Is there an easy way to describe Big Bang cosmology?

Existing evidence accumulated with ever increasing detail during the last 70 years suggests that the universe was once much denser and hotter than it is today.

As it cooled and continued to expand, galaxies and stars formed within a few billion years after the Big Bang.

It continues to expand today, and may do so indefinitely, if the gravity of all the stars and matter in our universe is not enough to halt the expansion at some distant future date, tens of billions of years from now.

Astronomical research hopes to determine whether the universe will expand forever or not, by weighing the universe gram by gram.

In 2003, the NASA WMAP satellite used detailed studies of the cosmic 'fireball' radiation left over from the Big Bang to determine the age of the universe as 13.7 billion years. It also 'weighed' the cosmos and confirmed that 73% of it is in a form called Dark Energy, 23% is in a form called Dark Matter, and the remaining 4% is in the matter which makes up the stars, galaxies and interstellar gas in the luminous objects in the universe.