Convert Seconds to Sidereal Days
Convert Seconds (s) to Sidereal Days (sid.d) instantly and accurately.
Conversion Formula
sid.d = s × 1.160576284e-5
About Seconds
The second (s) is the SI base unit of time, defined since 1967 as exactly 9,192,631,770 periods of the caesium-133 ground-state hyperfine transition at 0 K. Caesium fountain clocks realise this to ~10⁻¹⁶ (1 s lost per ~300 million years); optical lattice clocks (Sr, Yb) reach ~10⁻¹⁸. The second links to the metre via the defined speed of light c = 299,792,458 m/s exactly. 1 s = 1,000 ms = 1/60 min.
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.
Quick Reference Table
| Seconds (s) | Sidereal Days (sid.d) |
|---|---|
| 1 s | 1.161 × 10-5 sid.d |
| 2 s | 2.321 × 10-5 sid.d |
| 5 s | 5.803 × 10-5 sid.d |
| 10 s | 0.000116058 sid.d |
| 25 s | 0.000290144 sid.d |
| 50 s | 0.000580288 sid.d |
| 100 s | 0.00116058 sid.d |