space

In 1929, after Edwin Hubble discovered that the distance
between celestial bodies was related to their
incandescent redness, he discovered that the universe
was expanding faster. As a result, the world has been
assumed to be smaller, denser, and hotter than ever
before.
Albert Einstein proposed the theory of relativity in 1915.
The special theory of relativity defines the angles, temporal
and spatial relationships of observers moving relative to
each other, and related phenomena. Based on this, the
general theory of relativity has emerged that gravity is
caused by the curvature of space and time due to mass.