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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.