1 Observing the Most Violent Events in the Universe Virgo Barry Barish Director, LIGO Virgo Inauguration 23-July-03 Cascina 2003

2 Michelangelo “The Battle of Cascina” Unfinished Full Size Drawing of the Violence of War

3 Virgo Gravitational Waves Detecting Violent Events in the Cosmos like Colliding Black Holes Credit:: National Center for Supercomputing Applications (NCSA)

4 A Conceptual Problem is solved ! Newton’s Theory “instantaneous action at a distance” Einstein’s Theory information carried by gravitational radiation at the speed of light G  = 8  

5 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 radiation binary inspiral of compact objects

6 Detection of Gravitational Waves Detectors in space LISA Gravitational Wave Astrophysical Source Terrestrial detectors Virgo, LIGO, TAMA, GEO

7 International Network on Earth LIGO simultaneously detect signal detection confidence GEO Virgo TAMA AIGO locate the sourcesdecompose the polarization of gravitational waves

8 The effect … Stretch and squash in perpendicular directions at the frequency of the gravitational waves Leonardo da Vinci’s Vitruvian man

9 Detecting a passing wave …. Free masses

10 Detecting a passing wave …. Interferometer

11 I have greatly exaggerated the effect!! If the Vitruvian man was 4.5 light years high, he would grow by only a ‘hairs width’ Interferometer Concept The challenge ….

12 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 or meters Suspended Masses

13 How Small is Meter? Wavelength of light ~ 1 micron One meter ~ 40 inches Human hair ~ 100 microns Virgo sensitivity m Nuclear diameter m Atomic diameter m

14 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 !!!

15 Astrophysical Sources signatures  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”

16 Early Universe: “correlated noise” ‘Murmurs’ from the Big Bang Cosmic Microwave background WMAP 2003

17 International Network LIGO Hanford Observatory Livingston Observatory Caltech MIT

18 LIGO Livingston Observatory

19 LIGO Hanford Observatory

20 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

21 LIGO Sensitivity Livingston 4km Interferometer May 01 Jan 03 First Science Run 17 days - Sept 02 Second Science Run 59 days - April 03

22 Detect the Earth Tide from the Sun and Moon

23 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: First LIGO Science Data Hanford - Livingston

24 Gravitational Waves from the Early Universe E7 S1 S2 LIGO Adv LIGO results projected

25 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