Universe

Universe is a phenomena constitute with all of the space and time and
other constituents of space and time, such as stars, galaxies,
planets.

Though, it is impossible to measure the spatial size of entire
universe, it is possible to measure the size of observable universe.
Currently the observable universe is measured as 93 billion light year
diameters.

According to multiverse context, a one universe is the active
constituent of multiverse.

Big Bang theory is a description of the development of universe, where
it is said that once from a singular point entire universe is started
to expand.

According to big bang theory, space and time is merged together and
for this reason we say space time alltogather.