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Give use your best perpetual motion device ideas!

  1. Jun 3, 2004 #1
    This thought was inspired by reading the other thread "perpetuum mobile" where ZapperZ posted an interesting (but of course flawed) perpetual motion device. It was fun to analyze and to figure out why it didn't work and I was wondering if anybody else had neat ideas that seem to very convincingly display perpetual motion.

    So post your ideas and then the challenge is to show how it is impossible!
  2. jcsd
  3. Jun 3, 2004 #2


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    but it isnt
  4. Jun 3, 2004 #3
    It is. This is photon.
  5. Jun 5, 2004 #4
    I do not see any challenge. So all agree to accept the photon as perpetual machine.
  6. Jun 5, 2004 #5


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    But a photon is massless, therefore, by the definition of a perpetual motion machine which is energy out is greater than energy in, a photon cannot be a perpetual machine. To change the energy of the system, work must be done; to do work, a force must be applied, forget the distance the force must move through, there is no such thing as a force on a photon.

    But I am arguing from my strictly classical, undergraduate knowledge of physics. Come to think of it, that inspires a question rooted in my vague understanding of modern physics; since light is bent in a gravity field, that bending suggest to me a component of acceleration perpendicular to the linear trajectory of the light beam. Does that mean that light truly interacts with a g field? If a g field causes an acceleration, that implies that a photon must have a gravitational mass to experience the force of gravity causing this acceleration. So is this true? Do photons truly have a gravitational mass to explain their curving in g fields? Sorry, I didn't mean to end my answer to the post with a question, but it just came up as I was typing. An answer would be much appreciated, thanks.
  7. Jun 5, 2004 #6
    I hope, the following facts will be enough convincing.
    - a photon can live infinitely long;
    - a photon can move infinitely long;
    - a photon has energy;
    - a photon can transmit energy;
    - a photon is a final “element” of any decay process;
    - a photon is a primary “element” of all creating processes;
  8. Jun 5, 2004 #7


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    True the facts were interesting, but that doesn't answer the question. Using my reasoning from above, doesn't it imply that photons must have mass due to the curving of light in a gravity field?
  9. Jun 5, 2004 #8
    Whether or not it is perpetual motion, you are not the inventor, and I think it should be disqualified on that basis alone.
  10. Jun 5, 2004 #9
    Really, I have not invented a photon - this is creation of the nature (of God). I do not apply for authorship.
    But any invention of the person is the such creation because the person is creation too.
    Besides, I promise to be corrected and I‘ll present the working analogue of a photon.
  11. Jun 5, 2004 #10
  12. Jun 6, 2004 #11
    doesn't seem too perpetual motion to me if it needs hot and cold sources to operate...

    then again it doesn't really seem to claim itself as PMM. Hmm
  13. Jun 6, 2004 #12
    Depending on frequency (length of wave) a photon or combination of photons can exist as:
    - radiowave (massless);
    - microwave (massless);
    - visible light ( mass close to zero);
    - X – ray (low mass);
    - Gamma-ray (middle mass)
    - particles (high mass).

    For more details you may take a look here:

  14. Jun 6, 2004 #13
    it has been updated to exclude the need for temperature differences
  15. Jun 6, 2004 #14
    Concerning "perpetuum mobile" I should like to say how I was wondering last days in re-reading a very old book of Lichnerowicz (Theories of gravitation and electromagnetism; 1955). Only looking at this "1955" you certainly will say it is no more up to date. But true mathematical demonstrations are true for ever... A complete chapter is developped concerning these perpetual motions. You can verify that a perfect fluid with an equation of state (e.g. by my self: (volumetric density of matter/c²) + pressure = 0) has a permanent motion if and only if the Riemanian space is a stationnary one (One needs an holonom part of the space time associated with a metric...). My book also speaks about the Klein-Kaluza, the Jordan-Thiry and the Einstein-Schrödinger Theories but doesnot say anything about the entropy... Just as small contribution to this discussion. Blackforest
  16. Jun 6, 2004 #15
    I'm pretty certain sharpestone's intention was to discuss man made inventions that claim to sustain their own operation, and from which useful work can be harvested. People have been tantalized by the notion of this possibility since the first machine was invented, and thousands have been designed in the mind and on paper, and none at all has ever worked when actually built.

    I don't think he was asking for reiterations of Newton's first law, rather, stuff like this:

    The Museum of Unworkable Devices
    Last edited: Jun 6, 2004
  17. Jun 6, 2004 #16
    How and why gravity affects light is an important part of Einstein's General Relativity, I believe, and your best bet for good answers would be to post questions about it in the Relativity forum.
  18. Jun 6, 2004 #17
    Surely a PMM will have to work from gravity or permanent magnets.

    Without climbing into the atom, these forces are the only ones we know that are not bothered by the Conservation of Energy Law.

    Why does the earth not get "tired" of holding everything down ?
    How can a permanent magnet exist ?

    These forces can create movement without renewing their power source, into infinity.
    If we can harness this potential energy, by means of some special geometry, we might get lucky !

    Yip, Geometery...Why do orbits behave the way they do ? Kepler observed and written laws on orbital motion, but we should try to figure out why.

    So in short, we need to understand and replicate the solar system or the atom, right ?
  19. Jun 6, 2004 #18
    A room temperature superconductor combined with the Casimir effect gives the elusive "free energy"?
  20. Jun 6, 2004 #19
    The Hoover Dam, a few miles to the north, will be providing energy long, long after most of you are gone, effectively for eternity. The only input that is required to make the dam perpetual is the periodic maintenance that keeps the generators fom squeaking, all of this paid for, of course, from the spare change jar on the dam supeintendant's shelf. Mother Nature's generous gift of water, height and gravity provides the energy in perpetuity.

    I think those that come up with perpetual machines ought to win a new refrigerator or something.
  21. Jun 6, 2004 #20
    Mike- Once a phoon has been used and its energy consumed does not this put your photon in the classification of a log of wood tossed into the fireplace?

    I also agree that unless perturbed, or absorbed the photon will live forever (whata concept, huh?) , but don't we want to have some use from the perpetual nature of the 'machine'/

    Of course the universe has an effective supply of photons, so I would agree with you there that harnessing photons as an energy source would provide energy as long as the universe remained in a state of existence.
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