Free energy?

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Govalant
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Free energy?

Postby Govalant » Sat Nov 15, 2008 9:05 pm UTC

This is now the official free energy thread. If you have an idea that you think gives free energy, infinite energy, perpetual motion, or anything else that violates the Second Law of Thermodynamics, describe it here. We'll tell you why it doesn't do what you think it does in short order.

Note that there's already a thread for bringing up and discussing devices you already know can't work.


So I got this idea. Imagine a hollow steel sphere, a really thin one, such that the air inside weighs more than the container. Let's say I get all the air outside of it, by performing some work, yes. Now the sphere starts moving up by air buoyancy. We take the energy of this motion and stop the ball at let's say, 100 meters. Then we open some valve to let the air get in. The ball drops and we also use this energy.

We arrived at the same initial state, but, does the work made by gravity exceed the work I did? Because that amount of work is fixed but I can get more energy out of the ball by sending it further upwards.

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Re: Free energy?

Postby bcoblentz » Sat Nov 15, 2008 9:52 pm UTC

Bah, I'm not going to try to figure out why this is wrong because there's no such thing as free energy so it's already not going to work.

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Re: Free energy?

Postby Klotz » Sat Nov 15, 2008 10:45 pm UTC

So you have a sphere with air of a certain pressure inside, and then you open it so the pressure inside is equal to air pressure, then you just have a sphere that drops.

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Re: Free energy?

Postby Tass » Sat Nov 15, 2008 10:47 pm UTC

Obviously not.

You can't send it higher indefinetely. If you had a thicker atmospere you could send it higher, but i would take more energy to empty it. If done perfectly they cancel out exactly. The same goes for pumping air under water and other nice schemes like that. You actually dont have to do the math every single time, since it can be proven mathematically that they will all fail from the fact that gravity in a conservative force field.

First find a nonconservative force field in nature, then try to look for a way get the energy. (Hint: Magnets are conservative to)

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Re: Free energy?

Postby Hydralisk » Sat Nov 15, 2008 10:48 pm UTC

Build a working model of this and I shall believe every word of it.

Also, why steel? Aluminium or carbon fibre is much lighter, and will do the job just the same. Not that it will give free energy mind. :p

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Re: Free energy?

Postby danpilon54 » Sun Nov 16, 2008 6:02 pm UTC

if it does give any net increase in energy it will be taken from the atmosphere, and will not really be free.
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Re: Free energy?

Postby Omega_ » Sun Nov 16, 2008 6:27 pm UTC

You must think about where to draw the boundaries of your system. Many things may appear valid in a thermodynamic sense, if you draw your system in a particular way. But Nature doesn't care how you think about things...

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Re: Free energy?

Postby Xanthir » Sun Nov 16, 2008 6:42 pm UTC

Govalant wrote:So I got this idea. Imagine a hollow steel sphere, a really thin one, such that the air inside weighs more than the container. Let's say I get all the air outside of it, by performing some work, yes.
...
We arrived at the same initial state, but, does the work made by gravity exceed the work I did? Because that amount of work is fixed but I can get more energy out of the ball by sending it further upwards.

Pulling the air out of the sphere will take more energy than is produced by the rising+falling of the ball. You can't just "send it higher" - there is a maximum height it can rise to (where the air density matches the average density of the steel sphere + whatever air is left in it).

In a perfect world the air extraction wouldn't waste any energy and you could recover all the energy of rising and falling, leaving you with a sum of 0 net joules. In the real world, most of the energy produced by the vacuum motor will be output as heat rather than useful work, and you'll only be able to recover a fraction of the rising+falling energy, so you'll be quite a bit below unity.
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Re: Free energy?

Postby BlackSails » Sun Nov 16, 2008 7:31 pm UTC

^

What he said.

Yes, you are getting energy, but you are also spending (at least as much, assuming perfect machines, but more in a real world) energy to pump all the air out.

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Re: Free energy?

Postby djn » Sun Nov 16, 2008 7:47 pm UTC

It would, however, be an interesting art installation.

Rig a bowl-shaped hole (think Arecibo, though much smaller) with a launcher of this type mounted roughly in the middle. Have a hole in the bottom for recovering balls, and feed them to the launcher. Rig the balls to auto-open to outside air on a timer.

There's not enough slow-rise, fast-fall, open air metal ball fountains in the world.

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Re: Free energy?

Postby Charlie! » Mon Nov 17, 2008 2:31 am UTC

Shoot, we need to go make some metal balls!

