Convert Sidereal Months to Millennia
Convert Sidereal Months (sid.mo) to Millennia (ka) instantly and accurately.
Conversion Formula
ka = sid.mo × 7.480416898e-5
About Sidereal Months
The sidereal month = Moon's orbital period relative to the fixed stars = 27.3217 days = 2,360,591.6 s - the shortest lunar month. It is ~2.21 days shorter than the synodic month (29.53 d) because Earth advances ~27° along its orbit in the same period; the Moon must travel further to re-align with the Sun. Used in GPS orbit design, tidal modelling, and lunar laser ranging. 1 sid.mo = 27.3217 d.
About Millennia
A millennium (1 ka) = 1,000 Gregorian years ≈ 3.156 × 10¹⁰ s. Standard unit in archaeology and Quaternary geology: Neolithic transition ~10-12 ka BP; Last Glacial Maximum ~21 ka BP; Homo sapiens leaving Africa ~60-70 ka BP. Milankovitch cycles include the 41 ka obliquity and ~100 ka eccentricity cycle. EPICA Antarctic ice core spans ~800 ka. Precession completes ~26 ka. 1 ka = 1,000 yr.
Quick Reference Table
| Sidereal Months (sid.mo) | Millennia (ka) |
|---|---|
| 1 sid.mo | 7.48 × 10-5 ka |
| 2 sid.mo | 0.000149608 ka |
| 5 sid.mo | 0.000374021 ka |
| 10 sid.mo | 0.000748042 ka |
| 25 sid.mo | 0.0018701 ka |
| 50 sid.mo | 0.00374021 ka |
| 100 sid.mo | 0.00748042 ka |