2. LIGO-G020518-01-W What If We Could Listen to the Stars? Fred Raab LIGO Hanford Observatory

3. LIGO-G020518-01-W LIGO: Portal to Spacetime2 LIGO’s Mission is to Open a New Portal on the Universe In 1609 Galileo viewed the sky through a 20X telescope and gave birth to modern astronomy »The boost from “naked-eye” astronomy revolutionized humanity’s view of the cosmos »Ever since, astronomers have “looked” into space to uncover the natural history of our universe LIGO’s quest is to create a radically new way to perceive the universe, by directly listening to the vibrations of space itself LIGO consists of large, earth-based, detectors that will act like huge microphones, listening for the most violent events in the universe

4. LIGO-G020518-01-W LIGO: Portal to Spacetime3 LIGO (Washington)LIGO (Louisiana) The Laser Interferometer Gravitational-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.

5. LIGO-G020518-01-W LIGO: Portal to Spacetime4 LIGO Laboratories Are Unique National Facilities  Observatories at Hanford, WA (LHO) & Livingston, LA (LLO)  Support Facilities @ Caltech & MIT campuses LHO LLO

6. LIGO-G020518-01-W LIGO: Portal to Spacetime5 Part of Future International Detector Network LIGO Simultaneously detect signal (within msec) detection confidence locate the sources decompose the polarization of gravitational waves GEO Virgo TAMA AIGO

7. LIGO-G020518-01-W LIGO: Portal to Spacetime6 LIGO Laboratory & Science Collaboration LIGO Laboratory (Caltech/MIT) runs observatories and research/support facilities at Caltech/MIT LIGO Scientific Collaboration is the body that defines and pursues LIGO science goals »>400 members at 44 institutions worldwide (including LIGO Lab) »Includes GEO600 members & data sharing »Working groups in detector technology advancement, detector characterization and astrophysical analyses »Memoranda of understanding define duties and access to LIGO data

8. LIGO-G020518-01-W LIGO: Portal to Spacetime7 Big Question: What is the universe like now and what is its future? New and profound questions exist after nearly 400 years of optical astronomy »1850’s  Olber’s Paradox: “Why is the night sky dark?” »1920’s  Milky Way discovered to be just another galaxy »1930’s  Hubble discovers expansion of the universe; Zwicky finds shortage of luminous matter in galaxy clusters »mid 20 th century  “Big Bang” hypothesis becomes a theory, predicting origin of the elements by nucleosynthesis and existence of relic light (cosmic microwave background) from era of atom formation »1960’s  First detection of relic light from early universe »1970’s  Vera Rubin documents “missing mass”, a.k.a. “dark matter” in individual galaxies »1990’s  First images of early universe made with relic light »2003  High-resolution images imply universe is 13.7 billion years old and composed of 4% normal matter, 24% dark matter and 72% dark energy; 1 st stars formed 200 million years after big bang. We hope to open a new channel to help study this and other mysteries

9. LIGO-G020518-01-W LIGO: Portal to Spacetime8 A Slight Problem Regardless of what you see on Star Trek, the vacuum of interstellar space does not transmit conventional sound waves effectively. Don’t worry, we’ll work around that!

10. LIGO-G020518-01-W LIGO: Portal to Spacetime9 John Wheeler’s Picture of General Relativity Theory

11. LIGO-G020518-01-W LIGO: Portal to Spacetime10 General Relativity: A Picture Worth a Thousand Words

12. LIGO-G020518-01-W LIGO: Portal to Spacetime11 The New Wrinkle on Equivalence Not only the path of matter, but even the path of light is affected by gravity from massive objects Einstein Cross Photo credit: NASA and ESA A massive object shifts apparent position of a star

13. LIGO-G020518-01-W LIGO: Portal to Spacetime12 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:

14. LIGO-G020518-01-W What Phenomena Do We Expect to Study With LIGO?

15. LIGO-G020518-01-W LIGO: Portal to Spacetime14 Gravitational Collapse and Its Outcomes Present LIGO Opportunities f GW > few Hz accessible from earth f GW < several kHz interesting for compact objects

16. LIGO-G020518-01-W LIGO: Portal to Spacetime15 Supernovae time evolution The Brilliant Deaths of Stars Images from NASA High Energy Astrophysics Research Archive

17. LIGO-G020518-01-W LIGO: Portal to Spacetime16 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

18. LIGO-G020518-01-W LIGO: Portal to Spacetime17 The “Undead” Corpses of Stars: Neutron Stars and Black Holes Neutron stars have a mass equivalent to 1.4 suns packed into a ball 10 miles in diameter, enormous magnetic fields and high spin rates Black holes are the extreme edges of the space-time fabric Artist: Walt Feimer, Space Telescope Science Institute

19. LIGO-G020518-01-W LIGO: Portal to Spacetime18 Gravitational-Wave Emission May be the “Regulator” for Accreting Neutron Stars Neutron stars spin up when they accrete matter from a companion Observed neutron star spins “max out” at ~700 Hz Gravitational waves are suspected to balance angular momentum from accreting matter Credit: Dana Berry, NASA

20. LIGO-G020518-01-W LIGO: Portal to Spacetime19 Catching Waves From Black Holes Sketches courtesy of Kip Thorne

21. LIGO-G020518-01-W LIGO: Portal to Spacetime20 Detection of Energy Loss Caused By Gravitational Radiation In 1974, J. Taylor and R. Hulse discovered a pulsar orbiting a companion neutron star. This “binary pulsar” provides some of the best tests of General Relativity. Theory predicts the orbital period of 8 hours should change as energy is carried away by gravitational waves. Taylor and Hulse were awarded the 1993 Nobel Prize for Physics for this work.

