Beautiful, Simple and Profound -
Modern Tests of Relativity

Modern Tests of General Relativity

Gravitational lensing

  Recently, these telescopes have measured the deflection of
  radio waves by the Sun to extremely high precision,
  confirming the amount of deflection predicted by general
  relativity aspect to the 0.03% level. 

  Review of Astronomers' Tools


Light travel time delay testing


  Irwin I. Shapiro proposed another test, beyond the classical
  tests, which could be performed within the Solar System. It
  is sometimes called the fourth "classical" test of general
  relativity. He predicted a relativistic time delay (Shapiro
  delay) in the round-trip travel time for radar signals
  reflecting off other planets.

  Observing radar reflections from Mercury and Venus just
  before and after it is eclipsed by the Sun agrees with
  general relativity theory at the 5% level. More recently,
  the Cassini probe has undertaken a similar experiment which
  gave agreement with general relativity at the 0.002% level.

The Equivalence Principle
  Start at minute 13 to 23:30

  The equivalence principle, in its simplest form, asserts
  that the trajectories of falling bodies in a gravitational
  field should be independent of their mass and internal
  structure, provided they are small enough not to disturb the
  environment or be affected by tidal forces. This idea has
  been tested to extremely high precision by Eötvös torsion
  balance experiments, which look for a differential
  acceleration between two test masses.

Global Positioning System

  The Global Positioning System (GPS) uses accurate, stable
  atomic clocks in satellites and on the ground to provide
  world-wide position and time determination. These clocks
  have gravitational and motional frequency shifts which are
  so large that, without carefully accounting for numerous
  relativistic effects, the system would not work. This paper
  discusses the conceptual basis, founded on special and
  general relativity, for navigation using GPS. Relativistic
  principles and effects which must be considered include the
  constancy of the speed of light, the equivalence principle,
  the Sagnac effect, time dilation, gravitational frequency
  shifts, and relativity of synchronization.

Frame-dragging tests

  Lense-Thirring Precession


    In general relativity, Lense-Thirring precession or the
    Lense-Thirring effect (named after Josef Lense and Hans
    Thirring) is a relativistic correction to the precession
    of a gyroscope near a large rotating mass such as the
    Earth. It is a gravitomagnetic frame-dragging effect.
    According to a recent historical analysis by Pfister, the
    effect should be renamed as Einstein-Thirring-Lense
    effect. It is a prediction of general relativity
    consisting of secular precessions of the longitude of the
    ascending node and the argument of pericenter of a test
    particle freely orbiting a central spinning mass endowed
    with angular momentum S.

    The difference between de Sitter precession and the
    Lense-Thirring effect is that the de Sitter effect is due
    simply to the presence of a central mass, whereas the
    Lense-Thirring effect is due to the rotation of the
    central mass. The total precession is calculated by
    combining the de Sitter precession with the Lense-Thirring

  Gravity Probe B

    Gravity Probe B (GP-B) was a satellite-based mission to
    measure spacetime curvature near Earth, and thereby the
    stress-energy tensor (which is related to the distribution
    and the motion of matter in space) in and near Earth. 

    By August 2008, the frame-dragging effect had been
    confirmed to within 15% of the expected result, and the
    December 2008 NASA report indicated that the geodetic
    effect was confirmed to better than 0.5%.

  Einstein was right - again! (Satellite observations of
  Black Holes confirm frame-dragging effect 80 years after

Einstein Online - Spotlights on relativity