Clocks and Gravity
Claus Lämmerzahl and Hansjörg Dittus
Zentrum für Angewandte Raumfahrttechnologie und MikrogravitationCenter for Applied Space Technology and Microgravity(ZARM)
University of Bremen
AirlieFrom Quantum to Cosmos, May 22. – 24. 2006
C. Lämmerzahl (ZARM, Bremen) Clocks and Gravity Airlie, May 23, 2006 1 / 55
Clocks and Gravity
Well known issues
Gravitational redshift
Important effect within Einstein’s General RelativityNeeded for clock synchronization on EarthNeeded for GPS
Universality of gravitational redshift
Important for the structure of General Relativity
Points made here
Clocks are a universal tool
Clocks have many important practical applications
Most space missions may profit from clocks onboard
Time and position are independent observables
Technology and Fundamental Physics
C. Lämmerzahl (ZARM, Bremen) Clocks and Gravity Airlie, May 23, 2006 2 / 55
Outline
1 The situation of standard physicsThe statusApplicationsProblems?
C. Lämmerzahl (ZARM, Bremen) Clocks and Gravity Airlie, May 23, 2006 3 / 55
Outline
1 The situation of standard physicsThe statusApplicationsProblems?
2 Search for Quantum GravityNeed for Quantum GravityOn strategies for the search for QG effectsObservation vs. Experiment
C. Lämmerzahl (ZARM, Bremen) Clocks and Gravity Airlie, May 23, 2006 3 / 55
Outline
1 The situation of standard physicsThe statusApplicationsProblems?
2 Search for Quantum GravityNeed for Quantum GravityOn strategies for the search for QG effectsObservation vs. Experiment
3 Space conditions
C. Lämmerzahl (ZARM, Bremen) Clocks and Gravity Airlie, May 23, 2006 3 / 55
Outline
1 The situation of standard physicsThe statusApplicationsProblems?
2 Search for Quantum GravityNeed for Quantum GravityOn strategies for the search for QG effectsObservation vs. Experiment
3 Space conditions
4 Gravity anomalies (in Universe and within Solar system)AnomaliesSolar system anomalies
C. Lämmerzahl (ZARM, Bremen) Clocks and Gravity Airlie, May 23, 2006 3 / 55
Outline
1 The situation of standard physicsThe statusApplicationsProblems?
2 Search for Quantum GravityNeed for Quantum GravityOn strategies for the search for QG effectsObservation vs. Experiment
3 Space conditions
4 Gravity anomalies (in Universe and within Solar system)AnomaliesSolar system anomalies
5 Clocks and orbits
C. Lämmerzahl (ZARM, Bremen) Clocks and Gravity Airlie, May 23, 2006 3 / 55
Outline
1 The situation of standard physicsThe statusApplicationsProblems?
2 Search for Quantum GravityNeed for Quantum GravityOn strategies for the search for QG effectsObservation vs. Experiment
3 Space conditions
4 Gravity anomalies (in Universe and within Solar system)AnomaliesSolar system anomalies
5 Clocks and orbits
6 Summary and Outlook
C. Lämmerzahl (ZARM, Bremen) Clocks and Gravity Airlie, May 23, 2006 3 / 55
Outline
1 The situation of standard physicsThe statusApplicationsProblems?
2 Search for Quantum GravityNeed for Quantum GravityOn strategies for the search for QG effectsObservation vs. Experiment
3 Space conditions
4 Gravity anomalies (in Universe and within Solar system)AnomaliesSolar system anomalies
5 Clocks and orbits
6 Summary and Outlook
7 Final remark: Technology and Fundamental Phyiscs
C. Lämmerzahl (ZARM, Bremen) Clocks and Gravity Airlie, May 23, 2006 3 / 55
The situation of standard physics
Outline
1 The situation of standard physicsThe statusApplicationsProblems?
2 Search for Quantum GravityNeed for Quantum GravityOn strategies for the search for QG effectsObservation vs. Experiment
