Why do Saturn’s rings sometimes appear to disappear when seen from Earth?

Saturn’s rings appear to disappear when viewed from Earth because they are extremely thin—often no more than 100 metres (330 feet) in thickness—despite their vast diameter of 270,000 km (170,000 miles).1

Because Saturn’s rotational axis is tilted by 26.7° to its orbital plane, the rings are presented to observers on Earth at varying opening angles. Over a 30-year cycle, Earth-based observers see the rings at angles ranging from nearly 30° down to 0°. When Earth crosses the ring plane, the rings are viewed edge-on; at this specific geometry, they become essentially invisible or "disappear" from our perspective. This phenomenon was famously noted by Galileo in 1612, who was perplexed when the rings he had previously observed seemed to vanish.21