What is Lunar Eclipse: How & Why Does It Occur?

When Earth passes between the sun and the moon, a shadow is cast on the lunar surface, a phenomenon known as a lunar eclipse. Since they can only be seen at a full moon and don't require specialized equipment to enjoy, unlike solar eclipses, they are a favourite event for skywatchers all around the world.

Two lunar eclipses will occur on Earth in the year 2024: a partial lunar eclipse on September and a penumbral lunar eclipse that happened on March 25. To know more about lunar eclipses, keep reading!

What is a Lunar Eclipse?
When there is a lunar eclipse, Earth blocks the Moon's light from the Sun. This implies that a full moon darkens (or dims) during a lunar eclipse when Earth's shadow falls upon it. Because Earth's atmosphere bends some sunlight towards the Moon while absorbing other colours, the Moon can also seem reddish. Sunsets also take on their orange and red hues due to sunlight bending through the atmosphere and absorbing other colours. The Moon is illuminated by all of Earth's sunrises and sunsets when there is a total lunar eclipse.

Why Do Lunar Eclipses Occur?
When Earth blocks sunlight from reaching the moon, a shadow is cast across the lunar surface, resulting in a lunar eclipse. During a lunar eclipse, the moon is covered in two shadows formed by the sun-blocking Earth: the penumbra, which is a partial outer shade, and the umbra, which is a complete, black shadow. Differences between a lunar eclipse and other types of eclipses (e.g., solar eclipse).

Types of Lunar Eclipses

Depending on the alignment of the sun, Earth, and moon at the moment of the occurrence, there are three different types of lunar eclipses.

• Complete lunar eclipse: The whole moon is covered in the shadow of Earth.
• Partial Lunar Eclipse: A partial lunar eclipse seems as though the moon is taking a "bite" out of the surface of the Earth when only a portion of the moon is in Earth's shadow. On the side of the moon that faces Earth, Earth's shadow will seem dark. NASA states that the alignment of the sun, Earth, and moon determines how much of a "bite" humans experience.
• Penumbral lunar eclipse: The lunar surface is covered in a weak shadow cast by Earth's outermost region. Compared to the previous two, this eclipse is not as stunning.

Why does the moon appear red during Lunar Eclipse?
A complete lunar eclipse is known as a "blood moon" because it causes the lunar surface to turn a rusty red colour. The way sunlight interacts with Earth's atmosphere is what gives it its unsettling red hue. Different wavelengths of sunlight are scattered and filtered by our atmosphere as they reach Earth. The Natural History Museum states that larger wavelengths, like red light, are bent, or refracted, into Earth's umbra, while shorter wavelengths, like blue light, are dispersed outward. During a complete lunar eclipse, the moon appears blood-red due to the red light reflecting off the lunar surface as it passes through Earth's umbra.

Tips for observing a lunar eclipse

One of the easiest skywatching occurrences to witness is a lunar eclipse.
You just need to walk outside, look up, and enjoy seeing one. A telescope or any other specialized equipment is not required. Moonwatching is fascinating during and after an eclipse, but binoculars or a small telescope will highlight features on the lunar surface. If the eclipse falls during the winter, wrap yourself warm if you intend to remain outside for the whole time. Eclipses can last up to two hours. Bring cosy seats or blankets, and warm beverages.

In conclusion, lunar eclipses are fascinating celestial events visible to skywatchers globally. They occur when Earth's shadow covers the moon during a full moon phase, showcasing the interplay between the sun, Earth, and moon. Whether it's the dramatic red hue of a total lunar eclipse or the subtle shadow of a penumbral eclipse, each type offers a unique perspective on our planet's place in the cosmos. These events are easily observed without special equipment, making them accessible and awe-inspiring for everyone.