Solar and lunar eclipses
Sunlight makes the shadows of the Earth and Moon. A solar eclipse happens when the Moon passes between the Sun and Earth and blocks sunlight; it occurs only at new moon and is seen only in the narrow region where the Moon’s shadow falls: total eclipse in the centre of the shadow, partial in the penumbra. When the Moon is farther from the Earth its disc cannot fully cover the Sun, and an annular (“ring of fire”) eclipse results. A lunar eclipse happens when the Earth passes between the Sun and Moon and the Moon enters the Earth’s shadow; it occurs only at full moon and is visible from the whole night half of the Earth; in a total eclipse the Moon turns reddish. The Moon goes round the Earth in 29.5 days (the cycle of phases) and the Earth round the Sun in 365.26 days, but eclipses do not occur every month because the Moon’s orbit is tilted a little to the plane of the Earth’s orbit. Eclipses repeat about every 6585 days (about 18 years 11 days) — the saros cycle; ancient scholars predicted eclipses. Safety: watch a solar eclipse only through special eclipse glasses or a pinhole projection card; ordinary sunglasses, binoculars or looking directly can blind.
Model: in a dark room use a table lamp (Sun), a big ball or globe (Earth) and a tennis ball (Moon). Put the Moon between the Sun and Earth and watch the shadow on the Earth; then put the Earth between the Sun and Moon. Safety: do not point the lamp at faces; watch a real solar eclipse only with special glasses or projection, under adult supervision.