The Age of the Universe

Two main tools are used to measure the age of the universe.

Looking at faraway objects

The universe has been expanding since the big bang, so the oldest objects have been traveling away from the earth. Hence, looking at the distance of objects, you can estimate the age of objects. Using various instruments such as the Hubble Space Telescope, researchers found clusters of stars as old as 13.2 Billion Years.

To get a more accurate measurement, more indicators are used.

Redshifting

As the universe expands, the wavelength of electromagnetic radiation increases, and correspondingly the frequency decreases. Based on measuring the wavelengths of light and various calculations, astronomers gain further insight onto the age and distance of objects.

Expansion of the universe

In the late 1920s, scientists proved the expansion of the universe. The rate of change of this expansion allows researchers to find the exact time when the universe is a single point. Two major discoveries aid this discovery:

1a Supernova

Type 1a supernovae are a type of supernova in binary systems involving one white dwarf. The brightness of a supernova is uniform, and so they are called standard candles. In 2011, a team of scientists used these to prove the acceleration of expansion: The redshifts for the Type 1a supernovae were much lower than expected for faraway galaxies. This lead to them receiving the Nobel Prize in Physics.

Before that, a constant rate of expansion was assumed, leading to calculations resulting in a universe too young. Furthermore, bad standard candles lead to inaccurate measurements (like Hubble's measurement, using a type of star called a Cephied Variable, leading to a result of 2 billion years)

Cosmic Microwave Background

CMB is the microwave radiation that fills all of the universe's space left over from the big bang. It's temperature is 2.7K (-270C), but it's not constant everywhere. These temperature variations provide insight on the movements of objects and the densities of gases, both of which aid calculations of the rate of expansion of the universe.

Both of these helped the world zero in on the age of the universe: years.

Conclusion

The age of the universe is years, derived from sources such as the expansion of the universe and the redshifting of light.