1. 1 Einstein's Legacy: General Relativity, our Best Description of the Universe Barry C. Barish Caltech Vancouver Institute 16-April-05 Crab Pulsar

2. 2 Albert Einstein

3. 3

4. 4 Annus Mirabilis  In 1905, Albert Einstein wrote five revolutionary scientific papers.  These papers altered our understanding of the nature of light, proved the existence of atoms and molecules, and established the concept of special relativity.

5. 5 LIGHT  Is the behavior of light like a wave or like a particle? "A question so enormously important and difficult that everybody should work on it." ~Albert Einstein Light is often described as a wave. Sunlight and radio waves are both forms of light, but have different wavelengths. The colors you see in a rainbow demonstrate the wave-like nature of light. Light is also described as being individual particles -- photons. In a solar cells a photon collides with the atoms and generates electricity by knocking an electron out. This is the photoelectric effect.

6. 6 ATOMS  How do we know atoms and molecules exist? "My major aim in this was to find facts which would guarantee as much as possible the existence of atoms of definite finite size." ~Albert Einstein Einstein realized that if atoms did exist then they would continually bump into microscopic particles in their paths. He created a mathematical model where accurate measurements of these microscopic motions could be used to determine the actual size of molecules and atoms.

7. 7 RELATIVITY Is there a cosmic speed limit? Einstein argued that the laws of physics are the same in all reference frames. A scientist on the ground and a scientist in a fast moving space station will always agree that the laws of physics are the same. He argued that therefore the velocity of light is measured to be the same by all observers in all reference frames.

8. 8 ENERGY and MASS  For centuries, scientists believed that matter and energy could never be destroyed.  Before 1905, the law of conservation of energy and the law of conservation of mass were two fundamental principles of science that appeared to never be violated.  Einstein showed that these laws were fallible, and that they needed to be reconciled into a single theory unifying mass and energy. E = mc 2

9. 9 G  = 8   General Relativity the essential idea  Overthrew the 19 th -century concepts of absolute space and time  Gravity is not a force, but a property of space & time » Spacetime = 3 spatial dimensions + time » Perception of space or time is relative  Concentrations of mass or energy distort (warp) spacetime  Objects follow the shortest path through this warped spacetime; path is the same for all objects

10. 10 General Relativity Einstein theorized that a massive object warps the surrounding space

11. 11 General Relativity Smaller objects travel through space that is warped by larger objects

12. 12 Gravity a fundamental force

13. 13 Universal Gravitation  Solved most known problems of astronomy and terrestrial physics »eccentric orbits of comets »cause of tides and their variations »the precession of the earth’s axis »the perturbation of the motion of the moon by gravity of the sun  Unified the work of Galileo, Copernicus and Kepler unified.

14. 14 But, what causes the mysterious force in Newtons theory ? Although the equation explains nature very well, the underlying mechanism creating the force is not explained !

15. 15 After several hundred years, a small crack in Newton’s theory ….. perihelion shifts forward an extra +43”/century compared to Newton’s theory

16. 16 A new prediction of Einstein’s theory … Light from distant stars are bent as they graze the Sun. The exact amount is predicted by Einstein's theory.

17. 17 Confirming Einstein …. A massive object shifts apparent position of a star bending of light Observation made during the solar eclipse of 1919 by Sir Arthur Eddington, when the Sun was silhouetted against the Hyades star cluster

18. 18 Einstein’s Cross The bending of light rays gravitational lensing Quasar image appears around the central glow formed by nearby galaxy. The Einstein Cross is only visible in southern hemisphere.

19. 19 Gravitational Waves ?

20. 20 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

21. 21 Russel A. Hulse Joseph H.Taylor Jr Source: www.NSF.gov Discovered and Studied Pulsar System PSR 1913 + 16 with Radio Telescope The The The Evidence For Gravitational Waves

22. 22 Radio Pulsar Neutron Star

23. 23 The evidence for gravitational waves Hulse & Taylor   17 / sec Neutron binary system separation = 10 6 miles m 1 = 1.4m  m 2 = 1.36m  e = 0.617 period ~ 8 hr PSR 1913 + 16 Timing of pulsars Prediction from general relativity spiral in by 3 mm/orbit rate of change orbital period

24. 24 “Indirect” evidence for gravitational waves

25. 25 The Nature of Gravitational Waves Ringdown Inspiral Merger Compact Binary Inspiral

26. 26 The effect of a gravitational wave passing through space …

27. 27 Direct Detection Detectors in space LISA Gravitational Wave Astrophysical Source Terrestrial detectors LIGO, TAMA, Virgo,AIGO

28. 28 LISA The diagram shows the sensitivity bands for LISA and LIGO

29. 29 The frequency range of astronomy  EM waves studied over ~16 orders of magnitude »Ultra Low Frequency radio waves to high energy gamma rays

30. 30 Gravitational Waves in Space LISA Three spacecraft, each with a Y-shaped payload, form an equilateral triangle with sides 5 million km in length.

