CBSE Class 8 Answered

The Big Bang Theory is the leading explanation about how the universe began. It says the universe as we know it started with all matters concentrated in a single point, then this sinle point was inflated over the next 13.8 billion years to the cosmos that we know today.

To support  this theory,  Astronomers see the "echo" of the expansion through a phenomenon known as the cosmic microwave background.

This early soup would have been impossible to look at, because light could not carry inside of it. "The free electrons would have caused light (photons) to scatter ," NASA stated. Over time, however, the free electrons met up with nuclei and created neutral atoms. This allowed light to shine through about 380,000 years after the Big Bang.

This early light — sometimes called the "afterglow" of the Big Bang — is more properly known as the cosmic microwave background (CMB). It was first predicted by Ralph Alpher and other scientists in 1948, but was found only by accident almost 20 years later.