Or, really, mylar with a plastic frame and a lightweight vacuum pump hooked to a pressure sensor with enough batteries for 2 or 3 "bounces."
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Re: Free energy?

Postby Tass » Mon Nov 17, 2008 3:54 pm UTC

I don't know if it is at all possible, given our current material capabillities, to make a "vacuum ballon" like this. I think any material strong enough would be too heavy, and any material ligth enough would be too weak.

But I am not quite sure. How does it scale with size? Would it have to be very big or very small?

What I am asking is not about free energy the OP talked about, thats not possible. Rather it is whether it would be possible practically to build something ligther than air in this way, without using ligth gasses?

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Re: Free energy?

Postby Xanthir » Mon Nov 17, 2008 4:01 pm UTC

Tass wrote:I don't know if it is at all possible, given our current material capabillities, to make a "vacuum ballon" like this. I think any material strong enough would be too heavy, and any material ligth enough would be too weak.

But I am not quite sure. How does it scale with size? Would it have to be very big or very small?

What I am asking is not about free energy the OP talked about, thats not possible. Rather it is whether it would be possible practically to build something ligther than air in this way, without using ligth gasses?

Well, weight would scale roughly with the surface area, while average density would scale roughly with the inverse of the volume, so you have the mathematics of scale on your side at least.

I don't have sufficient materials knowledge to actually make an informed statement about the feasibility, however.
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Re: Free energy?

Postby Omega_ » Mon Nov 17, 2008 5:19 pm UTC

Charlie hit on a good possibility a few posts above: Mylar has some very interesting, extreme properties. Mylar is, I think, metallized polyethyleneterephthalate (PET). Same polymer as in a plastic Coke bottle, just different formulation. Density ~ 1.4 g/cm3. Of course, 1cm3 gives you a lot of potential surface area with Mylar!

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Re: Free energy?

Postby djn » Mon Nov 17, 2008 6:05 pm UTC

The main problem is of course that they need to be robust against outside pressure, not inside - some form of internal trussing might be needed.

Carbon fibre internal frame with soft but non-stretchable covering (coated kevlar?), perhaps? Or aluminium/aluminium, if a stiff material seems like a better idea.

Anyway.
To lift one kg, given a density of air at 1.2 kg/m³, needs 1/1.2=0.83m³.
0.83 m³ = (4*pi*r³) / 3
(0.83 * 3) / (4 * pi) = r³
cube root ( (0.83 * 3) / (4*pi)) = r
r = 0.58 m

Or, in other words, a sphere with a diameter of 1.16m to lift a kg. Can we build an 1.2m sphere stiff enough with a 1kg budget?
And why doesn't the TeX math mode work?

edit: Hmmmm. How about honeycomb between stiff spheres, in some combination of aluminium, beryllium or ceramics?
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Re: Free energy?

Postby Charlie! » Mon Nov 17, 2008 10:26 pm UTC

I think the geodesic/polyhedral/whatever frame (maybe give it some radial thickness for a slight "honeycomb" shape) plus flexible airtight covering idea would work pretty well. I don't know about having a stiff covering. Could you get the necessary strength while keeping it light?

And looking at vacuum pumps, I don't think it's possible to have a decent vacuum pump that could be lifted without making the balls quite large. You'd have to evacuate these things on the ground, then just have some sort of valve that would open after a while and drop them back to you.
Last edited by Charlie! on Mon Nov 17, 2008 11:30 pm UTC, edited 1 time in total.
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Re: Free energy?

Postby Mr. Beck » Mon Nov 17, 2008 10:40 pm UTC

I think that perhaps the best way would be to use an octahedron of mylar stretched over poles of carbon fiber (one pole for each axis). All the poles are in pure compression, and the mylar is in pure tension.

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Re: Free energy?

Postby djn » Mon Nov 17, 2008 10:50 pm UTC

Charlie! wrote:And looking at vacuum pumps, I don't think it's possible to have a decent vacuum pump that could be lifted without making the balls quite large. You'd have to evacuate these things on the ground, then just have some sort of valve that would open after a while and drop them back to you.


That was my idea as well, yes.

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Re: Free energy?

Postby Tass » Tue Nov 18, 2008 10:46 am UTC

Xanthir wrote:
Tass wrote:I don't know if it is at all possible, given our current material capabillities, to make a "vacuum ballon" like this. I think any material strong enough would be too heavy, and any material ligth enough would be too weak.

But I am not quite sure. How does it scale with size? Would it have to be very big or very small?