3 Space conditions
4 Gravity anomalies (in Universe and within Solar system)AnomaliesSolar system anomalies
5 Clocks and orbits
6 Summary and Outlook
7 Final remark: Technology and Fundamental Phyiscs
C. Lämmerzahl (ZARM, Bremen) Clocks and Gravity Airlie, May 23, 2006 4 / 55
The situation of standard physics The status
Outline
1 The situation of standard physicsThe statusApplicationsProblems?
2 Search for Quantum GravityNeed for Quantum GravityOn strategies for the search for QG effectsObservation vs. Experiment
3 Space conditions
4 Gravity anomalies (in Universe and within Solar system)AnomaliesSolar system anomalies
5 Clocks and orbits
6 Summary and Outlook
7 Final remark: Technology and Fundamental Phyiscs
C. Lämmerzahl (ZARM, Bremen) Clocks and Gravity Airlie, May 23, 2006 5 / 55
The situation of standard physics The status
Structure of standard physics
Einstein Equivalence Principle
Universalityof Free Fall
Universality ofGravitat. Redshift
LorentzInvariance
General Relativity
Gravity = MetricEinstein–equations
Equations of motion for matter
Maxwell–equationDirac–equation
Matter determinesgravity
Gravity determinesdynamics
C. Lämmerzahl (ZARM, Bremen) Clocks and Gravity Airlie, May 23, 2006 6 / 55
The situation of standard physics The status
The present situation
All aspects of Lorentz invariance are experimentally well tested and confirmed
Foundations
Postulates
c = constPrinciple of Relativity
C. Lämmerzahl (ZARM, Bremen) Clocks and Gravity Airlie, May 23, 2006 7 / 55
The situation of standard physics The status
The present situation
All aspects of Lorentz invariance are experimentally well tested and confirmed
Foundations
Postulates
c = constPrinciple of Relativity
Tests = Clock tests
Independence of c fromvelocity of the source
Universality of c
Isotropy of c
Independence of c fromvelocity of the laboratory
Time dilation
Isotropy of physics(Hughes–Dreverexperiments)
Independence of physics fromthe velocity of the laboratory
C. Lämmerzahl (ZARM, Bremen) Clocks and Gravity Airlie, May 23, 2006 7 / 55
The situation of standard physics The status
The present situation
Many aspects of the Universality of Free Fall are experimentally well tested andconfirmed
Postulate
In a gravitational field allstructureless test particles fall inthe same way
C. Lämmerzahl (ZARM, Bremen) Clocks and Gravity Airlie, May 23, 2006 8 / 55
The situation of standard physics The status
The present situation
Many aspects of the Universality of Free Fall are experimentally well tested andconfirmed
Postulate
In a gravitational field allstructureless test particles fall inthe same way
Tests
UFF for
Neutral bulk matter
Charged particles
Particles with spin
No test so far for
Anti particles
C. Lämmerzahl (ZARM, Bremen) Clocks and Gravity Airlie, May 23, 2006 8 / 55
The situation of standard physics The status
The present situation
Many aspects of the Universality of the Gravitational Redshift are experimentallywell tested and confirmed
Postulate
In a gravitational field all clocksbehave in the same way
g
C. Lämmerzahl (ZARM, Bremen) Clocks and Gravity Airlie, May 23, 2006 9 / 55
The situation of standard physics The status
The present situation
Many aspects of the Universality of the Gravitational Redshift are experimentallywell tested and confirmed
Postulate
In a gravitational field all clocksbehave in the same way
g
Tests (= Clock tests)
UGR for
Atomic clocks: electronic
Atomic clocks: hyperfine
Molecular clocks: vibrational
Molecular clocks: rotational
Resonators
Nuclear transitions(Mössbauer effect)
No test so far for
Anti clocks
C. Lämmerzahl (ZARM, Bremen) Clocks and Gravity Airlie, May 23, 2006 9 / 55
The situation of standard physics The status
Universal tool
Clocks are a universal tool for testing space–time properties
GR: Physics of position and time (trajectories of particles and light rays)
SR: Based solely on clock camparison experiments
UGR: clock comparison experiment
Clock 1ν1
Clock with hypotheticanomal dependence on
position, orientation, and velocity
Clock 2ν2
Clock with different hypotheticanomal dependence on
position, orientation, and velocity
×
comparisonν2 − ν1
C. Lämmerzahl (ZARM, Bremen) Clocks and Gravity Airlie, May 23, 2006 10 / 55
The situation of standard physics The status
Clocks
Clocks of different nature exhibit a different dependence on fundamental constants
Scaling of transition energies (in units of Rydberg energy)
Hyperfine energies g(me/mp)α2f(α)
Vibrational energies in molecules√
me/mp
Rotational energies in molecules me/mp
Fine-structure energies α2
Electronic energies (incl. relativistic effects) f(α)Cavity frequency 1/αWeak interaction splitting/Zeeman frequency GF
C. Lämmerzahl (ZARM, Bremen) Clocks and Gravity Airlie, May 23, 2006 11 / 55
The situation of standard physics The status
Test of time–dilation: Transport of clocks
Development of good clocks ⇒ clocks on aircraft: Experiment byHafele and Keating 1968 to test time dilation
We shall do the same today: Put the best clocks on spacecraft and test clockeffects!
C. Lämmerzahl (ZARM, Bremen) Clocks and Gravity Airlie, May 23, 2006 12 / 55
The situation of standard physics The status
The present situation
All predictions of Einstein’s General Relativity are experimentally well tested andconfirmed
Foundations
The Einstein EquivalencePrinciple
Universality of Free Fall
Universality of GravitationalRedshift
Local Lorentz Invariance
C. Lämmerzahl (ZARM, Bremen) Clocks and Gravity Airlie, May 23, 2006 13 / 55
The situation of standard physics The status
The present situation
All predictions of Einstein’s General Relativity are experimentally well tested andconfirmed
Foundations
The Einstein EquivalencePrinciple
Universality of Free Fall
Universality of GravitationalRedshift
Local Lorentz Invariance
Predictions from GR
Solar system effects
Perihelion shiftGravitational redshiftDeflection of lightGravitational time delayLense–Thirring effectSchiff effect
Strong gravitational fields
Binary systemsBlack holes
Gravitational waves
Cosmology
C. Lämmerzahl (ZARM, Bremen) Clocks and Gravity Airlie, May 23, 2006 13 / 55
The situation of standard physics Applications
Outline
1 The situation of standard physicsThe statusApplicationsProblems?
2 Search for Quantum GravityNeed for Quantum GravityOn strategies for the search for QG effectsObservation vs. Experiment
3 Space conditions
4 Gravity anomalies (in Universe and within Solar system)AnomaliesSolar system anomalies
5 Clocks and orbits
6 Summary and Outlook
7 Final remark: Technology and Fundamental Phyiscs
C. Lämmerzahl (ZARM, Bremen) Clocks and Gravity Airlie, May 23, 2006 14 / 55
The situation of standard physics Applications
Metrology
s
m
A
mol
cd
K
kg
GR ensuresuniqueness oftimekeeping in
gravitational fields
SR ensuresuniqueness oftimekeeping inmoving frames
GR ensuresuniqueness of
definition of mass
SR: Constancy ofspeed of light
3 · 10−15
10−124 · 10−8
8 · 10−8
10−4
3 · 10−7unknown ageingof prototype
SR & GR = Physics of space and time ≡ fundamental metrologyC. Lämmerzahl (ZARM, Bremen) Clocks and Gravity Airlie, May 23, 2006 15 / 55
The situation of standard physics Applications
Metrology
C. Lämmerzahl (ZARM, Bremen) Clocks and Gravity Airlie, May 23, 2006 16 / 55
The situation of standard physics Applications
TAI
C. Lämmerzahl (ZARM, Bremen) Clocks and Gravity Airlie, May 23, 2006 17 / 55
The situation of standard physics Applications
Time scales
C. Lämmerzahl (ZARM, Bremen) Clocks and Gravity Airlie, May 23, 2006 18 / 55
The situation of standard physics Applications
Practical application: Clocks and climate research
C. Lämmerzahl (ZARM, Bremen) Clocks and Gravity Airlie, May 23, 2006 19 / 55
The situation of standard physics Applications
Practical application: Clocks and climate research
C. Lämmerzahl (ZARM, Bremen) Clocks and Gravity Airlie, May 23, 2006 20 / 55
The situation of standard physics Applications
Practical application: Clocks and Earth dynamics
.
