Convert Sidereal Days to Megayears
Convert Sidereal Days (sid.d) to Megayears (Ma) instantly and accurately.
Conversion Formula
Ma = sid.d × 2.730431333e-9
About Sidereal Days
A sidereal day = Earth's rotation period relative to the stars = 23 h 56 min 4.0905 s = 86,164.0905 s - ~3 min 56 s shorter than the 24 h solar day because Earth advances ~1° in its orbit each day. Equatorial telescope mounts rotate at one turn per sidereal day to track stars. VLBI, GPS orbit determination, and polar-motion monitoring use sidereal rotation as their reference. 1 sid. day = 86,164.0905 s.
About Megayears
A megayear (1 Ma) = 10⁶ yr ≈ 3.156 × 10¹³ s - the timescale of geology and tectonic evolution. The K-Pg mass extinction at 66.0 Ma; Cambrian explosion ~538.8 Ma; Great Oxygenation Event ~2,400 Ma. Plate motion at 2-10 cm/yr = 200-1,000 km per Ma (Atlantic ~3,000 km wider since Pangaea rifting ~200 Ma ago). Background extinction rate measured in extinctions per million species-years. 1 Ma = 10⁶ yr.
Quick Reference Table
| Sidereal Days (sid.d) | Megayears (Ma) |
|---|---|
| 1 sid.d | 2.73 × 10-9 Ma |
| 2 sid.d | 5.461 × 10-9 Ma |
| 5 sid.d | 1.365 × 10-8 Ma |
| 10 sid.d | 2.73 × 10-8 Ma |
| 25 sid.d | 6.826 × 10-8 Ma |
| 50 sid.d | 1.365 × 10-7 Ma |
| 100 sid.d | 2.73 × 10-7 Ma |