The theory of → gravitation developed by Albert Einstein
(1916) that describes the gravitation as the → space-time
curvature caused by the presence of matter or energy.
Mass creates a → gravitational field which
distorts the space and changes the flow of time. In other words, mass
causes a deviation of the → metric of
space-time continuum from that of the “flat” space-time structure described by the
→ Euclidean geometry and treated in
→ special relativity.
General relativity developed from the
→ principle of equivalence between
gravitational and inertial forces.
According to general relativity, photons follow a curved path
in a gravitational field. This prediction was confirmed by the
measurements of star positions near the solar limb during the
total eclipse of 1919. The same effect is seen in the
delay of radio signals coming from distant space probes when
grazing the Sun’s surface. Moreover, the space curvature caused by
the Sun makes the → perihelion
of Mercury’s orbit advance by 43’’ per century more than that predicted by
Newton’s theory of gravitation. The → perihelion advance
can reach several degrees per year for
→ binary pulsar orbits.
Another effect predicted by general
relativity is the → gravitational reddening.
This effect is verified in the → redshift
of spectral lines in the
solar spectrum and, even more obviously, in
→ white dwarfs. Other predictions of the theory include
→ gravitational lensing,
→ gravitational waves, and the
invariance of Newton’s → gravitational constant.
See also: → general; → relativity.
