1) The first successful mass-produced personal computer, the IBM PC, was introduced in 1981 and played a significant role in popularizing the use of computers in homes and offices.

2) Michael Phelps, an American swimmer, has won a total of 28 Olympic medals, including 23 gold medals, making him the most decorated Olympian of all time.

3) The construction of the Great Wall of China began in the 7th century BC and was completed over several centuries, spanning thousands of miles.

4) Hindu mythology, deeply rooted in Indian culture, revolves around a pantheon of gods and goddesses, including Brahma, Vishnu, Shiva, Saraswati, and Lakshmi. These deities represent various aspects of existence and play important roles in Hindu religious traditions and epics like the Mahabharata and Ramayana.