Show Quick Read Key points generated by AI, verified by newsroom Scientists study solar corona; use certified viewing safety glasses. On this day, the world will witness the longest total solar eclipse of the 21st century, with totality lasting an extraordinary 6 minutes and 23 seconds in some regions. A total solar eclipse occurs when the Moon passes directly between the Earth and the Sun, completely blocking the Sun's visible disc for observers along a narrow path. While total solar eclipses are not uncommon, one lasting more than six minutes is extremely rare. Countries expected to witness the total eclipse include Spain, Gibraltar, Morocco, Algeria, Tunisia, Libya, Egypt, Saudi Arabia, Yemen and Somalia.