.
Clocks are of help tomeasure:
warming of oceans
motion of Earth’scrust, ...
...
C. Lämmerzahl (ZARM, Bremen) Clocks and Gravity Airlie, May 23, 2006 21 / 55
The situation of standard physics Applications
Practical application: Clocks and positions
C. Lämmerzahl (ZARM, Bremen) Clocks and Gravity Airlie, May 23, 2006 22 / 55
The situation of standard physics Problems?
Outline
1 The situation of standard physicsThe statusApplicationsProblems?
2 Search for Quantum GravityNeed for Quantum GravityOn strategies for the search for QG effectsObservation vs. Experiment
3 Space conditions
4 Gravity anomalies (in Universe and within Solar system)AnomaliesSolar system anomalies
5 Clocks and orbits
6 Summary and Outlook
7 Final remark: Technology and Fundamental Phyiscs
C. Lämmerzahl (ZARM, Bremen) Clocks and Gravity Airlie, May 23, 2006 23 / 55
The situation of standard physics Problems?
Problems?
Issues to be resloved
Need for Quantum Gravity
Gravity ”anomalies”
C. Lämmerzahl (ZARM, Bremen) Clocks and Gravity Airlie, May 23, 2006 24 / 55
Search for Quantum Gravity
Outline
1 The situation of standard physicsThe statusApplicationsProblems?
2 Search for Quantum GravityNeed for Quantum GravityOn strategies for the search for QG effectsObservation vs. Experiment
3 Space conditions
4 Gravity anomalies (in Universe and within Solar system)AnomaliesSolar system anomalies
5 Clocks and orbits
6 Summary and Outlook
7 Final remark: Technology and Fundamental Phyiscs
C. Lämmerzahl (ZARM, Bremen) Clocks and Gravity Airlie, May 23, 2006 25 / 55
Search for Quantum Gravity Need for Quantum Gravity
Outline
1 The situation of standard physicsThe statusApplicationsProblems?
2 Search for Quantum GravityNeed for Quantum GravityOn strategies for the search for QG effectsObservation vs. Experiment
3 Space conditions
4 Gravity anomalies (in Universe and within Solar system)AnomaliesSolar system anomalies
5 Clocks and orbits
6 Summary and Outlook
7 Final remark: Technology and Fundamental Phyiscs
C. Lämmerzahl (ZARM, Bremen) Clocks and Gravity Airlie, May 23, 2006 26 / 55
Search for Quantum Gravity Need for Quantum Gravity
The need for Quantum Gravity
Frame theories Interactions
Quantum theory Electrodynamics
Special Relativity Gravity
General Relativity Weak interaction
Statistical mechanics Strong interaction
Problem Wish
Incompatibility of quantumtheory and General Relativity
Unification of all interactions
Avoiding Singularities
Resolving the problem of time
Need of modifications of standard physics → search for modifications
C. Lämmerzahl (ZARM, Bremen) Clocks and Gravity Airlie, May 23, 2006 27 / 55
Search for Quantum Gravity Need for Quantum Gravity
Possible effects
Possible geometry relevant effects
Anisotropic speed of light
Anisotropy in quantum fields
Violation of UFF, UGR
Birefringence
Anomalous spin–coupling
Anomalous coupling of charge
Anomalous dispersion
Newton / Coulomb potential
Nonlinearities
Charge non–conservation
Active – passive mass andcharge
Other possible effects
Decoherence
Modified interference
Non–localities
Structure of parameters
Usually: parameters are asumedto be constant
In unification scenarios:parameters depend on time andposition, through scalar fields(dilaton, quintessence, varyinge) → scalar–tensor theories
Many of them typically clock tests
Clocks are an important device in the search for QGC. Lämmerzahl (ZARM, Bremen) Clocks and Gravity Airlie, May 23, 2006 28 / 55
Search for Quantum Gravity On strategies for the search for QG effects
Outline
1 The situation of standard physicsThe statusApplicationsProblems?
2 Search for Quantum GravityNeed for Quantum GravityOn strategies for the search for QG effectsObservation vs. Experiment
3 Space conditions
4 Gravity anomalies (in Universe and within Solar system)AnomaliesSolar system anomalies
5 Clocks and orbits
6 Summary and Outlook
7 Final remark: Technology and Fundamental Phyiscs
C. Lämmerzahl (ZARM, Bremen) Clocks and Gravity Airlie, May 23, 2006 29 / 55
Search for Quantum Gravity On strategies for the search for QG effects
Strategy: Exploration of new regimes
Standard physics experimentally well proven for standard energies, velocities,distances, ...Search for new effects ⇒ need to go to non–standard situations:
C. Lämmerzahl (ZARM, Bremen) Clocks and Gravity Airlie, May 23, 2006 30 / 55
Search for Quantum Gravity On strategies for the search for QG effects
Strategy: Exploration of new regimes
Standard physics experimentally well proven for standard energies, velocities,distances, ...Search for new effects ⇒ need to go to non–standard situations:Non–standard situations
Extreme high energies. Deviations from the standard dispersion relation
Extreme low energies. Space–time fluctuations, decoherence may affect quantumsystems at temperatures lower than 500 fK achieved in BECs
C. Lämmerzahl (ZARM, Bremen) Clocks and Gravity Airlie, May 23, 2006 30 / 55
Search for Quantum Gravity On strategies for the search for QG effects
Strategy: Exploration of new regimes
Standard physics experimentally well proven for standard energies, velocities,distances, ...Search for new effects ⇒ need to go to non–standard situations:Non–standard situations
Extreme high energies. Deviations from the standard dispersion relation
Extreme low energies. Space–time fluctuations, decoherence may affect quantumsystems at temperatures lower than 500 fK achieved in BECs
Extreme large distances.