What I am asking is not about free energy the OP talked about, thats not possible. Rather it is whether it would be possible practically to build something ligther than air in this way, without using ligth gasses?


Well, weight would scale roughly with the surface area, while average density would scale roughly with the inverse of the volume, so you have the mathematics of scale on your side at least.

I don't have sufficient materials knowledge to actually make an informed statement about the feasibility, however.


Except that the larger ones migth need a thicker shell. I too, lack the materials knowledge to say for sure, that is why I asked.

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Re: Free energy?

Postby rho » Tue Nov 18, 2008 6:15 pm UTC

Xanthir and Tass have already stated why this isn't 'free energy'. But because this is xkcd I feel it wouldn't be right to leave it in words. And because my maths homework for the night is multiple integrals, I'll procrastinate and do this instead.

To make things easier clearer, I'll analyse an analogous system. I hope you can see that the following would apply equally to a similar device in the atmosphere, or to the one described in the OP, with a few extra considerations which will not change the overall result. That result being that [imath]E_{in} \ge E_{out}[/imath]


My device is this:
An empty cube made of some material, which can vary it's length of side between 0 and L, it has a mass, m.*1

My environment is this:
A tank with dimensions w, l and h, filled with an incompressible fluid of density [imath]\rho[/imath], in a uniform gravitational field of strength g.*2


The pressure,P, at any depth, d, will be the acceleration due to gravity multiplied by the mass of the water 'above' the depth divided by the cross sectional area of the tank, or:
[math]P=\frac {g \rho x y d}{x y} = \rho g d[/math]
At, the bottom of the tank, d=h, at the top of the tank, d=0.

We will sink our device with length of side = 0 to the bottom of the tank, then remotely trigger the device to expand to length of side = L. This requires that we do work, the work done here is [imath]P dV = \rho g h L^3 = E_{in}[/imath]*3


Now, assuming that the density of our cube is < the density of our fluid (i.e. [imath]\frac {m}{L^3} < \rho[/imath] ) the cube will rise.
There is a pressure difference between the top and bottom of the cube which is where this buoyant force originates. Pressure acts equally in all directions.

Taking only the 'vertical' components (as they're the only ones we're interested in (as all the others cancel)) we can find the pressure and hence the force at the top face and bottom face of the cube:
[math]F_{top} = L^2 ( \rho g (h-L) )[/math][math]F_{bottom} = L^2 ( \rho g h )[/math]
So, our buoyant force is then: [math]F_{buoyant} = F_{bottom} - F_{top} = L^2 \rho g h - \rho g h + \rho g L = \rho g L^3[/math]
Which is constant for an incompressible fluid. (Compare with Ein and you can probably see where this is going...)

For the total force we then have to factor in gravity, simply, mg:[math]F_{total} = F_{buoyant} - mg[/math]
The energy 'gained' from the upwards movement is then:[math]\int_{0}^{h} F_{total}\, dh = F_{total}*h = \rho g L^3 h - m g h[/math]

The device is now floating on the surface, so we remotely allow it to contract back to L=0 and it will fall back through the fluid. The energy 'gained' from this downwards movement is then [imath]m g h[/imath]

So our total energy 'gained' is:[math]E_{out} = \rho g L^3 h - m g h + m g h = \rho g L^3 h[/math]...[math]E_{in} = E_{out}[/math]

Which satisfies our lack of free energy. It should be fairly easy to see where losses come into play if you were to build a real 'device' in a real fluid, you'd end up with Eout being much less than Ein.

Notes:
*1 It doesn't have to be a cube, any shape would do, but the cube makes things easier here. Some tough, fluid-proof and quite light material... I'll leave that to the Engineers. More realistically, L would become as small as possible, the 'shape' would be allowed to crumple into something arbitrarily point-like.

*2 A tank of water would do...

*3 There would be a pressure difference across the height of the cube, so it is not as simple as PdV because the bottom of the cube rests on the bottom of the tank. As the pressure varies linearly with depth, the situation being described is equivalent to the centre of the cube being at depth h and the centre remaining there as the cube expands. You can work out the work done on the cube as it expands with it's bottom resting at h if that's the kind of thing you do for fun, but also remember that the cube will not rise by a distance h, as it would then be sitting on the fluid's surface - the end result won't change.

The only real difference between this and OP's idea is that OP has a fluid where the density changes with height (the atmosphere) this merely makes the analysis more complicated, but doesn't change the over-all idea. You could think of my system as OP's except that the density changes very suddenly at d = 0 as opposed to however it varies in the atmosphere, presumably an exponential decrease for an increase in h.

