Question

How old is the universe? How was this age determined?

Answer 1

In 2012, WMAP estimated the age of the universe to be 13.772 billion years, with an uncertainty of 59 million years.

Explanation:

Taken liberally from http://www.space.com/24054-how-old-is-the-universe.html

In 2012, WMAP estimated the age of the universe to be 13.772 billion years, with an uncertainty of 59 million years.

There are 2 ways we can estimate the age of the Universe: the age of the stuff inside of it, and how fast it is expanding.

Working with the ages of stars (the Universe can't be less than the age of the stuff it contains), scientists have determined that since the oldest stars are at least 11 billion years old, the Universe is at least that old.

Working with the expansion of the Universe, scientists rely on missions such as NASA's Wilkinson Microwave Anisotropy Probe (WMAP) and The European Space Agency's Planck spacecraft. By measuring the thermal radiation left over from the Big Bang, missions such as these are able to determine the density, composition and expansion rate of the universe. The leftover radiation is known as the cosmic microwave background, and both WMAP and Planck have mapped it. - See more at: http://www.space.com/24054-how-old-is-the-universe.html#sthash.PeVxdS9M.dpuf