Welcome to the NavList Message Boards.

NavList:

A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding

Compose Your Message

Message:αβγ
Message:abc
Add Images & Files
    or...
       
    Reply
    Sunrise is a fiction
    From: Frank Reed
    Date: 2017 Oct 21, 16:40 -0700

    Well, not sunrise itself. The Sun does rise! Or so I have been told, and the hypothesis that the Sun rises is consistent with the fact that it is not normallly in the sky when I go to sleep and usually it is in the sky when I wake up. But the calculated times of sunrise and sunset and the methodology by which those times are computed --those are simply conventionalized values. They are convenient fictions.

    Ponder the attached image from a Google search I performed a few minutes ago. It provides the time of sunrise, 7:33 am, for tomorrow in Mexico City. This great city, founded by the Aztecs in the middle of Lake Texcoco (which is itself now mostly a fiction), is over two kilometers above sea level in a valley on a high plateau surrounded by mountains. How would one even define sunrise for Mexico City in a useful fashion? Rather than provide a reasonable number, tables of sunrise and sunset are computed using a conventional formula involving a point on the celestial sphere 50' of arc below the true horizon. This isn't science; it's fashion. Yes, there was some science in it originally when meteorologists settled on this definition in the early 20th century, but it is not a scientific answer to the question 'when does sunrise occur'. It tells us approximately when an observer at sea level with no height of eye on a wide body of water --an eyeball floating right on the water's surface-- and given some standard refraction conditions would see the Sun's upper limb break the horizon even if that location is miles above sea level and there is no large body of water for hundreds of miles in any direction. That concept of sunrise is a fiction. And just because a thing can be calculated to great precision does not mean that it is correct. The Sun does not rise tomorrow in Mexico City at 7:33 am.

    Frank Reed



    File:



       
    Reply
    Browse Files

    Drop Files

    NavList

    What is NavList?

    Join NavList

    Name:
    (please, no nicknames or handles)
    Email:
    Do you want to receive all group messages by email?
    Yes No

    You can also join by posting. Your first on-topic post automatically makes you a member.

    Posting Code

    Enter the email address associated with your NavList messages. Your posting code will be emailed to you immediately.
    Email:

    Email Settings

    Posting Code:

    Custom Index

    Subject:
    Author:
    Start date: (yyyymm dd)
    End date: (yyyymm dd)

    Visit this site
    Visit this site
    Visit this site
    Visit this site
    Visit this site
    Visit this site