The Moon appears red, often called a "blood moon," primarily during a lunar eclipse because of the way sunlight interacts with Earth's atmosphere.
Understanding the Red Moon Phenomenon
Here's a breakdown of why the moon turns red during a lunar eclipse:
- Lunar Eclipse: A lunar eclipse occurs when the Earth passes between the Sun and the Moon, casting a shadow on the Moon.
- Earth's Atmosphere as a Filter: As sunlight passes through Earth's atmosphere, it undergoes a process called scattering. Shorter wavelengths of light, such as blue and violet, are scattered away in all directions.
- Red Light Refraction: Longer wavelengths of light, like red and orange, are less prone to scattering. Instead, they are bent or refracted (also known as bent around the Earth) into Earth's umbra (the darkest part of Earth's shadow).
- The "Blood Moon" Effect: This refracted red light is what illuminates the Moon during a total lunar eclipse, giving it a reddish or coppery appearance, hence the term "blood moon." According to the reference, the moon turns red during an eclipse because of how the Sun's light interacts with Earth's atmosphere.
In summary, the red color of the Moon during an eclipse is due to the same phenomenon that causes sunsets and sunrises to appear red. Earth's atmosphere scatters away most of the blue light, allowing the red light to reach and illuminate the Moon.
