Welcome to the NavList Message Boards.


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

Compose Your Message

Add Images & Files
    Re: Lightning Strike Damage To Navigation Equipment
    From: Tom Sult
    Date: 2015 Mar 11, 19:49 -0500
    My son is a physicist at the U of Mn. He has access to powerful magnets. In the 2 tesla range (MRI type power). If the group can put together an experimental protocol I'm sure we can destroy the watch (err do the experiment). 

    Tom Sult, MD
    Author: JUST BE WELL

    On Mar 10, 2015, at 23:36, Bill Morris <NoReply_Morris@fer3.com> wrote:

    I wonder if I understand this correctly?

    When a boat is struck by lightning, many millions of volts and quite a lot of amps flow through various conductors in the boat to earth (or is it from earth?).

    This pulse of direct current causes a pulse of magnetism which induces current in conductors such as those in electronic circuits nearby the original current path.

    As these are used to a diet of only a few volts and they get many more, they die.

    The pulse, having a beginning and an end also radiates in the radio spectrum, which is why lightning (and switching the light on and off) causes scratchy noises on the radio.

    Iff I have understood the matter correctly, then a sextant should survive unless it is in the path of the original current, except perhaps for its lighting circuit. It is less clear that a mechanical chronometer would be unscathed if it has a steel balance spring, which could conceivably become magnetised. I once accidentally magnetised such a spring, with an immediate and large change in the rate of the chronometer. Needless to say, quartz chronometers and wrist watches are at risk as they contain low voltage electronic circuits. A modern mechanical wrist watch is likely to have a "non-magnetic" nickel steel balance spring such as Elinvar, but who knows how it might behave with very large pulses of magnetism. Does anyone own an MRI scanner? I have a mechanical watch I would be prepared to sacrifice for the good of NavList.

    Bill Morris


    New Zealand

    View and reply to this message

    Browse Files

    Drop Files


    What is NavList?

    Join NavList

    (please, no nicknames or handles)
    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 Settings

    Posting Code:

    Custom Index

    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