The Moon orbits the Earth about once every 27 days, and its cycle of phases takes about 29.5 days. Half of the Moon is always lit by the Sun. As it orbits, we see different amounts of the lit half: new moon, crescent, first quarter, gibbous, full moon, and back again. The Moon does not make its own light.
An eclipse happens when one body blocks light. In a solar eclipse the Moon passes between the Sun and the Earth and its shadow falls on the Earth. In a lunar eclipse the Earth is between the Sun and the Moon, and the Earth's shadow falls on the Moon. Seasons are caused by the tilt of the Earth's axis (about 23.5°): when your hemisphere tilts towards the Sun, sunlight is more direct and days are longer, so it is summer.
Worked example
What is the order of Sun, Earth and Moon during a lunar eclipse?
- In a lunar eclipse the Moon is in shadow.
- The Earth's shadow must fall on it.
Answer:So the order is Sun, Earth, Moon in a line.
Key words
- phase
- the shape of the lit part of the Moon we see
- solar eclipse
- the Moon blocks the Sun's light from Earth
- lunar eclipse
- the Earth's shadow falls on the Moon
- axis tilt
- the Earth's lean of about 23.5°
New questions every time.
NGSS-referenced: MS-ESS1-1