1) In Norse mythology, Ragnarok is a cataclysmic event that signifies the end of the world. It involves a series of apocalyptic battles and natural disasters, leading to the destruction of the gods and the world as it is known. From the ashes, a new world and a new generation of gods emerge.

2) The first consumer digital video recorder (DVR), the TiVo, was introduced in 1999 and allowed users to record and store television programs for later viewing.

3) In Hindu mythology, the Bhagavad Gita is a sacred text that contains a conversation between Prince Arjuna and the god Krishna, who serves as his charioteer. It delves into philosophical and moral dilemmas and provides guidance on duty, righteousness, and the path to spiritual enlightenment.

4) The intensity of cyclones is often measured using the Saffir-Simpson Hurricane Wind Scale, which categorizes them based on their sustained wind speeds.