Expert: Tom Whiting - 1/1/2009

Question
I understand that the sun "stands still" (apparently) at the solstices.  I thought that also means that the length of the day and night does not change at all for a few days at the solstices, then accelerates in the amount of daily change as we progress towards the equinoxes.  Is this correct?  I was discussing this with my father two days ago.  He thought that exactly the opposite occurs.  He said the length of days changes most rapidly at the solstices and decelerates as we approach the equinoxes.  Which is correct?  Can you explain WHY for me, please?  Also, could you point me to a good, basic astronomy book for laypersons, which I could look for at my local library?  Thank you!

Answer
Hi Michael,
The sun never "stands still" apparently, in our sky. It's apparent motion is the result of the Earth's rotation, so the sun always moves EASTWARD in our sky... by about 1 degree per day (twice it's own apparent diameter of 0.5 degree)...(365 days x 1 degree) = ~ 360 degrees per year, a full complete circle.
The apparent North-South motion, as a result of our tilted axis....that's what comes to a halt at the solstices....as it reaches the bottom of the sine-wave curve (or the top of the sine-wave curve in June). So yes, you are correct in that the most rapid (like following a sine-wave) north-south motion occurs at the equinoxes of Feb. Mar. and April, and it's corresponding southern motion in Aug. Sept. and Oct.  All the other months, the sun's apparent north-south motion begins to level off (decrease) at either the top or bottom of the sine wave curve at the solstices. So yes, you are correct that our length of daylight hours changes little in December and June, and the biggest gains (or losses) are at the equinoxes, at about 2 minutes per day.
There are many books on astronomy both on Amazon.com and the library, depending on the quality of your library. There are basically 2 types of people in astronomy.  There are the observers, who actually go outside at night to observe and then there are those who we call "fireside chat" people that just like to read about it. Us observers have the toughest job, and constitute only one in two thousand people, the other 1999/2000 people like to just sit in a warm room and read about it. (Although us pure observers like to read about it too)!
Just stay away from the occult or metaphysics books; you can easily identify them...Einstein was wrong, the Big Bang was not the correct process, any book that says we're WRONG, WRONG, WRONG,....or any book that bad-mouths and criticizes science right off the top, these are an easy tip-off to bad books and bad information on astronomy and science. So, depends on what you want to do. If you want to become an observer, then the best thing to do is read our club website, "Tom Whiting's Sound Advice to the Novice" at http://www.velocity.net/~bwhiting

The very best books on astronomy are actually college textbooks on astronomy 101..maybe you have a college nearby that teaches that course, so you can go purchase a textbook on the subject. Other than that, there are many fine books on the subject, in fact, I can't think of any bad ones. They all say about the same thing anyway, as we all know the facts behind the subject.For the observing end, you need a good star chart...I use Cambridge 2000.0 and Norton's Star Atlas and Reference Handbook, both of which cost around $30...but the star charts are good until 2050, so that's about 75 cents per year, cost-averaging it out over then next 4 decades.  Then once you own and use a Big scope, say 12 inch diameter or bigger, then you need a deeper star chart, like Uranometria 2000.0 for about $100....but I assume you're still quite a ways from that level.
This is a subject that is no longer taught as a specific course in our public school system since 1896, so if you want to learn astronomy, you have to dig it out and do it yourself...self-teach yourself as that's the only way to go in today's world.  We all had to do it that way at the public school level. (ages 10-18). That's why even very few of our public school teachers do not know much about the subject. So don't expect much from your school as they barely touch on the subject. Most even hate the subject...too abstract for them, they'd rather cover concrete subjects like meteorology, geology, volcanism, etc. in Earth science classes.(Where you can hold something in your hand like hail, slate, and basalt stones). You can't hold a star or planet in your hand.  Astronomy is all mental and visual.  
Hope all this helps,
Clear Skies,
Tom Whiting
Erie, PA


Hi again Michael,
Thanks for the very nice rating and comments. Unfortunately, we
do not have an "online" club, just a lowly website, attached to a
local group of about 50 members living in and around Erie County, PA.  If you live in that region, you are welcome to join our observing group, as that is all we do, observe...no meetings, no lectures, and no permanent location.
Clear Skies,
Tom