lower frequency band ~ next decade
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Closing remark
The age of discovery has not ended…
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Recommended Reading
“Was Einstein Right”, by Clifford Will. A bit ancient (more than 10 years old) accounting of progress in verifying Einstein’s theory.
“Black Holes and Time Warps: Einstein’s Outrageous Legacy”, by Kip Thorne. From basics to time travel in a long, but rewarding read.
“Einstein’s Unfinished Symphony”, by Marcia Bartusiak. A highly readable account of the search for gravitational waves.