Perpetual Motion and Earnshaw's Theorem

Discussion in 'Feedback and Suggestions' started by studiot, Jan 19, 2015.

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  1. studiot

    Thread Starter AAC Fanatic!

    Nov 9, 2007
    I am posting this in feedback rather than a more restricted forum so that members such as WBahn may comment if they wish.

    The rules on restricted topic are

    Now we quite rightly want to exclude devices contrary to the known laws of Physics.
    However the term 'perpetual motion' is not excluded excluded in Physics.

    It is a specific requirement of Earnshaw's Theorem.
    It is also a requirement of Newton's First Law.

    What are against the laws of Physics are devices which contravene the First or Second Laws of Thermodynamics and are correctly known as by the full titles as 'perpetual motion devices of the first or second kind' respectively.

    It would seem to me to be perverse for a website, that prides itself on its technical correctness and has a stated aim of teaching Physics to students, to create rules that support the opposite, the more particularly since Earnshaw's theorem is an electrical theorem.

    Since I don't believe that is the intention, we should observe caution in the way genuine attempts to subvert Physics are handled.
  2. Alec_t

    AAC Fanatic!

    Sep 17, 2013
    ... but the Forum Rules don't specify 'perpetual motion'. They specify 'over-unity devices and systems'. Isn't a Newtonian system an 'equal-unity' system? ;)
  3. studiot

    Thread Starter AAC Fanatic!

    Nov 9, 2007
    Which is why I wish to bring the matter to the attention of the members, and to suggest care in using the term 'perpetual motion'.
    Last edited: Jan 24, 2015
    GopherT likes this.
  4. #12


    Nov 30, 2010

    I misused that term just today...or was that yesterday?
    Fortunately, I consider correcting myself later to be sufficient to qualify as, "technical correctness". :D
  5. WBahn


    Mar 31, 2012
    I don't see anything about "perpetual motion" in the section of the ToS that you quoted. Is it elsewhere?

    That aside, I understand your point and sympathize. What change would you recommend to the ToS?

    Keep in mind that it is one thing to be technically rigorous and exact, but that something like the ToS also has to be comprehensible (I hope that's the right word) to the people it applies to. Many of the people that post about some overunity device have never heard of the laws of thermodynamics and so if the ToS stated that posting about 'perpetual motion devices of the first or second kind' was off limits then lot's of people would just claim that they thought theirs was some other kind. Or it the rules said that posting about devices that contravene the laws of thermodynamics was prohibited then many would claim (probably honestly) that they had no idea that their device contravened them or, in a lot of cases, insist that THEIR device doesn't contravene them (and if you'll just invest in their project they'll be able to prove it to you, if the government would only stop preventing them).

    I think the ToS language needs to be kept pretty simple. But perhaps it could point to a page where the details are laid out at some length.

    EDITS: Fix typos and grammar.
    Last edited: Jan 25, 2015
  6. WBahn


    Mar 31, 2012
    Beyond mentioning it every time you see "perpetual motion" used incorrectly (and that determination needs to be context sensitive), I don't see anyway to affect how members use any term. I certainly don't see any change to the ToS having any effect on it.
  7. Glenn Holland


    Dec 26, 2014
    Restricted topics.
    The following topics are regularly raised however are considered "off-topic" at all times and will result in Your thread being closed without question:
    •Any kind of over-unity devices and systems
    •Automotive modifications
    •Devices designed to electrocute or shock another person
    •LEDs to mains
    •Phone jammers
    •Rail guns and high-energy projectile devices
    •Transformer-less power supplies

    Has the moderator considered adding this one to the list?
    Earthquake Prediction :p
  8. Wendy


    Mar 24, 2008
    Given this is not off topic, keep it on topic.
    ErnieM likes this.
  9. ScottWang


    Aug 23, 2012
    Earthquake Prediction?
    Is this a joke?
    Even the water can be see the Earthquake happening.
  10. Ramussons

    Active Member

    May 3, 2013
    That's not prediction. That's NOW :rolleyes:
  11. Wendy


    Mar 24, 2008
    Since this is drifting badly off topic, I am closing this thread. If the OP wishes me to reopen it again he has but to ask.

    Geology is indeed a science, though an imperfect one. If you wish to pick this subject up elsewhere do so.
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