[X] My Assistant

[Bill Thompson]

We got a map of the new solar system from National Geographic that we have hung in my son's bedroom.

On one side it shows how long it takes each planet to revolve around the sun and rotate on its axis (what a "year" for each planet is and what a "day" is). I think someone got a phone call from National Geographic at GPL and they decided to have fun with them when they asked "how many hours in one Earth day" because according to this chart, there are 23.9 hours in one Earth Day.

Last I checked, it was almost precisely 24 hours. I remember a long time ago they had to add a fraction of a second at the end of a year. So I think our time pieces are very accurate about the length of a day. But I thought I would post this here to see if anyone has any special insight.

[jamescanvin]

The Earth's *sidereal* day is 23h 56m 4s which is 23.93 hours. So rounding to 23.9 is fair enough.

see for example: http://scienceworld.wolfram.com/astronomy/SiderealDay.html

James