It is a continuously (a)   space in which all matter is contained.

How old is the universe?

(a)  

The (a)   Theory is the leading explanation for how the universe began.

Simply put, the Big Bang Theory says that the universe as we know it started with an infinitely hot and dense single point that ________ and _________.

(a)  

Post-inflation, the universe is a seething, hot soup of

(a)  

A rapidly cooling cosmos permits quarks to clump into (a)  

Still too hot to form into atoms, charged electrons and protons prevent light from shining; the universe is a (a)   .

Electrons combine with protons and neutrons to form atoms, mostly ________ and _____.

(a)  

(a)   can finally shine.

(a)   makes hydrogen and helium gas coalesce to form the giant clouds that will become galaxies;

smaller clumps of gas collapse to form the first (a)   .

As galaxies cluster together under gravity, the first stars die and spew heavy elements into space; these will eventually form into new _____ and _______.

(a)