Eclipses: When Rahu and Ketu Do Their Job ഗ്രഹണങ്ങൾ: രാഹുവും കേതുവും ജോലി ചെയ്യുമ്പോൾ

Remember Rahu and Ketu from Day 8? The invisible lunar nodes - the two points where the Moon's orbit crosses the ecliptic? Eclipses are their job. A solar eclipse (Surya Grahan) happens when the Moon passes between Earth and Sun at New Moon, casting its shadow on Earth. A lunar eclipse (Chandra Grahan) happens when Earth's shadow falls on the Moon at Full Moon.

But why don't eclipses happen every New Moon and Full Moon? Because the Moon's orbit is tilted about 5.1° to the ecliptic. Most months, at New Moon, the Moon passes slightly above or below the Sun. Only when the New or Full Moon occurs near a node - near Rahu or Ketu - are the three bodies aligned closely enough for an eclipse. This is why tracking Rahu and Ketu was so important to ancient astronomers: their positions predict eclipse seasons.

Solar eclipses come in types: total (the Moon completely covers the Sun - spectacular), annular (the Moon is slightly too far away, leaving a ring of sunlight), and partial (only part of the Sun is covered). Lunar eclipses are total (the Moon turns deep red - "blood moon"), partial, or penumbral (subtle dimming). Orbit connects to eclipsedb.org - a catalog of 144,646 solar and lunar eclipses spanning 30,000 years, computed from first principles.