1) The concept of virtual reality (VR) involves creating a simulated environment that can be explored and interacted with using specialized headsets and input devices.

2) 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.

3) The Earth's core is primarily composed of iron and nickel and is as hot as the surface of the sun.

4) The process of nuclear fusion powers the sun and other stars, fusing hydrogen atoms together to form helium and releasing vast amounts of energy in the process.