OPERA: The numbers Measurement of distance (GPS) 732 km +/- 20 cm Time of flight (GPS) 2.43006 ms +/- 10 ns Velocity = distance/time Δv/v = 2.5 x 10 -5 (25 ppm) Note: proton pulse 10 μs long (10,000 ns) 60 ns early (18 m??)
OPERA: The snags Not direct comparison Light does not travel through mountain Accurate measurement of distance Relies on GPS Accurate measurement of time-of-flight Relies on GPS and statistics (pulses) Relatively short distance/time Need to direct beam at the moon Systematic error ?
II The theory of relativity (special) Laws of physics identical for observers in uniform motion Speed of light in vacuum a fundamental constant Length contraction Time dilation Mass increase E = mc 2 Implications for bodies at high speed
Early experiments Kaufmann, Bucherer Particle accelerators Length contraction Time dilation Mass increase Modern particle accelerators Speed limit Particle creation E = mc 2 Evidence for relativity
CERN (Geneva) energy increase velocity increase? K.E = 1/2mv 2 mass increases
Relativity skepticism Extraordinary concept Counter-intuitive Only observable at tremendous speeds Only observable for subatomic particles Simple maths Time and distance calculations Personalization Confusion of discovery and justification Speed of light plays role of infinity Dr Al Kelly Einstein wrong
III The general theory of relativity Gravity = curvature of space and time Laws of physics identical for all observers Speed of light in vacuum a universal constant Principle of equivalence New view of gravity Cosmological implications Matter warps space and time General Relativity (1915)
General relativity (evidence) Bending of starlight by sun Eddington experiment Time dilation by gravity Pound experiment Expanding universe Hubbles law Geodesic effect Everett experiment Breakdown at quantum scales
Skepticism from astronomy Supernova Huge implosion of massive star Light released Neutrinos released Supernova 1987a Neutrinos detected Light detected Time difference of 5 min Not 5 years !
IV Skepticism in science Many years for new result to be accepted Must be reproducible Must fit known data Paradigm shift Slow, gradual process (DJ) Consensus process If so Compare: accelerating universe Thomas Kuhn
Skepticism in the media Scientific skepticism misunderstood Attributed to conservatism Role of evidence misunderstood Balanced debate unweighted Science journalism: news driven Bjorn Lomborg
Summary Extraordinary result Indirect measurement Contradicts theory Special and general relativity Contradicts experiment Particle experiments Astronomy experiments Extraordinary evidence? X Explanation ?
The verdict Unreliable result Re-runs possible but not beneficial Reproducible? Many checks carried out Technical flaw discovered Cable to external GPS clock Accounts for time discrepancy A second flaw Internal clock We told you so
Lessons to be learnt 1.Unexpected result? Check, check, check Emphasis on simple errors 2. Do not publish If in conflict with theory and experiment 3. Do not underestimate the media Einstein wrong is a huge story Further reading: ANTIMATTER
Relativity and GPS Signal from satellite compare time received to transmitted synchronized clocks Convert time to distance x speed of radiowaves Assumes constancy of speed of light Triangulation using 4 sources accurate to within 5 metres
GPS: a relativistic correction Motion of satellite (SR) Clocks slow by 7 μs/day Reduced gravity field (GR) Clocks fast by 45 μs/day Satellite clocks fast by 38 μs/ day Well-known correction to GPS OPERA - new correction? (18m?) Synchronization of satellite/earth clocks
What if result stands? First evidence of string theory ? Extra dimensions Shortcut? Doesnt violate relativity Unified field theory 7 dimensions curled up? High energy Lightest particles Doesnt contradict previous results Further reading: ANTIMATTER
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