evanbpeters said:
@sysprog @BvU @DrClaude @Dr_Nate @anorlunda Thank you, everyone. I am super appreciative of your input.
Based on all of the feedback it looks like I can go ahead with the plot mechanism and not worry about experts scoffing at the absurdity of it.
Would Kepler's laws of planetary motion be applicable for referencing why the sun stays on course? I am planning on using dialogue about the function of a sundial to inspire the character to later use shadows to mark a location. I'm trying to come up with a snappy little monologue that references real world people/facts to sell it to the audience. (I am going to look into
@BvU 's recommendations as well)
Thank you all again!
Kepler's laws - they do describe planetary orbits.
Anyways, the shadow cast from one year to the next, same day, same time, will be off somewhat.
At the present epoch, the Earth takes 365 AND 1/4 days to complete a solar year, so a shadow lining up to the same "location" will be off by that quarter day.
See, from another thread about the equinoxes,
http://www.astropixels.com/ephemeris/soleq2001.html
2001 Mar 20 13:31 Jun 21 07:38 Sep 22 23:05 Dec 21 19:22
2002 Mar 20 19:16 Jun 21 13:25 Sep 23 04:56 Dec 22 01:15
2003 Mar 21 01:00 Jun 21 19:11 Sep 23 10:47 Dec 22 07:04
2004 Mar 20 06:49 Jun 21 00:57 Sep 22 16:30 Dec 21 12:42
2005 Mar 20 12:34 Jun 21 06:46 Sep 22 22:23 Dec 21 18:35
2006 Mar 20 18:25 Jun 21 12:26 Sep 23 04:04 Dec 22 00:22
2007 Mar 21 00:07 Jun 21 18:06 Sep 23 09:51 Dec 22 06:08
2008 Mar 20 05:49 Jun 21 00:00 Sep 22 15:45 Dec 21 12:04
2009 Mar 20 11:44 Jun 21 05:45 Sep 22 21:18 Dec 21 17:47
2010 Mar 20 17:32 Jun 21 11:28 Sep 23 03:09 Dec 21 23:38
You can see that there is about 6 hours difference between one vernal equinox to the next. After 4 years ( we have a leap year to keep the calendars and the sun in sinc ), the times just about line up but not quite. Same 6 hour difference for consecutive autumn equinox and the solstices.
The equinox is the time when the sun makes no shadow at some point along the equator.
So if you pick say the 2001 vernal equinox, Mar 20 at 13:31 , when there is no shadow. On Mar 20, 2002 at 13:31 at the same location there will be slight shadow of the sundial, since the 2002 year has not yet reached an equinox. Note that the locations on the Earth where the equinoxes occur are about 6 hours apart ( time zone distance ) from year to year.
Note also, the same location on Earth that had the sun casting no shadow at vernal equinox in 2001, is now on the opposite side of the earth, out of sunlight, and in darkness when the vernal equinox occurs in 2003.
Your not really interested in that, but rather how much the shadow differs from one year to the next at the same location, same time. The sun will have moved about a quarter of a degree in "its orbit around the earth", or 1 / 1440 of its total path in the sky. What that translates into shadow difference is not all that much, but definitely not zero.