Dark energy, dark matter, Pioneer anomalyUltra–low frequency gravitational waves (early universe)
Extreme small distances. Higher dimensional theories: violation of Newton’s lawat small (sub–mm) distances
C. Lämmerzahl (ZARM, Bremen) Clocks and Gravity Airlie, May 23, 2006 30 / 55
Search for Quantum Gravity On strategies for the search for QG effects
Strategy: Exploration of new regimes
Standard physics experimentally well proven for standard energies, velocities,distances, ...Search for new effects ⇒ need to go to non–standard situations:Non–standard situations
Extreme high energies. Deviations from the standard dispersion relation
Extreme low energies. Space–time fluctuations, decoherence may affect quantumsystems at temperatures lower than 500 fK achieved in BECs
Extreme large distances.
Dark energy, dark matter, Pioneer anomalyUltra–low frequency gravitational waves (early universe)
Extreme small distances. Higher dimensional theories: violation of Newton’s lawat small (sub–mm) distances
Extreme long timescales.
Search for space–time fluctuations in terms of 1/f–noiseTime dependence of constants
Extreme short timescales. Short time scales ↔ large energiesC. Lämmerzahl (ZARM, Bremen) Clocks and Gravity Airlie, May 23, 2006 30 / 55
Search for Quantum Gravity Observation vs. Experiment
Outline
1 The situation of standard physicsThe statusApplicationsProblems?
2 Search for Quantum GravityNeed for Quantum GravityOn strategies for the search for QG effectsObservation vs. Experiment
3 Space conditions
4 Gravity anomalies (in Universe and within Solar system)AnomaliesSolar system anomalies
5 Clocks and orbits
6 Summary and Outlook
7 Final remark: Technology and Fundamental Phyiscs
C. Lämmerzahl (ZARM, Bremen) Clocks and Gravity Airlie, May 23, 2006 31 / 55
Search for Quantum Gravity Observation vs. Experiment
Observations vs. Experiment
Comparison: high energy cosmic ray observation ↔ low energy laboratory exp.
C. Lämmerzahl (ZARM, Bremen) Clocks and Gravity Airlie, May 23, 2006 32 / 55
Search for Quantum Gravity Observation vs. Experiment
Observations vs. Experiment
Comparison: high energy cosmic ray observation ↔ low energy laboratory exp.Astrophysical observations
+ Availability of ultra high energies of more than 1021 eV– No systematic repeatability
– No unique interpretation
C. Lämmerzahl (ZARM, Bremen) Clocks and Gravity Airlie, May 23, 2006 32 / 55
Search for Quantum Gravity Observation vs. Experiment
Observations vs. Experiment
Comparison: high energy cosmic ray observation ↔ low energy laboratory exp.Astrophysical observations
+ Availability of ultra high energies of more than 1021 eV– No systematic repeatability
– No unique interpretation
Laboratory search (including space)
– Only small energies are available
+ Repeatability of the experiment, systematic variation of initial and boundaryconditions, used for:
Identification of causeImprovement of precision of result
+ Ultra–low temperatures, ultrastable devices like optical resonators can beobtained in the laboratory / in space only
C. Lämmerzahl (ZARM, Bremen) Clocks and Gravity Airlie, May 23, 2006 32 / 55
Search for Quantum Gravity Observation vs. Experiment
Observations vs. Experiment
Comparison: high energy cosmic ray observation ↔ low energy laboratory exp.Astrophysical observations
+ Availability of ultra high energies of more than 1021 eV– No systematic repeatability
– No unique interpretation
Laboratory search (including space)
– Only small energies are available
+ Repeatability of the experiment, systematic variation of initial and boundaryconditions, used for:
Identification of causeImprovement of precision of result
+ Ultra–low temperatures, ultrastable devices like optical resonators can beobtained in the laboratory / in space only
Due to stability and repeatability of experiments, laboratory searches for quantumgravity effects may be as promising as astrophysical observations
