While Eclipses are intriguing, one might wonder why eclipses do not occur with every new and full moon.
What are Eclipses?
Astronomical occurrences known as eclipses happen when the sun, moon, and Earth line up precisely.
Eclipses come in two main varieties: solar and lunar.
When the moon passes in front of the sun during a new moon, it blocks out the sun’s light, causing a solar eclipse.
On the other hand, a lunar eclipse happens when the Earth passes in front of the sun and moon during a full moon, shadowing the moon.
Why is there no eclipse every full and new moon?
Ans. Moon’s Unique Orbit
- Moon’s Path: The moon does one orbit around the planet every month or so.
- Ecliptic Plane: Ideally, we would see a solar eclipse at every new moon and a lunar eclipse during every full moon if the moon’s orbit aligned with Earth’s orbital plane, also known as the ecliptic.
- Moon’s Inclination: Nevertheless, irregular eclipse patterns result from the moon’s orbit being inclined at an inclination of roughly 5 degrees to the Earth’s orbital plane.
Role of Lunar Nodes
- Lunar Nodes: Depending on the direction of the moon’s orbit, the moon’s orbit crosses the Earth’s orbital plane at particular locations known as nodes. These nodes can be classified as ascending or descending.
- Eclipse Occurrence: Eclipses are caused by the sun, moon, and Earth being in alignment when a full or new moon passes near one of these nodes.
Eclipse Pairs and Seasons
- Eclipse Pairs: Usually, two weeks separate the time of a solar or lunar eclipse, with one occurring after the other.
- Eclipse Seasons: Typically, two eclipses—a solar and a lunar eclipse—occur during these about 34–35-day periods. Three eclipses may sometimes happen in one season.
- Relative to popular belief, there are more eclipses than one may think—there have been 230 lunar eclipses and 224 solar eclipses in the 21st century.
Understanding the Lunar Nodes and Eclipses
- Eclipse Seasons: When the lunar nodes precisely line up with the Earth and the sun, eclipse seasons occur around every 173 days.
- Moon’s Progression: Every month, the moon’s phases move the nodes by roughly 30 degrees along the zodiac.
- Future Eclipses: The next pair of eclipses normally happen approximately six months after the previous pair.