The Age of the Universe:
The Universe is all of space and time and all of its contents including moons, stars, planets, everything! The Universe is massive and incredibly old, older than everything contained within. But how old is it exactly? Scientists have approximated the age of the universe to be about 13.8 billion years old. This begs the question of the origin of this approximation. Considering that the Universe has to be older than anything within it, by studying the age of the oldest stars, scientists can put a limit on the age of the Universe.
The First Stars:
The first stars, known as Population III stars, were massive and short-lived. They primarily contained Hydrogen and Helium. However, through fusion began to create the elements that would help build the next generation of stars. Detecting traces of these stars can help obtain a rough estimate of the age of the Universe.
Globular Clusters can also provide hints regarding the age of the known universe. Globular Clusters are essentially dense collections of stars that have similar characteristics to the early universe. The oldest known Globular Clusters have stars that are aged between 11 and 18 billion years of age. This wide range comes from difficulty in pinpointing the distance to the clusters.
Expansion of the Universe:
Another way of estimating the age of the Universe is by analyzing the expanding nature of the universe. If the expansion rate is known, scientists can work backward and approximate the age of the universe. Thus finding the rate of expansion of the Universe, a constant known as the Hubble constant, is the key. There are a number of factors affecting this constant. The type of matter dominating the Universe, regular matter or dark matter is an important determining factor. The density of the Universe is also important. A less dense Universe is an older universe.
The Big Bang Theory’s Thermal Radiation:
The thermal radiation left over from the Big Bang helps determine the density, composition, and expansion rate of the Universe. The leftover radiation is known as cosmic microwave background radiation. Both NASA’s Wilkinson Microwave Anisotropy Probe (WMAP) and The European Space Agency’s Planck Spacecraft have mapped it. In 2012 the WMAP estimated the Universe to be 13.72 billion years old. Planck measured the age to be about 13.82 billion years.
This gives us a brief understanding of mankind’s attempt to understand the Universe we are living in. The Universe is ever expanding and aging. Hopefully, the future will yield more accurate results regarding its age.