C. Lämmerzahl (ZARM, Bremen) Clocks and Gravity Airlie, May 23, 2006 32 / 55
Space conditions
Outline
1 The situation of standard physicsThe statusApplicationsProblems?
2 Search for Quantum GravityNeed for Quantum GravityOn strategies for the search for QG effectsObservation vs. Experiment
3 Space conditions
4 Gravity anomalies (in Universe and within Solar system)AnomaliesSolar system anomalies
5 Clocks and orbits
6 Summary and Outlook
7 Final remark: Technology and Fundamental Phyiscs
C. Lämmerzahl (ZARM, Bremen) Clocks and Gravity Airlie, May 23, 2006 33 / 55
Space conditions
Space conditions
Particular space conditions and corresponding tests
Space conditions
Free fall – no gravitational force
Tests
C. Lämmerzahl (ZARM, Bremen) Clocks and Gravity Airlie, May 23, 2006 34 / 55
Space conditions
Space conditions
Particular space conditions and corresponding tests
Space conditions
Free fall – no gravitational force
Tests
Test of Universality of Free Fall
Long time for accumulatingsmall forces
C. Lämmerzahl (ZARM, Bremen) Clocks and Gravity Airlie, May 23, 2006 34 / 55
Space conditions
Space conditions
Particular space conditions and corresponding tests
Space conditions
Free fall – no gravitational force
Large differences in thegravitational potential
Tests
Test of Universality of Free Fall
Long time for accumulatingsmall forces
C. Lämmerzahl (ZARM, Bremen) Clocks and Gravity Airlie, May 23, 2006 34 / 55
Space conditions
Space conditions
Particular space conditions and corresponding tests
Space conditions
Free fall – no gravitational force
Large differences in thegravitational potential
Tests
Test of Universality of Free Fall
Test of Universality ofGravitational Redshift
Measurement of absolutegravitational redshift
Long time for accumulatingsmall forces
C. Lämmerzahl (ZARM, Bremen) Clocks and Gravity Airlie, May 23, 2006 34 / 55
Space conditions
Space conditions
Particular space conditions and corresponding tests
Space conditions
Free fall – no gravitational force
Large differences in thegravitational potential
Huge distances
Tests
Test of Universality of Free Fall
Test of Universality ofGravitational Redshift
Measurement of absolutegravitational redshift
Long time for accumulatingsmall forces
C. Lämmerzahl (ZARM, Bremen) Clocks and Gravity Airlie, May 23, 2006 34 / 55
Space conditions
Space conditions
Particular space conditions and corresponding tests
Space conditions
Free fall – no gravitational force
Large differences in thegravitational potential
Huge distances
Tests
Test of Universality of Free Fall
Test of Universality ofGravitational Redshift
Measurement of absolutegravitational redshift
Long time for accumulatingsmall forces
Newton at large distances
low frequency gravitationalwaves
C. Lämmerzahl (ZARM, Bremen) Clocks and Gravity Airlie, May 23, 2006 34 / 55
Space conditions
Space conditions
Particular space conditions and corresponding tests
Space conditions
Free fall – no gravitational force
Large differences in thegravitational potential
Huge distances
Large velocities
Tests
Test of Universality of Free Fall
Test of Universality ofGravitational Redshift
Measurement of absolutegravitational redshift
Long time for accumulatingsmall forces
Newton at large distances
low frequency gravitationalwaves
C. Lämmerzahl (ZARM, Bremen) Clocks and Gravity Airlie, May 23, 2006 34 / 55
Space conditions
Space conditions
Particular space conditions and corresponding tests
Space conditions
Free fall – no gravitational force
Large differences in thegravitational potential
Huge distances
Large velocities
Tests
Test of Universality of Free Fall
Test of Universality ofGravitational Redshift
Measurement of absolutegravitational redshift
Test of Lorentz invariance
Long time for accumulatingsmall forces
Newton at large distances
low frequency gravitationalwaves
C. Lämmerzahl (ZARM, Bremen) Clocks and Gravity Airlie, May 23, 2006 34 / 55
Space conditions
Space conditions
Particular space conditions and corresponding tests
Space conditions
Free fall – no gravitational force
Large differences in thegravitational potential
Huge distances
Large velocities
Low noise
Well–defined clocks
Tests
Test of Universality of Free Fall
Test of Universality ofGravitational Redshift
Measurement of absolutegravitational redshift
Test of Lorentz invariance
Long time for accumulatingsmall forces
Newton at large distances
low frequency gravitationalwaves
C. Lämmerzahl (ZARM, Bremen) Clocks and Gravity Airlie, May 23, 2006 34 / 55
Space conditions
Space conditions
Particular space conditions and corresponding tests
Free fall – no gravit. force
Large diff. in grav. pot.
Huge distances
Large velocities
Low noise
Well–defined time
Test of UFF
Long accumul. small forces
Test of UGR
absolute gravitat. redshift
Relativistic gravity
Newton at large distances
low frequency gravit. waves
Test of LI
MICROSCOPESTEP, GG, HYPER
GP-BHYPER
ACES, OPTIS, PARCS,SUMO, SPACETIME, RAC
ACES, GP-AOPTIS
LLR, CassiniLATOR, ASTROD
DSGE
LISAASTROD
ACES, OPTIS, PARCS,SUMO, RACE
C. Lämmerzahl (ZARM, Bremen) Clocks and Gravity Airlie, May 23, 2006 35 / 55
Space conditions
Example: OPTIS
OPTIS = OPtical Tests of the Isotropy of SpaceOPTIS = Mission for improved tests of Special and General Relativity
Objectives: Michelson–Morley, Kennedy–Thorndike, time dilation, UGR, absoluteredshift, perihelion shift, Lense–Thirring, Yukawa (→ poster)
C. Lämmerzahl (ZARM, Bremen) Clocks and Gravity Airlie, May 23, 2006 36 / 55
Gravity anomalies (in Universe and within Solar system)
Outline
1 The situation of standard physicsThe statusApplicationsProblems?
2 Search for Quantum GravityNeed for Quantum GravityOn strategies for the search for QG effectsObservation vs. Experiment
3 Space conditions
4 Gravity anomalies (in Universe and within Solar system)AnomaliesSolar system anomalies
5 Clocks and orbits
6 Summary and Outlook
7 Final remark: Technology and Fundamental Phyiscs
C. Lämmerzahl (ZARM, Bremen) Clocks and Gravity Airlie, May 23, 2006 37 / 55
Gravity anomalies (in Universe and within Solar system) Anomalies
Outline
1 The situation of standard physicsThe statusApplicationsProblems?
2 Search for Quantum GravityNeed for Quantum GravityOn strategies for the search for QG effectsObservation vs. Experiment
3 Space conditions
4 Gravity anomalies (in Universe and within Solar system)AnomaliesSolar system anomalies
5 Clocks and orbits
6 Summary and Outlook
7 Final remark: Technology and Fundamental Phyiscs
C. Lämmerzahl (ZARM, Bremen) Clocks and Gravity Airlie, May 23, 2006 38 / 55
Gravity anomalies (in Universe and within Solar system) Anomalies
But: Dark clouds over General Relativity?
