Rahu Kethu planets – Uni5 presentation to grade 6 children

Rahu and Ketu are the Moon's two orbital nodes — the points where the Moon's path crosses the ecliptic (the Sun's path). They drift backward around the zodiac, and that drift is genuine astronomy: the precession of the lunar nodes.
The number, derived. The node's circuit follows 1/T_node = 1/T_draconic − 1/T_sidereal. With the draconic month (Moon back to the same node) = 27.21222 d and the sidereal month (Moon back to the same star) = 27.32166 d:
1/27.21222 − 1/27.32166 = 0.0001472 per day → T_node = 6,793.5 days = 18.5996 years.
That is exactly the ~18.6-year Rahu/Ketu cycle.
The caution. 18.6 years is not the eclipse-repeat cycle. Eclipses recur on the Saros, because 223 synodic months almost equal 242 draconic months:
223 × 29.53059 d = 6,585.32 d and 242 × 27.21222 d = 6,585.36 d — agreeing to within an hour, so Sun, Moon and node realign and a near-identical eclipse returns. That is 6,585.3 days = 18.03 years (18 y 11 d) — a different cycle that only resembles 18.6 by coincidence.
So: the 18.6-year nodal regression (6,793.5 d) sets where the nodes sit, and hence where and when eclipses can occur; the Saros (6,585.3 d, 18 y 11 d) sets how often a given eclipse repeats. Rahu and Ketu track the former, not the latter.

Today I have presented Rahu-Kethu concept to grade 6 in Uni5 style. Based on Vinayagar Chathurthi celebration I wished to do this after our school poojas in Madras. Teacher: Have you seen 2 snakes to the left and right of Vinayagar? Children: Yes, they are cobras, naagaas. Manu: Even he has tied a snake at his waist. Teacher: Can we think why our ancestors have made such setting in their graphics of idol making? First they are Rahu and Kethu. [all started recollecting Navagrahas lesson and I crisply narrated how these shadow planets were created during Amritha madhanam] Now I want someone to say why they are called shadow planets. Rahul: A snake has been chopped into 2 half. Head and tail piece cannot be a snake separately. Tail is follower of head like our won shadow.

Teacher: You are extremely right. Head is being followed with tail and tail is always leaded by head of the creature. Rahu is the head part, Kethu is the tail part. These 2 are our thought processes. Let me give an example. When I announce a project if Hema looks into it with a good motive attitude and starts working well her project will have a good result. Do you agree? All: yes...yes! Teacher: Imagine if Balu is so lazy and hates this project. All laughed and made many comments of their age. Then my grading for his project will be very less. His very first negative attitude made him to get that low grade. When our thought process in very clear, good, positive it is Rahu in strong position. Lallu: Sir, Balu is so negative and his Rahu is weak.

Teacher: Yes all are correct. When you have positive Rahu, Kethu will be having a good clubbing with it. That means the result is good. If your Rahu is weak then Kethu will be also week. Now you say why these 2 planets - nature of mind is being placed with Ganesa. Kumar: Ganesa is the mooladhara - main source of initiation energy. So that energy controls these to processes. Correct! We pray to Ganesa when we are weak in mind and actions. He directs the Rahu Kethu inside us and makes us perfect.

Dev: Sir, what is Rahu swallowing Sun and moon? It is the eclipse depicted in Indian pattern. Sun is the awareness and Moon is the mind. Many children: Haa, we can say, when we does not think well with intellect and awareness Rahu has swallowed our Sun and when we are very sad, gloomy Rahu has swallowed our Moon. Good! In Tamil Nadu in many places we can see parikaaras for Rahu Kethu. Thiru Nageshwaram near Kumbakonam and Keel perum pallam near Poompuhar are Rahu - Kethu shrines.