1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

What am I missing here?

  1. Jun 28, 2011 #1
    This is kind of similar to those troll science threads, but what am I missing here?
    6t4J4.png
    What if those energy-to-mass and mass-to-energy converters can reach 99.999% efficiency when converting to electricity to mass and vice versa in the future? Those converters are theoretically possible, aren't they?

    Note, this is obviously an oversimplified diagram. The wires are simply meant to represent the transfer of energy from one area to another, in this case, from an area of lower gravitational potential to an area of higher gravitational potential.
     
  2. jcsd
  3. Jun 28, 2011 #2
    The increased matter from restoring the substance to it's original potential is only relativistic. There is nothing new here and no acute efficiency over something such as a water wheel.
     
  4. Jun 28, 2011 #3
    I know it's probably nothing new, I just want to understand why it won't work. And I don't quite understand your answer. The matter never really increases, either, it just goes through a cycle of energy and matter. I guess you could say the matter increases every time the energy is converted the matter at the top, but I'm not sure if that's what you're saying.
     
  5. Jun 28, 2011 #4
    It will work but energy will be lost to heat.

    You can increase the relativistic mass of an object by "carrying" it to a higher potential, therefor converting energy to mass though it is only relativistic and reference frame dependent.

    The equation E = mc^2 is a relativistic equation.
     
  6. Jun 28, 2011 #5

    SteamKing

    User Avatar
    Staff Emeritus
    Science Advisor
    Homework Helper

    It's easier to convert a small mass into a large amount of energy than it is to convert a lot of energy into a small mass, given the technology currently available. Haven't you wondered why we are not using transporters to get around (a la Star Trek)?
     
  7. Jun 28, 2011 #6
    Nevermind how easy it is...

    I don't think you can actually convert energy (bossons) into rest mass (fermions).
     
  8. Jun 28, 2011 #7

    Drakkith

    User Avatar
    Staff Emeritus
    Science Advisor

    Due to losses the amount of energy generated would be less and less each time. Over time the amount of matter produced at the top is less and less until you have none. You would be turning the matter into energy, just like any fuel sorce does. This is all assuming you even have a device that can efficiently create and destroy matter.
     
  9. Jun 29, 2011 #8
    It is obviously very difficult for us to create and destroy matter right now. But let's say in 500 years we have something that can get extremely high efficiency. I don't see any reason why this would be impossible. I don't see any proof that there is a natural "cap" to the efficiency of these conversions.

    The wheel could theoretically make up for the energy lost on a machine with something even as low as 80% efficiency. Let's say the top part (energy-to-matter) was 20 miles above the ground part (matter-to-energy). They could be connected by superconducting wire. There could, again theoretically, be hundreds of these water-wheels more than making up for the 80% efficiency.
     
    Last edited: Jun 29, 2011
  10. Jun 29, 2011 #9

    I like Serena

    User Avatar
    Homework Helper

    I like your diagram. :smile:

    I think the question is: what happens if your make a current go up against gravity.
    Energy conservation would imply that the electrical energy is lost when going up against gravity (that is, it is converted to potential energy).
     
  11. Jun 29, 2011 #10
    Haha, thanks.

    I had thought of that, but couldn't you just transfer energy mechanically with gears or whatever, and maybe a motor-generator combo or something (assuming this is the future and the motor and generator are super efficient)?

    As in, just use a different method of energy transfer? Would energy still be lost this way? How?
     
  12. Jun 29, 2011 #11

    Drakkith

    User Avatar
    Staff Emeritus
    Science Advisor

    ANY work you got out of the device would reduce the amount of matter (and energy) that you had. This is because work requires energy. The whole process would be 1000 times simpler if you just took out all the other stuff and left in the matter to energy converter.
     
  13. Jun 29, 2011 #12
    Perhaps it inheres in the answers above, but:

    WHY does the matter get converted back to energy? If you matter generator is cranking out iron, it falls on the wheel, generates electricity, and you've got slower-falling iron.

    There's a part missing in your machine.
     
  14. Jun 29, 2011 #13
    Those converters are just meant to be obscure objects. The fact that the matter is slowed should have little to no effect.
     
  15. Jun 29, 2011 #14
    I think the scenario is (assuming 100% efficiency for the sake of the argument):

    You have an object on top, you let it fall on a sort of "waterwheel" except it isn't using water but rather it gets it's energy from the collision of the falling object. When the object is at the bottom, to raise it back up you would need as much energy as you got out of the falling object assuming 100% efficiency. But if you convert the object into energy and transfer it to the top using electricity or gears or something else and then convert it back into the object, would you lose any energy by transferring it like that assuming 100% efficiency? And if you would keep on repeating the process, would this sort of a machine be able to do work without requiring extra energy being inputted?
     