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Re: Free energy?

Postby ducksan » Thu Nov 20, 2008 10:14 pm UTC

To get free energy, rob a gas station or put solar panels on your roof. Or ask some guy named Gibbs.
No, wait, that's not what you guys are talking about.

I can't think of much that would be stable against outside pressure and very thin.
It's a neat idea, but unless it was under completely ideal conditions you'd lose energy in the end.
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Infinity Energy - Magnets?

Postby YoungStudent » Sat Nov 22, 2008 12:25 pm UTC

Infinity Energy - Magnets?

Yes, its me, with another topic.

I dont have much knownledge about magnets...but isnt that possible to generate infinity energy from magnets?

Image

Isnt this non-metal pipe supposed to rotate? If we have super-big magnets like these and super-big non-metal pipe we sould be able to extract some massive energy from that rotating pipe, no?

I already know that its not going to work...but i want to know why...

Its exactly like when wind is rotating fan...expect that this time its magnetic force instead of wind.
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Re: Infinity Energy - Magnets?

Postby headprogrammingczar » Sat Nov 22, 2008 12:54 pm UTC

Let's put it this way. You have X magnets around the pipe. As X approaches 0, it stops having charge. If X=1, you have a pipe with a magnet on the far side of the other magnet. As X approaches infinity, you have a positive rectangular magnet repelling a positive circular magnet. It does not rotate because the repulsive force is applied to both sides of the pipe (not just the left side as in your picture).
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Re: Infinity Energy - Magnets?

Postby Mr_Rose » Sat Nov 22, 2008 12:57 pm UTC

Three things: One, your system requires monopole magnets which only exist in very very rare circumstances, theoretically maybe. Two, you haven't accounted for the fact that loading the system (which you will want to do unless you really only wanted a desk ornament) will eventually cause the magnets to lose their magnetism. Three, there will be, somewhere, a static equilibrium point if all the fields remain constant - motors only work because the field keeps changing.
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Re: Infinity Energy - Magnets?

Postby YoungStudent » Sat Nov 22, 2008 1:00 pm UTC

So anyone have better idea of extracting energy from magnets?
Okay, quote me - We try to explain magic, presence of spirits and supernatural with science, which only explains 'the physical world' that we observe. It's like blind earthworm declaring that there is no light.

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Re: Infinity Energy - Magnets?

Postby BlackSails » Sat Nov 22, 2008 2:58 pm UTC

YoungStudent wrote:So anyone have better idea of extracting energy from magnets?


Yes. Magnet + magnet made out of antimatter --> ENERGY

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Re: Infinity Energy - Magnets?

Postby YoungStudent » Sat Nov 22, 2008 3:08 pm UTC

Yeah, great, great idea...but where do we get antimatter? :D
Okay, quote me - We try to explain magic, presence of spirits and supernatural with science, which only explains 'the physical world' that we observe. It's like blind earthworm declaring that there is no light.

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Re: Infinity Energy - Magnets?

Postby Robert'); DROP TABLE *; » Sat Nov 22, 2008 3:13 pm UTC

By slamming regular matter together with large amounts of energy...

You should be able to tell why this doesn't work as an energy source. :o
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Re: Infinity Energy - Magnets?

Postby Tass » Sat Nov 22, 2008 6:45 pm UTC

Mr_Rose wrote:Three things: One, your system requires monopole magnets which only exist in very very rare circumstances, theoretically maybe.

True
Mr_Rose wrote:Two, you haven't accounted for the fact that loading the system (which you will want to do unless you really only wanted a desk ornament) will eventually cause the magnets to lose their magnetism.

Magnets doesn't lose their magnetism from moving, that is not why there is no free energy (which there isn't)
Mr_Rose wrote:Three, there will be, somewhere, a static equilibrium point if all the fields remain constant - motors only work because the field keeps changing.

Exactly! The fields magnets produce are conservative. This means that it is mathematically proven that once the system returns to the same state (after one revolution) the energy will also be the same. It will find the lowest energy state and stay there. You migth as well try to make a rollercoaster that goes downhill all the time, only difference is that it is easier intuitively to see that it cant be done.

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Re: Free energy?

Postby YoungStudent » Sat Nov 22, 2008 8:40 pm UTC

Well, we can always transform heat into energy. Why wont we DIGG 100km down the surface and transform heat of earth into energy?
Okay, quote me - We try to explain magic, presence of spirits and supernatural with science, which only explains 'the physical world' that we observe. It's like blind earthworm declaring that there is no light.

