The Museum of Unworkable Devices

Jippy_ writes "The quest for perpetual motion has been going on since at least the 11th century according to this site, and scientists have been getting it wrong ever since. Take a gander at some of the most valiant efforts (and ultimately the biggest failures) in trying to beat the laws of physics through the last 1000 years, along with other impossible inventions and devices."

Comments

A solution?

[Tweakmeister]

It's just not possible. Energy will always be taken away in the process that can't be "recycled." It's neat to watch people try to make super efficient machines though...I wonder if any low friction fluids, etc. have come out through the development of these inventions?

problem with PM machines

[cyko500]

In theory a PM machine CAN work. Only one itty bitty problem... The machine needs to be perfectly designed and built. Also, no mass can be gained or lost (A perpetual waterfall can't work because water evaporates). PE(potential energy)=KE(kinetic energy) so you use the KE to make more PE. The major problem comes in when someone wants to use this machine to power somthing. Then some of that KE is used for other work than "recharging"(adding PE back to) whatever medium you are using to power your PM machine. This causes the machine to slowly lose its energy and come to a halt. There must also be no interferance at all (no wind, rain, or movement of the machine). Gravity and atmosphere wouldn't cause the machine to stop though. Again... it is possible to make on of these machines but: a) It must be designed and built flawlessly and b) It cannot be used to power anything other than its own movement.

Poll: How many of us have tried?

[Neuronerd]

I am a scientist now and after studying physics I guess I am completely cured from the idea that there could be a perpetuum mobile, a machine that produces energy out of vacuum.

But I remember say 20 years ago I spent a long time trying to invent such machines. I kept trying to design it and kept asking people why it wouldnt work. It took a long (frustrating) time before I could sortof acknowledge that it didnt seem to work.

So honestly... who has undergone the same process?

Re:Poll: How many of us have tried?

[flonker]

"Why won't this work?" is a good way of learning all of the practical details of a system. "Why can't you put a wheel inside of a wheel inside of a wheel, and have them spin relative to the wheel just outside, and thus break the speed of light?" is a good one. Answer that, and you've just learned something. (Assuming just physics 101 knowledge.)

Re:Poll: How many of us have tried?

[An Onerous Coward]

In my 200-level physics class, I was constantly coming up with new "perpetual motion devices" for my teacher to shoot down. I understood full well that it was fundamentally impossible, but it's kind of nice to bash into your own preconceptions and watch them break.

Anyways, the most interesting things I came up with weren't perpetual motion devices per se. I came up with some ideas that sucked energy from Brownian motion in matter. I don't think anything like that has ever been fielded as a large-scale source of energy, and probably for good reason. But he seemed to agree that, when nanotech really improves, such devices are feasible.

I'm not taking credit for it. I'm sure there are similar ideas doodled in the notebooks of thousands of undergrads. I'm simply pointing out that, even though it was a pointless waste of time on one level, on another level it was a real eye-opener for me.

Re:Poll: How many of us have tried?

[You're All Wrong]

There are cheats, some are more subtly than others.

One that I've seen work was simply a bike wheel with thick black spokes (possibly dense rubber or plastic), no hidden batteries or anything.

It only worked because of its position in the room, in particular its position relative to the window (the museum was closed at night-time, and we guessed it would stop at night, but could test this hypothesis (heck we were 10, we didn't even know it was called a hypothesis!)).

To be precise, it only worked when it was illuminated more on one side (180 degrees, not one face), than on the other. The expansion in the spokes pulled the centre of gravity away from the axis it was supported on, and so it very slowly turned (thus bringing new spokes into the sun, and some others out of the sun).

Brilliant. Or at least to a 10-year-old it was.

I still want to build my own...

YAW.

First hand experience

[gsyswerda]

When I was younger, in early high school, I discovered that my father was trying to build a perpetual motion machine in his basement workshop. It was a rotating wheel with slots that contained ball bearings. The idea was that the bearings would roll in the slots in such a way that the wheel would constantly be unbalanced, causing it to rotate forever. He hadn't quite gotten it to work, of course, and was concerned about the angle of the slots and friction at the hub. I had taken some physics by then, and tried to explain to my dad about conservation of energy and how his machine, in principle, could never work. Maybe he was already discouraged by then, but he quit working on it shortly after that.

Weather and other perpetual motion

[tunesmith]

Isn't weather kind of a perpetual motion machine?

I feel like (as a non-scientist, non-physicist) that I have an intuitive understanding that all self-contained devices relying only on their own mechanics would never attain perpetual motion due to the dragging forces of gravity, friction, and other forms of external resistance.