Unexplained observations
C. Lämmerzahl (ZARM, Bremen) Clocks and Gravity Airlie, May 23, 2006 39 / 55
Gravity anomalies (in Universe and within Solar system) Anomalies
But: Dark clouds over General Relativity?
Unexplained observations
Dark Matter (Zwicky 1933)Needed to describe galactic rotation curves, lensing, structure formation
C. Lämmerzahl (ZARM, Bremen) Clocks and Gravity Airlie, May 23, 2006 39 / 55
Gravity anomalies (in Universe and within Solar system) Anomalies
But: Dark clouds over General Relativity?
Unexplained observations
Dark Matter (Zwicky 1933)Needed to describe galactic rotation curves, lensing, structure formation
Dark Energy (Turner 1999)Needed to describe the accelerated expansion of our universe
C. Lämmerzahl (ZARM, Bremen) Clocks and Gravity Airlie, May 23, 2006 39 / 55
Gravity anomalies (in Universe and within Solar system) Anomalies
But: Dark clouds over General Relativity?
Unexplained observations
Dark Matter (Zwicky 1933)Needed to describe galactic rotation curves, lensing, structure formation
Dark Energy (Turner 1999)Needed to describe the accelerated expansion of our universe
Pioneer Anomaly (Anderson et al 1998, 2002)Non–Newtonian acceleration of Pioneer spacecraft toward the Sun
C. Lämmerzahl (ZARM, Bremen) Clocks and Gravity Airlie, May 23, 2006 39 / 55
Gravity anomalies (in Universe and within Solar system) Anomalies
But: Dark clouds over General Relativity?
Unexplained observations
Dark Matter (Zwicky 1933)Needed to describe galactic rotation curves, lensing, structure formation
Dark Energy (Turner 1999)Needed to describe the accelerated expansion of our universe
Pioneer Anomaly (Anderson et al 1998, 2002)Non–Newtonian acceleration of Pioneer spacecraft toward the Sun
Flyby anomaly (ESA and NASA communications)Satellite velocities are too large by a few mm/s after fly–bys
C. Lämmerzahl (ZARM, Bremen) Clocks and Gravity Airlie, May 23, 2006 39 / 55
Gravity anomalies (in Universe and within Solar system) Anomalies
But: Dark clouds over General Relativity?
Unexplained observations
Dark Matter (Zwicky 1933)Needed to describe galactic rotation curves, lensing, structure formation
Dark Energy (Turner 1999)Needed to describe the accelerated expansion of our universe
Pioneer Anomaly (Anderson et al 1998, 2002)Non–Newtonian acceleration of Pioneer spacecraft toward the Sun
Flyby anomaly (ESA and NASA communications)Satellite velocities are too large by a few mm/s after fly–bys
Increase of Astronomical Unit (Krasinski & Brumberg 2005, Pitjeva 2005)Distance Earth–Sun increases by ∼ 10 m/cy
C. Lämmerzahl (ZARM, Bremen) Clocks and Gravity Airlie, May 23, 2006 39 / 55
Gravity anomalies (in Universe and within Solar system) Anomalies
But: Dark clouds over General Relativity?
Unexplained observations
Dark Matter (Zwicky 1933)Needed to describe galactic rotation curves, lensing, structure formation
Dark Energy (Turner 1999)Needed to describe the accelerated expansion of our universe
Pioneer Anomaly (Anderson et al 1998, 2002)Non–Newtonian acceleration of Pioneer spacecraft toward the Sun
Flyby anomaly (ESA and NASA communications)Satellite velocities are too large by a few mm/s after fly–bys
Increase of Astronomical Unit (Krasinski & Brumberg 2005, Pitjeva 2005)Distance Earth–Sun increases by ∼ 10 m/cy
Quadrupole and octopole anomaly (Tegmark et al 2004, Schwarz et al 2005)Quadrupole and octopole of CMB are correlated with Solar system ecliptic
C. Lämmerzahl (ZARM, Bremen) Clocks and Gravity Airlie, May 23, 2006 39 / 55
Gravity anomalies (in Universe and within Solar system) Anomalies
But: Dark clouds over General Relativity?
Unexplained observations
Dark Matter (Zwicky 1933)Needed to describe galactic rotation curves, lensing, structure formation
Dark Energy (Turner 1999)Needed to describe the accelerated expansion of our universe
Pioneer Anomaly (Anderson et al 1998, 2002)Non–Newtonian acceleration of Pioneer spacecraft toward the Sun
Flyby anomaly (ESA and NASA communications)Satellite velocities are too large by a few mm/s after fly–bys
Increase of Astronomical Unit (Krasinski & Brumberg 2005, Pitjeva 2005)Distance Earth–Sun increases by ∼ 10 m/cy
Quadrupole and octopole anomaly (Tegmark et al 2004, Schwarz et al 2005)Quadrupole and octopole of CMB are correlated with Solar system ecliptic
Is the gravitational physics in the Solar system really well understood?Gravity on large scales? ↔ influence of DM and/or DE?Additional exploration with clocks!
