Sunrise and sunset

We’ve probably done this before but I’m still not sure. Some days back, for us, it was a 07:32 sunrise and a 16:14 sunset.

All right, looking just at the sunset because that’s what I was looking at and noting at the time, it was nowhere near sunset at 16:14, although at 16:47, it very much was … at least by the definition I go by, which is that it’s too dark by then to see anything inside without lights on.

What is sunset then? When the local authority decides to turn the street lights on? Or is it when the sun sinks below a horizon none of us can see? Which still gives light for some time, of course, from below the horizon.

Or what?

13 comments for “Sunrise and sunset

  1. decnine
    November 16, 2018 at 10:35

    Have you tried Googling it?

  2. Bill
    November 16, 2018 at 10:37

    Same as the Greenwich meridian?

    • November 16, 2018 at 11:41

      The horizon?

      • Bill
        November 16, 2018 at 12:29

        Never gotten to the bottom of what that word actually is meant to define.

        Imaginary line is as close as I can fathom, so yes just like the Meridian and the equator, too boot.

  3. FrankH
    November 16, 2018 at 11:29

    “…a horizon none of us can see…”
    I used to live on the Cumbrian coast, I could see the horizon where the sun sets. There are many other places where some of us can see the horizon. (How would you explain the horizon to a blind man? 🙂 )

    Anyway: “The time of sunset is defined in astronomy as the moment when the upper limb of the Sun disappears below the horizon. Near the horizon, atmospheric refraction causes sunlight rays to be distorted to such an extent that geometrically the solar disk is already about one diameter below the horizon when a sunset is observed.” https://en.wikipedia.org/wiki/Sunset

    It takes about 2 minutes from when the sun “touches” the horizon to when it completely disappears.

    The other thing I know about sunset is that you have to have your sidelights on between sunset and sunrise and, if there are no street lights, headlights between half an hour after sunset and half an hour before sunrise.

    • November 16, 2018 at 11:42

      Sun’s got limbs – I learn a new thing everyday.

      • FrankH
        November 16, 2018 at 11:54

        That’s astronomers for you. They used to think that Saturn has ears.

        • Chuckles
          November 16, 2018 at 13:39

          I thought that was Walls? Or is that ‘Fun Flavours’?

  4. dearieme
    November 16, 2018 at 21:40

    God, this reminds me of a boring discussion in our Latin class about the difference between Sunrise and First Light. I’d have said the difference was self-explanatory.

  5. ivan
    November 16, 2018 at 23:38

    Years ago I had a program that calculated sunrise, sunset, daylight start and end, civil dawn start, nautical dawn start and astronomic dawn. You needed to give it you latitude, longitude and elevation and you got the information presented to you.

    I haven’t used it since I got my met station setup because it gives that information and also give the information of moon rise and set.

  6. November 17, 2018 at 00:26

    Well, people, there we go.

  7. CherryPie
    November 17, 2018 at 00:58

    If you really insist…

    Here are the technical details:

    http://aa.usno.navy.mil/faq/docs/RST_defs.php

Leave a Reply

Your email address will not be published. Required fields are marked *

This site uses Akismet to reduce spam. Learn how your comment data is processed.