<p>The diagram in this link holds the answer to your question.</p>
<p><a href="https://en.m.wikipedia.org/wiki/Sidereal_time" rel="nofollow noreferrer">https://en.m.wikipedia.org/wiki/Sidereal_time</a></p>
<p>The mean solar day is 4 minutes longer than the sidereal day.  The computation is as follows.</p>
<p>The earth travels 360 degrees in 365.2422 days.</p>
<p>360°/365.2422 = .99° per day or about one degree per day.  It moves faster in January and slower in June. This means the earth rotates 361° in 86400 seconds.</p>
<p>361° per 86400 seconds = .0042 degrees per sec</p>
<p>360°/.0042 degrees per sec=86160 sec</p>
<p>86400 sec -86160 sec =4 minutes</p>

CC BY-SA 4.0
2024-10-11T14:01:07.033Z
THANK YOU! I finally understood this after so much struggle!
tensorman666
CC BY-SA 4.0
2024-10-11T23:07:22.323Z
The computation gives the magnitude of the difference, but it isn't the reason why the solar day is longer, which is due to the direction of the rotation of the earth and the direction it orbits in both being counterclockwise when viewed from the north. If they were opposed (which would be unlikely given how planets form) then the sidereal day would be longer.
Pete Kirkham
CC BY-SA 4.0
2024-10-12T04:37:23.230Z
@PeteKirkham Are there any planets in which the direction of orbit and direction of rotation are in opposite direction?
tensorman666
CC BY-SA 4.0
2024-10-12T05:20:21.660Z
@tensorman666 Venus. Orbits in the same direction as all other planets but its rotation is in the opposite direction. Uranus is also pretty weird.
Michael MacAskill
CC BY-SA 4.0
2024-10-12T14:32:19.090Z
The calculation via degrees is unnecessary and confuses the issue, especially since the number of degrees in a circle happens to be close to the number of days in a year.  The key point is that in a year, the earth goes around the sun once, so its rotations relative to the sun will be 1 more or less than its rotations relative to the stars (+/– depending on whether the orbits are agreed or opposed).  So as there are 365.24 solar days in a year, there are 364.24 siderial days, so a sidereal day is 365.24/364.24 = 1 + 1/364.24 solar days, i.e. 1 solar day plus 3.95 minutes.
Peter LeFanu Lumsdaine
CC BY-SA 4.0
2024-10-12T15:39:42.827Z
Saying my explanation confuses the issue is a matter of opinion.  My explanation made direct use of the drawing in the link provided.  In one day the earth moves about a degree around the sun.  It's  slightly less than a degree in June and slightly more in December.  It's not a constant as your calculation implies.
lee pappas
CC BY-SA 4.0
2024-10-14T00:53:54.277Z
The annual variation in solar day length is around -21 to +30 seconds. Here's a graph using JPL data for the year 2000 at Greenwich. https://i.sstatic.net/wmiBJ.png
PM 2Ring
CC BY-SA 4.0
2024-10-11T11:58:27.307Z
2024-10-11T12:25:26.487Z
2024-10-11T12:25:26.487Z
lee pappas
<p>From what I have read so far this happens because &quot;The earth travels about 1 degree around the sun per day.&quot;</p>
<p>What does this statement exactly mean? I have been trying to understand this for so long but I am not getting such a supposedly trivial statement. Can someone please explain this using a diagram?</p>

CC BY-SA 4.0
2024-10-11T11:21:33.530Z
Do the diagrams here help? https://en.wikipedia.org/wiki/Sidereal_time
PM 2Ring
<solar-system>
Why is the solar day longer than the sidereal day
tensorman666
# Why is the solar day longer than the sidereal day

(Asked by: username_0 on 2024-10-11)

From what I have read so far this happens because "The earth travels about 1 degree around the sun per day."

What does this statement exactly mean? I have been trying to understand this for so long but I am not getting such a supposedly trivial statement. Can someone please explain this using a diagram?

**Tags:** solar-system

> **Comments:**
> **username_1**: Do the diagrams here help? https://en.wikipedia.org/wiki/Sidereal_time  

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## 1 answers

### Answer by username_2 on 2024-10-11. Score: 4 | Accepted answer

The diagram in this link holds the answer to your question.

<https://en.m.wikipedia.org/wiki/Sidereal_time>

The mean solar day is 4 minutes longer than the sidereal day. The computation is as follows.

The earth travels 360 degrees in 365.2422 days.

360°/365.2422 = .99° per day or about one degree per day. It moves faster in January and slower in June. This means the earth rotates 361° in 86400 seconds.

361° per 86400 seconds = .0042 degrees per sec

360°/.0042 degrees per sec=86160 sec

86400 sec -86160 sec =4 minutes

> **Comments:**
> **username_0**: THANK YOU! I finally understood this after so much struggle!  
> **username_3**: The computation gives the magnitude of the difference, but it isn't the reason why the solar day is longer, which is due to the direction of the rotation of the earth and the direction it orbits in both being counterclockwise when viewed from the north. If they were opposed (which would be unlikely given how planets form) then the sidereal day would be longer.  
> **username_0**: @username_3 Are there any planets in which the direction of orbit and direction of rotation are in opposite direction?  
> **username_4**: @username_0 Venus. Orbits in the same direction as all other planets but its rotation is in the opposite direction. Uranus is also pretty weird.  
> **username_5**: The calculation via degrees is unnecessary and confuses the issue, especially since the number of degrees in a circle happens to be close to the number of days in a year.  The key point is that in a year, the earth goes around the sun once, so its rotations relative to the sun will be 1 more or less than its rotations relative to the stars (+/– depending on whether the orbits are agreed or opposed).  So as there are 365.24 solar days in a year, there are 364.24 siderial days, so a sidereal day is 365.24/364.24 = 1 + 1/364.24 solar days, i.e. 1 solar day plus 3.95 minutes.  
> **username_2**: Saying my explanation confuses the issue is a matter of opinion.  My explanation made direct use of the drawing in the link provided.  In one day the earth moves about a degree around the sun.  It's  slightly less than a degree in June and slightly more in December.  It's not a constant as your calculation implies.  
> **username_1**: The annual variation in solar day length is around -21 to +30 seconds. Here's a graph using JPL data for the year 2000 at Greenwich. https://i.sstatic.net/wmiBJ.png  

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