  16. Jun 29, 2011 #15

    Drakkith

    User Avatar
    Staff Emeritus
    Science Advisor

    No, you would lose energy by transferring it against gravity.
     
  17. Jun 29, 2011 #16
    Aha!...huh?

    I meant you've got slower-falling matter falling into the obscure energy converting machine.

    Where is the part that coverts the matter into energy to feed into the energy-converting machine?

    Please just add that to the other 2 obscure converters. One more won't do any harm.

    You can fool the rest of these guys, but not me.
     
  18. Jun 29, 2011 #17

    Drakkith

    User Avatar
    Staff Emeritus
    Science Advisor

    What do you mean dan? The bottom device converts matter to energy and the top converts energy to matter. I think it is just a representation of an actual device.
     
  19. Jun 29, 2011 #18
    Ah, you're right. I just superficially glanced at the E, and confused it for the input.

    OK, I'll buy stock.
     
  20. Jun 29, 2011 #19

    I like Serena

    User Avatar
    Homework Helper

    It's an interesting problem! :smile:

    If you would have a gear system running without transferring energy no energy would be lost.
    However, if you take out energy at the top, and pump in energy at the bottom (with for instance a dynamo and an electric motor), some of the energy must be lost due to conservation of energy (i.e. the conversion to potential energy).
    But exactly why that is? :confused:

    The fun thing is that if the gear system were horizontal, then no energy would be lost! :smile:
     
  21. Jun 29, 2011 #20

    Vanadium 50

    User Avatar
    Staff Emeritus
    Science Advisor
    Education Advisor
    2017 Award

    It is. Think about it as electron flow and its obvious.
     
  22. Jun 29, 2011 #21

    I like Serena

    User Avatar
    Homework Helper

    It's not obvious to me. :confused:

    The simplest explanation that I can think of, would be that the electrons would gain potential gravity energy.
    But that doesn't hold since the same number of electrons that go up, would go down.

    Edit: Oh wait! The electrons that go up would be heavier (that is, contain more energy) than the electrons that go down?
     
    Last edited: Jun 29, 2011
  23. Jun 29, 2011 #22

    Drakkith

    User Avatar
    Staff Emeritus
    Science Advisor

    Part of the kinetic energy is used by the "waterwheel", resulting in less energy gained at the matter-energy machine compared to what was released at the top. Repeated steps would cause the amount of matter dropped to dwindle until none was left.

    IE: 100 protons are dropped from the top. They hit the wheel, cause work, and then fall to the bottom. The bottom device converts them to electrical energy and sends them to the topl. But wait! There isn't enough energy to send all 100 back to the top! So the device uses the energy of 1 proton to send the other 99. The process repeats and now only 98 can be sent to the top. After about 100 steps, there are no more protons! (By sending them to the top, I mean that it transfers enough energy to form 99 protons. Not that they are actually being transported)
     
  24. Jun 29, 2011 #23
    Would you if you used a mechanical method of transfer like gears, though (zero friction, maximum efficiency)?

    Yeah, thanks, much better way of saying it.

    One easy way to think of why energy should be lost is this: say there was a solar panel at the top and a laser at the bottom hitting the solar panel. Let's say this method of transfer would be 100% efficient (in a perfect world) if the solar panel and laser were at the same altitude. Now let's imagine the solar panel is higher than the laser. When the laser is shown up, the photons are going to lose a little energy due to gravity, and therefore the solar panel would not absorb as much energy due to the fact that the photons are carrying more energy.

    I tried to wrap my head around electricity, but I don't quite understand in a superconducting scenario. The easy way to think of it is as the electrons go up the wire, they slow down and therefore lose energy due to gravity. But, there are also electrons going down a different wire that would gain energy, and wouldn't that make up for the energy lost by the electrons going up?

    The main thing I don't understand is how energy is lost when it is transported mechanically against gravity. Maybe something weird with special relativity or something?
     
    Last edited: Jun 29, 2011
  25. Jun 29, 2011 #24

    edguy99

    User Avatar
    Gold Member

    Hey, nice idea - heres another one. Say you shoot a gamma ray (energy) straight up, it hits your top converter and is converted into an electron and a positron (mass). The mass (electron/positron) now falls through the wheel and does some work, gets to the lower converter, the electron/positron join together and shoot straight up as a gamma ray again completing the cycle.

    Where do we make up the energy? All I can think of is maybe we would loose energy to frequency shift as the lower converter is in a higher gravitational field.

    No idea if this is correct...
     
  26. Jun 29, 2011 #25

    I like Serena

    User Avatar
    Homework Helper

    Yes, it is clear that energy is taken out by the wheel (from the gained potential gravity energy).

    What is not yet clear, is why energy is lost (converted to gravity energy) transferring it back up.
    What's the difference with transferring it horizontally?

    Yep! I think that we do. :)
     
    Last edited: Jun 29, 2011
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook