atmosphere, which causes Earth's atmosphere to filter or block out most of the blue light. However, a partial lunar eclipse happens when only a part of the moon enters Earth's shadow. What people see from Earth during a partial lunar eclipse depends on how the sun, Earth and the moon are lined up.

　　A lunar eclipse usually lasts for a few hours. At least two partial lunar eclipses happen every year, but total lunar eclipses are rare. It is safe to look directly at a lunar eclipse although a pair of binoculars can certainly help the viewer appreciate the beauty of this phenomenon.

　　Sometimes when the moon orbits Earth, it moves between the sun and Earth. When this happens, the moon prevents the light of the sun from reaching Earth. This causes an eclipse of the sun, or a solar eclipse. During a solar eclipse, the moon casts a shadow onto Earth.

　　There are three types of solar eclipses:total solar eclipses, partial solar eclipses and annular eclipses (日环食). During a solar eclipse, the moon casts two shadows on Earth. Solar eclipses happen once every 18 months. Unlike lunar eclipses, solar eclipses only last for a few minutes.

　　Scientists use solar eclipses as an opportunity to study the sun's corona (日冕). The corona is the sun's top layer. During an annular eclipse, NASA (the U.S. space agency) uses ground and space instruments to view the corona when the moon blocks the sun's glare. The sudden blocking of the sun during an eclipse reduces the light and changes the temperature on the ground. This creates conditions that can affect local weather and animal behavior.

　　It's important to never look directly at the sun-it can permanently damage your eyes!Solar radiation that occurs during an eclipse of the sun can cause a form of burns of one's eyes known as eclipse blindness. In fact, the only way to safely view a solar eclipse is by using specially-designed equipment.

1.What can we know about "a lunar eclipse"?

A.It may create conditions that can affect local weather and animal behavior.

B.It can be seen when the moon and the sun are on exact opposite sides of Earth.