A total eclipse of the sun is one of nature’s most spectacular astronomical phenomena, caused when the moon passes in front of the sun, temporarily blocking out most of the light. They are so impressive because the Moon and the Sun appear almost the same size. In reality the Moon is about 400 times smaller than the Sun, but by an amazing coincidence, it is also more or less 400 times closer to us than the sun.
Near the beginning and end of total eclipses, the thin slice of the Sun that is visible appears broken up into blobs of light. These blobs are called 'Baily's beads' after the British astronomer Francis Baily. They happen because the edge of the Moon is not smooth but jagged with mountain peaks. When just one bead is visible, the effect is often likened to a diamond ring.