C. Lämmerzahl (ZARM, Bremen) Clocks and Gravity Airlie, May 23, 2006 39 / 55
Gravity anomalies (in Universe and within Solar system) Solar system anomalies
Outline
1 The situation of standard physicsThe statusApplicationsProblems?
2 Search for Quantum GravityNeed for Quantum GravityOn strategies for the search for QG effectsObservation vs. Experiment
3 Space conditions
4 Gravity anomalies (in Universe and within Solar system)AnomaliesSolar system anomalies
5 Clocks and orbits
6 Summary and Outlook
7 Final remark: Technology and Fundamental Phyiscs
C. Lämmerzahl (ZARM, Bremen) Clocks and Gravity Airlie, May 23, 2006 40 / 55
Gravity anomalies (in Universe and within Solar system) Solar system anomalies
The Pioneer anomaly
The observation (Anderson et al 1998, 2002)
Measured constant acceleration
aPioneer = (8.74 ± 1.33) · 10−10 m/s2
Acceleration constant and toward the Sun
New information from
Clock on new DSGE
Drift of clocks on Earth may simulate the effect → clock comparison
C. Lämmerzahl (ZARM, Bremen) Clocks and Gravity Airlie, May 23, 2006 41 / 55
Gravity anomalies (in Universe and within Solar system) Solar system anomalies
Theory
Theoretical considerations
Cosmological influence orders of magnitude too small in order to explain thePioneer anomaly (e.g. C.L. & Dittus 2005, Giulini & Matteo 2006)
Yukawa describing galactic rotation curve can be used to describe Pioneeranomaly (Dittus & C.L. 2005)
Cosmological constant cannot be responsible for Pioneer anomaly(Kagramanova, Kunz & C.L. 2006)
C. Lämmerzahl (ZARM, Bremen) Clocks and Gravity Airlie, May 23, 2006 42 / 55
Gravity anomalies (in Universe and within Solar system) Solar system anomalies
Outlook: New mission
C. Lämmerzahl (ZARM, Bremen) Clocks and Gravity Airlie, May 23, 2006 43 / 55
Gravity anomalies (in Universe and within Solar system) Solar system anomalies
Outlook: New mission
Active spacecraft, passive test mass
Accurate tracking of test mass
2–step–tracking
Radio: Earth — spacecraftLaser: spacecraft — test mass
Flexible formation: varying distance
Test mass is at environmentally quietdistance from spacecraft ∼ 200 mOccasional manoeuvres to maintainformation
New Pioneer Explorer should be equippedwith stable clockFor Pioneer anomaly:
ΔPioneerνν
=1c2
∫ 90 AUJupiter
aPioneerdx = 10−13
C. Lämmerzahl (ZARM, Bremen) Clocks and Gravity Airlie, May 23, 2006 43 / 55
Gravity anomalies (in Universe and within Solar system) Solar system anomalies
The flyby anomaly
Observation
After satellite flybys at Earth the velocity is too large by a few mm/s
First Galileo flyby 1990, NEAR flyby 1998, Cassini flyby 1999, Rosetta flyby2005,Messenger flyby 2005
GEGA1:Two–way S–bandDoppler residuals &range residuals
C. Lämmerzahl (ZARM, Bremen) Clocks and Gravity Airlie, May 23, 2006 44 / 55
Gravity anomalies (in Universe and within Solar system) Solar system anomalies
The flyby anomaly
Observation
After satellite flybys at Earth the velocity is too large by a few mm/s
First Galileo flyby 1990, NEAR flyby 1998, Cassini flyby 1999, Rosetta flyby2005,Messenger flyby 2005
NEGA:Two–way X–bandDoppler residuals &range residuals
C. Lämmerzahl (ZARM, Bremen) Clocks and Gravity Airlie, May 23, 2006 44 / 55
Gravity anomalies (in Universe and within Solar system) Solar system anomalies
The flyby anomaly
Observation
After satellite flybys at Earth the velocity is too large by a few mm/s
First Galileo flyby 1990, NEAR flyby 1998, Cassini flyby 1999, Rosetta flyby2005,Messenger flyby 2005
NEGA:Two–way X–bandDoppler residuals &range residuals
New information from:
Better time resolution of velocity increase: continuous observation
Clock on spacecraft
Observation of Mars flyby (Rosetta)
C. Lämmerzahl (ZARM, Bremen) Clocks and Gravity Airlie, May 23, 2006 44 / 55
Gravity anomalies (in Universe and within Solar system) Solar system anomalies
Increase of Astronomical Unit
Observation
Various groups reported
Krasinsky & Brumberg 2005: 15 ± 4 m/cyPitjeva 2005: 7 ± 1 m/cy
Remarks / Questions
Ġ excluded by LLR
Mass loss of Sun leads only to 1 m/cy
Influence of cosmic expansion by many orders of magnitude too small
Interplanetary plasma?
Effect can again be simulated by drift of clocks
C. Lämmerzahl (ZARM, Bremen) Clocks and Gravity Airlie, May 23, 2006 45 / 55
Gravity anomalies (in Universe and within Solar system) Solar system anomalies
Summary
Possible questions
Influence of cosmic expansion? (aPioneer ≈ cH)Something wrong with weak gravity?
Do clocks on Earth behave properly?