31. 31 LISA The three LISA spacecraft will be placed in orbits that form a triangular formation with center 20 o behind the Earth

32. 32 stretch and squash in perpendicular directions at the frequency of the gravitational waves Leonardo da Vinci’s Vitruvian man

33. 33 Detecting a passing wave …. Free masses

34. 34 Detecting a passing wave …. Interferometer

35. 35 stretch and squash in perpendicular directions at the frequency of the gravitational waves Leonardo da Vinci’s Vitruvian man I have greatly exaggerated the effect!! If the Vitruvian man was 4.5 light years high, he would grow by only a ‘hairs width’

36. 36 laser Gravitational Wave Detection Laser Interferometer free masses h = strain amplitude of grav. waves h =  L/L ~ 10 -21 L = 4 km  L ~ 10 -18 m

37. 37 The Detection Technique  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 LIGO are 4km  Measure difference in length to one part in 10 21 or 10 -18 meters

38. 38 How Small is 10 -18 Meter? Wavelength of light ~ 1 micron One meter ~ 40 inches Human hair ~ 100 microns LIGO sensitivity 10 -18 m Nuclear diameter 10 -15 m Atomic diameter 10 -10 m

39. 39 LIGO Laser Interferometer Gravitational-wave Observatory Hanford Observatory Livingston Observatory Caltech MIT

40. 40 LIGO Livingston, Louisiana 4 km

41. 41 Flooding in Louisiana

42. 42 LIGO Hanford Washington 4 km 2 km

43. 43 Also a Few Glitches in Hanford, but Science Moves On …

44. 44 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

45. 45 Evolution of LIGO Sensitivity

46. 46 An earthquake occurred, starting at UTC 17:38. From electronic logbook 2-Jan-02 Detecting Earthquakes

47. 47 Detect the Earth Tide from the Sun and Moon

48. 48 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”

49. 49 Directed Pulsar Search 28 Radio Sources

50. 50 Detection of Periodic Sources  Known Pulsars in our galaxy  Frequency modulation of signal due to Earth’s motion relative to the Solar System Barycenter, intrinsic frequency changes.  Amplitude modulation due to the detector’s antenna pattern. NEW RESULT 28 known pulsars NO gravitational waves e < 10 -5 – 10 -6 (no mountains > 10 cm ALL SKY SEARCH enormous computing challenge

51. 51 Einstein@Home  A maximum-sensitivity all-sky search for pulsars in LIGO data requires more computer resources than exist on the planet.  The world’s largest supercomputer is arguably SETI@home »A $599 computer from Radio Shack is a very powerful computational engine. »Currently runs on a half-million machines at any given time.  With help from the SETI@home developers, LIGO scientists have created a distributed public all-sky pulsar search.

52. 52 Einstein@Home Usage Already have about 35K Users 20x LIGO computing capacity

53. 53 Einstein@Home Users  I'm from Germany and was interested in the mysteries of the universe since I was a little boy. I read lots of magazines about astrophysics and astronomy. When I heard about the Einstein@Home project it was no question for me to participate.  My job is to make original- sized design models of new Mercedes-Benz cars, especially the interieur. When I don't work I often play keyboards and percussions and sing some backing vocals in my cover-rock-band "Gilga- Mesh"

54. 54 Einstein@Home Users  Hi, my name's John Slattery. I'm a 62 year old English teacher, originally from Boston, MA, currently living in Santa Fe, New Mexico where I'm tutoring, and teaching ESL.  My hobbies: fitness, camping, hiking, reading, writing, surfing the Net  I'm so very new at this; I'm not even sure what's going on. But it seemed, from the little I could understand, to be a worthwhile project.

55. 55 Einstein@Home Users

56. 56 Einstein@Home LIGO Pulsar Search using home pc’s BRUCE ALLEN Project Leader Univ of Wisconsin Milwaukee LIGO, UWM, AEI, APS http://einstein.phys.uwm.edu