The Value of the Obliquity of the Ecliptic
About 4000 years ago Āryabhata said, and then Mahabharata [Vanaparva] some 5000 years ago. The value of the obliquity is 24. In ancient times, they used Devanagari letters for mathematics. For instance, कगच means ka X ga X cha = 1X3X6 = 18. In fact, nobody notices all this.
Obliquity of the ecliptic is the term used by astronomers for the inclination of Earth’s equator with respect to the ecliptic, or of Earth’s rotation axis to a perpendicular to the ecliptic. It is about 23.4° and is currently decreasing 0.013 degrees (47 arc seconds) per hundred years because of planetary perturbations.
The angular value of the obliquity is found by observation of the motions of Earth and other planets over many years.