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Observing the Most Violent Events in the Universe

VirgoBarry Barish

Director, LIGO

Virgo Inauguration23-July-03

Cascina 2003

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Michelangelo“The Battle of Cascina”

Unfinished Full Size Drawing of the Violence of War

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VirgoGravitational Waves

Detecting Violent Events in the Cosmos like Colliding Black HolesCredit:: National Center for Supercomputing Applications (NCSA)

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A Conceptual Problem is solved !

Newton’s Theory“instantaneous action

at a distance”

Einstein’s Theoryinformation carried

by gravitational radiation at the speed of light

G= 8

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Einstein’s Theory of Gravitation

a necessary consequence of Special Relativity with its finite speed for information transfer

gravitational waves come from the acceleration of masses and propagate away from their sources as a space-time warpage at the speed of light

gravitational radiationbinary inspiral

of compact objects

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Detectionof

Gravitational Waves

Detectors in space

LISA

Gravitational Wave

Astrophysical Source

Terrestrial detectorsVirgo, LIGO, TAMA, GEO

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International Network on Earth

LIGO

simultaneously detect signal

detection confidence

GEO VirgoTAMA

AIGOlocate the sourcesdecompose the polarization of

gravitational waves

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The effect …

Stretch and squash in perpendicular directions at the frequency of the gravitational

waves

Leonardo da Vinci’s Vitruvian man

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Detecting a passing wave ….

Free masses

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Detecting a passing wave ….

Interferometer

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I have greatly exaggerated the effect!!

If the Vitruvian man was 4.5 light years high, he would grow by only a ‘hairs width’

InterferometerConcept

The challenge ….

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Interferometer Concept Laser used to measure

relative lengths of two orthogonal arms

As a wave passes, the arm lengths change in different ways….

…causing the interference

pattern to change at the photodiode

Arms in Virgo are 3km Measure difference in

length to one part in 1021 or 10-18 meters

SuspendedMasses

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How Small is 10-18 Meter?

Wavelength of light ~ 1 micron100

One meter ~ 40 inches

Human hair ~ 100 microns000,10

Virgo sensitivity 10-18 m000,1

Nuclear diameter 10-15 m000,100

Atomic diameter 10-10 m000,10

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The Search has Begun …

Virgo joins the international effort to detect gravitational waves and to open a new window on the Universe

On behalf of LIGO and the rest of the international community, I welcome

Virgo into this exciting adventure

Congratulations !!!

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Astrophysical Sourcessignatures

Compact binary inspiral: “chirps”» NS-NS waveforms are well described» BH-BH need better waveforms » search technique: matched templates

Supernovae / GRBs: “bursts” » burst signals in coincidence with signals in

electromagnetic radiation » prompt alarm (~ one hour) with neutrino

detectors

Pulsars in our galaxy: “periodic”» search for observed neutron stars

(frequency, doppler shift)» all sky search (computing challenge)» r-modes

Cosmological Signal “stochastic background”

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Early Universe: “correlated noise”

‘Murmurs’ from the Big Bang

Cosmic Microwave

background

WMAP 2003

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International NetworkLIGO

Hanford Observatory

LivingstonObservatory

Caltech

MIT

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LIGO Livingston Observatory

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LIGO Hanford Observatory

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What Limits LIGO Sensitivity? Seismic noise limits low

frequencies

Thermal Noise limits middle frequencies

Quantum nature of light (Shot Noise) limits high frequencies

Technical issues - alignment, electronics, acoustics, etc limit us before we reach these design goals

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LIGO SensitivityLivingston 4km Interferometer

May 01

Jan 03

First ScienceRun

17 days - Sept 02

Second ScienceRun

59 days - April 03

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Detect the Earth Tide from the Sun and Moon

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Signals from the Early Universe

Strength specified by ratio of energy density in GWs to total energy density needed to close the universe:

Detect by cross-correlating output of two GW detectors:

GW ( f )1

critical

dGWd(ln f )

First LIGO Science Data

Hanford - Livingston

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Gravitational Waves from the Early Universe

E7

S1

S2

LIGO

Adv LIGO

results

projected

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Gravitational Waves A New Window on the

Universe

Virgo and its international partners will

provide a new way to view the

dynamics of the Universe