1) In Norse mythology, the Valkyries are divine maidens who serve Odin, the chief god. They are responsible for selecting warriors worthy of entering Valhalla and escorting them to the afterlife. They are often depicted as powerful and beautiful figures, riding winged horses and wielding spears.

2) The COVID-19 pandemic has highlighted the importance of global collaboration and solidarity in addressing public health emergencies, with efforts focused on vaccine sharing, equitable distribution, and support for developing countries.

3) The Hubble Space Telescope, launched in 1990, has provided breathtaking images of distant galaxies and deep space.

4) The ozone layer, located in the Earth's stratosphere, protects us from harmful ultraviolet (UV) radiation.