In this
subdirectory the brief introduction to Special and General Relativity
is presented. Here I describe the main ideas of Special and General
Relativity with simple physical explanation. Let list the main ideas
of General Relativity and the main difference of Newtonian gravity from
the General Relativity (GR below).

The space
- time in GR is curved.

The main object in GR is metric.

The metric coefficient determine the property of space - time and the
property of gravitational field.

The gravitational field in Newtonian physics is determined by the one
scalar value which is gravitational potential.

In
GR the gravitational field is 10 function which are metric coefficients.
The metric of space -time determines both

geometry of space and time and properties of gravitational field.

The law of motion in cosmology (for instance, the light ray law) is
the motion laws on the curved nonstationary background.

The source of gravitational field in Newtonian gravity is mass. This
is no longer valid in GR. The source of gravitational field in GR is
stress - energy tensor which has 10 independent component. It provides
more complex behaviour of gravitational field in GR.

In particular conditions gravitational attraction can trasforms into
gravitational repulsion. In the modern cosmology these conditions are
called the negative pressure or false vacuum conditions.