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Re: Free energy?

Postby rho » Sat Nov 22, 2008 8:51 pm UTC

YoungStudent wrote:Well, we can always transform heat into energy. Why wont we DIGG 100km down the surface and transform heat of earth into energy?

We do.
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Re: Free energy?

Postby gmalivuk » Sat Nov 22, 2008 8:55 pm UTC

YoungStudent wrote:Well, we can always transform heat into energy.

We can only use heat when there's a temperature gradient between the place our heat is being made and some colder place. And since transferring energy away from the heated place makes it colder, this is also only a finite process.
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Re: Free energy?

Postby Valgerth » Sun Nov 23, 2008 12:47 am UTC

Well since it seems now we're not arguing "free energy" in the strictest sense, as in not from any source(such as with geothermal) then I have a proposal for a different way to harvest solar energy. I was toying with a way to use solar energy to power a stirling engine and I came across a video of someone who uses a fresnel lens to do exactly that. You focus the fresnel lense so that all the heat generated from its point of light is on the hot chamber of the stirling engine. You can than use the power from that engine just like you would any other engine and magnets to create electricity. All we would need is someone to manufacture newer up to date sterling engins of larger size than older ones and your could put a system like this virtually anywhere it seems.

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Re: Free energy?

Postby Minerva » Sun Nov 23, 2008 6:20 am UTC

Some of you may be interested in the Museum of Unworkable Devices (http://www.lhup.edu/~dsimanek/museum/unwork.htm), which goes through all the traditional proposals for perpetual motion machines that people dream up with permanent magnets and such, and explains why they don't work.
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Re: Free energy?

Postby Tass » Sun Nov 23, 2008 9:05 am UTC

Valgerth wrote:Well since it seems now we're not arguing "free energy" in the strictest sense, as in not from any source(such as with geothermal) then I have a proposal for a different way to harvest solar energy. I was toying with a way to use solar energy to power a stirling engine and I came across a video of someone who uses a fresnel lens to do exactly that. You focus the fresnel lense so that all the heat generated from its point of light is on the hot chamber of the stirling engine. You can than use the power from that engine just like you would any other engine and magnets to create electricity. All we would need is someone to manufacture newer up to date sterling engins of larger size than older ones and your could put a system like this virtually anywhere it seems.


It is being investigated for commercial viability. The trouble is not getting energy, it is getting the energy cheap enough, and yes this may be a good idea.

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Re: Free energy?

Postby AFedchuck » Sun Nov 23, 2008 12:11 pm UTC

bcoblentz wrote:Bah, I'm not going to try to figure out why this is wrong because there's no such thing as free energy so it's already not going to work.

No such thing as free energy?
Quick, someone tell Gibbs & Helmholtz, they're going to be mighty disappointed.

sorry

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Re: Free energy?

Postby Tass » Sun Nov 23, 2008 3:46 pm UTC

AFedchuck wrote:
bcoblentz wrote:Bah, I'm not going to try to figure out why this is wrong because there's no such thing as free energy so it's already not going to work.

No such thing as free energy?
Quick, someone tell Gibbs & Helmholtz, they're going to be mighty disappointed.

sorry


Haha

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Re: Free energy?

Postby SunAvatar » Mon Nov 24, 2008 10:41 pm UTC

It is a theorem, derivable from the currently understood laws of physics, that free energy is impossible.

Therefore, if you have designed a machine that seems to produce free energy, there are two possibilities: either
  • you are positing new, previously unknown laws of physics, and should be able to point to where your machine's behavior deviates from the standard model; or
  • you have made a mistake.
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Re: Free energy?

Postby bcoblentz » Tue Nov 25, 2008 9:50 am UTC

Of course I meant free energy in the colloquial, pseudoscientific sense. While I know less physics than any of the other physics majors I graduated with, I know enough not to be amused by that joke.

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Re: Free energy?

Postby eternauta3k » Thu Nov 27, 2008 1:56 am UTC

bcoblentz wrote:Of course I meant free energy in the colloquial, pseudoscientific sense. While I know less physics than any of the other physics majors I graduated with, I know enough not to be amused by that joke.


It's funny*. Laugh.



*signified by the apology, which referred to the bad pun the joke consisted of.
VectorZero wrote:It takes a real man to impact his own radius

That's right, slash your emo-wrists and spill all your emo-globin


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