How Old is the Universe?

For centuries, astronomers have measured objects' brightnesses, colours, and positions in the nighttime sky, as one generation after another has sought to understand the nature and behaviour of the remote objects shining in the heavens. And recently, astronomers have made great strides.

Barely 200 years ago, they were unable to measure the distances to even the closest stars, let alone use the properties of stars to measure distances to galaxies 100 million light-years away. Now they boldly claim to know the age of our universe to an accuracy of better than 1 per cent: 13.7 billion years.

Scientists while looking for many other more minor things, stumbled upon this question. Some looking to calculate distance, some are trying to find the properties of something, others looking for traces of life, and so much more.

But it all starts with a question.

Scientists can easily calculate the intrinsic brightness of a star by measuring the number of photons that reach the earth emitted by the said star. This calculation combined with how bright it appears helps scientists determine how far a star really is. And the time it takes for the light to reach us also tells us how long it has existed, or in other terms, “how old it is”.

The values of the distances between objects in space are very useful.

We use such data to build machines like ballistic missiles which calculate their trajectory and path in preparation to launch. Not only on Earth but in space, it helps us predict the path and other properties of the heavenly bodies.

Eratosthenes back in the 3rd century BCE was fascinated by the earth and wanted to make a world map, for which he need to calculate the earth’s circumference. He compared the location of the sun and the zenith (the direction directly upward from the ground locally), in 2 cities in Egypt and deduced that the distance between the cities must be 1/15th of the circumference of the earth, and thus calculated the circumference to be approximately 40000 Km.

Little did he know that this one measurement will go on to be a stepping stone in calculating the distance between stars. And thus in the next few centuries, the astronomical unit, lightspeed and parsec were later on discovered.

While looking out into the night sky to find the object the furthest away, scientists discovered the CMB (cosmic microwave background radiation). This is light from the oldest events ever recorded. This light with the help of other calculations of their intensity and apparent brightness, was said to be from around 13.7 billion years ago.

Scientists believe that this is the age of our ever-expanding universe, but some still remain unconvinced looking for more clues to find the truly oldest heavenly body.

Are you willing to answer the question? Are YOU willing to find OUT?

Article Written By: Shantanu Shahji (Writing Associate, TAO) Design By: Soham Agrawal (Managing Director, TAO)