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An overview of the key differences between newtonian and relativistic frameworks, specifically focusing on the concepts of rigid geometry, universal clocks, gravitational force, and interaction with distorted spacetime. It also discusses the scientific method and three 'classic' tests of general relativity, including the precession of mercury's orbit, deflection of starlight, and gravitational redshift.
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Newtonian:Rigid flat geometry, universal clocksGravitational force between objects“Magic” dependence on mass
Relativistic:Objects interact withdistorted spacetime“Natural” reference framesare in free fall Docsity.com
Is^ There^ a^ Real
(i.e.^ measurable)
Distinction
between^ General
Relativity^ and
the Newtonian^
Viewpoint?
-^ Absolutely! •^ Discriminating
-^ Was^ Einstein
The^3 “Classic”
Tests^ of^ General Relativity
-^ Precession^ of
-^ Deflection^ of
-^ Gravitational
Newtonian^
General Relativity
-^ Light^ is^ deflected
by gravitational field – called “gravitational^ lensing”
-^ Much^ like^ ball^ deflected
by divot
Deflection^ of
Starlight^ During
an Eclipse If deflection = 1.74 arcseconds
General Relativity Prediction If deflection = 0.87 arcseconds
Newtonian Prediction If deflection = 0.0 arcseconds
Both wrong!!
As^ GR^ predicts,
starlight^ is^ deflected
Principle (universality^ of^ free
‐fall)^ by pinging^ moon^ with^
laser^ pulse
-^ GR^ relies^ completely
on^ this principle:^ accelerations independent^ of^ mass
gravity^ can be^ “fictitious”^ force • Test^ Earth^ and^ Moon
in^ free^ fall toward^ (around)^ Sun
-^ Precisely^ time^ round
‐trip^ light time^ to^ moon^ (2.5^ s) • Previous^ experiments
got^ 2– cm^ accuracy • APOLLO^ gets^1 mm^
accuracy
-^ Carefully^ measure
orbit^ and look for distortions^ or displacements not^ consistent with GR (^14) • One part in 10 precision!
Apollo 11 reflector array Apache Point Observatory 3.5 mtelescope (NM)
LIGO is a pair of L-shaped laser interferometers (4 km vacuum pipe legs!),with one station in Hanford WA, and the other in Livingston LA.Could be the first to detect grav. waves as black holes inspiral and merge.http://www.ligo.caltech.edu/
LISA:^ A^ space
‐based^ grav.
wave observatory LISA is like a LIGO in space, with three legs, 5 million km long. Will see gravity waves full time, from many sources (a symphony of waves).Joint European/US project not yet fully funded
http://lisa.nasa.gov/