But I don't have such an intuitive understanding that a machine that takes advantage of outside consistent forces as a source of energy (like gravity) could not attain perpetual motion. Especially if we loosen the definition of "outside consistent forces" from the scientific definition (those natural forces that always balance themselves) to the practical definition, like those forces that aren't naturally occuring but happen all the time anyway, like the directional airflow in a building's exit corridor, or the vibration of a dance floor, or all the other places in the world where energy is being expended and not captured. If we made machines that were built to rely on those forces always happening, and capturing them to convert them to energy, wouldn't that be generating more energy than is expended to run it, considering that the expended energy it depends on would be happening anyway? I know it's mathematically lazy but there's no reason why we can't double-count that stuff.

Perpetual Motion Machines of the First Kind

[MillionthMonkey]

I got the page to load before it got slashdotted, and it looks like these are all perpetual motion machines of the first kind. These machines violate conservation of energy.

Perpetual motion machines of the second kind don't violate conservation of energy, but they rely on a decrease in entropy. With a machine like that a ship could run an engine that extracts energy from the ambient water temperature to do work, leaving a trail of colder seawater behind the ship. That doesn't violate conservation of energy, but it does cause a global reduction of entropy.

It takes more cleverness to come up with a machine of the second kind, and it's usually less obvious why they don't work.

Here's a machine like that. Assume we have a propellor made of some heat resistant material like ceramic, inside a larger ceramic housing in which it is free to rotate. Stick a big permanent magnet around it so that there is a magnetic field running through it, parallel to the propellor axis. Now inject a hot plasma of some sort into the device. Electrons in the plasma move in tight little counterclockwise circles because of the field. Protons move in much wider clockwise circles (they're heavier), so they hit the propellor blades preferentially in one direction and make it rotate.

Of course the plasma is going to cool down quickly if the protons in it are imparting kinetic energy to the propellor. So as a perpetual motion machine of the first kind, it's obviously going to run down and stop. But take the whole machine and drop it on a planet where the ambient temperature is high enough to keep the plasma hot. As the propellor extracts energy, more heat flows into the machine. What's wrong with it now?

Re:Perpetual Motion Machines of the First Kind

[hankwang]

>Now inject a hot plasma of some sort into the device. Electrons in the plasma move in tight little counterclockwise circles because of the field. Protons move in much wider clockwise circles (they're heavier), so they hit the propellor blades preferentially in one direction and make it rotate.

Hmm, some kind of Maxwell's demon. My intuition says that the transfered momentum per unit of time is the same for all particles, but I can't seem to prove it mathematically. The particles make circular trajectories with a radius r = mv/Bq, where m is the particle mass, v the velocity in the plane of the rotor, B the magnetic field, and q the charge. A particle in such a trajectory has an angular momentum J = mvr = m^2v^2/Bq. The torque that colliding particles exert on the rotor is

T = nvAJ = nAm^2v^3/Bq, (eq. 1)

where n is the number of particles per unit volume and A is the surface of the rotor. (I assume that every collision transfers the full angular momentum from the particle to the rotor) Now, thermodynamics say that <mv^2> = 2kT, where k is Boltzmann's constant and T is the temperature. If we substitute in eq. (1), we obtain

T = nA m^(1/2) (2kT)^(3/2) / Bq (eq. 2)

which unfortunately still contains the mass. If the numbers of positive and negative particles are the same, then still the protons would cause more momentum because of the proportionality to m^(1/2). So this attempt to solve the problem has failed. :-( I need m^2 v^4 instead of m^2 v^3 in eq. (1).

Either I did something wrong in the reasoning, or I overlooked a more fundamental issue, but I tried. :-) Now please tell us the real solution! solution.

Magnets and PM

[mark-t]

I was quite surprised to not see a so-called PM device on this page which incorporated permanent magnets with the following explanation for why it cannot work:

One cannot expect to use permanent magnetism as a source of perpetual motion because when a permenant magnet does work, it loses a certain amount of its magnetism in the process. This phenomenon can be seen directly with the following simple home-science experement: Place two magnets side by side, such that like poles are adjacent to eachother. Let go of one and note how far it gets pushed away. Now in a PM device, the magnets will obviously have to be brought back together at regular intervals -- so tape them together so that you effectively create an environment where the repulsion action is perpetual (which is what you are trying to achieve). Leave it alone for a few weeks. Come back after that time and remove the tape. Repeat the experiment that you did at the beginning and you will notice that the free magnet gets pushed quite a bit less than before -- sometimes not even at all! What is of particular interest is the stronger the magnets were originally, the more pronounced this loss of magnetism is, so powerful magnets quickly become weak magnets, which are capable of doing less work, and therefore require more time to lose a measurable amount of their magnetism.

tanstaafl

Re:People will always try

[Anonymous Coward]

The British Museum has a clock that comes close. It uses about 50 pounds of Mercury and uses the Mercury's daily thermal expansion. The Mercury was used during the war. Donate 50 pounds of Mercury and thay can get it going again.

The aneroid clocks are better known.

