Let’s have a look into the Universe.
Although most scientists agree that the Universe began with the Big Bang, there were some who disagreed. Three British scientists put forward the Steady State Theory. According to this theory, the Universe looks the same no matter the view point, and the Universe has always looked like this. To put it simply, the Universe is uniform throughout both time and space, and has no ‘beginning’. The Steady State theory is simple, but it had no answer to the many phenomena found in the Universe. As a result, it gradually lost its supporters.
If you look up at the night sky, you will see fuzzy patches. Do you know what they are? They are the galaxies beyond our own, and their study has helped us to understand that the Universe is expanding. How? This is because when a galaxy moving away from us, its light waves are stretched, and appear to be redder. This phenomenon is called ‘red shift’. When a galaxy approaches you, its light waves become short and bluer. A great American astronomer called Edward Hubble spread out the light observed from each galaxy into a spectrum. By doing so, he was able to work out what it was made up of, and how fast it was moving. To his surprise, he found that, spectral lines of the light from the other galaxies were moving towards the red color, which shows that they are moving away from us. This is an indication that the Universe is expanding.
It is now generally accepted that the Universe began with a Big Bang. The next question is, when did this happen? Astronomers can calculate the age of the Universe in three ways. First they can figure out the ages of some of the oldest stars in the Universe by studying globular clusters. A globular cluster is a dense collection of close to a million stars, of all which formed at roughly the same time. The life cycle of a star depends upon its mass, and by calculating the mass, the age of a global cluster can be calculated too. The oldest global clusters, which were probably formed when the Universe began, are much smaller and dimmer than our sun, and their age is an indication of the age of the Universe. Another way to estimate the age of the Universe is to measure its current expansion rate, and then go back or ‘rewind’ to find out when it started expanding. The third method is to check meteorites for radioactive elements that were produced in the stars since the Big Bang. The elements are constantly decaying at a known rate, and by studying them we can find out how old the Universe is. So, how old is the Universe? The answer is the universe is about fourteen billion years old.