In this lesson, you will learn what a lunar eclipse is and how frequently lunar eclipses occur. You will also learn facts related to lunar eclipses, which are studied by scientists all over the world.
Lunar Eclipse Background
Have you ever observed the marvel of a lunar eclipse? Witnessing a lunar eclipse is quite an exciting experience that has been pondered by cultures throughout history. In this lesson, you’ll learn the scientific reasons why lunar eclipses occur.
Lunar Eclipse Definition
In our solar system, an eclipse happens when a celestial object, such as a planet or moon, passes between another planet or moon and its light source, the sun. The moon is in constant orbit around Earth, leading to changes in how much of the moon is lit by the sun or how much of the moon we can see from Earth. A lunar eclipse occurs when Earth crosses between the moon and the sun, which casts a shadow of Earth onto the moon.A lunar eclipse can only happen during a full moon and when the moon passes through Earth’s shadow. Earth has two types of shadows referred to as the umbra and the penumbra.The shadowing of the moon by Earth can lead to a partial lunar eclipse, where only a portion of the moon is darkened by Earth’s penumbra shadow. A total lunar eclipse results when the sun, Earth, and moon are perfectly aligned, resulting in a complete darkening and/or reddening of the moon because no direct sunlight reflects off of the moon’s surface.
During a total lunar eclipse, the moon is in Earth’s umbra shadow because all direct light from the sun is blocked.
Lunar Eclipse Frequency
Lunar eclipses generally last from a few minutes to a few hours. The length of time the eclipse is visible depends on where on the planet the eclipse is being viewed and on the type of eclipse that is happening. Partial lunar eclipses occur at least twice a year, while total lunar eclipses are rarer.
Lunar Eclipse Facts
The reddening of the moon, or the blood moon phenomenon, is due to light from the sun being scattered by Earth’s atmosphere. The light traveling from the sun to the edges of Earth is forced to pass through thick layers of Earth’s atmosphere.
The shorter wavelengths of light, such as blue and purple, are scattered by the dense, thick atmosphere, allowing only the longer wavelengths of light, such as red, to reach the moon.NASA has a lunar eclipse website that allows users to track past and future lunar eclipse events. Each lunar eclipse is documented by its date of visibility, the locations on Earth where the eclipse will be visible, and more. There is even a millennium catalog that tracks lunar eclipses over thousands of years from -1999 to +3000.NASA scientists study lunar eclipses to learn more about the moon and its cooling patterns when blocked from direct sunlight. By studying how quickly the moon’s surface cools during a lunar eclipse, scientists are able to identify what the moon is made up of, which areas of the moon are flat, or which areas are more rocky and take longer to cool down when blocked from direct sunlight.
Lunar eclipses occur when Earth is in between the sun and the moon, and the moon is therefore in Earth’s shadow. There are two types, partial lunar eclipse, where part of the moon is in the penumbra shadow, and total lunar eclipse, where the entire moon is in the umbra shadow. Lunar eclipses can last for minutes up to hours depending on where you are viewing the eclipse and what type of eclipse is occurring. During a lunar eclipse, something called the blood moon phenomenon occurs when the moon reddens due to light from the sun being scattered by Earth’s atmosphere.
Scientists have studied lunar eclipses in great detail, from learning more about the moon’s surface and how it cools during a lunar eclipse event to creating an extensive database that documents past and future lunar eclipses over 5000 years from -1999 to +3000.