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
    Re: How many ways to define a day?
    From: Frank Reed
    Date: 2021 Jun 12, 20:15 -0700

    Matus Tejiscak, you wrote:
    "I tried to guess where you are. I started by assuming the US."

    Aha! That's an interesting puzzle to solve from the available information. The result that you found "Albany NY" is a bit far off, but I thought you might like a little more data from that weather website (I had clipped off the full details last time). The image here is for today, 12 June 2021, but a different location. I do believe that the numbers listed here are correct for the chosen location within one minute of time (maybe they round up/down or truncate seconds ...I don't have conclusive evidence either way). But given that assumed level of accuracy in the numbers, can you determine the observer's approximate latitude and longitude, and with what error bars? 

    I switched the location because many people following NavList messages know where I live, and you could figure it out from just a little poking around in my recent messages, too. So this makes it much more challenging and other folks can play along, too. 

    By the way, I'm appalled (appalled!) by the symbology that this website uses for the phases of the Moon. :) 

    We can get back to this business of different ways to define a day another time, but a couple come to mind right now. First there's the LAN-to-LAN day. Geoffrey Kolbe's neat prism experiment can capture the instant of local meridian passage to about a second, so we could time how long it is from one local noon to the next. It will only rarely be exactly 24 hours. The second definition that comes to mind is the true rotation period of the Earth relative to the "fixed stars" (or the cosmological rest frame, or similar). That's close to but not identical to the sidereal day. Does it have an established name??

    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