Crash Course Video

 

 

 

 

 

 

 

 

 

 

Sun, Moon and Earth

 

    Sometimes you can see the moon at night. Sometimes you can even see it during the day. The moon looks as if it is shining with its own light, just as the sun does. But the moon does not really produce its own light. You can see the moon because sunlight reflects off the moon's surface.

    The gravity between the moon and the Earth keeps the moon in its orbit. Because it moves, the moon stays in its orbit and doesn't crash into Earth. The moon makes a complete trip around Earth in about 27.3 days.

    The moon spins around an axis. Each time the moon completes a spin, it also travels around Earth. As a result, the same side of the moon is always facing earth. That is the only side you can see from Earth.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Phases of the Moon

    If you look at the moon at different times of the month, its shape appears to change. Half of the moon faces the sun, and sunlight is reflected from the surface of that half. When the lighted half of the moon directly faces Earth, the moon appears as a full circle of light. It is called a full moon.

    We see a full moon only briefly each time the moon revolves around Earth. The rest of the time, only part of the lighted half of the moon faces Earth. Then, you can see only part of the full circle of light. For a short time, you cannot see any of the lighted part of the moon. So, you do not see the moon at all. Between the times you see the full moon and the time you cannot see any moon at all, the moon appears to have different shapes. All the moon's shapes are called the phases of the moon.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Eclipses

 

When one object in space gets between the sun and another object and casts its shadow on the other object, an eclipse occurs. Eclipses happen when the moon passes through Earth's shadow and when the moon's shadown falls on part of Earth.

 

Lunar Eclipses

    Most of the time, reflected sunlight lights up the moon. However, during some full moons, the moon and the sun are on opposite sides of earth. Often, the moon passes above or below Earth's shadown. A lunar eclipse occurs when the moon passes through Earth's shadow. 

    If only part of the moon is in Earth's shadown during the eclipse, the moon might look as if something took a bite out of it. This is a partial eclipse. If the whole moon is in Earth's shadown, the eclipse is a total lunar eclipse. A lunar eclipse can last as long as 100 minutes. It can happen several times in the same year Each eclipse is visible only in certain places. Where on Earth the eclipse can be viewed depends on the moon's position in Earth's shadow.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Solar Eclipses

    When the moon passes between the sun and Earth and casts its shadow on Earth, a solar eclipse occurs. From Earth, this looks like something slowly covering up the sun. A solar eclipse can be seen only at the places on Earth where the moon casts its shadow. 

    During a total solar eclipse, the day can become as dark as night. Total solar eclipses last up to 7.5 minutes. Solar eclipses occur two to five times each year.