All bodies in the solar system are in constant motion.
Day vs. Night
- The Earth rotates on its axis as it revolves around the Sun. It takes approximately 24 hours, a day, for a complete rotation to occur. This counterclockwise motion occurs from west to east, causing the Sun to appear to rise in the east and set in the west.
- While the Earth rotates on its axis, it is also revolving around the Sun. It takes 365 ¼ days, a year, for this motion/orbit to occur.
- The Earth revolves around the Sun in an elliptical orbit.
Lunar (Moon) Movement
- The Moon rotates on its axis and revolves around the Earth as the Earth revolves around the Sun.
- It takes about 27 Earth days for the Moon to rotate on its axis and about 29 ½ Earth days (month) for it to revolve around the Earth.
- Because the Moon’s period (time) of rotation on its axis and period of revolution around the Earth are nearly the same, the same side of the Moon always faces Earth.
- Changes in the Moon’s position as it revolves around the Earth results in more or less of the sunlight reflected form the Moon being visible when observing the Moon from the Earth. This causes the Moon to appear to change shape.
Phases of the Moon
- New Moon- The Moon is positioned between the Sun and the Earth so that the side of the Moon that is viewed from Earth is cannot be seen. Because of this, there appears to be no Moon in the night sky.
- Full Moon- The Sunlit portion of the Moon is facing the Earth while the Earth is positioned between the Sun and Moon. The Moon is visible in the sky.
- The Sunlit portion of the Moon that is visible from Earth appears to either increases (waxes) or decreases (wanes), as the Moon orbits the Earth.
- Crescent Moon-either waxing or waning; less than ½ of the Sunlit portion of the Moon is visible.
- Gibbous Moon-either waxing or waning; Greater than ½ of the Sunlit portion of the Moon is visible.
- First/Third Quarter-1/2 of the Sunlit portion of the Moon is visible.
- A first quarter follows the waxing crescent.
- A third quarter occurs when ½ of the Moon is visible.
Can you correctly name each moon phase?
Why does the Moon have phases?
- Eclipses occur when an object in space passes directly between two other objects or between the object and the viewer.
- A solar eclipse occurs when the Moon passes directly between the Sun and Earth, blocking the Sun’s light and casting a shadow over a certain area on Earth. This can only occur during a New Moon.
- A lunar eclipse occurs when Earth passes directly between the Sun and the Moon, blocking the Sun’s light so that Earth’s shadow hits the Moon casting a shadow over the Moon. This can only occur during a Full Moon.
- An eclipse does not occur at every New Moon and Full Moon because of the angle of the Moon’s orbit around the Earth.
Why don't eclipses occur every month?...
The angle of the Moon's orbit around the Earth is tilted.
- Tides are the rise and fall of the surface levels of Earth’s ocean water caused by the gravitational effects of the Sun and Moon on Earth. The effects of tides are most noticeable along ocean shorelines.
- As the Moon orbits Earth, the waters of Earth closest to the Moon bulge outward toward the Moon. This bulge is the high tide. Another high tide occurs on the opposite side of Earth. Low tides occur in the areas between the two high tides.
- As the Earth rotates on its axis, any given location will rotate into and out of the tidal bulge. This results in the changes between high and low tides over the course of 24 hours.
- When the Sun and the Moon are aligned so that the Moon is between the Sun and the Earth (New Moon) or the Earth is between the Sun and the Moon (Full Moon) high tides are higher and the low tides are lower. These are called spring tides. When the Sun and the Moon are at right angles to each other (first and last quarter), lower high tides and higher low tides are experienced. These tides are called neap tides.
What causes the tides?