The expansion of the universe is the increase in distance between gravitationally unbound parts of the observable universe with time. It is an intrinsic...

Observations show that the expansion of the universe is accelerating, such that the velocity at which a distant galaxy recedes from the observer is continuously...

uniformity of the universe, known as the flatness problem, is explained through cosmic inflation: a sudden and very rapid expansion of space during the earliest...

and the accelerated expansion of the universe due to cosmic inflation. Tiny ripples in the universe at this stage are believed to be the basis of large-scale...

depends on knowing the rate of expansion, average density of matter, and the physical properties of the mass–energy in the universe. There is a strong...

the acceleration of the expansion of the universe, and about 25.8%±1.1% is dark matter. Ordinary ('baryonic') matter is therefore only 4.84%±0.1% of the...

beginning of the cosmological expansion. Initially, it was estimated that there may be 2 trillion galaxies in the observable universe. That number was reduced...

radiation give the cooling time of the universe since the Big Bang, and measurements of the expansion rate of the universe can be used to calculate its approximate...

observations suggest that the expansion of the universe will continue forever. The prevailing theory is that the universe will cool as it expands, eventually...

The expansion of the universe is parametrized by a dimensionless scale factor a {\displaystyle a} . Also known as the cosmic scale factor or sometimes...