A total solar eclipse will occur at the Moon's descending node of orbit on Saturday, September 4, 2100, with a magnitude of 1.0402. It will be the last solar eclipse of the 21st century. A solar eclipse occurs when the Moon passes between Earth and the Sun, thereby totally or partly obscuring the image of the Sun for a viewer on Earth. A total solar eclipse occurs when the Moon's apparent diameter is larger than the Sun's, blocking all direct sunlight, turning day into darkness. Totality occurs in a narrow path across Earth's surface, with the partial solar eclipse visible over a surrounding region thousands of kilometres wide.