1) The term "bull market" refers to a period of rising stock prices, while a "bear market" refers to a period of falling stock prices.

2) The first successful human heart transplant was performed by Dr. Christiaan Barnard in 1967.

3) Usain Bolt of Jamaica holds the world records for the 100 meters and 200 meters sprints, with times of 9.58 seconds and 19.19 seconds, respectively.

4) In Norse mythology, Valhalla is a majestic hall located in Asgard, the realm of the gods. It is the afterlife destination for brave warriors who die in battle, where they are greeted by the Valkyries and engage in feasting, drinking, and preparing for the final battle of Ragnarok.