Re:Perpetual motion *IS* possible

[UniverseIsADoughnut]

" So? If you spin a wheel in space, it'll rotate forever. Same concept, perpetual motion, but it isn't a machine because there is no energy conversion - part of the definition of a machine is (afaik) that it converts energy."

Well not quit, now yes if you spin a wheel in space it will probably spin for a hella long time. But forever is no garentee, or even possible. Space is not perfect. It's not absolute zero and it's not a perfect vacuum. It runs slightly above abs zero and has plently of trace hydrogen. Plus the anoying Planet and Star Partials floating around. Anyways. Those things will cause some enegry losses. Well just the fact your wheel when you start will be warmer then space it's going to throw off energy. Also it will always be influnced by gravity. Not much and probably not the earths but it's always near some other mass so it will expericance gravity. Actully it will experiance Earth's gravity no matter where it is in the universe, just very faintly. I suppose if you had a massless wheel that might avoid the gravity issue, but then again a impossible loophole is pointless. Also there is radiation going on causing transfer of energy all over the place. At any rate you could go on forever finding ways it will loose energy thus speed. Heck it's going to crash into something eventully.

So no, your wheel will not spin forever.

atoms

[Unregistered]

atoms seem to be stable. electrons are moving. Isn't this perpetual motion? I know it's not the same but i've never heard a good reason why.

They don't call it the Zero Point field for nuthin

[gobbo]

The whole perpetual motion thing really hangs on just how good we get at tapping into the zero point field, which is the energy that's seething away at less than 10^-33 m wavelengths even at zero K. The whole 'enough energy in a cup of tea to boil an ocean' cliche -- if only we can get at it.

Now there's been a fair bit of scoffed at yet strenuously researched scientific endeavour in this area, but all the successes seem to be in the snake oil category, though there are some humble curiosities like John Hutchison's work. Still, we don't understand dick about it: it doesn't really fit into the currently popular physics models, it is beyond the reach of our current instruments, and so any use of it, if it's really there, is either impossible or really dangerous.

So what's the point? We aren't ready.

Re:People will always try

[pla]

I don't mean to argue with Carnot, but simple thought-experiment will demonstrate that you *can* do better, asymptotically aproaching 100%...

Take a "perfect" Carnot-cycle engine. submerge it in a vat of water. The waste heat will warm the water, which you can then use to generate electrical energy clearly in excess of the Carnot limit.


Additionally, the laws of thermodynamics have a serious flaw, which most folks who like to wag their finger and screech "The second! The second!" like so many autistic howler-monkeys, fail to recognize...

It describes high-level statistical phenomena within a closed system, not the behavior of individual smaller "open" systems within a larger one. So no, we cannot "create" energy, or attain a "proper" perpetual motion machine... But despite the cries of "you can't do that!", from the pseudo-scientific skeptics trying to look cool, nothing stops us from exploiting "unusual" sources of energy (such as vacuum pressure ala the Casimir effect, or the massive neutrino flux through our local region of space). Despite the assertion of the Priests of Science, we do *NOT* fully grasp the entirety of how our universe works, nor IMO do we even understand the *majority* of it. Every day I hear about some new phenomena or astronomical object that we can't explain, or for which the "old" explanation has proven false, or the like.

It always bothers me when "scientists" don't even stop to consider some of the "really out there" sources of energy, writing them off as perpetual motion and thus in violation of thermodynamics. Most of the current (quite legitimate) research in that area doesn't *claim* to have no energy source, they just can't say where it comes from. These do not mean the same thing.

Tapping the Zero-Point Energy

[xtal]

I read a good book on this a long time ago, Tapping the ZPE by Moray B. King. The idea is that there are a set of circumstances that can cause a random system to move toward order. The work was based on the 1977 Nobel Prize winner in Chemistry, who discovered the circumstances that can cause that to happen. This was done without violating the second law of thermodynamics, and is probably why the guy got the Nobel Prize. I don't know his name.

If I remember right, the circumstances were that the system had to be non-linear, far from equilibrium, and energy had to be expended to maintain that state.

The question is if you can build some sort of device to make the ZPE less random and extract energy from, literally, nothing. Just to say that "that's impossible" discounts the fact that we realy do not have a unified theory of everything, and there is likely a long way to go before we do have a GUT. I would perfer to keep an open mind about these things, and look for results. It is especially difficult to attempt to apply science - engineer a device - when the science is a great unknown to even the best minds on the planet now. Nothing is impossible, and everything in the universe came from nothingness originally!

One problem of any device like that is the energy density of the ZPE is absolutely insane. You could make a very deadly weapon from it. Nikola Tesla, one of the oldschool proponents of ether theories oft noted that unlimited energy would not be a good thing for mankind. He was probably right.

We don't need a free energy device anyhow. There's a huge ball of free energy 93 million miles away. We just need to engineer better ways to use that "free energy", first.