# What is the definition of "down"? (revisited)

**URL:** <https://boards.straightdope.com/t/what-is-the-definition-of-down-revisited/420655>\
**Category:** Cecil's Columns/Staff Reports\
**Created:** [September 27, 2007, 7:31am UTC](https://boards.straightdope.com/t/what-is-the-definition-of-down-revisited/420655 "2007-09-27T07:31:48Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![EdThelen](https://avatars.discourse-cdn.com/v4/letter/e/b19c9b/32.png) [@EdThelen](https://boards.straightdope.com/u/EdThelen)\
**Post date:** [September 27, 2007, 7:31am UTC](https://boards.straightdope.com/t/what-is-the-definition-of-down-revisited/420655/1 "2007-09-27T07:31:48Z")

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re: [http://www.straightdope.com/mailbag/mgeoid.html](http://www.straightdope.com/mailbag/mgeoid.html)

A further ?related? question -

At middle latitudes,  
say latitude 40.81739, the latitude of the Allen Telescope Array,  
the gravitational vector added to the rotational force vector  
results in a plum bob offset from 40.81739 -

- “up” does not intersect stars at declination 40.81739.

I am too lazy and unknowledgeable to try to work out the error,  
if any, between

- geographical latitude,
- the astronomical latitude (“plum bob latitude”)
- and stellar declination.

(I am trying to figure how the pros would point the  
beam at ATA, and what corrections they have to make  
to stay within an error of less than an angle of one second.)  
(One source says the error is up to one minute of angle  
at an unstated latitude.)

(Right ascension and time seems tougher !!!)

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**Author:** ![DSYoungEsq](https://avatars.discourse-cdn.com/v4/letter/d/c6cbf5/32.png) [@DSYoungEsq](https://boards.straightdope.com/u/DSYoungEsq)\
**Post date:** [September 27, 2007, 11:00am UTC](https://boards.straightdope.com/t/what-is-the-definition-of-down-revisited/420655/2 "2007-09-27T11:00:50Z")

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Welcome to the Board, **EdThelen**! We always enjoy people who have complications to add about things. 🙂

This thread belongs in the [Comments About Staff Reports](http://boards.straightdope.com/sdmb/forumdisplay.php?f=6) forum. I am certain that some moderator will be along shortly to move it for you. 🙂

Stick around, we grow on you. 😉

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**Author:** ![C\_K\_Dexter\_Haven](https://avatars.discourse-cdn.com/v4/letter/c/b2d939/32.png) [@C\_K\_Dexter\_Haven](https://boards.straightdope.com/u/C_K_Dexter_Haven)\
**Post date:** [September 27, 2007, 1:22pm UTC](https://boards.straightdope.com/t/what-is-the-definition-of-down-revisited/420655/3 "2007-09-27T13:22:20Z")

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Yep, so moved. No biggie, you’ll know for next time. And, indeed, welcome!

This is a fairly long-ago report, I’ll let **Karen** know to see if she’d like to comment.