Clocks
Clocks are essential in helping to explore
Pioneer anomaly
Flyby anomaly
Secular increase of AU
C. Lämmerzahl (ZARM, Bremen) Clocks and Gravity Airlie, May 23, 2006 46 / 55
Clocks and orbits
Outline
1 The situation of standard physicsThe statusApplicationsProblems?
2 Search for Quantum GravityNeed for Quantum GravityOn strategies for the search for QG effectsObservation vs. Experiment
3 Space conditions
4 Gravity anomalies (in Universe and within Solar system)AnomaliesSolar system anomalies
5 Clocks and orbits
6 Summary and Outlook
7 Final remark: Technology and Fundamental Phyiscs
C. Lämmerzahl (ZARM, Bremen) Clocks and Gravity Airlie, May 23, 2006 47 / 55
Clocks and orbits
Gravity, geometry, clocks, and particle motion
Gravity = geometry = metric + connection = clock and particle motionFor the full exploration of gravity one needs position and time
Measurement of time
Clocks measure proper time related to dxμ
T =∫
worldline
ds with ds2 = g(x, dx) , g(x, λdx) = λ2g(x, dx)
For Riemanian space–time metric ds2 = gμνdxμdxν
T =∫
worldline of clock
√gμνdxμdxν ≈
∫ (1 − U + ẋ2)dx0 +
∫g0idx
i
Two clocks at different positions: gravitational redshift
C. Lämmerzahl (ZARM, Bremen) Clocks and Gravity Airlie, May 23, 2006 48 / 55
Clocks and orbits
Gravity, geometry, clocks, and particle motion
Motion of particles
Equation of motion for particles: Weak Equivalence Principle ⇒
0 = vν∂μvν + Hμ(x, v) = { μρσ } vμvσ + hμ(x, v)
3–acceleration
ẍi = ∂iU︸︷︷︸Newton
+ (∂ihj − ∂jhi)ẋj︸ ︷︷ ︸Lense−Thirring
+Υi + Υij ẋj + Υijkẋ
j ẋk + . . .
Equation of motion respects UFF but violates Einstein’s elevator
Such terms may play a role in Pioneer anomaly or flyby anomaly
Need of precise clocks for tracking of satellites in oder to determine theseterms
Time and orbit of spacecraft are independent observablesOnly in Einstein’s General Relativity both are governed by the space–time metricSpacecraft should carry clocks onboard
C. Lämmerzahl (ZARM, Bremen) Clocks and Gravity Airlie, May 23, 2006 49 / 55
Summary and Outlook
Outline
1 The situation of standard physicsThe statusApplicationsProblems?
2 Search for Quantum GravityNeed for Quantum GravityOn strategies for the search for QG effectsObservation vs. Experiment
3 Space conditions
4 Gravity anomalies (in Universe and within Solar system)AnomaliesSolar system anomalies
5 Clocks and orbits
6 Summary and Outlook
7 Final remark: Technology and Fundamental Phyiscs
C. Lämmerzahl (ZARM, Bremen) Clocks and Gravity Airlie, May 23, 2006 50 / 55
Summary and Outlook
Summary
Summary
Clocks are needed for most space projects
Clocks are essential for the search of quantum gravity effects
Clocks will play an important role in resolving current gravity puzzles
C.L. & Dittus 2000
Dittus & C.L. (eds) 2003: Special Issue of Gen. Rel. Grav. on FundamentalPhysics on the ISS
Dittus, C.L & Turyshev 2007 (forthcoming book (Springer) on spacetechnologies and missions)
C. Lämmerzahl (ZARM, Bremen) Clocks and Gravity Airlie, May 23, 2006 51 / 55
Summary and Outlook
Gravity plays a major role in modern physics
Outlook: experiment/observation in gravitational physics
Data basis improves
New gravitating systems: binary pulsar → new tests of GR, non–linearities, ...Longer data span: LLR → Ġ/G, equivalence principle, ...Longer data span: ephemerides → increase of AUImproved data from new measurements: Planck → cosmology, quadrupole, ...UHECR: Auger, .... → dispersion relation, search for QG, ...Gravitational waves → black holes, binary systems, ...Satellite navigation → flybyNew Horizon mission
New Pioneer mission ....
Vastly increasing knowledge about gravity ...
Gravity is a very dynamic field – new important applications for daily life
C. Lämmerzahl (ZARM, Bremen) Clocks and Gravity Airlie, May 23, 2006 52 / 55
Final remark: Technology and Fundamental Phyiscs
Outline
1 The situation of standard physicsThe statusApplicationsProblems?
2 Search for Quantum GravityNeed for Quantum GravityOn strategies for the search for QG effectsObservation vs. Experiment
3 Space conditions
4 Gravity anomalies (in Universe and within Solar system)AnomaliesSolar system anomalies
5 Clocks and orbits
6 Summary and Outlook
7 Final remark: Technology and Fundamental Phyiscs
C. Lämmerzahl (ZARM, Bremen) Clocks and Gravity Airlie, May 23, 2006 53 / 55
Final remark: Technology and Fundamental Phyiscs
Technology vs. Fundamental Phyiscs
From Philosophy of Science:
⇒ ”Fundamental Physics makes technological progress possible”⇐ ”Technology stimulates scientific inventiveness”, e.g. Einstein–Poincaré
simultaneity (Gallison 2003)
Not possible: To have solely technological development (Carrier 2006):
⇔ ”... practical challenges cannot appropriately be met without treatingproblems in basic science ... applied research naturally grows into basicscience ... Applied research tends to transcend applied questions formethodological reasons. A lack of deeper understanding of a phenomenoneventually impairs the prospects of its technological use. ... Uncovering therelevant mechanisms and embedding them in a theoretical framework is ofsome use typically for ascertaining or improving the applicability of a finding.Scientific understanding makes generalizations robust ... Treating appliedquestions appropriately requires not treating them exclusively as appliedquestions.”
Even the demand of mere technology needs Fundamental Physics.
C. Lämmerzahl (ZARM, Bremen) Clocks and Gravity Airlie, May 23, 2006 54 / 55
Final remark: Technology and Fundamental Phyiscs
Final Conclusion
C. Lämmerzahl (ZARM, Bremen) Clocks and Gravity Airlie, May 23, 2006 55 / 55
The situation of standard physicsThe statusApplicationsProblems?
Search for Quantum GravityNeed for Quantum GravityOn strategies for the search for QG effectsObservation vs. Experiment
Space conditionsGravity anomalies (in Universe and within Solar system)AnomaliesSolar system anomalies
Clocks and orbitsSummary and OutlookFinal remark: Technology and Fundamental Phyiscs
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