1) The coldest known temperature in the universe was achieved in a laboratory in 2019, reaching a fraction of a degree above absolute zero (-273.15 degrees Celsius).

2) The Amazon rainforest produces more than 20% of the world's oxygen.

3) The concept of sovereignty refers to the supreme authority and power of a state to govern itself, make decisions, and control its own territory without interference from external forces.

4) In Greek mythology, the Trojan War is a legendary conflict between the city of Troy and the Greeks, sparked by the abduction of Helen of Troy. It is immortalized in Homer's epic poems, the Iliad and the Odyssey, and features famous heroes like Achilles, Hector, and Odysseus.