22. LIGO-G020518-01-W LIGO: Portal to Spacetime21 Sounds of Compact Star Inspirals Neutron-star binary inspiral: Black-hole binary inspiral:

23. LIGO-G020518-01-W LIGO: Portal to Spacetime22 Searching for Echoes from Very Early Universe Sketch courtesy of Kip Thorne

24. LIGO-G020518-01-W How does LIGO detect spacetime vibrations?

25. LIGO-G020518-01-W LIGO: Portal to Spacetime24 Important Signature of Gravitational Waves Gravitational waves shrink space along one axis perpendicular to the wave direction as they stretch space along another axis perpendicular both to the shrink axis and to the wave direction.

26. LIGO-G020518-01-W LIGO: Portal to Spacetime25 Laser Beam Splitter End Mirror Screen Viewing Sketch of a Michelson Interferometer

27. LIGO-G020518-01-W LIGO: Portal to Spacetime26 Core Optics Suspension and Control Local sensors/actuators provide damping and control forces Mirror is balanced on 1/100 th inch diameter wire to 1/100 th degree of arc Optics suspended as simple pendulums

28. LIGO-G020518-01-W LIGO: Portal to Spacetime27 Suspended Mirror Approximates a Free Mass Above Resonance

29. LIGO-G020518-01-W LIGO: Portal to Spacetime28 How Small is 10 -18 Meter? Wavelength of light, about 1 micron One meter, about 40 inches Human hair, about 100 microns LIGO sensitivity, 10 -18 meter Nuclear diameter, 10 -15 meter Atomic diameter, 10 -10 meter

30. LIGO-G020518-01-W LIGO: Portal to Spacetime29 Vacuum Chambers Provide Quiet Homes for Mirrors View inside Corner Station Standing at vertex beam splitter

31. LIGO-G020518-01-W LIGO: Portal to Spacetime30 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

32. LIGO-G020518-01-W LIGO: Portal to Spacetime31 Seismic Isolation – Springs and Masses damped spring cross section

33. LIGO-G020518-01-W LIGO: Portal to Spacetime32 Seismic System Performance 10 2 10 0 10 - 2 10 - 4 10 - 6 10 - 8 10 -10 Horizontal Vertical 10 -6 HAM stack in air BSC stack in vacuum

34. LIGO-G020518-01-W LIGO: Portal to Spacetime33 Evacuated Beam Tubes Provide Clear Path for Light

35. LIGO-G020518-01-W LIGO: Portal to Spacetime34 All-Solid-State Nd:YAG Laser Custom-built 10 W Nd:YAG Laser, joint development with Lightwave Electronics (now commercial product) Frequency reference cavity (inside oven) Cavity for defining beam geometry, joint development with Stanford

36. LIGO-G020518-01-W LIGO: Portal to Spacetime35 Core Optics Substrates: SiO 2 »25 cm Diameter, 10 cm thick »Homogeneity < 5 x 10 -7 »Internal mode Q’s > 2 x 10 6 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

37. LIGO-G020518-01-W LIGO: Portal to Spacetime36 Sensing the Effect of a Gravitational Wave Laser signal Gravitational wave changes arm lengths and amount of light in signal Change in arm length is 10 -18 meters, or about 2/10,000,000,000,000,000 inches

38. LIGO-G020518-01-W LIGO: Portal to Spacetime37 Steps to Locking an Interferometer signal Laser X Arm Y Arm Composite Video

39. LIGO-G020518-01-W LIGO: Portal to Spacetime38 Watching the Interferometer Lock for the First Time in October 2000 signal X Arm Y Arm Laser

40. LIGO-G020518-01-W LIGO: Portal to Spacetime39 Why is Locking Difficult? One meter, about 40 inches Human hair, about 100 microns Wavelength of light, about 1 micron LIGO sensitivity, 10 -18 meter Nuclear diameter, 10 -15 meter Atomic diameter, 10 -10 meter Earthtides, about 100 microns Microseismic motion, about 1 micron Precision required to lock, about 10 -10 meter

41. LIGO-G020518-01-W LIGO: Portal to Spacetime40 Background Forces in GW Band = Thermal Noise ~ k B T/mode Strategy: Compress energy into narrow resonance outside band of interest  require high mechanical Q, low friction x rms  10 -11 m f < 1 Hz x rms  2  10 -17 m f ~ 350 Hz x rms  5  10 -16 m f  10 kHz

42. LIGO-G020518-01-W LIGO: Portal to Spacetime41 Thermal Noise Observed in 1 st Violins on H2, L1 During S1 Almost good enough for tracking calibration.

43. LIGO-G020518-01-W LIGO: Portal to Spacetime42 We Have Continued to Progress…

44. LIGO-G020518-01-W LIGO: Portal to Spacetime43 And despite a few difficulties, science runs started in 2002…

45. LIGO-G020518-01-W LIGO: Portal to Spacetime44 Binary Neutron Stars: S1 Range Image: R. Powell

46. LIGO-G020518-01-W LIGO: Portal to Spacetime45 Binary Neutron Stars: S2 Range Image: R. Powell S1 Range

47. LIGO-G020518-01-W LIGO: Portal to Spacetime46 Binary Neutron Stars: Initial LIGO Target Range Image: R. Powell S2 Range

48. LIGO-G020518-01-W LIGO: Portal to Spacetime47 What’s next? Advanced LIGO… Major technological differences between LIGO and Advanced LIGO Initial Interferometers Advanced Interferometers Open up wider band Reshape Noise Quadruple pendulum Sapphire optics Silica suspension fibers Advanced interferometry Signal recycling Active vibration isolation systems High power laser (180W) 40kg

49. LIGO-G020518-01-W LIGO: Portal to Spacetime48 Binary Neutron Stars: AdLIGO Range Image: R. Powell LIGO Range