Sidereal Years to Seconds (yr (sid) to s)
1 sidereal year equals 31,558,149.76 seconds (rounded).
How to convert sidereal years to seconds
To convert sidereal years to seconds, multiply the number of sidereal years by 31,558,149.76. The factor is rounded to 10 significant digits. To go the other way, multiply seconds by 3.168753579×10⁻⁸ (rounded).
seconds = sidereal years × 31,558,149.76
Example: 10 sidereal years = 315,581,497.6 seconds.
Months and years are not constant. This site uses the average Gregorian year of 365.2425 days, so one 'year' converts to 365.2425 days, not 365; use 'common year' for exactly 365 days.
Approximate value. Standards for the sidereal year varied by place and period, so this converter uses the most commonly cited value. Treat results as estimates, not exact figures.
About these units
Sidereal Year (yr (sid))
About 365.256363 days, the time for Earth to return to the same position relative to the fixed stars.
Measured against the fixed stars, one orbit of Earth around the Sun takes about 365.256363 days, or roughly 365 days 6 hours 9 minutes 10 seconds. That is the sidereal year, and it is about 20 minutes 25 seconds longer than the mean tropical year used for the seasons.
The gap exists because of the precession of the equinoxes, which Hipparchus identified in 127 BC after comparing the two kinds of year. Ptolemy later reported his sidereal figure as about 365 days 6 hours 10 minutes, already close to the modern value. Earlier peoples had tracked the year by star events instead, such as the Egyptian watch for the rising of Sirius before the Nile flood, and Hesiod's farming advice tied to the Pleiades.
Indian astronomy kept the sidereal year in its calendars. The Surya Siddhanta gave a value near 365 days 6 hours 12 minutes 36.56 seconds, slightly long by modern measurement. NASA's fact sheet lists the sidereal orbital period of Earth as 365.256 days.
1 sidereal year = 31,558,149.76 seconds (approximately).
Sources: Wikipedia: Sidereal year; NASA Earth Fact Sheet
Second (s)
The SI base unit of time, defined by the radiation frequency of the cesium-133 atom: 9,192,631,770 cycles per second.
Our word second is a leftover of Latin. Medieval scholars divided a degree, and later the hour, into 60 parts called pars minuta prima, the first small part, and divided those again into pars minuta secunda, the second small part. NIST traces the roots further back: Babylonian and Greek astronomers split the circle into 360 degrees, and around 150 C.E. Ptolemy split each degree into 60 minutes and each minute into 60 seconds. Clocks that could show seconds appeared only in the later 16th century, and Christiaan Huygens's pendulum clock of 1656 was the first able to keep time accurately to the second.
For most of history the second was a fraction of a day, and in 1956 it was redefined as a fraction of the tropical year, a definition the SI took over in 1960. In 1967 the 13th CGPM switched to atoms: 9,192,631,770 periods of the radiation tied to a hyperfine transition of caesium-133. The 2019 SI revision restated this by fixing the caesium frequency at 9,192,631,770 hertz. NIST reports that commercial caesium clocks stay within about a three-millionth of a second per year, and experimental clocks based on other atoms are roughly ten thousand times more precise.
The second is the reference unit for time on this site.
Sources: NIST: the second and the SI redefinition; BIPM: SI Brochure, 9th edition; Wikipedia: Second
Related conversions
- Seconds to sidereal years (reverse)
- Sidereal years to minutes
- Sidereal years to hours
- Sidereal years to days
- Sidereal years to weeks
- Sidereal years to months
- Sidereal years to years
- Minutes to seconds
- Hours to seconds
- Days to seconds
- Weeks to seconds
- Months to seconds
- Years to seconds
- Milliseconds to seconds
- Microseconds to seconds
- Nanoseconds to seconds
- Decades to seconds
- Centuries to seconds
- Millennia to seconds
See all time units.