Dot Physics

When is the Sun directly overhead?

Question: When is the Sun directly overhead? (assume you are in the United States of America)

Common Answers:

  • Everyday at noon.
  • On the summer solstice (June 21ish)

Answer: For continental U.S. the answer is never. Since the Earth’s rotation axis is tilted 23.5 degrees with respect to its orbital motion around the Sun, one would have to be less than 23.5 degrees above or below the equator to have the Sun pass directly overhead (once per year).

Here is a video I made over the course of a day in Louisiana. Note that it rains and then the clay softens the pen falls. At the end, my dog hit the camera even though I explained I was making a time lapse video. My dog never listens.

Comments

  1. #1 Kitty Conrad
    February 11, 2010

    Wouldn’t it be twice per year for points 23.5 degrees above and below the equator and once per year for only those points that are exactly 23.5 degrees from the equator?

  2. #2 Anthony Fernandez
    August 4, 2010

    Hello Mr. Allain,
    I am a 65 year old resident of central Florida. Thanks for your answer to the question of “high noon” (Sun directly overhead) While I know that you are technically correct,(i.e. “For continental U.S. the answer is never.”), I would just like to add that from a casual observers’ point, the Sun will achieve something very close to “directly overhead” at noon, in our latitude soon (as the days grow shorter), but I haven’t been able to predict that upcoming date. As of today (Aug. 4th) it was overhead (things on the ground not casting a shadow) at about 1:45 PM. A guess would be that it will happen at exactly noon around the end of August. Agree – Disagree – If you have time.

    Also, I once demonstrated to some friends how they can use the Sun’s shadow to measure the height of a tree. I used a yard stick – measured the length of it’s shadow – did the math (ratio),and then measured the shadow cast by the tree.
    Final Answer? =36 1/2 feet. They didn’t believe me. I re-performed the concept to measure the height of a lamp post (which I could then prove) and et voulez… proof of concept. I’m sort of my neighborhood’s Science Guy! I love this stuff! Thanks for you site and your insight.

    By the way, I found this, which I think is completely comprehensive and very nicely illustrated. See if you agree. http://www.physicalgeography.net/fundamentals/6h.html

    For continuing education and “you CAN teach an old dog new tricks”,
    I remain,
    Anthony Fernandez – in Winter haven, Florida.

  3. #3 Tamjeed Ali
    August 16, 2010

    Not never. I believe it happens in Hawaii.

  4. #4 Brett Wiens
    September 24, 2010

    Hawaii, by most estimates, is not a part of the continental United States. I rather like the re-orientation of “High Noon” to “Noon on the day the sun is highest in the sky.” Even if it is just the point during the day when the sun is highest. Language /= Math

  5. #5 Asfaw Mesret
    March 31, 2011

    Initially I’m not clear with the term Overhead Sun though I know the main season on the Northern and southern Hemispher.

  6. #6 J. Snabb
    March 23, 2012

    I was disappointed for such a US centric and non-scientific answer. I am trying to figure out the two days of the year when the sun is above 10°N where I live but this article is completely useless for that.