the search for black holes and gravitational waves: the ultimate tests of einstein’s relativity
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The Search for Black Holes and Gravitational Waves: The Ultimate Tests of Einstein’s Relativity. Edmund Bertschinger MIT Department of Physics and Kavli Institute for Astrophysics and Space Research. What is a black hole?. A massive spacetime curvature singularity, - PowerPoint PPT PresentationTRANSCRIPT
Edmund Bertschinger
MIT Department of Physics andKavli Institute for Astrophysics and
Space Research
The Search for Black Holes and Gravitational Waves:
The Ultimate Tests of Einstein’s Relativity
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What is a black hole?
A massive spacetime curvature singularity,
Surrounded by an event horizon
(a point or ring of infinite density and tidal acceleration)
(a spacetime boundary between causally disconnected regions of the universe)
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Einstein’s Strangest Theory:Curved Space, Warped Time
The gravity of massive objects can make space non-Euclidean:
Cosmology:
Black hole:
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Are Black Holes Giant Spacetime Trampolines?
Figure from NASA/GSFC Imagine
What does Stephen
Hawking say?
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Einsteinian time warps
Minkowski diagram without a black hole
x
ct
y
My worldline (trajectory)
If you pass inside this cone, I can communicate with you!
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i was considering howwithin night's loosesack a star'snibbling in-fin-i-tes-i-mal-ly devoursdarkness thehungry starwhichwill e.-ventu-al-ly jigglethe bait ofdawn and be jerkedintoeternity. when over my head ashootingstarBurs(tinto a stale shrieklike an alarm-clock)
-- e.e. cummings
Collapse through the horizon:N. Rumiano,http://nrumiano.free.fr/Eindex.html
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What happens at the event horizon?
Classically, nothing — it’s just a dangerous border crossing.
Quantum mechanically, Hawking radiation Particle vacuum state fluctuates with creation/annihilation
of virtual pairs of particles Negative energy particles fall in, positive energy ones
escape, black hole loses mass as blackbody radiation Completely negligible for astrophysical black holes
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How can matter escape from a BH?
Quantum tunneling produces a Particle-Antiparticle pair from the vacuum!http://superstringtheory.com/blackh/blackh3.html
Hawking radiation is extremely weak and may never be observed. Yet it raises profound questions of quantum gravity that perhaps only Superstring Theory will be able to answer!
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Black holes in Nature
The afterlife of giant starsBlack hole masses 3-15 solar masses
Giant sinkholes in galaxy centersBlack hole masses million to billion
solar masses
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How we find black holes (and neutron stars): X-rays!
MIT-ledRossiX-Ray TimingExplorersatellite,launched 1995
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How do black holes emit X-rays?
They get indigestion from eating a companion star, which gets compressed and heated in an accretion disk!
Artistic conception 1Artistic conception 2
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How can we prove these are the BH of Einstein’s theory?
Measure the gravitational waves emitted as two black holes merge.
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Gravitational Radiation
Newtonian gravity is action at a distance, in clear violation of the principle of relativity. How does general relativity fix this? By adding WAVES that travel at the speed of light
How are they produced and how are scientists preparing to detect them? Produced by accelerating masses: for example, two black holes
merging Detected by their TINY effect on test masses, using LASERS
bouncing back and forth between moving mirrors
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Neutron Binary System – Hulse & Taylor (Nobel Prize)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
Gravitational waves — the Evidence
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Left: Artist’s conception of gravitational waves produced by a binary system
Bottom: LIGO design
http://www.ligo.caltech.edu/
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Effect of a GW on matter
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Global network of detectors
LIGO
LIGO
LISA
VIRGO
TAMA
GEO
• Detection confidence• Source polarization• Sky location
AIGO
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LIGO: Laser Interferometer Gravitational-wave
Observatory
3030 km(±10 ms)
LA
WA
4 km
2 km
4 km
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Science Runs and Sensitivity
S22nd Science Run
Feb - Apr 03(59 days)
S11st Science Run
Sept 02(17 days)
S33rd Science RunNov 03 – Jan 04
(70 days)
LIGO Target Sensitivity
Frequency (Hz)
Str
ain
(1/r
tHz)
L strain x 4000 m 10-18 m rms
S3 Duty Cycle
H1 69%
H2 63%
L1 22%
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H1 strain sensitivity – S1 to S4+
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What’s the latest? S5 (goals) Sensitivity (in terms of inspiral reach)
H1 11 Mpc (10 to 14 Mpc) H2 5 Mpc (6 to 9 Mpc) L1 11 Mpc (10 to 14 Mpc)
Stability and duty cycle 70% individual 40% triple coincidence
Schedule Started in November, 2005 Get 1 year of data at design sensitivity Enhancements over next 3 years
Advanced LIGO: 2008, 15 times more sensitive than initial LIGO
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Laser Interferometer Space Antenna (LISA, 2013+)
1 AU = 1.5x108 km
Three spacecraft triangular formation separated by 5 million km
Formation trails Earth by 20° Approx. constant arm-lengths Constant solar illumination
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LISA and LIGO
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Ultimate success…New Instruments, New Field, the Unexpected…
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Special Thanks to
Prof. Nergis Mavalvala and the LIGO Scientific Collaboration
YOU can get involved in LIGO data analysis: “Einstein at Home”
http://einstein.phys.uwm.edu/
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Additional Credits and InformationCredits:
Black hole animated gif courtesy Andrew J.S. HamiltonRossi X-Ray Timing Explorer figure courtesy NASA/Goddard
Space Flight CenterLIGO and other gravitational wave images courtesy Nergis
MavalvalaStephen Hawking’s voice was simulated and used without
permission.
Books:The Elegant Universe: Superstrings, Hidden Dimensions, and
the Quest for the Ultimate Theory, Brian Greene (more advanced than The Fabric of the Cosmos)
Black Holes and Time Warps: Einstein’s Outrageous Legacy, Kip S. Thorne (more advanced)