Sidereal days - amateur question

Okay, it takes 365.25 (roughly) solar days to orbit the sun. So how many
sidereal days does it take? Can't find an answer to this anywhere and it's
starting to bug me. If you know the answer could you also explain it please
(if you have the time).

I'm probably just being thick.

Thanks in advance,

Bish

"Bish Khan" wrote in message
...
Okay, it takes 365.25 (roughly) solar days to orbit the sun. So how many
sidereal days does it take? Can't find an answer to this anywhere and it's
starting to bug me. If you know the answer could you also explain it
please
(if you have the time).

I'm probably just being thick.

Thanks in advance,
One extra. :-)
The stars rise 2 hours earlier, every month, so in a year, an 'extra'
sideral day is fitted in (12*2).

Best Wishes

From surfing the 'net I find

"There is approximately 1 sidereal day more than the number of solar days in
a year". You can dig thru this PDF file here for details:

http://www.cgtp.duke.edu/~plesser/ph...ork/ex3ans.pdf.

hth,

Bob Doyle


"Bish Khan" wrote in message
...
Okay, it takes 365.25 (roughly) solar days to orbit the sun. So how many
sidereal days does it take? Can't find an answer to this anywhere and it's
starting to bug me. If you know the answer could you also explain it
please
(if you have the time).

I'm probably just being thick.

Thanks in advance,

Bish

HI there. sidereal day. A sidereal day (how long it takes for the
Earth to rotate once with respect to the stars) is 23 hrs 56 minutes
4.092 seconds in length. A mean solar day is 24 hours 0 minutes 0.001
seconds long. Thus, the solar day is about 3.9318 minutes longer than
the Sidereal day due to the fact that the Earth is moving about the sun
in its orbit. We generally use the solar day for our standard of what a
"day" actually is. There are actually several types of "years" used in
Astronomy. The Sidereal Year (fixed star transit to fix star transit)
is 365.256363 solar days long. The Tropical year (Equinox to equinox)
is 365.242190 days. The Anomalistic Year (the time it takes the Earth
to go from one perhelion to the next) is 365.259635 days. Clear skies
to you.
--
David W. Knisely
Prairie Astronomy Club: http://www.prairieastronomyclub.org
Hyde Memorial Observatory: http://www.hydeobservatory.info/

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"Bish Khan" wrote in
:

Okay, it takes 365.25 (roughly) solar days to orbit the sun. So how
many sidereal days does it take? Can't find an answer to this anywhere
and it's starting to bug me. If you know the answer could you also
explain it please (if you have the time).


The sidereal day is roughly 4 minutes shorter than the solar day. Convert
24 hours to minutes (multiply by 60). That's the length of the solar day.
Subtract 4 minutes. That's the length of the siderial day. Divide the
length of the solar day by the length of the siderial day and multiply that
by 365.25. You'll get roughly 366.25 sidereal days in a year.

Note that that is just one more sidereal day in the year. It's no
coincidence. As we advance in our orbit around the sun, the Earth has to
rotate a little bit "extra" each day to complete one solar day; i.e., to go
from high noon to the next high noon at a given location. That's why the
mean solar day is longer than the sidereal day. In the course of a year,
the Earth has to turn a total on 1 "extra" time with respect to the stars.



--
Steve Gray