# earth's orbit and seasons

**URL:** <https://boards.straightdope.com/t/earths-orbit-and-seasons/22782>\
**Category:** Factual Questions\
**Created:** [June 18, 2000, 3:54pm UTC](https://boards.straightdope.com/t/earths-orbit-and-seasons/22782 "2000-06-18T15:54:08Z")\
**Posts on this page:** 4\
**Page:** 3

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**Author:** ![RM\_Mentock](https://avatars.discourse-cdn.com/v4/letter/r/e274bd/32.png) [@RM\_Mentock](https://boards.straightdope.com/u/RM_Mentock)\
**Post date:** [June 26, 2000, 1:38pm UTC](https://boards.straightdope.com/t/earths-orbit-and-seasons/22782/41 "2000-06-26T13:38:27Z")

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> [@](#):
>
> Do you still contend that the difference can be no greater than 1 second?

I never contended that. I think that what you’re referring to was my objection to your claim that the time between meridian crossings on Dec. 25 and 26 was about 30 seconds less than the time between meridian crossings on Dec. 26 and 27. That difference is actually less than a second, and that is true of any pair of consecutive days.

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**Author:** ![sailor](https://avatars.discourse-cdn.com/v4/letter/s/a587f6/32.png) [@sailor](https://boards.straightdope.com/u/sailor)\
**Post date:** [June 26, 2000, 4:05pm UTC](https://boards.straightdope.com/t/earths-orbit-and-seasons/22782/42 "2000-06-26T16:05:57Z")

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RM Mentock said:  
\>\> I agree with your point but I’m suspicious of the data

I calculated those using a spreadsheet and the formulas from a book (almanac for computers) which would provide results which are not as accurate as those calculated for the nautical almanac. I built this spreadsheet long time ago and it seemed to give good enough results but I have no idea for what accuracy it may have.

My intuition would say that your assertion that \*\*the time between two consecutive meridian crossings does not change by more than a second \*\* or two could well be correct but I have no proof one way or the other.

I have just done quite a few random sample checks of the 1995 nautical almanac and they all confirm that. You are very probably correct.

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**Author:** ![jrepka](https://avatars.discourse-cdn.com/v4/letter/j/ee59a6/32.png) [@jrepka](https://boards.straightdope.com/u/jrepka)\
**Post date:** [June 26, 2000, 9:52pm UTC](https://boards.straightdope.com/t/earths-orbit-and-seasons/22782/43 "2000-06-26T21:52:08Z")

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> [@](#):
>
> …my objection to your claim that the time between meridian crossings on Dec. 25 and 26 was about 30 seconds less than the time between meridian crossings on Dec. 26 and 27. That difference is actually less than a second, and that is true of any pair of consecutive days.

Mea culpa. What I should have said (and did say, in subsequent posts) was that the length of a given solar day can vary by up to 30 seconds _from the mean_, not from the previous day.

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**Author:** ![RM\_Mentock](https://avatars.discourse-cdn.com/v4/letter/r/e274bd/32.png) [@RM\_Mentock](https://boards.straightdope.com/u/RM_Mentock)\
**Post date:** [June 27, 2000, 3:23pm UTC](https://boards.straightdope.com/t/earths-orbit-and-seasons/22782/44 "2000-06-27T15:23:36Z")

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> [@](#):
>
> **sailor wrote:**  
> I calculated those using a spreadsheet and the formulas from a book (almanac for computers) which would provide results which are not as accurate as those calculated for the nautical almanac.

According to Sky Map, an astronomy program, the first and last times were off only by a second–but the middle one was off by ten seconds. Try it again, and see what pops out.

**jrepka** : cool

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