An Etymological Dictionary of Astronomy and Astrophysics
English-French-Persian

The laws of physics are the same in all → inertial reference frames and are invariant under the → Lorentz transformation. The → speed of light is a → physical constant, i.e. it is the same for all observers in uniform motion. Einsteinian relativity is prompted by the → Newton-Maxwell incompatibility. See also: → Galilean relativity, → Newtonian relativity.

→ Einstein; → relativity.

The principle according to which the fundamental laws of physics are the same in all frames of reference moving with constant velocity with respect to one another (→ inertial reference frames). Same as → Galilean invariance and → Newtonian relativity.
See also: → Galilean transformation, → Einsteinian relativity.

→ Galilean; → relativity.

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.

→ general; → relativity.

The Newton's equations of motion, if they hold in any → reference frame, they are valid also in any other reference frame moving with uniform velocity relative to the first.

→ Newtonian; → principle; → relativity.

The laws of physics are unchanged under → Galilean transformation. This implies that no mechanical experiment can detect any intrinsic diff between two → inertial frames. Same as → Galilean relativity.

→ Newton; → relativity.

The first postulate in Einstein's theory of → special relativity whereby all the laws of physics are the same in every → inertial reference frame. In other words, no physical measurement can distinguish one inertial reference frame from another. See also → principle of constancy.

→ principle; → relativity.

General: The state or fact of being relative.
Physics: 1) Short for the → Galilean relativity.
2) Short for the → relativity theory of Einstein.

Relativity, from → relative + → -ity.

A basic concept of → special relativity whereby → events that are simultaneous in one → reference frame are not simultaneous in another reference frame moving with respect to the first.

→ relativity; → simultaneity.

The requirement employed by Einstein in his relativity theories, that the equations describing the laws of physics are the same in all frames of reference. This statement and that of the constancy of the speed of light constitute the founding principles of special relativity.

Relativity; → principle.

The → theory of relativity.

→ theory; → relativity.

The theory formulated by A. Einstein in 1905, which is based on the following two → postulates:
1) → Principle of relativity: The laws of physical phenomena are the same when studied in terms of two reference systems moving at a constant velocity relative to each other.
2) → Principle of constancy: The → velocity of light in free space is the same for all observers and is independent of the relative velocity of the source of light and the observer.
The term "special theory of relativity" refers to the restriction in the first postulate to reference systems moving at a constant velocity relative to each other (→ inertial reference frame). See also → general relativity.

→ special; → relativity.

Any of the two theories put forward by Albert Einstein: → special relativity (1905) and → general relativity (1916).

→ theory; → relativity;